This file was created by the TYPO3 extension publications --- Timezone: CEST Creation date: 2026-04-23 Creation time: 12:31:44 --- Number of references 51 article Galeczka2025141 Article 2025 10.5194/adgeo-65-141-2025 Advances in Geosciences 65 141 – 148 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85214782538&doi=10.5194%2fadgeo-65-141-2025&partnerID=40&md5=941031856855737eef3619b497e275e7 Cited by: 0; All Open Access, Gold Open Access Iwona Galeczka Finnbogi Óskarsson Kiflom Gebrehiwot Mesfin Jón Einar Jónsson conference Pálsson20242974 Conference paper 2024 Transactions - Geothermal Resources Council 48 2974 – 2983 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85214263568&partnerID=40&md5=e291566c1e82137d92826803043f2448 Cited by: 0 Bjarni Pálsson article Simakin2022 Article 2022 10.1093/petrology/egac074 Journal of Petrology 63 8 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85160756713&doi=10.1093%2fpetrology%2fegac074&partnerID=40&md5=a3966fa4fab8fa77d0e3b4b7598f0ed1 Cited by: 5 A.G. Simakin I.N. Bindeman article Zierenberg2021 Article 2021 10.1029/2021GC009747 Geochemistry, Geophysics, Geosystems 22 11 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85119882731&doi=10.1029%2f2021GC009747&partnerID=40&md5=81e828e42ded15d28f9ff8e0ba0f5b88 Cited by: 6; All Open Access, Hybrid Gold Open Access Robert A. Zierenberg Guðmundur Ó. Friðleifsson Wilfred A. Elders Peter Schiffman Andrew P. G. Fowler article Saubin20211815 The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy. © 2021 Geological Society of America 2021 English 00167606 10.1130/B35598.1 Bulletin of the Geological Society of America 133 Geological Society of America 1815-1830 School of Earth and Environment, University of Canterbury, Christchurch, New Zealand; Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom; Department of Earth Sciences, University of Oregon, Eugene, Oregon, 97403, United States; Mineralogical Museum, Moscow, Russian Federation; Landsvirkjun National Power Company of Iceland, Reykjavik, Iceland; School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand; Department of Earth Sciences, Lower Mountjoy, Durham University, Durham, DH1 3LE, United Kingdom; Earth and Planetary Sciences, University of California, Davis, California 95616, United States; Chair for Subsurface Engineering, Montanuniversität Leoben, Austria 9-10 Chemical analysis; Geothermal power plants; Geothermal prospecting; Geothermal wells; Glass; Hydration; Infill drilling; Melting; Particle size analysis; Silica; Textures, Geophysical monitoring; Glass particles; Hazard Assessment; High temperature; Higher resolution; Iceland deep drilling projects; Rhyolitic melts; Textural heterogeneities, Geothermal energy, drilling; geochemistry; glass; magma; melt; rhyolite; texture; time series analysis, Iceland; Krafla https://www.scopus.com/inward/record.uri?eid=2-s2.0-85115211895&doi=10.1130%2fB35598.1&partnerID=40&md5=e2067847ba9ba5a5510abd91a4053189 cited By 2 E. Saubin B. Kennedy H. Tuffen A.R.L. Nichols I. Bindeman A. Mortensen C.I. Schipper F.B. Wadsworth T. Watson R. Zierenberg article Eichelberger20201 Article 2020 10.3390/geosciences10060212 Geosciences (Switzerland) 10 1 – 26 6 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086126902&doi=10.3390%2fgeosciences10060212&partnerID=40&md5=68c2c001c338419e57723d70acc2619c Cited by: 21; All Open Access, Gold Open Access, Green Open Access John Eichelberger article Nono2020 Article 2020 10.1016/j.jvolgeores.2018.04.021 Journal of Volcanology and Geothermal Research 391 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047402066&doi=10.1016%2fj.jvolgeores.2018.04.021&partnerID=40&md5=003cfac308bec4cef179fc9815ac3d77 Cited by: 29; All Open Access, Bronze Open Access, Green Open Access Franck Nono Benoit Gibert Fleurice Parat Didier Loggia Sarah B. Cichy Marie Violay article Bali20201221 Article 2020 10.1130/G47791.1 Geology 48 1221 – 1225 12 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096411629&doi=10.1130%2fG47791.1&partnerID=40&md5=78df0f56a2c9cea6277bbef45ec2a280 Cited by: 21; All Open Access, Bronze Open Access, Green Open Access Enikő Bali Guðmundur H. Guðfinnsson László E. Aradi Ábel Szabó Csaba Szabó Robert Zierenberg Larryn W. Diamond Thomas Pettke Guðmundur Ó Friðleifsson article Kummerow2020 Article 2020 10.1016/j.jvolgeores.2018.05.014 Journal of Volcanology and Geothermal Research 391 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048866149&doi=10.1016%2fj.jvolgeores.2018.05.014&partnerID=40&md5=b849279c887c4cecadc7de81d48c3a3f Cited by: 8 Juliane Kummerow Siegfried Raab Jan A. Schuessler Romain Meyer article Friðleifsson2020 The aim of the Iceland Deep Drilling Project is to drill into supercritical geothermal systems and examine their economic potential. The exploratory well IDDP-2 was drilled in the Reykjanes geothermal field in SW Iceland, on the landward extension of the Mid-Atlantic Ridge. The Reykjanes geothermal field produces from a &lt;300 °C reservoir at 1 to 2.5 km depth and is unusual because it is recharged by seawater. The well was cased to 3000 m depth, and then angled towards the main up-flow zone of the system, to a total slant depth of 4659 m (~4500 m vertical depth). Based on alteration mineral assemblages, joint inversion of wireline logging, and rate of heating measurements, the bottom hole temperature is estimated to be about 535 °C. The major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth. Drilling continued without recovering drill cuttings, consequently spot coring provided the only deep rock samples from the well. These cores are characteristic of a basaltic sheeted dike complex, with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies, hornblende hornfels, and pyroxene hornfels, allowing the opportunity to investigate water-rock interaction in the active roots of an analog of a submarine hydrothermal system. As they have not yet been sampled, the composition of the deep fluids at Reykjanes is unknown at present. Cold water is currently being injected with the aim of enhancing permeability at depth, before allowing the well to heat up prior to flow tests planned for early 2019. The well has at least two fluid feed zones, a dominant one at 3.4 km depth and a second smaller one at 4.5 km. Extensive geophysical surveys of the Reykjanes Peninsula completed recently allow correlation of geophysical signals with rocks properties and in-situ conditions in the subsurface. Earthquake activity monitored with a local seismic network during drilling the IDDP-2 drilling detected abundant small earthquakes (ML ≤ 2) within the depth range of 3–5 km. A zone at 3–5 km depth below the producing geothermal field that was generally aseismic prior to drilling, but became seismically active during the drilling. The drilling of the IDDP-2 has achieved number of scientific and engineering firsts. It is the deepest and hottest drill hole so far sited on an active mid-ocean spreading center. It penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems. © 2018 Elsevier B.V. 2020 English 03770273 10.1016/j.jvolgeores.2018.08.013 Journal of Volcanology and Geothermal Research 391 Elsevier B.V. HS Orka, Svartsengi, Grindavík, 240, Iceland; Dept. of Earth Sciences, University of California, Riverside, CA 92521, United States; Dept. of Earth and Planetary Sciences, University of California, Davis, CA 95616, United States; Department of Earth Sciences, University of Minnesota, Minneapolis, United States; ÍSOR, Grensásvegur 9, Reykjavík, 108, Iceland; Statoil Research Centre, Trondheim, Norway; Géosciences Montpellier, Université de Montpellier, France; Université de Pau, France; University of Potsdam and GFZ, Potsdam, Germany Clay alteration; Drilling fluids; Earthquakes; Effluent treatment; Geothermal fields; Hydraulic structures; Mineral exploration; Rhenium compounds; Rock drills; Silicate minerals; Smoke; Supercritical fluids, Black smokers; Deep drilling; Geothermal; IDDP; Reykjanes, Infill drilling, amphibolite facies; analog model; black smoker; Deep Sea Drilling Project; drilling; exploration; flow field; geothermal system; greenschist facies; hydrothermal alteration; mineral alteration; spreading center; supercritical flow, Atlantic Ocean; Iceland; Mid-Atlantic Ridge; Reykjanes Peninsula https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053010956&doi=10.1016%2fj.jvolgeores.2018.08.013&partnerID=40&md5=b752b14100c9498cbddf7133a8bbc07d cited By 29 G.Ó. Friðleifsson W.A. Elders R.A. Zierenberg A.P.G. Fowler T.B. Weisenberger K.G. Mesfin Ó. Sigurðsson S. Níelsson G. Einarsson F. Óskarsson E.Á. Guðnason H. Tulinius K. Hokstad G. Benoit F. Nono D. Loggia F. Parat S.B. Cichy D. Escobedo D. Mainprice article Masotta2018603 Article 2018 10.1016/j.chemgeo.2018.03.031 Chemical Geology 483 603 – 618 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044331691&doi=10.1016%2fj.chemgeo.2018.03.031&partnerID=40&md5=60aad59f566190ef80223f2e1f62cc14 Cited by: 21 M. Masotta S. Mollo M. Nazzari V. Tecchiato P. Scarlato P. Papale O. Bachmann conference Elders20181914 Conference paper 2018 Transactions - Geothermal Resources Council 42 1914 – 1927 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059884523&partnerID=40&md5=37772d677a7436332586a6484f9d84e4 Cited by: 7 Wilfred A. Elders James Shnell Guðmundur Ó. Friðleifsson Albert Albertsson Robert A. Zierenberg article Fridleifsson20171 The Iceland Deep Drilling Project research well RN-15/IDDP-2 at Reykjanes, Iceland, reached its target of supercritical conditions at a depth of 4.5 km in January 2017. After only 6 days of heating, the measured bottom hole temperature was 426 °C, and the fluid pressure was 34MPa. The southern tip of the Reykjanes peninsula is the landward extension of the Mid-Atlantic Ridge in Iceland. Reykjanes is unique among Icelandic geothermal systems in that it is recharged by seawater, which has a critical point of 406 °C at 29.8MPa. The geologic setting and fluid characteristics at Reykjanes provide a geochemical analog that allows us to investigate the roots of a mid-ocean ridge submarine black smoker hydrothermal system. Drilling began with deepening an existing 2.5 km deep vertical production well (RN-15) to 3 km depth, followed by inclined drilling directed towards the main upflow zone of the system, for a total slant depth of 4659m (~4.5 km vertical depth). Total circulation losses of drilling fluid were encountered below 2.5 km, which could not be cured using lost circulation blocking materials or multiple cement jobs. Accordingly, drilling continued to the total depth without return of drill cuttings. Thirteen spot coring attempts were made below 3 km depth. Rocks in the cores are basalts and dolerites with alteration ranging from upper greenschist facies to amphibolite facies, suggesting that formation temperatures at depth exceed 450 °C. High-permeability circulation-fluid loss zones (feed points or feed zones) were detected at multiple depth levels below 3 km depth to bottom. The largest circulation losses (most permeable zones) occurred between the bottom of the casing and 3.4 km depth. Permeable zones encountered below 3.4 km accepted less than 5% of the injected water. Currently, the project is attempting soft stimulation to increase deep permeability. While it is too early to speculate on the energy potential of this well and its economics, the IDDP-2 is a milestone in the development of geothermal resources and the study of hydrothermal systems. It is the first well that successfully encountered supercritical hydrothermal conditions, with potential high-power output, and in which on-going hydrothermal metamorphism at amphibolite facies conditions can be observed. The next step will be to carry out flow testing and fluid sampling to determine the chemical and thermodynamic properties of the formation fluids. © Author(s) 2017. 