All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2619.
Deccan volcanic activity and its links to the end-Cretaceous extinction in northern China
Global and Planetary Change,
210
2022
ISSN: 09218181
Publisher: Elsevier B.V.
Keywords:▾
Boundary mass; Chemostratigraphy; Deccan trap volcanism; End-cretaceous mass extinction; Hg chemostratigraphy; Hg isotope; K-pg boundaries; Mass extinction; Northern China; Volcanic activities, Climate change, chemostratigraphy; climate change; Cretaceous; Cretaceous-Paleogene boundary; Deccan Traps; mass extinction; volcanism, China
Abstract: ▾ The Cretaceous-Paleogene (K-Pg) boundary mass extinction is commonly attributed to the Chicxulub impact and/or the Deccan Traps (DT) volcanism, but the underlying trigger remains uncertain. The lack of detailed identification of the DT eruptive pluses impedes the full assessment of their relationship to the K-Pg boundary mass extinction. Here we present the first mercury (Hg) chemostratigraphy records on the paleo Asian plate, coupled with climatic and biotic data, to constrain the effects of the DT on the Late Cretaceous climate change and mass extinction. In northern China, a total Hg (THg) spike follows warming caused by the DT volcanism and corresponds to the significant species losses. Our study suggests that this most intense pulse of the DT (~50 kyr duration) occurred just before the K-Pg boundary and suggests that it contributed to the end-Cretaceous mass extinction in northern China. © 2022 Elsevier B.V.
2618.
De-noising distributed acoustic sensing data using an adaptive frequency-wavenumber filter
Geophysical Journal International,
231
(2)
944 – 949
2022
2617.
Deep sourced fluids for peridotite carbonation in the shallow mantle wedge of a fossil subduction zone: Sr and C isotope profiles of OmanDP Hole BT1B
Journal of Geophysical Research: Solid Earth,
127
(1)
e2021JB022704
2022
2616.
Depositional history of Lake Chala (Mt. Kilimanjaro, equatorial East Africa) from high-resolution seismic stratigraphy
Journal of African Earth Sciences,
189
2022
ISSN: 1464343X
Publisher: Elsevier Ltd
Keywords:▾
deposition; environmental change; glacial-interglacial cycle; lacustrine deposit; lake; mass wasting; reconstruction; sediment; seismic stratigraphy, Kilimanjaro [Kilimanjaro (RGA)]; Kilimanjaro [Tanzania]; Tanzania
Abstract: ▾ Sediments deposited in Lake Chala (Kenya/Tanzania) constitute a high-resolution archive of past climate and environmental change in equatorial East Africa spanning two glacial-interglacial cycles. To correctly interpret the proxy records it contains, it is crucial to understand the evolution of lacustrine sedimentation in this volcanic crater basin. Building on previous seismic stratigraphic analysis by Moernaut et al. (2010) of a dense grid of 37 km high-resolution seismic reflection profiles with up to 270 ms two-way travel time (ca. 210 m depth) of sub-bottom penetration, this study presents a seismic-based reconstruction of the complete depositional history of Lake Chala as well as a first-order age model for the major documented stages in lake evolution. The seismic stratigraphic sequence comprises 16 distinct and finely-stratified units (U1-U16, youngest to oldest), grouped into five major depositional stages. Stage I (U16, ca. 249-212 ka) marks the initiation of sedimentation in an originally ring-shaped depositional area surrounding two central tuff cones emerging from the basin floor. Stage II (U15-U12, ca. 212-114 ka) represents the onset of basinwide sedimentation above the tuff cones, implying a gradual rise in lake depth and shift to more strictly hemipelagic sedimentation. Stage III (U11-U8, ca. 114-97 ka) represents the development of a relatively flat lake floor during a period of significantly reduced lake depth. Stage IV (U7-U4, ca. 97–20.5 ka) is again characterized by largely undisturbed hemipelagic sedimentation under mostly high lake-depth conditions. Stage V (U3-U1, 20.5 ka BP to Present) represents the establishment of the present-day, very broad and flat basin floor under fluctuating lake level. Reassessing the Moernaut et al. (2010) suggestion of a minor disconformity at ca. 100 m sub-bottom depth, we here interpret this seismic feature as a thick turbidite related to a mass wasting event. Consequently we can affirm continuity of lacustrine sedimentation in the depocenter of Lake Chala throughout the past ca. 250,000 years. © 2022 Elsevier Ltd
2615.
