All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1944.
Detrital zircon geochronology of sandstones of the 3.6-3.2 Ga Barberton greenstone belt: No evidence for older continental crust
Geology,
45
(9)
803 – 806
2017
DOI:10.1130/G39255.1
1943.
A comparison of the use of X-ray and neutron tomographic core scanning techniques for drilling projects: Insights from scanning core recovered during the Alpine Fault Deep Fault Drilling Project
Scientific Drilling,
2235-42
2017
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Atoms; Neutrons; Recovery; Scanning; Tomography, Atomic numbers; Drilling projects; Highest resolutions; Neutron tomography; Non destructive; Scanning techniques; Tomographic scanning; X-ray computed tomography, Computerized tomography
Abstract: ▾ It is now commonplace for non-destructive X-ray computed tomography (CT) scans to be taken of core recovered during a drilling project. However, other forms of tomographic scanning are available, and these may be particularly useful for core that does not possess significant contrasts in density and/or atomic number to which X-rays are sensitive. Here, we compare CT and neutron tomography (NT) scans of 85mm diameter core recovered during the first phase of the Deep Fault Drilling Project (DFDP-1) through New Zealand's Alpine Fault. For the instruments used in this study, the highest resolution images were collected in the NT scans. This allows clearer imaging of some rock features than in the CT scans. However, we observe that the highly neutron beam attenuating properties of DFDP-1 core diminish the quality of images towards the interior of the core. A comparison is also made of the suitability of these two scanning techniques for a drilling project. We conclude that CT scanning is far more favourable in most circumstances. Nevertheless, it could still be beneficial to take NT scans over limited intervals of suitable core, where varying contrast is desired. © Author(s) 2017.
1942.
Earthquake-enhanced permeability – evidence from carbon dioxide release following the ML 3.5 earthquake in West Bohemia
Earth and Planetary Science Letters,
46060 – 67
2017
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Bohemia; Czech Republic; Germany; Vogtland; Carbon dioxide; Faulting; Flow of gases; Structural geology; crustal CO2; Earthquake fault; Earthquake swarms; Enhanced permeability; Fault-valve; Fluid pressure pulse; Low permeability; Two dimensional model; carbon dioxide; degassing; earthquake epicenter; earthquake magnitude; earthquake mechanism; earthquake swarm; lower crust; permeability; trigger mechanism; Earthquakes
Abstract: ▾ The West Bohemia/Vogtland region is characterized by earthquake swarm activity and degassing of CO2 of mantle origin. A fast increase of CO2 flow rate was observed 4 days after a ML 3.5 earthquake in May 2014 in the Hartoušov mofette, 9 km from the epicentres. During the subsequent 150 days the flow reached sixfold of the original level, and has been slowly decaying until present. Similar behavior was observed during and after the swarm in 2008 pointing to a fault-valve mechanism in long-term. Here, we present the results of simulation of gas flow in a two dimensional model of Earth's crust composed of a sealing layer at the hypocentre depth which is penetrated by the earthquake fault and releases fluid from a relatively low-permeability lower crust. This simple model is capable of explaining the observations, including the short travel time of the flow pulse from 8 km depth to the surface, long-term flow increase and its subsequent slow decay. Our model is consistent with other analyse of the 2014 aftershocks which attributes their anomalous character to exponentially decreasing external fluid force. Our observations and model hence track the fluid pressure pulse from depth where it was responsible for aftershocks triggering to the surface where a significant long-term increase of CO2 flow started 4 days later. © 2016 Elsevier B.V.
1941.
Hydrological and temperature change in Arctic Siberia during the intensification of Northern Hemisphere Glaciation
Earth and Planetary Science Letters,
457136-148
2017
ISSN: 0012821X
Publisher: Elsevier B.V.
Keywords:▾
Atmospheric chemistry; Carbon dioxide; Climate change; Glycerol; Isotopes; Lakes; Paraffins; Sea ice; Sea level; Sedimentology; Vegetation, arctic; branched GDGT; Hydrogen isotope; Northern hemisphere glaciations; Palaeoclimate; Pliocene, Glacial geology, alkane; glaciation; hydrogen isotope; hydrological change; Northern Hemisphere; paleoclimate; Pliocene; temperature, Arctic; Chukchi; Elgygytgyn Lake; Russian Federation; Siberia
Abstract: ▾ The Pliocene epoch represents an analog for future climate, with atmospheric carbon dioxide concentrations and continental configurations similar to present. Although the presence of multiple positive feedbacks in polar regions leads to amplified climatic changes, conditions in the Pliocene terrestrial Arctic are poorly characterized. High latitude sedimentary records indicate that dramatic glacial advance and decay occurred in the Pliocene Arctic, with attendant effects on global sea-level. Understanding these deposits and their implications for Earth's future requires developing a sense of climatic evolution across the Pliocene–Pleistocene transition and during the intensification of Northern Hemisphere Glaciation (iNHG) ∼2.7 million yr ago (Ma). Here we reconstruct Arctic terrestrial environmental change from 2.82–2.41 Ma (Marine Isotope Stages (MIS) G10–95) using the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the isotopic composition of plant leaf waxes (δDwax) in a sedimentary archive from Lake El'gygytgyn, Northeast Russia. Our records reveal changes in proxy behavior across this interval that we attribute to changing boundary conditions, including sea level, sea ice, vegetation and pCO2 during different MISs. We find that brGDGT temperatures and δDwax are decoupled for most of the record, although both show an increasing range of glacial–interglacial variability following iNHG. δDwax is stable from MIS G10–G4 despite changes in vegetation and temperature, suggesting different sources or pathways for moisture to Lake El'gygytgyn during the Late Pliocene. © 2016 Elsevier B.V.