2017 English 18168957 10.5194/sd-23-1-2017 Scientific Drilling 23 Copernicus GmbH 1-12 HS Orka, Svartsengi, Grindavík, 240, Iceland; Department of Earth Sciences, University of California, Riverside, CA 92521, United States; Department of Earth and Planetary Sciences, University of California, Davis, CA 95616, United States; ÍSOR, Grensásvegur 9, Reykjavík, 108, Iceland Drilling fluids; Economics; Geothermal energy; Geothermal fields; Geothermal wells; Seawater; Thermodynamic properties, Bottom hole temperatures; Formation temperature; Geothermal resources; Hydrothermal system; Iceland deep drilling projects; Supercritical condition; Supercritical hydrothermal; Total circulation loss, Rhenium compounds https://www.scopus.com/inward/record.uri?eid=2-s2.0-85036665131&doi=10.5194%2fsd-23-1-2017&partnerID=40&md5=6c3f2329598f2dcb59e984f6eee789f9 cited By 62 G.Ó. Fridleifsson W.A. Elders R.A. Zierenberg A.P. Fowler T.B. Weisenberger B.S. Hararson K.G. Mesfin article Reinsch2017 Supercritical geothermal systems are very high-temperature geothermal systems that are located at depths near or below the brittle–ductile transition zone in the crust where the reservoir fluid is assumed to be in the supercritical state, that is for pure water, temperature and pressure are, respectively, in excess of 374 °C and 221 bar. These systems have garnered attention in recent years as a possible type of unconventional geothermal resource due to their very high enthalpy fluids. Supercritical conditions are often found at the roots of volcanic-hosted hydrothermal systems. More than 25 deep wells drilled in geothermal fields such as The Geysers, Salton Sea, and on Hawaii (USA), Kakkonda (Japan), Larderello (Italy), Krafla (Iceland), Los Humeros (Mexico), and Menengai (Kenya) have encountered temperatures in excess of 374 °C, and in some cases have encountered magma. Although fluid entries were documented for some of these wells, it remains an open question if permeability can be maintained at high enthalpy conditions. The IDDP-1 well at Krafla encountered magma, and ended up producing very high enthalpy fluids; however, these fluids were very corrosive and abrasive. Innovative drilling and well completion techniques are therefore needed to deal with the extreme temperatures and aggressive fluid chemistry compositions of these systems. New efforts are underway in Japan (northern Honshu), Italy (Larderello), Iceland (Reykjanes peninsula and Krafla), Mexico (Los Humeros), USA (Newberry), and New Zealand (Taupo Volcanic Zone) to investigate supercritical systems. Here, we review past studies, describe current research efforts, and outline the challenges and potential opportunities that these systems provide for international collaboration to ultimately utilize supercritical geothermal systems as a geothermal energy resource. © 2017, The Author(s). 2017 English 21959706 10.1186/s40517-017-0075-y Geothermal Energy 5 SpringerOpen GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany; Energy Geosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States; Fukushima Renewable Energy Institute, AIST, Koriyama, Fukushima, Japan; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Trieste, Italy; Direction des Géoressources, Bureau de Recherches Géologiques et Minières, Orléans, France 1 Energy resources; Enthalpy; Geothermal energy; Geothermal wells; International cooperation; Volcanoes; Well completion, Extreme temperatures; Geothermal resources; Geothermal systems; International collaborations; Supercritical condition; Supercritical systems; Taupo Volcanic Zone; Temperature and pressures, Geothermal fields, chemical composition; enthalpy; geothermal system; high temperature; hydrothermal system; permeability; reservoir; transition zone; well completion, California; Geysers; Hawaii [United States]; Honshu; Iceland; Italy; Iwate; Japan; Kakkonda Geothermal Field; Kenya; Krafla; Larderello; Los Humeros; Menengai Volcano; Mexico [North America]; Nakuru; New Zealand; Newberry Volcano; North Island; Oregon; Pisa [Tuscany]; Puebla [Mexico]; Reykjanes Peninsula; Salton Sea; Taupo Volcanic Zone; Tohoku; Tuscany; United States https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029441941&doi=10.1186%2fs40517-017-0075-y&partnerID=40&md5=c4a96742d995c1a8f726d51687e7721b cited By 114 T. Reinsch P. Dobson H. Asanuma E. Huenges F. Poletto B. Sanjuan conference Stefánsson2017512 Conference paper 2017 Transactions - Geothermal Resources Council 41 512 – 522 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038214846&partnerID=40&md5=d696bf73686675fdca8b0f63a9fb0f13 Cited by: 7 Ari Stefánsson Pór Gíslason Ómar Sigurdsson Gudmundur Ó. Fridleifsson conference Zierenberg20171599 The Iceland Deep Drilling Project (IDDP) well IDDP-2 was drilled to 4,659 m in the seawaterrecharged and basalt-hosted Reykjanes geothermal system in Iceland. Spot drill cores were recovered between drilling depths of 3,648.00 m and 4,657.58 m. Temperature and pressure conditions at the base of IDDP-2 were over 426°C and 340 bar immediately following drilling, exceeding the critical point of seawater (406°C and 298 bar). The IDDP-2 cores are the first samples ever recovered from the supercritical roots of an active basalt-hosted hydrothermal system. We provide some preliminary hand sample descriptions, supplemented where possible by thin section petrography and mineral composition analyses for the IDDP-2 drill cores. The cores recovered between 3,648 m and the bottom of the hole at 4,659 m are from a sheeted dike complex and are generally pervasively altered. Despite the extensive alteration, veining is relatively minor and open space veins are very rare. Veins tend to be discontinuous and anastomosing and lack sharp wall rock contacts. They are interpreted as hydrothermal replacement veins formed in the transition zone between brittle and ductile deformation. Important initial findings include the transition from epidote-actinolite alteration to hornblende hornfels alteration at approximately 3,650 m, and the development of hydrothermal biotite in rocks below ∼4,250 m. Felsic (plagiogranite) segregation veins are not common on the Reykjanes peninsula west of the Hengill volcanic system, but are present in minor amounts in most of the dikes cored below ∼4,300 m. Detailed petrographic and geochemical analysis of the samples is on-going. We have also sampled what appears to be hypersaline supercritical/magmatic brine trapped in pore spaces of porous felsite veins and adjacent wall rock, which manifests as a yellow potassium-iron chloride salt that precipitates on the cut edge of the core as pore fluid evaporates. Some of the core at these depths was stained by hematite that formed on the outer core surface by oxidation of ferrous iron in the formation fluid reacting at elevated temperature with oxygenated surface water used as drilling fluid. Further evidence for supercritical brine is apparent in complex fluid inclusions within quartz that contain multiple solid phases. The drill core samples are of immense scientific value for studying chemical conditions in the supercritical roots of high-enthalpy geothermal resources and submarine hydrothermal systems, with implications for improved understanding of ore-forming processes. Conference paper 2017 English 0934412227 01935933 Transactions - Geothermal Resources Council 41 Geothermal Resources Council 1599 – 1615 Department of Earth and Planetary Sciences, University of California, Davis, CA, United States; HS Orka, Orkubraut 3, Svartsengi, Grindavík, 240, Iceland; Department of Earth Sciences, University of California, Riverside, CA, United States; ÍSOR (Iceland GeoSurvey), Grensávegur 9, Reykjavík, 108, Iceland Analytical geochemistry; Basalt; Chlorine compounds; Core drilling; Drilling fluids; Drills; Geothermal fields; Geothermal wells; Hematite; Hydraulic structures; Hydrochemistry; Levees; Lithology; Mica; Petrography; Potassium chloride; Recovery; Silicate minerals; Surface waters; Wall rock, Alteration; Drill core; Enhanced geothermal systems; Geothermal systems; Iceland deep drilling projects; Supercritical, Core samples https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041071902&partnerID=40&md5=8f3731cc71242b3a05aff0690c098400 Cited by: 13 Robert A. Zierenberg Andrew P. G. Fowler Gudmundur Ó. Fridleifsson Wilfred A. Elders TobiaS. B. Weisenberger conference Fridleifsson20171095 The Iceland Deep Drilling Project (IDDP) passed a significant milestone in January 2017 when its IDDP-2 well penetrated a supercritical reservoir at a depth of 4.5 km. After only 6 days of heating, the temperature measured at the bottom of the well was ∼426°C, with fluid pressure of 340 bars, with indications of permeability at depth. The IDDP is a project of a consortium of Icelandic energy companies, National Energy Authority of Iceland and Statoil, aimed at greatly increasing the production of usable geothermal energy by drilling deep enough to reach the supercritical zone beneath high-temperature geothermal fields. Modeling indicates that, because of the higher enthalpy of supercritical fluid, and more favorable flow properties, a well producing supercritical water could produce an order of magnitude more usable energy than that produced from conventional high-temperature geothermal wells. The IDDP-2 well is located in the Reykjanes geothermal field which lies near the southern tip of the Reykjanes Peninsula, the landward extension of the Mid-Atlantic Ridge. At Reykjanes, some 34 production and injection wells supply a 100 MWe power plant, producing from a < 300°C reservoir at 1 to 2.5 km depth. It is unique among Icelandic geothermal systems because its reservoir is recharged by seawater, which has a critical point of the 406°C at 298 bars. Drilling the IDDP-2 began by using an existing 2.5 km deep production well, RN-15, that was deepened and cased to 3,000 m depth and then angled towards the main upflow zone of the system for a total slant depth of 4,659 m (∼4.5 km vertical depth). Total circulation losses were encountered below 3 km depth which could not be cured by lost circulation materials or by multiple cement jobs. Accordingly, drilling continued "blind" to total depth, without return of drill cuttings. We attempted 13 core runs below 3 km depth, only 