Diatom community responses to environmental change in Lake Ohrid (Balkan Peninsula) during the mid-Pleistocene Transition
Quaternary International,
6221 – 9
2022
2614.
Discovery and geological implications of the Early Cretaceous basaltic andesites in SK2 borehole; [? 科二井早白垩世早期玄武安山岩的 ? 现 ? 地质 ?]
Yanshi Xuebao/Acta Petrologica Sinica
(6)
1756 – 1770
2022
ISSN: 10000569
Publisher: Science Press
Keywords:▾
Basalt; Binary alloys; Boreholes; Geochemistry; Geochronology; Lead alloys; Neodymium alloys; Strontium alloys; Tectonics; Uranium alloys; Zircon; Basaltic andesite; Early Cretaceous; Magmatisms; Northeast China; Okhotsk; Pacific plates; Rollback of the paleo-pacific plate; SK2 borehole; Songliao basin; Zircon U-Pb dating; Isotopes
Abstract: ▾ A continuous sedimentary-volcanic core of Songliao Basin has been obtained through ultra-deep drilling of the SK2 borehole, which provides excellent materials for systematically investigating the formation of the Songliao Basin and the tectonic evolution history of Northeast China. In this study, we conducted a combined study of zircon U-Pb dating, whole-rock geochemical and Sr-Nd isotopic analysis on basaltic andesite samples from SK2 borehole with depths ranging from -6035m to -6084m. These SK2 basaltic andesite samples belong to Huoshiling Formation and they were formed at Early Cretaceous (141.6±1.4Ma) according to the zircon U-Pb dating results. The SK2 basaltic andesites are enriched in large ion lithophile elements, depleted in high field strength elements, and their geochemical signatures are consistent with arc magmas. These rocks show depleted Sr-Nd isotope characteristics ((87Sr/86Sr)i=0.70496~0.70478, ϵNd(t)=1.05~1.61), suggesting a depleted mantle source. In the Early Cretaceous, the evolution of Northeast China was mainly controlled by the southward subduction of the Mongol-Okhotsk oceanic plate and the western subduction of the Paleo-Pacific Plate. Previous study has shown that the subduction of Mongolia-Okhotsk Ocean induced coeval magmatism in the Great Xing'an Range, however, it is not clear whether its influence extends into the Songliao Basin. The initial subduction of Paleo-Pacific lithosphere may induce Late Mesozoic magmatism in the west of Songliao Basin. The Early Cretaceous formation and evolution of Songliao Basin were mainly affected by the activities of Mongolia Okhotsk Ocean or Paleo-Pacific lithosphere remains controversial. The Th/Hf (1.10~2.87) and Zr/Y ratios (10.1~18.7) of the SK2 basaltic andesites are similar to the within-plate basaltic magmas, we therefore suggest that SK2 samples belong to intraplate magmatism. The samples also show higher Zr, Hf and Ti contents, higher Nb/Ta ratios and more depleted Nd isotope compositions than the coeval mafic rocks in the Great Xing'an Range, indicating the SK2 samples formed in a different tectonic background. Accordingly, the Early Cretaceous volcanic rocks in Songliao Basin are most likely occurred by rollback of the subducting Paleo-Pacific Plate, while incidental lithospheric extension may promote the formation of Songliao Basin. © 2022 Science Press. All rights reserved.
2613.