1940.
GONAF - The borehole geophysical observatory at the North Anatolian Fault in the eastern Sea of Marmara
Scientific Drilling,
2219-28
2017
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Earthquakes; Geophysics, Historical seismicity; Istanbul; North Anatolian Fault; North Anatolian Fault Zone; Population centers; Recurrence time; Sea of Marmara; Under water, Observatories
Abstract: ▾ The Marmara section of the North Anatolian Fault Zone (NAFZ) runs under water and is located less than 20 km from the 15-million-person population center of Istanbul in its eastern portion. Based on historical seismicity data, recurrence times forecast an impending magnitude M > 7 earthquake for this region. The permanent GONAF (Geophysical Observatory at the North Anatolian Fault) has been installed around this section to help capture the seismic and strain activity preceding, during, and after such an anticipated event. © Author(s) 2017.
1939.
Grain size-dependent strength of phyllosilicate-rich gouges in the shallow crust: Insights from the SAFOD site
Journal of Geophysical Research: Solid Earth,
122
(7)
5789-5812
2017
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
brittle deformation; coseismic process; creep; crust; deformation mechanism; fault gouge; grain size; phyllosilicate; pressure; San Andreas Fault; slip; strain rate; strength
Abstract: ▾ The San Andreas Fault Observatory at Depth (SAFOD) drilling project directly sampled a transitional (between creeping and locked) segment of the San Andreas Fault at 2.7 km depth. At the site, changes in strain rate occur between periods of coseismic slip (>10−7 s−1) and interseismic creep (10−10 s−1) over decadal scales (~30 years). Microstructural observations of core retrieved from the SAFOD site show throughgoing fractures and gouge-rich cores within the fractures, evidence of predominantly brittle deformation mechanisms. Within the gouge-rich cores, strong phases show evidence of deformation by pressure solution once the grain size is reduced to a critical effective grain size. Models of pressure solution-accommodated creep for quartz-phyllosilicate mixtures indicate that viscous weakening of quartz occurs during the interseismic period once a critical effective grain size of 1 μm is achieved, consistent with microstructural observations. This causes pronounced weakening, as the strength of the mixture is then controlled by the frictional properties of the phyllosilicate phases. These results have pronounced implications for the internal deformation of fault zones in the shallow crust, where at low strain rates, deformation is accommodated by both viscous and brittle deformation mechanisms. As strain rates increase, the critical effective grain size for weakening decreases, localizing deformation into the finest-grained gouges until deformation can no longer be accommodated by viscous processes and purely brittle failure occurs. ©2017. American Geophysical Union. All Rights Reserved.
1938.
Granite-gneiss basement below Deccan Traps in the Koyna region, western India: Outcome from scientific drilling
Journal of the Geological Society of India,
90
(6)
776-782
2017
ISSN: 00167622
Publisher: Geological Society of India
Keywords:▾
basalt; basement rock; Deccan Traps; drilling; gneiss; granite; microstructure; petrology; seismic zone, India; Koyna; Maharashtra
Abstract: ▾ The Koyna region, located in the Deccan Flood Basalt Province of western peninsular India has been experiencing reservoir triggered seismicity since the impoundment of the Shivajisagar water reservoir in 1962. Scientific drilling carried out to 1522 m depth in the vicinity of the seismogenic zone exposed the granitic basement that lay below the Deccan Traps and provided a unique opportunity to study the rock types, petrological characteristics and microstructures. Cores obtained from drilling at four sites considered to be representative of the Koyna region, were studied. The boreholes include KBH-1 (Rasati) in the northern part, KBH-5 (Phansavle) in the western part, KBH-6 (Ukhalu) and KBH-7 (Panchgani) in the eastern part of the region. Each borehole penetrates the entire pile of Deccan basalt and pass through a few hundred metres of the granitic basement. The salient results are as follows: (i) The basement granitoids are dominantly composed of granite-gneiss, granite and migmatitic gneiss, typical of cratonic gneiss exposed in peninsular India. (ii) Petrology and microstructure study confirm the occurrence of strained quartz and unstrained plagioclase feldspars in the basement granitoids. (iii) Localized fault zones within the basement section, with prominent evidences of fault breccia, fault gouge, slicken lines with slickensides and pseudotachylite veins are observed in the individual boreholes. (iv) Anastomosing fracture network within these fault zones are good pathways for water channelization, which is supported by the higher abundances of ferruginous and siliceous secondary precipitations following the fractures. © 2017, Geological Society of India.