9 of which recovered some core. The cores are basalts and dolerites in a sheeted dike swarm with alteration ranging from lower greenschist facies to lower amphibolite facies, suggesting formation temperatures >450°C, but with low water/rock ratios. A perforated liner was inserted to 4,620 m and the well subsequently logged for temperature, pressure and injectivity. The T-log showed the main permeable zones to be at above 3380 m, with smaller feed zones at 3,820 m, 3,990 m, 4,100, 4,200 m, 4,375 m, and 4,550 m depths. The deeper feed zones accepted ∼5% of the injected water. This year we will attempt to enhance the deeper permeability by massive soft stimulation, and then carry out flow tests to determine the thermodynamic and chemical properties of the fluid produced. Conference paper 2017 English 0934412227 01935933 Transactions - Geothermal Resources Council 41 Geothermal Resources Council 1095 – 1107 HS Orka, Orkubraut 3, Svartsengi, Grindavík, 240, Iceland; Dept. of Earth Sciences, University of California, Riverside, CA 92521, United States Effluent treatment; Geothermal wells; Hydraulic structures; Rhenium compounds; Supercritical fluids; Temperature; Well drilling; Well stimulation, DEEPEGS; Formation temperature; Iceland deep drilling projects; Lost circulation materials; National energy authorities; Reykjanes; Supercritical; Total circulation loss, Geothermal fields https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041042063&partnerID=40&md5=30c093d9908d7a3d2866d6ad08b90e0a Cited by: 16 Gudmundur Ó. Fridleifsson Wilfred A. Elders article Fowler20164772 Hydrothermal activity results in element exchanges between seawater and oceanic crust that contribute to many aspects of ocean chemistry; therefore, improving knowledge of the associated chemical processes is of global significance. Hydrothermally altered basaltic drill core samples from the seawater-recharged Reykjanes geothermal system in Iceland record elemental gains and losses similar to those observed in samples of hydrothermally altered oceanic crust. At Reykjanes, rocks originally emplaced on the seafloor were buried by continued volcanism and subsided to the current depths (>2250 m below surface). These rocks integrate temperature-dependent elemental gains and losses from multiple stages of hydrothermal alteration that correspond to chemical exchanges observed in rocks from different crustal levels of submarine hydrothermal systems. Specifically, these lithologies have gained U, Mg, Zn, and Pb and have lost K, Rb, Ba, Cu, and light rare earth elements (La through Eu). Alteration and elemental gains and losses in lithologies emplaced on the seafloor can only be explained by a complex multistage hydrothermal alteration history. Reykjanes dolerite intrusions record alteration similar to that reported for the sheeted dike section of several examples of oceanic crust. Specifically, Reykjanes dolerites have lost K, Rb, Ba, and Pb, and gained Cu. The Reykjanes drill core samples provide a unique analog for seawater-oceanic crust reactions actively occurring at high temperatures (275–345°C) beneath a seafloor hydrothermal system. © 2016. American Geophysical Union. All Rights Reserved. 2016 English 15252027 10.1002/2016GC006595 Geochemistry, Geophysics, Geosystems 17 Blackwell Publishing Ltd 4772-4801 Department of Earth and Planetary Sciences, University of California, Davis, CA, United States 11 Clay alteration; Core drilling; Core samples; Drills; Europium compounds; Geothermal fields; Hydraulic structures; Hydrochemistry; Lithology; Magnesium; Rubidium; Seawater; Uranium, Drill core; Hydrothermal alterations; ICDP; Oceanic crust; Reykjanes, Europium, emplacement; geothermal system; hydrothermal alteration; hydrothermal system; lithology; oceanic crust; recharge; seawater; temperature effect; volcanism, Iceland https://www.scopus.com/inward/record.uri?eid=2-s2.0-85005807547&doi=10.1002%2f2016GC006595&partnerID=40&md5=7eabe4a2313379daf7f70e4cae3804b0 cited By 9 A.P.G. Fowler R.A. Zierenberg article Kaldal20161 Flow testing of IDDP-1, the first Icelandic Deep Drilling Project (IDDP) well drilled in the Krafla geothermal field in Iceland, demonstrated promising results by producing superheated steam. During an unavoidable quenching of the well the innermost casing failed presumably due to tensile stresses caused by thermal contraction. Since the structural integrity of casings is essential for utilization of high temperature geothermal wells, the well has not been discharged again. In this paper, the casings of the well are analyzed structurally with a nonlinear finite-element model. The load history of the casings is followed from installation and through several thermal cycles, but the well was discharged at least six times before it was quenched with cold water. The results show that changes in stiffness due to the presence of casing shoes and changes in casing thickness have an effect on the stress and strain formations in neighboring casings. The results illustrate that during each thermal cycle, the wellbore thermal load is more severe for the production casing than for the external casings that are somewhat protected, provided that cementing in between is adequate. © 2016 Elsevier Ltd. 2016 English 03756505 10.1016/j.geothermics.2016.02.002 Geothermics 62 Elsevier Ltd 1-11 Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland, Hjardarhagi 2-6, Reykjavik, IS-107, Iceland Geothermal fields; Geothermal wells; Shoe manufacture; Structural analysis; Thermal cycling, High temperature; IDDP; Krafla geothermal field; Non-linear finite element model; Production casings; Steel casing; Structural modeling; Thermal contraction, Finite element method, finite element method; geothermal energy; geothermal power; numerical model; structural analysis, Iceland https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960351589&doi=10.1016%2fj.geothermics.2016.02.002&partnerID=40&md5=dec1188ca9991a53d47e1a00d851ebfd cited By 14 G.S. Kaldal M.T. Jonsson H. Palsson S.N. Karlsdottir article Fowler201547 We describe the lithology and present spatially resolved geochemical analyses of samples from the hydrothermally altered Iceland Deep Drilling Project (IDDP) drill core RN-17B. The 9.3m long RN-17B core was collected from the seawater-dominated Reykjanes geothermal system, located on the Reykjanes Peninsula, Iceland. The nature of fluids and the location of the Reykjanes geothermal system make it a useful analog for seafloor hydrothermal processes, although there are important differences. The recovery of drill core from the Reykjanes geothermal system, as opposed to drill cuttings, has provided the opportunity to investigate evolving geothermal conditions by utilizing in-situ geochemical techniques in the context of observed paragenetic and spatial relationships of alteration minerals. The RN-17B core was returned from a vertical depth of ~2560m and an in-situ temperature of ~345°C. The primary lithologies are basaltic in composition and include hyaloclastite breccia, fine-grained volcanic sandstone, lithic breccia, and crystalline basalt. Primary igneous phases have been entirely pseudomorphed by calcic plagioclase+magnesium hornblende+chlorite+titanite+albitized plagioclase+vein epidote and sulfides. Despite the extensive hydrothermal metasomatism, original textures including hyaloclastite glass shards, lithic clasts, chilled margins, and shell-fragment molds are superbly preserved. Multi-collector LA-ICP-MS strontium isotope ratio (87Sr/86Sr) measurements of vein epidote from the core are consistent with seawater as the dominant recharge fluid. Epidote-hosted fluid inclusion homogenization temperature and freezing point depression measurements suggest that the RN-17B core records cooling through the two-phase boundary for seawater over time to current in-situ measured temperatures. Electron microprobe analyses of hydrothermal hornblende and hydrothermal plagioclase confirm that while alteration is of amphibolite-grade, it is in disequilibrium and the extent of alteration is dependent upon protolith type and water/rock ratio. Alteration in the RN-17B core bares many similarities to that of Type II basalts observed in Mid-Atlantic Ridge samples. © 2015 Elsevier B.V. 2015 English 03770273 10.1016/j.jvolgeores.2015.06.009 Journal of Volcanology and Geothermal Research 302 Elsevier 47-63 Department of Earth and Planetary Sciences, University of California, DavisCA 95616, United States; Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States; HS Orka, hf, Reykjanesbaer, Iceland Analytical geochemistry; Basalt; Core drilling; Drills; Electron probe microanalysis; Feldspar; Geochemistry; Geothermal fields; Isotopes; Lithology; Microanalysis; Mineralogy; Rock drilling; Rocks; Seawater; Silicate minerals; Strontium, Drill core; Epidote; Geothermal; Hydrothermal alterations; Icelands; Reykjanes, Core samples, deep drilling; epidote; geochemistry; geothermal system; hydrothermal alteration; lithology; paragenesis; seawater, Iceland; Reykjanes Peninsula https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933073486&doi=10.1016%2fj.jvolgeores.2015.06.009&partnerID=40&md5=d6e1cbaadb3794b302b5d1a518eabcb2 cited By 15 A.P.G. Fowler R.A. Zierenberg P. Schiffman N. Marks G.O. Frileifsson article Marks201534 The Iceland Deep Drilling Program well RN-17 was drilled 3km into a section of hydrothermally altered basaltic crust in the Reykjanes geothermal system in Iceland. The system is located on the landward extension of the Mid-Atlantic Ridge, and the circulating hydrothermal fluid is modified seawater, making Reykjanes a useful analog for mid-oceanic ridge hydrothermal systems. We have determined whole-rock Sr and O isotope compositions, and Sr isotope compositions of epidote grains from the RN-17 cuttings and RN-17B core. Whole rock oxygen isotope ratios range from -0.13 to 3.61‰ V-SMOW, and are isotopically lighter than fresh MORB (5.8±0.2‰). The concentrations of Sr in the altered basalt range from well below to well above concentrations in fresh rock, and appear to be strongly correlated with the dominant alteration mineralogy. Whole rock Sr isotope ratios ranged from 0.70329 in the least altered crystalline basalt, to 0.70609 in the most altered hyaloclastite samples; there is no correlation with depth. Sr isotope ratios in epidote grains measured by laser ablation MC-ICP-MS ranged from 0.70360 to 0.70731. Three depth intervals, at 1000m, 1350m, and 1650m depth, have distinctive isotopic signatures, where 87Sr/86Sr ratios are elevated (mean value>0.7050) relative to background levels (mean altered basalt value ~0.7042). These areas are proximal to geothermal feed zones, and the 1350m interval directly overlies the transition from dominantly extrusive to dominantly intrusive lithologies. Oxygen isotope measurements yield integrated water/rock ratios of 0.4 to 4.3, and suggest that hydrothermal fluids must have formerly had a component of meteoric water. Strontium isotopic measurements provide a more sensitive indication of seawater interaction and require significant exchange with seawater strontium. Both isotopic systems indicate that the greenschist-altered basalts were in equilibrium with hydrothermal fluids at a relatively high mean water/rock (Wt.) ratio ranging from about 0.5 to 4. These ratios are higher than estimates from ODP Hole 504B and IODP Hole 1256D, but are consistent with values inferred from vent fluids from 21° and 13°N on the East Pacific Rise (Albarède et al., 1981; Michard et al., 1984; Alt et al., 1996; Harris et al., 2015). © 2015 Elsevier B.V. 2015 English 00092541 10.1016/j.chemgeo.2015.07.006 Chemical Geology 412 Elsevier 34-47 Department of Geology, University of California, DavisCA 95616, United States Aluminum; Basalt; Crystalline rocks; Geothermal fields; Isotopes; Laser ablation; Minerals; Oxygen; Rocks; Seawater; Silicate minerals, Alteration; Geothermal; Hydrothermal; Icelands; Oxygen isotopes; Reykjanes; Strontium isotopes, Strontium, concentration (composition); geothermal system; hydrothermal alteration; hydrothermal fluid; hydrothermal vent; isotopic composition; mid-ocean ridge basalt; oceanic crust; oxygen isotope; strontium isotope, East Pacific Rise; Iceland; Pacific Ocean; Reykjanes Peninsula https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938090234&doi=10.1016%2fj.chemgeo.2015.07.006&partnerID=40&md5=bbb4285c0d4bc181faff8317b465e9dd cited By 18 N. Marks R.A. Zierenberg P. Schiffman article HAUKSSON201476 Material tests and scrubbing experiments were carried out at the IDDP-1 well in the Krafla geothermal field in Iceland. The 450°C superheated steam contained acid gas (approx. 