Discing behavior and mechanism of cores extracted from Songke-2 well at depths below 4,500 m
International Journal of Rock Mechanics and Mining Sciences,
149
2022
ISSN: 13651609
Publisher: Elsevier Ltd
Keywords:▾
Fracture; Morphology; Rock mechanics; Rocks; Stresses, Deep rocks; Discing; Fracture morphology; Fracture process; Fracture surfaces; Insitu stress; Integrity coefficient of disced rock sample; Integrity coefficients; Rock sample; Songke-2 well, Fractal dimension, fracture; in situ stress; rock mechanics; surface roughness; tensile stress
Abstract: ▾ Understanding in-situ stresses is the foundation for investigating deep rock mechanics. In practice, the fracture morphology of a disced core can often reflect its in-situ environment and disturbance-induced fracture process to some extent. In this study, three-dimensional dynamic scanning technology is used to reconstruct the fracture morphology of the disced cores extracted from Songke-2 as well as part of the Chinese Continental Scientific Drilling Project. The roughness of various regions of the fracture surfaces of the cores is investigated. Additionally, a parametric system is developed for the quantitative study of the integrity coefficient of the disced rock samples. Furthermore, the mechanisms and characteristics of the fractures along the stress paths are investigated. According to the findings, when shallow cores undergo discing, they have notable saddle-shaped coarse fractures, which may be related to the properties of the cores at these depths. Deep cores demonstrate discing behavior, but the generated discs are relatively thick. Deep core fracture surfaces are mostly smooth and straight, possibly propagating from the outside to the inside. Under excavation disturbance in the hydrostatic state, the extreme values of the maximum tensile stress at the core stubs show a saddle-shaped distribution. In general, the results of this study can serve as a theoretical foundation for the quantitative assessment of the intactness of disced cores. Furthermore, because disc patterns and characteristics are associated with stress states, this approach can be used to evaluate in-situ stress environments. © 2021 Elsevier Ltd
2612.
Ductile deformation during carbonation of serpentinized peridotite
NATURE COMMUNICATIONS,
13
(1)
2022
2611.
Early Jurassic coprolites: insights into palaeobotany and the feeding behaviour of dinosaurs
Papers in Palaeontology,
8
(2)
2022
2610.
Early Jurassic dinosaur-dominated track assemblages, floristic and environmental changes in the Holy Cross Mountains region, Poland
Geological Quarterly,
66
(3)
2022
DOI:10.7306/gq.1660
2609.
Earth’s oldest land ecosystem spotted in drilled cores
Science Advances,
376228-229
2022
2608.
Ecological resilience in tropical Andean lakes: A paleolimnological perspective
Limnology and Oceanography,
67
(S1)
S23 – S37
2022
Keywords:▾
Ecuador; anthropogenic effect; community composition; community response; diatom; ecosystem structure; lacustrine deposit; lacustrine environment; lake ecosystem; paleolimnology; tracking; tropical environment
Abstract: ▾ Little is known about whether changes in lake ecosystem structure over the past 150 years are unprecedented when considering longer timescales. Similarly, research linking environmental stressors to lake ecological resilience has traditionally focused on a few sentinel sites, hindering the study of spatially synchronous changes across large areas. Here, we studied signatures of paleolimnological resilience by tracking change in diatom community composition over the last 2000 years in four Ecuadorian Andean lakes with contrasting ecoregions. We focused on climate and anthropogenic change, and the type of biological responses that these changes induced: gradual, elastic, or threshold. We combined multivariate ordination techniques with nonlinear time-series methods (hierarchical generalized additive models) to characterize trajectories of community responses in each lake, and coherence in such trajectories across lakes. We hypothesized that remote, high-elevation lakes would exhibit synchronous trends due to their shared climatic constraints, whereas lower elevation lakes would show less synchronous trends as a consequence of human density and land-cover alteration. We found that gradual and elastic responses dominated. Threshold-type responses, or regime shifts, were only detected in the less remote lake, after a long period of gradual and elastic changes. Unexpected synchrony was observed in diatom assemblages from geographically distant and human-impacted lakes, whereas lakes under similar broad-scale environmental factors (climate and ecoregion) showed asynchronous community trajectories over time. Our results reveal a complex ecological history and indicate that Andean lakes in Ecuador can gradually adapt and recover from a myriad of disturbances, exhibiting resilience over century to millennial timescales. © 2021 Association for the Sciences of Limnology and Oceanography.