1937.
High resolution core scan facility at BGRL-MoES, Karad, India
Journal of the Geological Society of India,
90
(6)
795-797
2017
ISSN: 00167622
Publisher: Geological Society of India
Keywords:▾
core logging; data management; digital image; grain size; image resolution; mapping; pixel; texture, India; Karad; Maharashtra
Abstract: ▾ A high-resolution, optical core scan laboratory has been set up at Borehole Geophysics Research Laboratory (BGRL), Ministry of Earth Sciences (MoES), Karad. The facility provides a DMT® CoreScan3 optical core scanner and digital drill core data management system for core logging and analysis since July 2016. High resolution images are being produced in 360° mode for detailed unwrapped full circumference of drill core or plane mode for top surface image of slabbed drill core. Planar images of fractured cores and cuttings are also obtained. Image resolution ranges from 5 pix/mm (∼16 megapixel equivalent) to 40 pix/mm (∼1024 megapixel equivalent) for mapping of ultra high resolution data. The scanned core images are combined to create a digital core library. The facility helps in core sample analysis, structural analysis, textural and grain-size analysis, geotechnical studies, and integration with geophysical log data. © 2017, Geological Society of India.
1936.
High-velocity frictional properties of Alpine Fault rocks: Mechanical data, microstructural analysis, and implications for rupture propagation
Journal of Structural Geology,
9771-92
2017
ISSN: 01918141
Publisher: Elsevier Ltd
Keywords:▾
Bearings (machine parts); Core drilling; Data flow analysis; Fracture energy; Friction; Infill drilling; Microstructure; Shear bands; Shear flow; Velocity, Alpine Faults; Crystallographic preferred orientations; Friction coefficients; Frictional properties; High-velocity frictions; Micro-structural observations; Microstructural analysis; Rupture propagation, Fault slips, fault; microstructure; rock mechanics; rupture; shear band, Alpine Fault Zone; New Zealand; South Island
Abstract: ▾ The Alpine Fault in New Zealand is a major plate-bounding structure that typically slips in ∼M8 earthquakes every c. 330 years. To investigate the near-surface, high-velocity frictional behavior of surface- and borehole-derived Alpine Fault gouges and cataclasites, twenty-one rotary shear experiments were conducted at 1 MPa normal stress and 1 m/s equivalent slip velocity under both room-dry and water-saturated (wet) conditions. In the room-dry experiments, the peak friction coefficient (μp = τp/σn) of Alpine Fault cataclasites and fault gouges was consistently high (mean μp = 0.67 ± 0.07). In the wet experiments, the fault gouge peak friction coefficients were lower (mean μp = 0.20 ± 0.12) than the cataclasite peak friction coefficients (mean μp = 0.64 ± 0.04). All fault rocks exhibited very low steady-state friction coefficients (μss) (room-dry experiments mean μss = 0.16 ± 0.05; wet experiments mean μss = 0.09 ± 0.04). Of all the experiments performed, six experiments conducted on wet smectite-bearing principal slip zone (PSZ) fault gouges yielded the lowest peak friction coefficients (μp = 0.10–0.20), the lowest steady-state friction coefficients (μss = 0.03–0.09), and, commonly, the lowest specific fracture energy values (EG = 0.01–0.69 MJ/m2). Microstructures produced during room-dry and wet experiments on a smectite-bearing PSZ fault gouge were compared with microstructures in the same material recovered from the Deep Fault Drilling Project (DFDP-1) drill cores. The near-absence of localized shear bands with a strong crystallographic preferred orientation in the natural samples most resembles microstructures formed during wet experiments. Mechanical data and microstructural observations suggest that Alpine Fault ruptures propagate preferentially through water-saturated smectite-bearing fault gouges that exhibit low peak and steady-state friction coefficients. © 2017 The Authors
1935.