90mg/kg HCl and 7mg/kg HF) and was highly corrosive when it condensed making it unsuitable for utilization without scrubbing. The acid gas could effectively be scrubbed from the steam with water. The steam contained gasous sulfur compond (80–100mg/kgS), which could only be scrubbed from the steam with alkaline water. The steam contained both silica dust and dissolved silica which was effectively washed from the steam with wet scrubbing. Experiments on corrosion and erosion resistance of metals and alloys were problematic to run because of equipment clogging by silica dust. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.07.003 Geothermics 49 76-82 Steam scrubbing, Acid, Sulfur, Silica dust https://www.sciencedirect.com/science/article/pii/S0375650513000515 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Trausti Hauksson Sigurdur Markusson Kristján Einarsson Sigrun Nanna Karlsdóttir Ásbjörn Einarsson Aðalsteinn Möller Þorsteinn Sigmarsson article THORHALLSSON201416 The aim of the Iceland Deep Drilling Projects (IDDP) was to drill to a depth of 4–5km in known high-temperature areas to investigate their roots. The paper describes the design of the “generic” IDDP well and what the plans were. The challenges are to drill a large well with five cemented casing strings to 4500m into a reservoir which can have a temperature of 400–600°C. In 2009 well IDDP-1 was drilled according to these plans but could not reach below 2100m due to the intersection of magma, as will be described in other papers in this special issue of Geothermics. The paper is thus for the historical record of the original design premises and intentions. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.08.004 Geothermics 49 16-22 Iceland Deep Drilling, Well design, Supercritical steam https://www.sciencedirect.com/science/article/pii/S0375650513000606 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma S. Thórhallsson B. Pálsson S. Hólmgeirsson K. Ingason M. Matthíasson H.Á. Bóasson H. Sverrisson article HJARTARSON201483 When a dry steam containing volatile chloride cools to saturation temperature, the compound dissolves in the condensate and forms hydrochloric acid. This can have tremendous consequences for equipment as hydrochloric acid aggressively attacks steel and other metals, causing severe pitting corrosion, crystalline corrosion and stress corrosion cracking of stainless steel components. The Icelandic Deep Drilling Project is dealing with extreme circumstances with high enthalpy, superheated steam possibly containing hydrogen chloride. Successful corrosion mitigation is essential for the feasibility of the development. The goal of this work is to examine different technologies to utilize such a steam, with regard to exergy conservation. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.08.008 Geothermics 49 83-89 IDDP, Volatile chloride, Corrosion mitigation, Superheated geothermal steam https://www.sciencedirect.com/science/article/pii/S0375650513000709 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Steindór Hjartarson Guðrún Sævarsdóttir Kristinn Ingason Bjarni Pálsson William S. Harvey Halldór Pálsson article FRIDLEIFSSON20142 Calculations discussed in the Iceland Deep Drilling Project feasibility study in 2003 indicated that, for same volumetric flow rate of steam, a geothermal well producing from natural supercritical fluid would have the potential to generate power outputs an order of magnitude greater than from conventional high-temperature wells (240–340°C). To reach supercritical hydrous fluid conditions in natural geothermal systems requires deep drilling to a minimum depth of some 3.5–5km were temperature conditions can be expected to range between 400 and 600°C in reasonably active high-temperature fields. Three geothermal fields in Iceland, Reykjanes, Hengill and Krafla, were selected as suitable locations for deep drilling to test this concept in search of natural supercritical geothermal fluid systems. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.03.004 Geothermics 49 2-8 Iceland Deep Drilling Project, Supercritical geothermal fluid systems https://www.sciencedirect.com/science/article/pii/S0375650513000217 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma G.Ó. Friðleifsson W.A. Elders A. Albertsson article MORTENSEN201431 The stratigraphy, alteration mineralogy and temperature conditions in well IDDP-1 were established through drill cutting analyses and geophysical logs. The stratigraphy comprises basaltic lava and hyaloclastite sequences extending to 1362m succeeded by an intrusive complex. Intrusions comprise basaltic dykes, dolerites and below 2020m, granophyre and felsites. Rhyolitic magma was intersected below 2100m. Alteration reflects cooling in the upper ∼1500m of the reservoir. Below 1600m temperature follows the boiling-point-depth curve. Alteration minerals are scarce in vicinity to the feed zone at 2035–2080m correlating with a superheated steam zone above the magma, but estimated bottom-hole temperature is ∼500°C. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.09.013 Geothermics 49 31-41 IDDP-1, Krafla, Alteration, Magma, Superheated conditions https://www.sciencedirect.com/science/article/pii/S0375650513000874 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma A.K. Mortensen Þ. Egilson B. Gautason S. Árnadóttir Á. Guðmundsson article FRIDLEIFSSON20149 This paper describes the site selection for the IDDP-1 well within the Krafla volcano in 2008. In a feasibility study in 2003, 12 potential well sites within three geothermal areas were suggested and prioritized to meet the goal of finding supercritical temperatures and pressures together with high permeability. In 2006 one of these priority sites was selected within the Krafla field, but in autumn 2007 due to its proximity to the Krafla power plant a new location had to be selected only a few months before drilling. Choice of that new site was justified by new MT-resistivity survey data, seismic data and information from an earlier nearby production well, K-36. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.06.001 Geothermics 49 9-15 IDDP-1 well site at Krafla, Superheated and supercritical reservoir conditions, MT-resistivity data https://www.sciencedirect.com/science/article/pii/S037565051300045X Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma G.Ó. Friðleifsson H. Ármannsson Á. Guðmundsson K. Árnason A.K. Mortensen B. Pálsson G.M. Einarsson article FRIDLEIFSSON2014119 Preparation has begun for drilling the second deep IDDP well into the saline Reykjanes high-temperature field in SW-Iceland. The site selection for the IDDP-2 drillhole is under review and the prime candidate is essentially the same as the 1st priority site suggested for the Reykjanes field in 2003. More recent drillhole data and new MT surveys have amplified the justification for selecting that site. Deep drilling to 4–5km depth is an important part of the HS Orka exploration strategy for enhanced power production, either by direct use of high energy steam, or by attempting to enhance the field performance by re-injecting geothermal fluid deep into very hot rocks. Pending on several decisions and development in Iceland, outside the control of the IDDP energy consortium, the IDDP-2 well might possibly be drilled to 4–5km depth as early as 2014. 2014 English 0375-6505 https://doi.org/10.1016/j.geothermics.2013.05.006 Geothermics 49 119-126 HS Orka hf, Brekkustígur 36, 260 Reykjanesbær, Iceland; ISOR, Iceland GeoSurvey, Grensásvegur 9, 108 Reykjavík, Iceland; Department of Earth Sciences, University of California, Riverside, CA 92521-0423, United States Supercritical fluids, Iceland Deep Drilling Project, IDDP-2 well at Reykjanes, Black smoker analog https://www.sciencedirect.com/science/article/pii/S0375650513000436 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma G.Ó. Friðleifsson O. Sigurdsson D. Þorbjörnsson R. Karlsdóttir Þ. Gíslason A. Albertsson W.A. Elders article Lepland201420 All known forms of life require phosphorus, and biological processes strongly influence the global phosphorus cycle. Although the record of life on Earth extends back to 3.8 billion years ago and the advent of biological phosphate processing can be tracked to at least 3.5 billion years ago, the earliest known P-rich deposits appeared only 2 billion years ago. The onset of P deposition has been attributed to the rise of atmospheric oxygen 2.4-2.3 billion years ago and the related profound biogeochemical shifts, which increased the riverine input of phosphate to the ocean and boosted biological productivity and phosphogenesis. However, the P-rich deposits post-date the rise of oxygen by about 300 million years. Here we use microfabric, trace element and carbon isotope analyses to assess the environmental setting and redox conditions of the 2-billion-year-old P-rich deposits of the vent-or seep-influenced Zaonega Formation, northwest Russia. We identify phosphatized microorganism fossils that resemble modern methanotrophic archaea and sulphur-oxidizing bacteria, analogous to organisms found in modern seep settings and upwelling zones with a sharp redoxcline. We therefore propose that the P-rich deposits in the Zaonega Formation were formed by phosphogenesis mediated by sulphur bacteria, similar to modern sites, and by the precipitation of calcium phosphate minerals on microbial templates during early diagenesis. © 2014 Macmillan Publishers Limited. 