2607.
Evidence from the Vredefort Granophyre Dikes points to crustal relaxation following basin-size impact cratering
Icarus,
374
2022
Abstract: ▾ The timescale of the modification stage of basin-sized impact structures is not well understood. Owing to ca. 10 km of erosion since its formation, the Vredefort impact structure, South Africa, is an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from the Vredefort Granophyre Dikes, which were derived from the - now eroded - Vredefort impact melt sheet. The dikes have been studied mostly in terms of their composition, while the timing and duration of their emplacement remain controversial. We examined the modern depth extent of five dikes, with three from the inner crystalline core of the central uplift, and two from the boundary between the core and the supracrustal collar of the central uplift, using two-dimensional electrical resistivity tomography. We found that the core dikes terminate near the present erosion surface (i.e., <5 m depth). In contrast, the dikes at the core-collar boundary extend to a depth ≥ 9 m. These observations suggest that the core dikes are exposed near their lowermost terminus. In addition, we obtained bulk geochemical composition of the dikes, finding that the andesitic composition phase is present in the core-collar dikes that is not found in the core dikes. The presence of this phase indicates the episodic emplacement of impact melt into subvertical crater floor fractures. We conclude that the dike formation was protracted and occurred over a time span of at least 104 years. The sequential formation of the Vredefort Granophyre Dikes points to horizontal extension of crust below the impact melt sheet above a kinematic velocity discontinuity, a crustal instability resulting from the dynamic collapse of the transient cavity. © 2021 Elsevier Inc.
2606.
Evidence of Carboniferous arc magmatism preserved in the Chicxulub impact structure
Bulletin of the Geological Society of America,
134
(1-2)
241-260
2022
DOI:10.1130/B35831.1
Abstract: ▾ Determining the nature and age of the 200-km-wide Chicxulub impact target rock is an essential step in advancing our understanding of the Maya Block basement. Few age constraints exist for the northern Maya Block crust, specifically the basement underlying the 66 Ma, 200 km-wide Chicxulub impact structure. The International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364 core recovered a continuous section of basement rocks from the Chicxulub target rocks, which provides a unique opportunity to illuminate the pre-impact tectonic evolution of a terrane key to the development of the Gulf of Mexico. Sparse published ages for the Maya Block point to Mesoproterozoic, Ediacaran, Ordovician to Devonian crust are consistent with plate reconstruction models. In con- trast, granitic basement recovered from the Chicxulub peak ring during Expedition 364 yielded new zircon U-Pb laser ablation-in-ductively coupled plasma-mass spectrometry (LA-ICP-MS) concordant dates clustering around 334 ± 2.3 Ma. Zircon rare earth element (REE) chemistry is consistent with the granitoids having formed in a continental arc setting. Inherited zircon grains fall into three groups: 400-435 Ma, 500-635 Ma, and 940-1400 Ma, which are consistent with the incorporation of Peri-Gondwanan, PanAfrican, and Grenvillian crust, respectively. Carboniferous U-Pb ages, trace element compositions, and inherited zircon grains indicate a pre-collisional continental volcanic arc located along the Maya Block’s northern margin before NW Gondwana collided with Laurentia. The existence of a continental arc along NW Gondwana suggests southward-directed subduction of Rheic oceanic crust beneath the Maya Block and is similar to evidence for a continental arc along the northern margin of Gondwana that is documented in the Suwannee terrane, Florida, USA, and Coahuila Block of NE México. © 2022 Geological Society of America. All Rights Reserved.
2605.