How to choose a right drilling site for the ICDP Cretaceous Continental Scientific Drilling in the Songliao Basin (SK2), Northeast China
Earth Science Frontiers,
24
(1)
216-228
2017
ISSN: 10052321
Publisher: Science Frontiers editorial department
Keywords:▾
Climate change; Geology; Global warming; Greenhouses; Rocks; Sedimentology; Site selection; Stratigraphy; Tectonics; Volcanic rocks; Water supply, Continental scientific drillings; Greenhouse climates; Oceanic Anoxic Event; Regional tectonics; Sedimentary records; Sedimentary sequence; Songliao basin; Tithonian to Albian, Sedimentary rocks
Abstract: ▾ The Continental Scientific Drilling in the Songliao Basin has been done since 2005, which include the SK1, having finished in 2007, and the SK2 that started drilling in 2014 and is expected to finish in 2017. The purposes of the project are as followings, to drilling through the whole Cretaceous sequence of the Songliao Basin, to obtain continuous high resolution continental geological records by the means of the so-called “2 wells 4 holes drilling procedures”, to research the Cretaceous greenhouse climate changes in order to be better prepared with the challenge caused by the nowadays global warming event. According to the goals above we proposed the rules for the site selection of the SK2 as follows. Firstly, stratigraphic sedimentary records should be continuous. Secondly, sedimentary rocks are preferred, especially the lacustrine fine clastic rocks. Thirdly, thickness of the overburden cap rocks should be as thin as possible. Fourthly, faults should be avoided of. At last, ground conditions should be as good as possible such as roads, electric power, water supply, and so forth. We finally chose the site of SK2 in the Songzhan area where the lacustrine mudstone is well developed in the Xujiaweizi faulted depression of the Songliao Basin. The major target drilling succession is the Lower Cretaceous, namely, Yingcheng, Shahezi, and Huoshiling Formations. The strata under drilling are interbedding sequence of sandstone, siltstone, mudstone and coal, which are intercalated with volcanic rocks and pyroclastic rocks. They are mainly dark rocks of lacustrine facies which reflect the reduced environment. We shall drill through the top boundary (T4) and bottom boundary (T5) of rift fill successions, the boundary between the Upper and Lower Cretaceous, the boundary between Cretaceous and Jurassic (K/J). All these boundaries indicate important geological events which reflect changes of regional tectonics and basin filling styles. With the continuous coring section, we can also obtain some other important geological records with global meanings such as the Cretaceous normal polarity superchron (CNS) and oceanic anoxic event (OAE-1). © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
1934.
Iceland drilling project aims to unearth how islands form
Nature,
547
(7664)
387-388
2017
ISSN: 00280836
Publisher: Nature Publishing Group
Keywords:▾
hot water; mineral; sea water, biosphere; drilling fluid; microbial community; microorganism; pristine environment; project assessment; sea level change; seafloor; seawater; volcanic eruption; volcanic island; volcanic rock, biosphere; biotechnology; contamination; drill; Iceland; island (geological); nuclear waste; organismal interaction; priority journal; rock; sea level; seashore; Short Survey; volcano; animal; bird; ecosystem; history; microbiology; microflora; physiology; plant; sediment, Atlantic Ocean; Atlantic Ocean (North); Heimaey; Iceland; New Zealand; North Island; Surtsey; Taupo; Waikato, Animals; Birds; Ecosystem; Geologic Sediments; History, 20th Century; History, 21st Century; Iceland; Islands; Microbiota; Plants; Volcanic Eruptions
1933.
Geophysical techniques of reservoir monitoring for marine gas hydrate exploitation
Earth Science Frontiers,
24
(5)
368-382
2017
ISSN: 10052321
Publisher: Science Frontiers editorial department
Keywords:▾
Acoustic properties; Deformation; Earthquake effects; Electromagnetic prospecting; Gas hydrates; Gases; Geophysics; Heat flux; Hydration; Risk assessment; Seismology; Shear flow; Shear waves, Commercial exploitation; Gas-hydrate production; Geophysical monitoring; MCSEM; Production optimization; Reservoir monitoring; Seafloor deformation; Seismic system, Monitoring
Abstract: ▾ Marine gas hydrate is an important resource of clean energy for the future, but its exploitation requires not only the innovation of development techniques but also serious consideration of protection of marine environment. For a timely response to production process, monitoring of the dynamic change of gas hydrate reservoir in real time is a basic requirement for a successful exploitation. However, in previous successful gas hydrate production experiments, either in terrestrial permafrost area (Mallik of Canada and Ignik Sikumi of USA) or on continental slope in deep sea (Nankai Trough of Japan), monitoring was carried out mainly through the instruments installed in the two or three observation wells which were only tens of meters away from the production well, and consequently the monitoring might have covered only a limited area. At the present the monitoring technique for large-scale monitoring of gas hydrate reservoir has not been established worldwide, even systematic discussion and scheme design are absent. Based on the acoustic and electrical responses to the saturation change and granular contact mode of gas hydrate layer, several seismic and electromagnetic exploration methods have been compared to see their feasibility and merits and drawbacks for large-scale monitoring of marine gas hydrate development, and an advanced geophysical monitoring scheme is proposed for the upcoming gas hydrate experimental production in South China Sea and future commercial exploitation. The integrated geophysical monitoring system is comprised of (1) a set of geophysical sensors to be installed in the observation wells, which will continuously collect the key physical parameters as temperature, pressure, electrical resistivity, streaming potential, heat flux, etc.; (2) a high sensitive and endurable full fiber 4-component ocean bottom seismic cable system to record the time lapse variations of reservoir acoustic properties of both compressive and shear waves; (3) a net of multifunctional ocean bottom nodes around the production well to measure the seafloor surface deformation/depression during production, and to directly detect and visually observe possible methane leakage. On a well designed protocol, this monitoring system can quantitatively measure the key geophysical variations associated with gas hydrate dissociation, and the data to be acquired will provide scientific basis for production optimization, environment protection and risk assessment for marine gas hydrate exploitation. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
1932.
Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC-1 borehole
Journal of Geophysical Research: Solid Earth,
122
(5)
3999--4019
2017
ISSN: 2169-9356Keywords:▾
breakout growth, elastic properties, foliation and fracture, in situ stress, time dependency
Abstract: ▾ Stress-induced borehole deformation analysis in the Collisional Orogeny in the Scandinavian Caledonide deep scientific borehole establishes in situ stress orientation in a poorly characterized region in central Sweden. Two acoustic televiewer logging campaigns, with more than 1 year between campaigns, provide detailed images along the full length of the 2.5 km deep borehole for breakout, drilling-induced tensile fracture (DITF), and natural occurring structural analysis. Borehole breakouts occur in 13 distinct zones along total length of 22 m, indicating an average maximum horizontal stress, SHmax, orientation of 127° ± 12°. Infrequent DITFs are constrained within one zone from 786 to 787 m depth (SHmax orientation: 121° ± 07°). These SHmax orientations are in agreement with the general trend in Scandinavia and are in accordance with many mechanisms that generate crustal stress (e.g., ridge push, topographic loading, and mantel driven stresses). The unique acquisition of image logs in two successions allows for analysis of time-dependent borehole deformation, indicating that six breakout zones have crept, both along the borehole axis and radially around the borehole. Strong dynamic moduli measured on core samples and an inferred weak in situ stress anisotropy inhibit the formation of breakouts and DITFs. Natural fracture orientation below 800 m is congruent to extensional or hybrid brittle shear failure along the same trend as the current SHmax. Analysis of foliation in the image logs reinforces the interpretation that the discontinuous seismic reflectors with fluctuating dip observed in seismic profiles are due to recumbent folding and boudinage.
1931.
Implications of S1 tephra findings in Dead Sea and Tayma palaeolake sediments for marine reservoir age estimation and palaeoclimate synchronisation
Quaternary Science Reviews,
170269-275
2017
ISSN: 02773791
Publisher: Elsevier Ltd
Keywords:▾
Plants (botany); Reservoirs (water); Submarine geology, Early Holocene; Eastern Mediterranean; Lake sediments; Marine reservoir age; NW Arabian Peninsula; Palaeoclimate; S1 tephra; Tephrochronology, Sediments, age determination; Holocene; lacustrine deposit; marine environment; marine record; marine sediment; paleoclimate; radiocarbon dating; tephra; tephrochronology; volcano, Anatolia; Arabian Peninsula; Dead Sea; Egypt; Lebanon; Levantine Sea; Mediterranean Region; Mediterranean Sea; Red Sea [(GVR) Egypt]; Saudi Arabia; Sodmein Cave; Tabuk [Saudi Arabia]; Tayma; Turkey
Abstract: ▾ Here we report on the first findings of a cryptotephra in the Holocene lacustrine sediment records of the Dead Sea and Tayma palaeolake (NW Arabian Peninsula). The major element glass composition of this rhyolitic tephra is identical to the distal ‘S1’ tephra layer identified in the Yammoûneh palaeolake (Lebanon), in a marine sediment record from the SE Levantine basin and in the Sodmein Cave archaeological site in Egypt. The S1 tephra corresponds to the early Holocene ‘Dikkartın’ dome eruption of the Erciyes Dağ volcano in central Anatolia (Turkey) and has been dated in the marine record at 8830 ± 140 cal yr BP. We present new age estimates of the S1 tephra based on radiocarbon dating of terrestrial plant remains and pollen concentrates revealing ages of 8939 ± 83 cal yr BP in the Dead Sea sediments and 9041 ± 254 cal yr BP in Tayma. The precise date from the Dead Sea allows refining the early Holocene marine reservoir age in the SE Levantine Sea to ca. 320 ± 50 years. Synchronisation of marine and terrestrial palaeoclimate records in the eastern Mediterranean region using the S1 tephra further suggests a time-transgressive expansion of the early Holocene humid period. © 2017 Elsevier Ltd
1930.
Increased sedimentation following the Neolithic Revolution in the Southern Levant
Global and Planetary Change,
152199 – 208
2017
1929.
Interpreting Soft Sediment Deformation and Mass Transport Deposits as Seismites in the Dead Sea Depocenter
Journal of Geophysical Research: Solid Earth,
122
(10)
8305 – 8325
2017
1928.