2014 English 17520894 10.1038/ngeo2005 Nature Geoscience 7 20-24 Geological Survey of Norway, 7491 Trondheim, Norway; Tallinn University of Technology, Institute of Geology, 19086 Tallinn, Estonia, Estonia; Centre for Arctic Gas Hydrate, Environment and Climate, University of Tromsø, 9037 Tromsø, Norway; University of Tartu, Department of Geology, 50411 Tartu, Estonia; Department of Earth and Environmental Sciences, University of St Andrews, St-Andrews-KY16-9AL, United Kingdom; Institute of Geology, Karelian Science Centre, Pushkinskaya 11, 185610 Petrozavodsk, Russian Federation; Ivan Rakovec Institute of Paleontology, ZRC, SAZU, SI-1000 Ljubljana, Slovenia; NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, United Kingdom; Scottish Universities, Environmental Research Centre, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, G75 0QF, United Kingdom; Géobiosphère Actuelle et Primitive, Institut de Physique du Globe de Paris, Université Paris Diderot, 1 rue Jussieu, 75238 Paris cedex 5, France; GeoForschungsZentrum Potsdam, Telegrafenberg, Chemistry and Physics of Earth Materials, D-14473 Potsdam, Germany; GNS Science, Private Bag 1930, 9054 Dunedin, New Zealand 1 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893853853&doi=10.1038%2fngeo2005&partnerID=40&md5=87a1aa53dcd7d3f8c7840e4250e27adc cited By 44 A. Lepland L. Joosu K. Kirsimäe A.R. Prave A.E. Romashkin A.E. Črne A.E. Fallick P. Somelar K. Üpraus K. Mänd N.M.W. Roberts M.A. Van Zuilen A. Schreiber article SCHIFFMAN201442 A rhyolite magma body within the Krafla geothermal system that was encountered at a depth of 2.1km during drilling of the IDDP-1 borehole is producing high temperature metamorphism within a conductive boundary layer (CBL) in adjacent host rocks. Cuttings recovered during drilling within a few meters of the intrusive contact in IDDP-1 are mainly comprised of granoblastic hornfelses, the rock type which confirms the presence of the CBL at the base of the IDDP-1 bore hole. The two pyroxenes in these hornfelses record temperatures that are in the range of 800–950°C. The minimum heat flow across the CBL is 23Wm−2. Country rocks at distances beyond 30m of the intrusive contact are essentially unaltered, implying that they have been emplaced very recently and/or as yet unaffected by hydrothermal fluid flow. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2012.11.002 Geothermics 49 42-48 Krafla, IDDP-1, Geothermal, Contact metamorphism https://www.sciencedirect.com/science/article/pii/S0375650512000673 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Peter Schiffman Robert A. Zierenberg Anette K. Mortensen Guðmundur Ó. Friðleifsson Wilfred A. Elders article AXELSSON201449 The transient temperature conditions near the bottom of well IDDP-1 in Krafla, which was drilled into a magma intrusion, have been simulated by some simple models of: (i) evolution of temperature conditions at the magma intrusion, (ii) cooling of the producing zone, a permeable layer above the intrusion, due to circulation losses during drilling and subsequent injection, (iii) reheating of the permeable layer after drilling and (iv) temperature evolution during the early phases of discharge testing in 2010. The modelling is not definitive, and does not consider later, more long-term flow testing (2011–2012), because the necessary down-hole data are lacking. However, results indicate that the evolution of the temperature conditions can be explained by these models. If the magma was emplaced during the most recent Krafla volcanic episode 25–35 years ago, the intrusion must have a thickness of at least 50–100m. The effective thickness of the permeable layer is estimated to be about 45m and its equilibrium temperature to be 390–400°C. No direct contact of the fluid with the magma is needed to explain the superheated steam discharged by the well. The situation near the bottom of the well clearly warrants further study, both through more advanced modelling and input of further data. The IDDP-1 well had to be quenched in July 2012. Whether it can maintain in the long-term the high energy output (15–40MWe), achieved during discharge testing, depends on sufficient recharge and efficient heat-exchange, if it can be rehabilitated. Carefully executed reinjection may be the solution if long-term recharge is not sufficient. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.05.003 Geothermics 49 49-57 Geothermal, Krafla, IDDP-1, Magma intrusion, Temperature conditions, Modelling, Superheated steam https://www.sciencedirect.com/science/article/pii/S0375650513000400 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Gudni Axelsson Thorsteinn Egilson Sigrídur Sif Gylfadóttir article ARMANNSSON201466 The Leirbotnar field, where IDDP-01 is situated consists of an upper liquid dominated zone to 1000–1400m depth, 190–220°C, sulphate major anion, and a lower two phase zone, 300°C chloride main anion. The IDDP-01 fluid is dry steam, local origin, pH 3. The major anion is chloride (20–166mg/kg), probably of magmatic origin. The major metallic cations, Fe (5–100mg/kg), Cr (0–6mg/kg), Ni (0–5mg/kg) and Mn (0.1–0.8mg/kg) seem to be derived from the well casing and sampling equipment. The gas content is low (about 0.1%) and the gas is apparently not directly emitted from magma. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.08.005 Geothermics 49 66-75 IDDP, Krafla, Geochemistry, Acid well fluids https://www.sciencedirect.com/science/article/pii/S0375650513000618 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Halldór Ármannsson Thráinn Fridriksson Gudmundur H. Gudfinnsson Magnús Ólafsson Finnbogi Óskarsson Dadi Thorbjörnsson article ELDERS20141 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.08.012 Geothermics 49 1 https://www.sciencedirect.com/science/article/pii/S0375650513000746 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Wilfred A. Elders Guðmundur Ó. Friðleifsson Bjarni Pálsson article ASMUNDSSON201490 During the early years of the Iceland Deep Drilling Project (IDDP), development of three distinctive technological and scientific approaches were formalised and then carried out until 2010 within a European funded project called HiTI (high temperature instruments for supercritical geothermal reservoir characterisation and exploitation). These approaches were: (1) development of several downhole instruments allowing them to function up to 300°C and 400°C, (2) identification of two new Na/Li cation ratio geothermometric relationships valid at very high temperature, (3) tracer testing with high temperature tolerant organic isomers and finally and (4) basalt rock deformation and petrophysical properties laboratory investigations at high temperature and pressure conditions. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.07.008 Geothermics 49 90-98 High temperature, Supercritical, Downhole, Geothermometers, Televiewer, Basalt experiments https://www.sciencedirect.com/science/article/pii/S0375650513000564 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma Ragnar Ásmundsson Bernard Sanjuan Jan Henninges Jean-Luc Deltombe Nigel Halladay François Lebert Alain Gadalia Romain Millot Benoit Gibert Marie Violay Thomas Reinsch Jean-Marc Naisse Pierre Azaïs David Mainprice Costas Karytsas Colin Johnston article PALSSON201423 The first well of three proposed by the Iceland Deep Drilling Project (IDDP) was drilled in the Krafla Geothermal Field in 2008–2009 by Landsvirkjun, the National Power Company of Iceland. The well was designed to reach supercritical conditions at 4500m, temperatures above 374°C and pressures above 22MPa. Drilling progress was as planned down to around 2000m when drilling became quite challenging, including becoming stuck at 2094 and 2095m depth, followed by twist offs and subsequent side tracking. Finally, drilling came to an end at 2096m depth in the third leg when cuttings of fresh glass indicated the presence of a magma body at the bottom. As the well had such a rigorous well design, the steering committee of the IDDP decided to complete and flow test the well, rather than abandoning it. The well was very powerful and the project has proved to be a valuable experience for drilling supercritical wells in the future and what happens when magma is encountered. Most importantly, it has been proven that it is possible to drill and complete a well in a very hot zone and produce fluid from an environment near a magma body. If sustained long term production proves possible, the drilling of well IDDP-1 will mark a new era in power production in Krafla. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.08.010 Geothermics 49 23-30 Iceland Deep Drilling Project, Drilling, Magma, Superheat https://www.sciencedirect.com/science/article/pii/S0375650513000722 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma B. Pálsson S. Hólmgeirsson Á. Guðmundsson H.Á. Bóasson K. Ingason H. Sverrisson S. Thórhallsson article ELDERS2014111 Drilling deeper in high-temperature geothermal systems by the IDDP is aimed at increasing the power output of shallower high-temperature geothermal fields by an order of magnitude without increasing their environmental footprints. The main thrust of the IDDP is to develop deep supercritical systems, but an unexpected encounter with a shallow body of magma demonstrated that very high power outputs are also possible from the contact zone of an intrusion. In the future it may be feasible to produce energy directly from magma. Favorable environments to implement these concepts are likely worldwide wherever active volcanoes and young volcanic rocks occur. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.05.001 Geothermics 49 111-118 Magma energy, Supercritical geothermal energy, Krafla Iceland https://www.sciencedirect.com/science/article/pii/S0375650513000382 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma W.A. Elders G.Ó. Friðleifsson A. Albertsson article INGASON201458 The initial discharge of IDDP-1 took place in March 2010 and the well was discharged intermittently until July 2012. In the beginning a mixture of steam and water flowed from the well but soon the fluid became superheated and enthalpy gradually increased, approaching 3200kJ/kg. The flow rate from the well was up to 50kg/s. The design condition at well head turned out to be challenging due to high pressure, temperature, corrosion and erosion. Valves, rated for higher pressure and temperature, failed during operation. Five different designs of discharge systems were installed. The well had to be quenched when the master valves failed. Plans for its future are still being evaluated. 