Experimental Study on Physical Characteristics of Deep Rocks at Different Depths in Songliao Basin
Geofluids,
2022
2022
ISSN: 14688115
Publisher: Hindawi Limited
Keywords:▾
China; Songliao Basin; density; depth; experimental study; mineral; physical property; porosity; rock property; wave velocity
Abstract: ▾ Deep earth science is the basic of deep resource exploitation, and the research on the physical and mechanical characteristics of deep rock is a research hotspot at present. In order to study the physical characteristics of deep rock at different depths, based on the cores at different depths of 4900-6830 m in Songke Well 2 (SK-2), Songliao Basin, this paper carried out the study including the rock characteristics of mineral, wave velocity, density, and pore, the variation law of physical characteristics of deep rock with depth is studied, and the relationship between different physical parameters of deep rocks is explored. It is found that the core composition minerals of SK-2 at the depth of 4900-6830 m vary greatly with the depth, in which the quality of hard phase minerals accounts for a large proportion. After entering the basement stratum, the mineral content of different phases tends to be close. With the increase of depth, the wave velocity, density, and dynamic elastic modulus of rocks show a linear increase trend, and there is a positive correlation between density and wave velocity. In the range of 4900-6830 m depth, the porosity generally shows a downward trend with the increase of depth. In the range of 6000-6830 m, the porosity tends to be close to 7% with the increase of depth, indicating that formation compaction has little impact on the development of igneous pores in this formation. There is a negative correlation between wave velocity and porosity, and the empirical formula is fitted. This study can provide a reference for the exploration of deep geoscience and deep engineering practice. © 2022 Mingqing Yang et al.
2604.
Quantifying the axial magma lens dynamics at the roof of oceanic magma reservoirs (dike/gabbro transition): Oman Drilling Project GT3 site survey
Journal of Geophysical Research: Solid Earth,
126
(5)
e2020JB021496
2021
ISSN: 21699313
Publisher: Wiley Online Library
Keywords:▾
dike; drilling; gabbro; heat flux; hydrothermal system; hydrothermal vent; magma chamber; seafloor; spreading center; thermal evolution
Abstract: ▾ At oceanic spreading centers, the interactions between the igneous system that builds the crust, and the hydrothermal system that cools it govern the plumbing system architecture and its thermokinetic evolution. At fast-spreading centers, most of those interactions occur around the axial magma lens (AML) that feeds the upper crust, and possibly part of the underlying mushy igneous reservoir. Heat extracted from crystallizing AML is transferred through a conductive boundary layer to the overlying hydrothermal system. Quantifying the AML physical and thermal evolutions and its interactions with hydrothermal system is therefore essential to understand oceanic accretion. Those general issues were the rationale of drilling ICDP OmanDP Hole GT3A, and we present herein the geological, structural, and petrological data that were used as a site survey to select its location. GT3 area enables observations in three dimensions of fossilized AMLs and overlying dikes. The new field data and corresponding mineral compositions are used together with thermokinetic and thermodynamic models to deliver an integrated dynamic model for the AML/hydrothermal system interactions. Results attest that the isotropic gabbro interval is composite, with gabbro bodies intruding and reheating both gabbros and dikes (up to 1,040°C). We show that AMLs should be considered as transient igneous bodies that likely crystallize from primitive MORBs in decades, releasing heat to the intruded hosts, and feeding high temperature vents on the seafloor. We show for the first time that the thermal gradient recorded in AML roof is consistent with the heat fluxes reported at active hydrothermal vents. © 2021. The Authors.
2603.
Phytoliths, pollen, and microcharcoal from the Baringo Basin, Kenya reveal savanna dynamics during the Plio-Pleistocene transition
Palaeogeography, Palaeoclimatology, Palaeoecology,
570
2021
ISSN: 00310182
Publisher: Elsevier B.V.