Investigations of continued reservoir triggered seismicity at Koyna, India
Geological Society Special Publication,
445
(1)
151-188
2017
ISSN: 03058719
Publisher: Geological Society of London
DOI:10.1144/SP445.11
Abstract: ▾ Koyna, located in the Deccan Volcanic Province in western India, is the most significant site of reservoir triggered seismicity (RTS) globally. The largest RTS event of M 6.3 occurred here on December 10,1967. RTS at Koyna has continued. This includes 22 M> 5.0 and thousands of smaller events over the past 50 years. The annual loading and unloading cycles of the Koyna Reservoir and the nearby Warna Reservoir influence RTS. Koyna provides an excellent natural laboratory to comprehend the mechanism of RTS because earthquakes here occur in a small area, mostly at depths of 2-7 km, which are accessible for monitoring. A deep borehole laboratory is therefore planned to study earthquakes in the near-field to understand their genesis, especially in an RTS environment. Initially, several geophysical investigations were carried out to characterize the seismic zone, including 5000 line kilometres of airborne gravity gradiometry and magnetic surveys, high-quality magnetotelluric data from 100 stations, airborne LiDAR surveys over 1064 km2, drilling of 8 boreholes of approximately 1500 m depth and geophysical logging. To improve the earthquake locations a unique network of borehole seismometers was installed in six of these boreholes. These results, along with a pilot borehole drilling plan, are presented here. © 2017 The Author(s). Published by The Geological Society of London.
1927.
Effect of an 860-m thick, cold, freshwater aquifer on geothermal potential along the axis of the eastern Snake River Plain, Idaho
Geothermal Energy,
5
(1)
2017
ISSN: 21959706
Publisher: SpringerOpen
Keywords:▾
Aquifers; Basalt; Clay alteration; Flow of fluids; Geothermal fields; Geothermal logging; Rivers; Water; X ray diffraction, Bottom hole temperatures; Corehole; Equilibrium temperatures; Freshwater aquifer; Geothermal gradients; Geothermal potential; Geothermometers; Temperature log, Thermal logging, aquifer; basalt; geothermal system; geothermometry; heat flow; temperature gradient; thermal alteration; X-ray diffraction, Idaho; Snake River Plain; United States, Calluna vulgaris
Abstract: ▾ A 1912-m exploration corehole was drilled along the axis of the eastern Snake River Plain, Idaho. Two temperature logs run on the corehole display an obvious inflection point at about 960 m. Such behavior is indicative of downward fluid flow in the wellbore. The geothermal gradient above 935 m is 4.5 °C/km, while the gradient is 72–75 °C/km from 980 to 1440 m. Projecting the higher gradients upward to where they intersect the lower gradient on the temperature logs places the bottom of the cold, freshwater Snake River Plain aquifer, which suppresses the geothermal gradient at this location, at least 860 m below the surface. The average heat flow for the corehole between 983 and 1550 m is 132 mW/m2. Although the maximum bottom-hole temperature extrapolated from a measured time–temperature curve was only 59.3 °C, geothermometers suggest an equilibrium temperature on the order of 125–140 °C based on a single fluid sample from 1070 m. Furthermore, below 960 m the basalt core shows obvious signs of alteration, including a distinct color change, the formation of smectite clay, and the presence of secondary minerals filling vesicles and fracture zones. This alteration boundary could act as an effective cap or seal for a hot-water geothermal system. © 2017, The Author(s).
1926.
Gold mobility during Palaeoarchaean submarine alteration
Earth and Planetary Science Letters,
46247 – 54
2017
1925.
Integration of multiple soft data sets in MPS thru multinomial logistic regression: a case study of gas hydrates
Stochastic Environmental Research and Risk Assessment,
31
(7)
1727-1745
2017
ISSN: 14363240
Publisher: Springer New York LLC
Keywords:▾
Facsimile; Gas hydrates; Hydration; Regression analysis, Distance functions; Geostatistical simulation; Logistic regression classifier; Methane hydrates; Multinomial logistic regression; Multiple-point geostatistics; Patch based; Soft data, Probability, computer simulation; data set; gas hydrate; geostatistics; methane; probability; regression analysis
Abstract: ▾ A new approach is described to allow conditioning to both hard data (HD) and soft data for a patch- and distance-based multiple-point geostatistical simulation. The multinomial logistic regression is used to quantify the link between HD and soft data. The soft data is converted by the logistic regression classifier into as many probability fields as there are categories. The local category proportions are used and compared to the average category probabilities within the patch. The conditioning to HD is obtained using alternative training images and by imposing large relative weights to HD. The conditioning to soft data is obtained by measuring the probability–proportion patch distance. Both 2D and 3D cases are considered. Synthetic cases show that a stationary TI can generate non-stationary realizations reproducing the HD, keeping the texture indicated by the TI and following the trends identified in probability maps obtained from soft data. A real case study, the Mallik methane-hydrate field, shows perfect reproduction of HD while keeping a good reproduction of the TI texture and probability trends. © 2016, Springer-Verlag Berlin Heidelberg.
1924.