2014 0375-6505 https://doi.org/10.1016/j.geothermics.2013.05.002 Geothermics 49 58-65 Krafla, IDDP-1, Geothermal well head, Geothermal well discharge, Geothermal superheated steam, Corrosion, Erosion https://www.sciencedirect.com/science/article/pii/S0375650513000394 Iceland Deep Drilling Project:The first well, IDDP-1, drilled into Magma K. Ingason V. Kristjánsson K. Einarsson article Elders201435 Scientists, engineers, and policy makers gathered at a workshop in the San Bernardino Mountains of southern California in October 2013 to discuss the science and technology involved in developing high-enthalpy geothermal fields. A typical high-enthalpy geothermal well between 2000 and 3000m deep produces a mixture of hot water and steam at 200-300 °C that can be used to generate about 5-10MWe of electric power. The theme of the workshop was to explore the feasibility and economic potential of increasing the power output of geothermal wells by an order of magnitude by drilling deeper to reach much higher pressures and temperatures. Development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Plans for resource assessment and drilling in such higher enthalpy areas are already underway in Iceland, New Zealand, and Japan. There is considerable potential for similar developments in other countries that already have a large production of electricity from geothermal steam, such as Mexico, the Philippines, Indonesia, Italy, and the USA. However drilling deeper involves technical and economic challenges. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope of investigation. An excellent example of such collaboration is the Iceland Deep Drilling Project (IDDP), which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs, and this approach could serve as model for future developments elsewhere. A planning committee was formed to explore creating a similar initiative in the USA. 2014 English 18168957 10.5194/sd-18-35-2014 Scientific Drilling 18 Copernicus GmbH 35-42 Dept. of Earth Sciences, University of California, Riverside, CA 92521, United States; DOSECC Exploration Sciences, 2075 S. Pioneer Rd., Salt Lake City, UT 84104, United States; Dept. of Geology, University of California Davis, 1 Shields Avenue, Davis, CA 95616, United States; CalEnergy Operating Corp, 7030 Gentry Road, Calipatria, CA 92233, United States Electric power generation; Enthalpy; Geothermal energy; Geothermal wells; Well drilling, Economic challenges; Economic feasibilities; Environmental footprints; Geothermal reservoir; Iceland deep drilling projects; Resource assessments; Science and Technology; Southern California, Geothermal fields https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926287342&doi=10.5194%2fsd-18-35-2014&partnerID=40&md5=f045a3ac57e3c14fb118c1ba1a531d46 cited By 4 W.A. Elders D. Nielson P. Schiffman Jr. Schriener article Fridleifsson201373 A summary workshop report describing the progress made so far by the Iceland Deep Drilling Project (IDDP) is presented below. The report provides recommendations concerning technical aspects related to deep drilling, and invites international participation in both the engineering and the scientific activities of the next phase of the IDDP. No issues were identified at the workshop that should rule out attempting the drilling, sampling and testing of the proposed IDDP-2 well. Although technically challenging, the consensus of the workshop was that the drilling of such a hot deep well, and producing potentially hostile fluids, is possible but requires careful contingency planning. The future well will be explored for supercritical fluid and/or superheated steam beneath the current production zone of the Reykjanes geothermal field in SW Iceland. This deep borehole will provide the first opportunity worldwide to directly investigate the root zone of a magma-hydrothermal system which is likely to be similar to those beneath the black smokers on the worldencircling mid-ocean rift systems. © Author(s) 2013. 2013 English 18168957 10.5194/sd-16-73-2013 Scientific Drilling 73-79 HS Orka hf., Brekkustígur 36, 260 Reykjanesbær, Iceland; Department of Earth Sciences, University of California, Riverside, CA 92521, United States; GNS Science, Wairakei Research Centre, Karetoto Road, Taupo, New Zealand 16 Contingency planning; Current production; Deep boreholes; Deep drilling; Iceland deep drilling projects; Scientific activity; Superheated steam; Technical aspects, Drilling fluids; Effluent treatment; Geothermal fields; Supercritical fluids, Boring https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892840331&doi=10.5194%2fsd-16-73-2013&partnerID=40&md5=0f5f4a1c8694c8a03d16a2a3d06724c7 cited By 9 G.Ó. Fridleifsson W.A. Elders G. Bignall article Zierenberg2013327 The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and -118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO2 content as the rhyolite melt but is distinguished by higher K2O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO2 relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt-wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation. © 2012 Springer-Verlag. 2013 English 00107999 10.1007/s00410-012-0811-z Contributions to Mineralogy and Petrology 165 Springer Verlag 327-347 Department of Geology, University of California-Davis, Davis, CA, 95616, United States; Lawrence Livermore National Labs, 7000 East Avenue, Livermore, CA, 94550, United States; U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA, 94025, United States; Iceland GeoSurvey (ISOR), Grensásvegur 9, IS 108 Rekjavik, Iceland; Department of Geological and Environmental Sciences, Stanford University, Stanford, CA, 94305, United States; Natural History Museum of Denmark, Copenhagen University, Øster Voldgrad 5-7, 1350 København K, Denmark; Department of Geological Sciences, 1272 University of Oregon, Eugene, OR, 97403, United States; HS Orka hf, Brekkustigur 36, IS 260 Reykjanesbær, Iceland; Department of Earth Sciences, University of California-Riverside, Riverside, CA, 92521, United States 2 augite; basalt; chemical composition; deep drilling; emplacement; geothermal system; hydrogen isotope; hydrothermal fluid; partial melting; phenocryst; pigeonite; plagioclase; rare earth element; rhyolite; stable isotope; strontium isotope; titanomagnetite; zoning, Iceland; Krafla https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872796536&doi=10.1007%2fs00410-012-0811-z&partnerID=40&md5=08bc4157924fc4ff28489112ec696fb6 cited By 51 R.A. Zierenberg P. Schiffman G.H. Barfod C.E. Lesher N.E. Marks J.B. Lowenstern A.K. Mortensen E.C. Pope D.K. Bird M.H. Reed G.Ó. Fridleifsson W.A. Elders article Elders2011231 Magma flowed into an exploratory geothermal well at 2.1 km depth being drilled in the Krafla central volcano in Iceland, creating a unique opportunity to study rhyolite magma in situ in a basaltic environment. The quenched magma is a partly vesicular, sparsely phyric, glass containing ~1.8% of dissolved volatiles. Based on calculated H2O-CO2 saturation pressures, it degassed at a pressure intermediate between hydrostatic and lithostatic, and geothermometry indicates that the crystals in the melt formed at ~900 °C. The glass shows no signs of hydrothermal alteration, but its hydrogen and oxygen isotopic ratios are much lower than those of typical mantle-derived magmas, indicating that this rhyolite originated by anhydrous mantle-derived magma assimilating partially melted hydrothermally altered basalts. © 2011 Geological Society of America. 2011 English 00917613 10.1130/G31393.1 Geology 39 231-234 Department of Earth Sciences, University of California-Riverside, Riverside, CA 92521, United States; HS Orka hf, Brekkustigur 36, Reykjanebær IS 260, Iceland; Department of Geology, University of California-Davis, Davis, CA 95616, United States; Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, United States; Iceland GeoSurvey (ÍSOR), Grensásvegur 9, Reykjavik IS 108, Iceland; Landsvirkjun Power, Háaleitisbraut 68, Reykjavik, IS 103, Iceland; U.S. Geological Survey, 345 Middlefield Road, Menlo Park CA 94025, United States; Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, Socorro, NM 87801, United States; Department of Geological Sciences, University of Oregon, Eugene, OR 97403, United States 3 Anhydrous mantle; Geothermometry; Hydrothermal alterations; Hydrothermally; Icelands; In-situ; Oxygen isotopic; Saturation pressure, Geothermal wells; Glass; Granite; Oxygen; Volcanoes, Well drilling, basalt; geothermal system; hydrogen isotope; hydrothermal alteration; magma assimilation; magma chamber; mantle source; oxygen isotope ratio; rhyolite; volcanology, Iceland; Krafla https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951695875&doi=10.1130%2fG31393.1&partnerID=40&md5=e08238af55bd0fc92830d50c59a96bd8 cited By 84 W.A. Elders G.Ó. Fridleifsson R.A. Zierenberg E.C. Pope A.K. Mortensen Á. Gudmundsson J.B. Lowenstern N.E. Marks L. Owens D.K. Bird M. Reed N.J. Olsen P. Schiffman conference Frioleifsson2011347 The Iceland Deep Drilling Project (IDDP) is being carried out by an international industry-government consortium in Iceland, in order to investigate the economic feasibility of producing electricity from supercritical geothermal reservoirs. Modeling suggests that producing superheated steam from a supercritical reservoir could potentially increase power output of geothermal wells by an order of magnitude. To test this concept, the consortium planned to drill a deep well in each of three different geothermal fields in Iceland, namely, Krafla, and at the Hengill and Reykjanes fields in SW-Iceland. In 2009 the drilling of the first deep well, IDDP-1, was attempted in the active central volcano at Krafla in NE Iceland. However the drilling had to be terminated at 2.1 km depth when 900°C rhyolite magma was intersected. The well, IDDP-1, was highly productive, capable of producing some 25 MWe from 380°C superheated steam during a flow test undertaken in 2010. The well was shut in August 2010, to allow the wellhead and surface equipment to be modified to withstand corrosive fluids. Starting in May 2011 flow-testing, wet and dry scrubbing of the steam and a test of a heat exchange system will be conducted. This flow test is expected to last through the rest of 2011. Preliminary results from these tests should be available to report at the GRC Annual Meeting in October 2011. The second deep IDDP well, IDDP-2, could possibly be drilled to 4-5 km depth as early as 2012-2013, into the saline Reykjanes high-temperature field in SW-Iceland. The design of the IDDP-2 well will benefit from lessons learned during drilling of the IDDP-1 at Krafla. Here we review the geological and geophysical characteristics of the Reykjanes field, based on pre-existing and very recent data. According to both 1 dimensional and 3 dimensional interpretations of the new magnetotelluric (MT) data, the IDDP-2 site is located above a major heat source occurring at some 10 km depth. 