Keywords:▾
Baringo; East African Rift; Kenya; Tugen Hills; Chloridoideae; Panicoideae; abundance; glaciation; Northern Hemisphere; phytolith; Pliocene; Pliocene-Pleistocene boundary; pollen; precipitation (climatology); savanna; woodland
Abstract: ▾ As part of the Hominin Sites and Paleolakes Drilling Project (HSPDP), phytoliths, pollen, and microcharcoal were examined from the 228 m (3.29 to 2.56 Ma) Baringo-Tugen Hills-Barsemoi drill core (BTB13). A total of 652 samples were collected at ~10 to 32 cm intervals, corresponding to sub-millennial to millennial scale temporal resolution. Microcharcoal was well-preserved throughout the core and often peaked in abundance ~5 kyr before and after insolation peaks. Phytolith preservation varied between excellent to total dissolution in alternating intervals throughout the core. Pollen was rarely preserved. These combined datasets indicate that prior to ~3.1 Ma, woody cover fluctuated between open savanna (< 40% cover), woodland (40–80% cover), and forest (> 80% cover) at typically precessional (19–23 kyr) periodicities. During the mid-Piacenzian Warm Period (MPWP; 3.26–3.01 Ma), intervals with exceptionally high microcharcoal abundance suggest that regional turnover from wooded to open habitats was driven in part by fire. After ~3.1 Ma, low-elevation woody cover likely never exceeded 40%, with oscillations between mesic tall-grass vs. xeric short-grass savanna at precessional periodicities. Mesic C4 tall-grass (Panicoideae) peaked in abundance during insolation maxima, whereas xeric C4 short-grass (Chloridoideae) peaked during insolation minima. The onset of Northern Hemisphere glaciation (NHG) at ~2.75 Ma coincided with the appearance of deep lake phases and increases in grass density and fire frequency. Spectral analysis and intervals with well-preserved phytoliths indicate that precession and interhemispheric insolation gradients influenced vegetation via their effects on equatorial precipitation and fire. This study fills a crucial gap in Pliocene vegetation reconstructions from the East African Rift Valley and its associated hominin localities. It also provides orbitally resolved regional vegetation data useful in paleodata–model comparisons for the onset of the MPWP (which is often used as an analog for future warming) and NHG. © 2020 Elsevier B.V.
2602.
Planktonic diatom counts from Lake Ohrid core ICDP5045-1 (DEEP)
PANGAEA
2021
Abstract: ▾ In 2013 a coring campaign was carried out as part of the project Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) and under the umbrella of the International Continental Scientific Drilling Program (ICDP). A 584 m sediment succession was retrieved from the central part (DEEP site) of ancient Lake Ohrid at a water depth of 243 m. The upper 446.65 mcd that represent the entire lacustrine history back to ca. 1.363 Ma contain a remarkably well-preserved record, especially of planktonic diatoms. We here present the count data of planktonic diatoms from core ICDP5045-1 spanning the period from 1.363 Ma until present. Diatom count data were generated from 350 sediment samples taken at a temporal resolution of 2.0{\textendash}4.0 ka and each slide was analysed across random transects to count 200{\textendash}400 diatom valves.
2601.
Pressure, temperature and lithological dependence of seismic and magnetic susceptibility anisotropy in amphibolites and gneisses from the central Scandinavian Caledonides
Tectonophysics,
820229113
2021
ISSN: 0040-1951Keywords:▾
Amphibolite, Anisotropy of magnetic susceptibility, Gneiss, Petrophysics, Scandinavian Caledonites, Seismic anisotropy
Abstract: ▾ As a petrofabric indicator, anisotropy of magnetic susceptibility (AMS) can potentially be used to infer seismic properties of rocks, and in particular seismic anisotropy. To evaluate the link between AMS and seismic anisotropy we present laboratory measurements of elastic wave velocities and anisotropy of magnetic susceptibility (AMS) for eight samples from the deep drilling investigation forming a part of the Collisional Orogeny in the Scandinavian Caledonides (COSC) project. The samples consist of a representative suite of mid crustal, deformed rock types, namely felsic and biotite-rich gneisses, and amphibolites (mafic gneisses). Compressional (P) and shear (S) waves were measured at confining pressures from room pressure to 600 MPa and temperature from room condition to 600 °C. Seismic anisotropy changes with increasing temperature and pressure, where the effect of pressure is more significant than temperature. Increasing pressure, considering the range of samples, results in an increase in mean wave speed values from 4.52 to 7.86 km/s for P waves and from 2.75 to 4.09 km/s for S waves. Biotite gneiss and amphibolite exhibit the highest anisotropy with P wave anisotropy (AVp) in the ranges of {\textasciitilde}9% to {\textasciitilde}20%, and maximum S- wave anisotropy exceeds 10%. In contrast, Felsic gneisses are significantly less anisotropic, with AVp of {\textless}7% and AVs of {\textless}6%. Up to 20% anisotropy may be generated by microcracks at 600 MPa and 600 °C, which is likely originating from thermal expansion of anisotropic minerals. An agreement is found between AMS and seismic anisotropy, although this is only a case if mean magnetic susceptibility (kmean) ranges between {\textasciitilde}1 × 10−5 to {\textasciitilde}1 × 10−3 [SI]. Such kmean values are common in rocks dominated by paramagnetic matrix minerals. Based on our results we propose that such samples are the most likely to be useful for the prediction of seismic anisotropy based on their AMS.