Geology and in situ stress of the MH-2 borehole, Idaho, USA: Insights into western Snake River Plain structure from geothermal exploration drilling
Lithosphere,
9
(3)
476 – 498
2017
ISSN: 19418264
Publisher: Geological Society of America
DOI:10.1130/L609.1
Keywords:▾
Idaho; Snake River Plain; United States; Air; Basalt; Boreholes; Boring; Clay alteration; Core analysis; Faulting; Fracture; Geology; Geophysics; Geothermal fields; Geothermal prospecting; Horizontal drilling; Rivers; Rock drills; Sedimentary rocks; Software testing; Stratigraphy; Stresses; Strike-slip faults; Structural geology; Volcanic rocks; Volcanoes; Well logging; Continental scientific drillings; Drilling-induced tensile fractures; Geothermal exploration; Hydrostatic gradients; Hydrothermal alterations; Mechanical stratigraphy; Sedimentary horizons; Structural environment; artesian well; borehole geophysics; geological survey; geomechanics; geothermal system; hydrothermal activity; hydrothermal fluid; in situ stress; petrology; strike-slip fault; Fault slips
Abstract: ▾ Project HOTSPOT, the Snake River Scientific Drilling Project (International Continental Scientific Drilling Program), tested for deep geothermal resources and examined the petrology of volcanic rocks with three drillholes in the central and western Snake River Plain (western USA). The MH-2 drillhole targeted fractured crystalline and hydrothermally altered basalt in the area of the Mountain Home Air Force Base (Idaho) to a total depth of 1821 m. At 1745 m depth the drillhole encountered flowing artesian hydrothermal fluids of at least 150 °C. We integrate geological analyses of core, image log, and borehole geophysical data, and in situ stress analyses to describe the structural environment that produces permeability for artesian flow. The rocks in the lower 540 m of the drillhole consist of basalt flows as much as 30 m thick, altered basalt, and thin sedimentary horizons. The mechanical stratigraphy is defined by nine mechanical horizons that are in three ranges of rock strength on the basis of experimentally determined strength data, core logging, and geophysical log signatures. Hydrothermal alteration products and mineralization in the core are associated with three highly faulted sections; the lowermost section is associated with the zone of flowing thermal water. Shear slip indicators on faults observed in core indicate slip ranging from pure strike slip to normal failure mechanisms in the stronger horizons. The borehole breakouts indicate that the maximum horizontal stress, SH, is oriented 047° ± 7°, and drilling-induced tensile fractures indicate that SH is oriented at 67° ± 21°.The in situ stress orientations exhibit little variation over the depth of the measured interval, but the SH magnitude varies with depth, and is best explained by an oblique normal fault stress regime.The geomechanical model indicates that if pore pressures at depth are elevated above the normal hydrostatic gradient, as observed here, the system has the potential to deform by mixed normal and strike-slip failure. Our observations and interpretations suggest that the MH-2 borehole was drilled into oblique normal faults that intersect a buried 300°-trending fault block masked by the basaltic volcanic complex. These data indicate that the transition from the central to western Snake River Plain is characterized by complex structures developed in response to a transitional stress state related to Snake River Plain and western Basin and Range stress regimes. The western Basin and Range stress and tectonic regime may extend from northern Nevada into western Idaho and may enhance the potential for geothermal resources by creating interconnected fracture and fault-related permeability at depth. © 2017 Geological Society of America.
1923.
Extreme hydrothermal conditions at an active plate-bounding fault
Nature,
546
(7656)
137-140
2017
ISSN: 00280836
Publisher: Nature Publishing Group
Keywords:▾
active fault; deformation; earthquake magnitude; earthquake rupture; fluid dynamics; heating; hydrostatic pressure; hydrothermal activity; hydrothermal system; movement; plate boundary; pressure effect; seismic zone; temperature effect; temperature gradient; topography, Article; earthquake; environmental temperature; heat; heating; hydrostatic pressure; pressure gradient; priority journal; rock; shear stress; topography
Abstract: ▾ Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional-mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
1922.