2011 English 9781618394828 01935933 Transactions - Geothermal Resources Council 35 1 347-354 HS Orka hf, Reykjanesbaer, Iceland; Department of Earth Sciences, University of California, Riverside, CA, United States; ISOR, Iceland GeoSurvey, Reykjavík, Iceland; Landsvirkjun, Reykjavik, Iceland 3-dimensional; Black smokers; Corrosive fluids; Deep drilling; Deep wells; Economic feasibilities; Flow tests; Geothermal reservoir; Heat exchange systems; Heat sources; High temperature; Icelands; Power out put; Super-critical; Superheated steam; Surface equipment; Wet and dry, Deep oil well drilling; Effluent treatment; Geothermal fields; Geothermal prospecting; Supercritical fluids, Geothermal wells https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860873592&partnerID=40&md5=2031d66c914d41627f225d860cdbbad0 cited By 17 G.O. Frioleifsson A. Albertsson W.A. Elders O. Sigurdsson R. Karlsdóttir B. Pálsson article Marks2011 Granoblastic hornfels identified in cuttings from the Reykjanes seawater-dominated hydrothermal system contains secondary pyroxene, anorthite, and hornblendic amphibole in locally equilibrated assemblages. Granoblastic assemblages containing secondary orthopyroxene, olivine, and, locally, cordierite and spinel occur within groups of cuttings that show dominantly greenschist facies hydrothermal alteration. Granoblastic plagioclase ranges continuously in composition from An54 to An96, in contrast with relict igneous plagioclase that ranges from An42 to An80. Typical hydrothermal clinopyroxene compositions range from Wo49En3Fs48 to Wo 53En30Fo17; clinopyroxene from the granoblastic grains is less calcic with an average composition of Wo48En 27Fs25. The hornfels is interpreted to form during contact metamorphism in response to dike emplacement, resulting in local recrystallization of previously hydrothermally altered basalts. Temperatures of granoblastic recrystallization estimated from the 2-pyroxene geothermometer range from 927°C to 967°C. Redox estimates based on the 2-oxide oxybarometer range from log fO2 of -13.4 to -15.9. Granoblastic hornfels comprised of clinopyroxene, orthopyroxene, and calcic plagioclase have been described in a number of ancient hydrothermal systems from the conductive boundary layer between the hydrothermal system and the underlying magma source, most notably in Integrated Ocean Drilling Program Hole 1256D, Ocean Drilling Program Hole 504B, and in the Troodos and Oman ophiolites. To our knowledge, this is the first evidence of high-grade contact metamorphism from an active geothermal system and the first description of equilibrated amphibole-absent pyroxene hornfels facies contact metamorphism in any mid-ocean ridge (MOR) hydrothermal system. This contribution describes how these assemblages develop through metamorphic reactions and allows us to predict that higher-temperature assemblages may also be present in MOR systems. Copyright 2011 by the American Geophysical Union. 2011 English 15252027 10.1029/2011GC003569 Geochemistry, Geophysics, Geosystems 12 Blackwell Publishing Ltd Department of Geology, University of California, Davis, CA 95616, United States; Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States 8 Feldspar; Geothermal fields; Geothermal prospecting; Hydraulic structures; Igneous rocks; Oceanography; Offshore oil wells; Olivine; Recrystallization (metallurgy); Seawater; Submarine geology, alteration; Average composition; Clinopyroxenes; contact metamorphism; Fluid-rock interaction; Geothermal systems; Geothermometers; Greenschist; Hydrothermal alterations; Hydrothermal system; hydrothermal systems; Hydrothermally; Magma sources; Metamorphic reactions; Mid-ocean ridges; Mid-oceanic ridges; Ocean drilling programs; Oman ophiolite; Orthopyroxene, Metamorphic rocks, clinopyroxene; contact metamorphism; fluid-structure interaction; geothermal system; geothermometry; greenschist facies; hydrothermal alteration; hydrothermal system; mid-ocean ridge; Ocean Drilling Program; P-T conditions; recrystallization; spreading center, Atlantic Ocean; Reykjanes Ridge https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860410767&doi=10.1029%2f2011GC003569&partnerID=40&md5=56e336775dfd812171028e9546d996f3 cited By 19 N. Marks P. Schiffman R.A. Zierenberg article Oliva-Urcia2011155 Active high-temperature (&gt;150 °C) geothermal areas like the Krafla caldera, NE-Iceland, often show distinct magnetic lows in aeromagnetic anomaly maps suggesting a destruction of magnetic minerals by hydrothermal activity. The main alteration processes in such an environment are low-temperature oxidation (&lt;350 °C, maghemitization) and fluid-rock interactions. We investigated the rock magnetic properties [natural remanent magnetization (NRM) magnetic susceptibility and their temperature and field variation] and the mineralogy, using X-ray diffraction, microscopic methods and electron microprobe analyses, of two drill cores (KH1 and KH3) from the rim of the Krafla caldera. The drill cores have distinctly lower NRM values (average &lt;3 A m-1) compared to younger surface basalts (average 20 A m-1) along with a large variation in magnetic susceptibility (1.3 × 10-7- 4.9 × 10-5 m3 kg-1). The secondary mineral assemblage (sulphides, sphene, rutile and chlorite) indicates an alteration within the chlorite-smectite zone for both cores without depth zoning. Optical miscroscopy in combination with the Bitter technique and backscatter electron microscopy along with the thermomagnetic analyses allow distinguishing two different magnetomineralogical groups of titanomaghemite: (1) titanomaghemite with intermediate titanium concentration and probably high vacancy concentration, and (2) titanomaghemite with low titanium concentration and low vacancy concentration. The mineral assemblages, textures and magnetic properties deduced from the mentioned magnetic measurements indicate two-stage transformation mechanism: (1) Dissolution of titanium at low pH under oxidizing conditions. The ulvöspinel component of titanomagnetite and ilmenite forms rutile or sphene, and Fe2 + migrates out of the spinel lattice forming titanomaghemite. (2) Formation of pyrite and dissolution of remaining titanomaghemite under reducing and acidic conditions. The latter mechanism produces ghost textures (all titanomaghemite is transformed and only their former grain shapes are preserved), with only paramagnetic minerals left and ferrimagnetic minerals nearly dissolved. This mechanism could explain the significant magnetization loss, which is seen in many local magnetic anomaly lows within the oceanic crust and volcanic islands like Iceland or Hawaii. The production of nanoporous textures in titanomaghemites is suggested as a mechanism for the enhancement of the magnetic susceptibility values related to the hydrothermal alteration of Krafla. © 2011 The Authors. Geophysical Journal International © 2011 RAS. 2011 English 0956540X 10.1111/j.1365-246X.2011.05029.x Geophysical Journal International 186 155-174 Institute of Applied Geosciences, Karlsruher Institute of Technology, Hertzstrasse 16, 76187, Germany; Dpto. Ciencias de la Tierra, Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain; Eriksfiord AS, Kunnskapsparken, Postboks 8034, 4068 Stavanger, Norway; Geological Sciences, University of Michigan, 1100 CC, Little Building, Ann Arbor, MI, United States 1 Acidic conditions; Backscatter electron microscopy; Drill core; Ferrimagnetic minerals; Fluid-rock interaction; Geothermal areas; Geothermal systems; Grain shapes; High temperature; Hydrothermal activity; Hydrothermal alterations; Hydrothermal system; Icelands; Krafla caldera; Latter mechanism; Low-temperature oxidation; Magnetic anomalies; Magnetic mineralogy; Magnetic minerals; Magnetization loss; Microscopic methods; Mineral assemblage; Nano-porous; Natural remanent magnetization; Oceanic crust; Oxidizing conditions; Rock magnetic properties; Spinel lattices; Thermomagnetic analysis; Titanomagnetites; Two-stage transformations; Vacancy concentration; Volcanic islands, Basalt; Clay minerals; Concentration (process); Core drilling; Crystallography; Dissolution; Drills; Electron probe microanalysis; Geothermal fields; Lithology; Magnetic susceptibility; Magnetization; Mineralogy; Natural resources management; Oxide minerals; Paramagnetism; Petrography; Rocks; Silicates; Textures; Titanium; X ray diffraction; X ray diffraction analysis, Geomagnetism, basalt; caldera; chlorite; dissolution; geomagnetism; geothermal system; high temperature; hydrothermal activity; hydrothermal alteration; hydrothermal system; magnetic anomaly; magnetic susceptibility; magnetization; mineralogy; natural remanent magnetization; oceanic crust; oxidation; petrology; pyrite; smectite; volcanic island, Iceland; Krafla https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959197694&doi=10.1111%2fj.1365-246X.2011.05029.x&partnerID=40&md5=6d71222c4f181f2dd087414772103f60 cited By 21 B. Oliva-Urcia A. Kontny C. Vahle article Dietze2011109 This study presents rock magnetic properties along with magnetic field measurements of different stratigraphic and lithologic basalt units from Reykjanes, the southwestern promontory of the Reykjanes peninsula, where the submarine Reykjanes Ridge passes over into the rift zone of southwestern Iceland. The basaltic fissure eruptions and shield lava of tholeiitic composition (less than 11500 a old) show a high natural remanent magnetization (NRM, Jr) up to 33.6 A/m and high Koenigsberger ratio (Q) up to 52.2 indicating a clear dominance of the NRM compared to the induced part of the magnetization. Pillow basalts and picritic shield lava show distinctly lower Jr values below 10 A/m. Magnetic susceptibility (κ) ranges for all lithologies from 2.5 to 26 × 10-3 SI. Heterogeneously distributed titanomagnetite with small grain sizes is the main carrier of magnetization. Magnetic susceptibility vs. temperature (κ-T) curves reveal multiple Curie temperatures from 35 to 570 °C suggesting different Ti-concentrations in titanomagnetite. A minor oxidation to titanomaghemite is indicated by the irreversibility of some of the κ-T curves. Intra flow variation of the magnetic minerals is relatively high depending on crystallization history and resulting primary composition and amount of titanomagnetite as well as high-temperature oxidation. The total geomagnetic field was measured for regional field variations along three profiles normal to the spreading zone at Reykjanes. These measurements along with the rock magnetic data and field observations were used for modeling the geological subsurface. The models are in agreement with a feeder dyke system related to the youngest Stampahraun 4 fissure eruption in the western part and a hydrothermally active fault system in the eastern part of Reykjanes. Furthermore, topographic features like fault scarps, pillow basalt - hyaloclastite ridges and shield lava are considered. © 2011 Institute of Geophysics of the ASCR, v.v.i. 2011 English 00393169 10.1007/s11200-011-0007-4 Studia Geophysica et Geodaetica 55 Kluwer Academic Publishers 109-130 Institut für Angewandte Geowissenschaften, Karlsruher Institut für Technologie (KIT), Hertzstr. 