2600.
2599.
Provenance and paleogeography of Archean Fig Tree siliciclastic rocks in the East-Central Barberton Greenstone Belt, South Africa
Precambrian Research,
354
2021
2598.
Review of recent drilling projects in unconventional geothermal resources at campi flegrei caldera, cornubian batholith and williston sedimentary basin
Energies,
14
(11)
2021
ISSN: 19961073
Publisher: MDPI AG
Keywords:▾
Geothermal fields; Geothermal power plants; Renewable energy resources; Resource valuation; Trees (mathematics); Communication strategy; Energy development; Energy productions; Extensional faulting; Geothermal resources; Power generation from renewable; Scientific drilling; Unconventional resources; Infill drilling
Abstract: ▾ Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources are already used. Three recent drilling experiences focused on the characterization of unconventional resources are described and compared: the Campi Flegrei Deep Drilling Project (CFDDP) in Italy, the United Downs Deep Geothermal Power (UDDGP) project in the United Kingdom, and the DEEP Earth Energy Production in Canada. The main aspects of each project are described (geology, drilling, data collection, communication strategies) and compared to discuss challenges encountered at the tree sites considered, including a scientific drilling project (CFDDP) and two industrial ones (UDDGP and DEEP). The first project, at the first stage of pilot hole, although not reaching deep supercritical targets, showed extremely high, very rare thermal gradients even at shallow depths. Although each project has its own history, as well as social and economic context, the lessons learned at each drilling site can be used to further facilitate geothermal energy development. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
2597.
Quaternary environmental changes in tropical Lake Towuti, Indonesia, inferred from end-member modelling of X-ray fluorescence core-scanning data
Journal of Quaternary Science,
36
(6)
1040 – 1051
2021
ISSN: 02678179
Publisher: John Wiley and Sons Ltd
DOI:10.1002/jqs.3338
Keywords:▾
Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; data set; depositional environment; environmental change; geochemistry; marine sediment; Quaternary; sediment analysis; sediment transport; X-ray fluorescence
Abstract: ▾ Continental and marine sediments are composed of a mixture from different sources and are influenced by a variety of environmental factors and transport processes prior to deposition. For analysis and interpretation, these sources and processes are often challenging to disentangle. We show that end-member modelling of X-ray fluorescence (XRF) core-scanning data helps to overcome these challenges by unmixing different environmental signals from high-resolution sediment geochemical records. We apply this approach to a 100 m long lacustrine succession from Lake Towuti, Indonesia, to separate the regional climate and tectonic history from local ecological and diagenetic processes. The resulting six end-members (EMs) are interpreted to represent changes in ecological (EM1), climatic (EMs 2–4), tectonic (EM 5) and geomorphic (EM6) processes determining changes in sediment composition. Because end-member analysis allows for the tracking of transient and overlapping processes, climatic changes can be followed throughout the 100 m-long succession, suggesting alternating wet and dry periods in Central Sulawesi over long (several 100 000 years) time scales. We show that end-member analysis on elemental data sets offers a detailed and objective means to disentangle depositional processes in sedimentary successions resulting from varying tectonic and environmental factors involved in sediment formation and deposition. © 2021 John Wiley & Sons, Ltd.
2596.