Effects of shock pressure and temperature on titanomagnetite from ICDP cores and target rocks of the El’gygytgyn impact structure, Russia
Studia Geophysica et Geodaetica,
61
(1)
162-183
2017
ISSN: 00393169
Publisher: Springer Netherlands
Keywords:▾
impact structure; magnetic susceptibility; meteorite; oxidation; pressure effect; temperature effect; titanomagnetite; volcanic rock, Okhotsk-Chukotka Volcanic Belt; Russian Federation
Abstract: ▾ The aim of this study was to investigate the effect of meteorite impacts on magnetic properties including magnetic susceptibility and the Verwey transition of Ti-poor titanomagnetite of volcanic rocks from the 3.6 Ma old El’gygytgyn impact structure located in the Okhotsk-Chukotka volcanic belt in north-eastern Russia. The target rocks consist mainly of rhyolite with some andesites, and is a rare example of impact structures within volcanic target rocks on Earth. 27 samples from outside the crater, the crater rim and from the depth interval 316 to 517 m below lake bottom (mblb) of the El’gygytgyn ICDP drilling were studied. A significant decrease of the average specific magnetic susceptibility by around 90% was observed between felsic volcanic rocks from the surface (18.1 × 10-6 m3/kg) and the drill cores from near the crater central uplift (1.9 × 10-6 m3/kg). Ferrimagnetic Fe-Ti oxide assemblages (Verwey transition temperature, TV: -161 to -150°C, Curie temperature, TC: 451 to 581°C), occurring in all studied samples, differ significantly. At the surface titanomaghemite is ubiquitously associated with titanomagnetite. The drill cores lack titanomaghemite, but either show a transformation into titanomagnetite and ilmenite or a strong fragmentation associated with a second TV between -172 and -188°C. Reversible curves of temperature dependence of magnetic susceptibility in the suevite indicate high depositional temperatures of at least 500°C. In the polymict and monomict impact breccia mechanical deformation of titanomagnetite and temperatures of at least 200-350°C related to the shock are suggested from temperature dependent magnetic susceptibility cycling. Lowtemperature oxidation along strongly brecciated grain surfaces in titanomagnetite is suggested to cause the lower TV and we suggest that this phenomenon is related to postimpact hydrothermal activity. The strong magnetic susceptibility decrease at El’gygytgyn is mainly influenced by shock, and post-impact hydrothermalism causes a significant additional depletion. These observations explain why magnetic lows are a ubiquitous phenomenon over impact structures. © 2017, Institute of Geophysics of the ASCR, v.v.i.
1921.
Geoelectrical and electromagnetic methods applied to paleolimnological studies: Two examples from desiccated lakes in the Basin of Mexico
Boletin de la Sociedad Geologica Mexicana,
69
(2)
279-298
2017
ISSN: 14053322
Publisher: Instituto de GeologÃa, Universidad Nacional Autónoma de México
Abstract: ▾ Paleolimnological studies require a broad understanding of the geometry and depth of the sedimentary fill of lake basins prior to coring campaigns. Seismic methods are routinely employed for the indirect characterization of lake-bottom sediments. However, the use of seismic methods might occasionally be limited due to surface conditions or poor seismic contrasts between the stratigraphic units, which lead to data quality that is too poor to provide sufficient information for the selection of drill sites. Sources of cultural noise are one of the main reasons why seismic methods fail in study areas near or within large cities, such as Mexico City. Under certain conditions, electrical and electromagnetic methods might be a suitable substitute or complement to seismic exploration, as they respond to different physical properties of the subsurface. To evaluate the applicability of such methods, here we present two recent case studies from the desiccated lakes Chalco and Xochimilco both located in urban areas within the Basin of Mexico where electrical resistivity tomography (ERT), transient electromagnetic (TEM) and magnetotelluric (MT) soundings were conducted for the characterization of lake basement and lacustrine sediments. In both examples, the results of the geophysical exploration contributed valuable stratigraphic information for the following drilling and core recovery, which highlights the potential of electrical and electromagnetic methods in paleolimnological studies.
1920.
Effect of graphene and graphene oxide addition on lubricating and friction properties of drilling fluids
Nanoscience and Nanotechnology Letters,
9
(4)
446-452
2017
ISSN: 19414900
Publisher: American Scientific Publishers
Abstract: ▾ This study has examined the potential improvement of the lubricating properties of drilling fluid by adding graphene and graphene oxide (GO). The effects of different concentrations of graphene and GO addition on lubricating properties and friction reduction of drilling fluid have been studied by using an extreme pressure lubrication device and a pin-on-disk tester. In pin-on-disk tests, the pin material was AISI316 steel (casing material) and the disk material was 7075 aluminum alloy (drill pipe material). The pin-on-disk friction and wear tests were carried out under the condition that the pin and disk are immerged in drilling fluid. Results indicated that the lubricating properties of drilling fluid significantly improved by adding appropriate amount of GO materials, while, on the other hand, addition of graphene had limited effect on the lubricating properties of drilling fluid. The lubricating factor of drilling fluid dropped 12.6% by an addition of 0.075 wt% GO. The coefficient of friction between the friction pairs dropped 19.8% by an addition of 0.075 wt% GO. Moreover, the wear volume (WV) of aluminum alloy disc decreased to the minimum value of 0.32 mm3 by an addition of 0.075 wt% GO. On the basis of experimental results, 0.075 wt% GO was added to the oil-based drilling fluids used in an SK-II well, a scientific continental drilling project in the Cretaceous Songliao Basin of Northeast China. Results showed that the lubricating factor of the drilling fluid was reduced by 15.6%, the friction coefficient reduction rate was increased by 24.3% and the aluminum disc wear volume decreased by 20.5%. © 2017 American Scientific Publishers All rights reserved.