16, D-76187 Karlsruhe, Germany; Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany; Eriksfiord AS, Kunnskapsparken, Postboks 8034, 4068 Stavanger, Norway 1 active fault; basalt; fissure; geomagnetic field; geomagnetism; lava; lithology; magnetic anomaly; magnetic mineral; magnetic property; magnetic susceptibility; oxidation; remanent magnetization; rift zone; stratigraphy; tholeiite; titanomagnetite, Atlantic Ocean; Iceland; Reykjanes Peninsula; Reykjanes Ridge https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951526718&doi=10.1007%2fs11200-011-0007-4&partnerID=40&md5=4711e9ba6996c2b096812546b5911e92 cited By 7 F. Dietze A. Kontny I. Heyde C. Vahle article Fowler2010731 Recent experimental work has shown that, when a vertical column of rock under large pressure is suddenly depressurized, the column can 'explode' in a structured and repeatable way. The observations show that a sequence of horizontal fractures forms from the top down, and the resulting blocks are lifted off and ejected. The blocks can suffer secondary internal fractures. This experiment provides a framework for understanding the way in which catastrophic explosion can occur, and is motivated by the corresponding phenomenon of magmatic explosion during Vulcanian eruptions. We build a theoretical model to describe these results, and show that it is capable of describing both the primary sequence of fracturing and the secondary intrablock fracturing. The model allows us to suggest a practical criterion for when such explosions occur: firstly, the initial confining pressure must exceed the yield stress of the rock, and, secondly, the diffusion of the gas by porous flow must be sufficiently slow that a large excess pore pressure is built up. This will be the case if the rock permeability is small enough. © 2010 The Royal Society. 2010 English 13645021 10.1098/rspa.2009.0382 Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466 Royal Society 731-752 MACSI, Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland; Earth and Environmental Sciences, LMU München, Theresienstrasse 41/111, 80333 München, Germany; School of Mathematics, Statistics and Operations Research, Victoria University of Wellington, New Zealand 2115 Brittle fracture; Explosions; Nitration; Submarine geophysics; Yield stress, Brittle fragmentation; Catastrophic explosion; Confining pressures; Excess pore pressure; Explosive fragmentation; Explosive volcanism; Horizontal fractures; Internal fracture; Magma fragmentation; Magmatic explosion; Porous flow; Primary sequences; Rock permeability; Silicic magmas; Theoretical models; Topdown; Vertical columns, Explosives https://www.scopus.com/inward/record.uri?eid=2-s2.0-75949126427&doi=10.1098%2frspa.2009.0382&partnerID=40&md5=e05ac6a65261045d3008d5be257730f0 cited By 35 A.C. Fowler B. Scheu W.T. Lee M.J. McGuinness article Skinner201040 The science program of the Iceland Deep Drilling Project (IDDP) requires as much core as possible in the transition zone to supercritical and inside the supercritical zone (>374°C), in the depth interval 2400-4500 m. The spot coring system selected has a 7 1/4″ (184.15 mm) OD at 10 m length and collects a 4″ (101.6 mm) diameter core using an 8 1/2″ (215.9 mm) OD core bit. It incorporates design characteristics, materials, clearances and bearings compatible with operation of the core barrel at temperatures as high as 600°C. Special attention was given to the volume of flushing which could be applied to the core barrel and through the bit while running in and out of the borehole and while coring. In November 2008 a successful spot coring test using the new core barrel was performed at 2800 m depth in the production well RN-17 B at Reykjanes, Iceland, where the formation temperature is 322°C. A 9.3-m hydrothermally altered hyaloclastite breccia was cored with 100% core recovery, in spite of it being highly fractured. A core tube data logger was also designed and placed inside the inner barrel to monitor the effectiveness of cooling. The temperature could be maintained at 100°C while coring, but it reached 170°C for a very short period while tripping in. The effective cooling is attributed to the high flush design and a top drive being employed, which allows circulation while tripping in or out, except for the very short time when a new drill pipe connection is being made. 2010 English 18168957 10.2204/iodp.sd.10.05.2010 Scientific Drilling 40-45 ACS Coring Services, 13 Riccarton Drive, Currie, Edinburgh, EH14 5PN, Scotland, United Kingdom; Rok-Max Drilling Tools Ltd., P.O. Box 87, United Kingdom; Iceland Geosurvey (ISOR), Grensasvegur 9, Reykjavik, IS-108, Iceland; HS Orka hf, Brekkustígur 36, 260 Reykjanesbær, Iceland 10 Core barrel; Core tube data logger; Deep drilling; Design characteristics; Drill pipe connection; Formation temperature; Hydrothermally; Icelands; Inner Barrel; Production wells; Running-in; Science programs; Short periods; Spot coring; Super-critical; Transition zones, Design, Drill pipe https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651588219&doi=10.2204%2fiodp.sd.10.05.2010&partnerID=40&md5=b958630914026fcaa2f7d5d5da78ef5f cited By 3 A.C. Skinner P. Bowers S. Pórhallsson G.Ó. Fridleifsson H. Gudmundsson article Skinner201018 The science program of the Iceland Deep Drilling Project (IDDP) requested that as much coring as possible should be done in the transition zone to supercritical and inside the supercritical zone in the depth interval 2,400-4,500m. The coring system selected is of conventional design, non-wireline with a 184.15mm OD and capable of collection of a 101.6mm diameter core using a 215.9mm OD core bit. The effective cooling is attributed to a top drive being employed that allows circulation while tripping in or out, except for the very short time when a new drill pipe connection is being made. The core barrels were made by Rok-Max Drilling Tools Ltd and the core bits were made by GeoGem Ltd, both UK companies with a good track record in making specialist coring equipment. The cored section consisted of a hyaloclastite breccia, thoroughly altered to greenschist facies mineralogy. 2010 English 09693769 Geodrilling International 18-22 162 https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952928408&partnerID=40&md5=89ca12faec73abe89148aa026be88691 cited By 3 A. Skinner P. Bowers S. Pórhallsson G.O. Frioleifsson H. Guomundsson article Marks2010172 The Reykjanes geothermal system is a seawater-recharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low water/rock alteration. The similarities make the Reykjanes system a useful proxy for seafloor vents. At some time during the Pleistocene, the system was dominated by meteoric water recharge, and fluid composition at Reykjanes has evolved through time as a result of changing proportions of meteoric water influx as well as differing pressure and temperature conditions. The purpose of this study is to characterize secondary mineralization, degree of metasomatic alteration, and bulk composition of cuttings from well RN-17 from the Reykjanes geothermal system. The basaltic host rock includes hyaloclastite, breccia, tuff, extrusive basalt, diabase, as well as a marine sedimentary sequence. The progressive hydrothermal alteration sequence observed with increasing depth results from reaction of geothermal fluids with the basaltic host rock. An assemblage of greenschist facies alteration minerals, including actinolite, prehnite, epidote and garnet, occurs at depths as shallow as 350 m; these minerals are commonly found in Icelandic geothermal systems at temperatures above 250 °C (Bird and Spieler, 2004). This requires hydrostatic pressures that exceed the present-day depth to boiling point curve, and therefore must record alteration at higher fluid pressures, perhaps as a result of Pleistocene glaciation. Major, minor, and trace element profiles of the cuttings indicate transitional MORB to OIB composition with limited metasomatic shifts in easily mobilized elements. Changes in MgO, K2O and loss on ignition indicate that metasomatism is strongly correlated with protolith properties. The textures of alteration minerals reveal alteration style to be strongly dependent on protolith as well. Hyaloclastites are intensely altered with calc-silicate alteration assemblages comprising calcic hydrothermal plagioclase, grandite garnet, prehnite, epidote, hydrothermal clinopyroxene, and titanite. In contrast, crystalline basalts and intrusive rocks display a range in alteration intensity from essentially unaltered to pervasive and nearly complete albitization of igneous feldspar and uralitization of clinopyroxene. Hydrothermal anorthite (An92-An98) occurs in veins in the most altered basalt cuttings and is significantly more calcic than igneous feldspar (An48-An79). Amphibole compositions change from actinolite to hornblende at depth. Hydrothermal clinopyroxene, which occurs in veins, has greater variation in Fe content and is systematically more calcic than igneous pyroxene and also lacks uralitic textures. Solid solutions of prehnite, epidote, and garnet indicate evolving equilibria with respect to aluminum and ferric iron. © 2009 Elsevier B.V. All rights reserved. 2010 English 03770273 10.1016/j.jvolgeores.2009.10.018 Journal of Volcanology and Geothermal Research 189 172-190 Department of Geology, University of California, Davis, CA 95616, United States; ISOR, Iceland GeoSurvey, Grensasvegur 9, 108 Reykjavik, Iceland; Hitaveita Sudurnesja Ltd. Brekkustigur 36, 260 Reykjanesbaer, Iceland 1-2 Albitization; Amphibole compositions; Bulk compositions; Clinopyroxenes; Deep drilling; Fe content; Ferric iron; Fluid composition; Fluid pressures; Geothermal fluids; Geothermal systems; Greenschist; Host rocks; Hyaloclastites; Hydrothermal alterations; Hydrothermal system; Icelandics; Icelands; Intrusive rocks; Loss on ignition; Meteoric waters; Pleistocene; Prehnite; Pressure and temperature; Protoliths; Sea floor; Seafloor hydrothermal systems; Sedimentary sequence, Basalt; Boiling point; Crystalline rocks; Feldspar; Garnets; Geothermal fields; Geothermal prospecting; Glacial geology; Hydrostatic pressure; Mineralogy; Minerals; Seawater; Sedimentary rocks; Silicate minerals; Textures; Trace elements; Underwater mineral resources; Well drilling, Igneous rocks, amphibole; basalt; breccia; diabase; geothermal system; host rock; hyaloclastite; hydrothermal alteration; hydrothermal system; mid-ocean ridge basalt; mineralization; Pleistocene; seafloor; solid solution; tuff; water-rock interaction, Iceland; Reykjanes Peninsula, Aves https://www.scopus.com/inward/record.uri?eid=2-s2.0-72649091290&doi=10.1016%2fj.jvolgeores.2009.10.018&partnerID=40&md5=c12f29a5ef60672a95a86cb0f6c27629 cited By 60 N. Marks P. Schiffman R.A. Zierenberg H. Franzson G.Ó. Fridleifsson article Fridleifsson200726 2007 English 18168957 10.2204/iodp.sd.4.04.2007 Scientific Drilling 26-29 ISOR, Iceland GeoSurvey, Grensasvegur 9, IS-108 Reykjavik, Iceland; Department of Earth Sciences, University of California, Riverside, CA 92521, United States 4 https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651524241&doi=10.2204%2fiodp.sd.4.04.2007&partnerID=40&md5=c35bad59946474038f8c2ff5465e47ec cited By 4 G.Ó. Fridleifsson W.A. Elders article Fridleifsson2005269 Article 2005 10.1016/j.geothermics.2004.11.004 Geothermics 34 269 – 285 3 https://www.scopus.com/inward/record.uri?eid=2-s2.0-19144362878&doi=10.1016%2fj.geothermics.2004.11.004&partnerID=40&md5=262a25b40145097c5d59ff34446b8eaa Cited by: 126 Gudmundur Ó. Fridleifsson Wilfred A. Elders