Rapid alteration of fractured volcanic conduits beneath Mt Unzen
Bulletin of Volcanology,
83
(5)
2021
ISSN: 02588900
Publisher: Springer Science and Business Media Deutschland GmbH
Keywords:▾
clay mineral; dike; emplacement; hydrothermal alteration; lava dome; permeability; porosity; volcanic arc; volcanic eruption, Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano
Abstract: ▾ The nature of sub-volcanic alteration is usually only observable after erosion and exhumation at old inactive volcanoes, via geochemical changes in hydrothermal fluids sampled at the surface, via relatively low-resolution geophysical methods or can be inferred from erupted products. These methods are spatially or temporally removed from the real subsurface and thus provide only indirect information. In contrast, the ICDP deep drilling of the Mt Unzen volcano subsurface affords a snapshot into the in situ interaction between the dacitic dykes that fed dome-forming eruptions and the sub-volcanic hydrothermal system, where the most recent lava dome eruption occurred between 1990 and 1995. Here, we analyse drill core samples from hole USDP-4, constraining their degree and type of alteration. We identify and characterize two clay alteration stages: (1) an unusual argillic alteration infill of fractured or partially dissolved plagioclase and hornblende phenocryst domains with kaolinite and Reichweite 1 illite (70)-smectite and (2) propylitic alteration of amphibole and biotite phenocrysts with the fracture-hosted precipitation of chlorite, sulfide and carbonate minerals. These observations imply that the early clay-forming fluid was acidic and probably had a magmatic component, which is indicated for the fluids related to the second chlorite-carbonate stage by our stable carbon and oxygen isotope data. The porosity in the dyke samples is dominantly fracture-hosted, and fracture-filling mineralization is common, suggesting that the dykes were fractured during magma transport, emplacement and cooling, and that subsequent permeable circulation of hydrothermal fluids led to pore clogging and potential partial sealing of the pore network on a timescale of ~ 9 years from cessation of the last eruption. These observations, in concert with evidence that intermediate, crystal-bearing magmas are susceptible to fracturing during ascent and emplacement, lead us to suggest that arc volcanoes enclosed in highly fractured country rock are susceptible to rapid hydrothermal circulation and alteration, with implications for the development of fluid flow, mineralization, stress regime and volcanic edifice structural stability. We explore these possibilities in the context of alteration at other similar volcanoes. © 2021, The Author(s).
2595.
Reconstructing two millennia of copper and silver metallurgy in the Lake Titicaca region (Bolivia/Peru) using trace metals and lead isotopic composition
Anthropocene,
34
2021
Keywords:▾
South America; copper; extraction method; isotopic composition; lacustrine deposit; lead isotope; silver; trace metal
Abstract: ▾ Copper, silver, and gold exploitation has been a foundation of economic and socio-cultural development of Andean societies, at least for the last three millennia. The main centers of pre-colonial metallurgy are well-known from archeological artifacts, but temporal gaps inherent in this record handicap a finer understanding of the modalities of ore exploitation by succeeding civilizations. A continuous record over time of trace metals emitted during ore smelting operations make lake sediments excellent candidates to fill those gaps. Two millennia of metallurgy were reconstructed from atmospherically derived metals together with lead (Pb) isotope ratios in two dated sediment cores from Lake Titicaca. The first evidence for metallurgy is found during the apogee of the Tiwanaku state (AD 800–1150), with a higher copper (Cu) accumulation that can be attributed to the smelting of local Cu ores, based on Pb isotopic fingerprinting. During the Late Intermediate Period (AD 1150–1450), recorded peaks in metal deposition that persisted for ∼ twenty years show that mining activities were intensive but discontinuous. Pb isotope ratios suggest diversified extractive activities, mainly located in the southern part of the central Altiplano. Finally, the most intense mining epoch began during the Inca Empire (ca. AD 1500) and lasted until the end of the Colonial Period (AD 1830), with unprecedented metal deposition over this interval. Pb isotope fingerprinting shows that mining operations occurred mainly in the Lake Titicaca and Potosi areas and were responsible for metal emissions recorded in the entire Altiplano, as evidenced by other studies. © 2021 Elsevier Ltd