All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
2784.
Deciphering the tectonometamorphic history of subducted metapelites using quartz-in-garnet and Ti-in-quartz (QuiG-TiQ) geothermobarometry—A key for understanding burial in the Scandinavian Caledonides
Journal of Metamorphic Geology,
n/a
(n/a)
2023
ISSN: 1525-1314Keywords:▾
40Ar/39Ar dating, Scandinavian Caledonides, P–T–D–t evolution, quartz-in-garnet, Ti-in-quartz thermobarometry
Abstract: ▾ The Seve Nappe Complex is a subduction-related high-grade metamorphic unit that was emplaced onto the margin of Baltica during Caledonian orogenesis. In this paper, the tectonometamorphic evolution of the Lower Seve Nappe in the Scandinavian Caledonides was characterized with the help of the continuous Collisional Orogeny in the Scandinavian Caledonides (COSC-1) drill core, using a combination of various P–T estimation techniques based on garnet–quartz mineral pairs (quartz-in-garnet and Ti-in-quartz [QuiG–TiQ]), conventional thermobarometry and thermodynamic modelling of phase equilibria. This multi-method approach yields complementary results and delivers critical data to constrain a comprehensive pressure–temperature–deformation–time (P–T–D–t) evolutionary path for the metasedimentary rocks of the Lower Seve Nappe. In the garnetiferous metasedimentary rocks, quartz inclusions in garnet preserve the P–T conditions of three distinct garnet growth stages corresponding to three metamorphic stages Ms1 to Ms3, including prograde and peak metamorphic conditions. Ms1 and Ms2 stages were constrained via quartz inclusions in garnet core and mantle. They are relatively close in the P–T space and could be considered as one single continuous prograde event occurring at epidote–amphibolite facies conditions of 460–520°C and 0.6–0.85 GPa. The growth of the garnet outermost rim defines the Ms3 stage at amphibolite facies conditions of 590–610°C and 1.13–1.18 GPa and corresponds to the peak metamorphic conditions. The microstructural analysis shows that the finite ductile strain pattern of the Lower Seve Nappe results from the superposition of four deformation phases. The initial phase D1 is defined by the S1 foliation that is still preserved as a curved inclusion trail in the garnet core. The D2 phase initiated contemporaneously with garnet core growth and the development of muscovite–biotite–plagioclase S2 foliation. Garnet outermost rim growth marks the end of the prograde path and peak metamorphic conditions. This stage is overprinted by the D3 phase and Ms4 stage associated with the development of the main regional metamorphic and mylonitic fabric S3 associated with C′-type shear bands along the retrograde path. Ms4 stage, which was constrained using traditional thermobarometric techniques, corresponds to the chemical re-equilibration of the metasedimentary minerals and occurred under amphibolite facies conditions at 570–610°C and 0.78–1.00 GPa. The D3 phase is then generally weakly to strongly overprinted by later lower grade deformation D4 phase at greenschist facies conditions (Ms5). 40Ar/39Ar ages of syn-kinematic white mica and biotite indicate that the final stage of the thrusting of the Lower Seve Nappe and thus the timing of its emplacement onto the Offerdal Nappe occurred at c. 423 Ma. Collectively, these results are consistent with previous estimates of the timing and conditions of metamorphism derived from the Lower Seve Nappe especially in west-central Jämtland. However, application of QuiG–TiQ thermobarometry demonstrated that quartz inclusions in garnet can preserve different aspects of garnet growth, which are not accessible by traditional methods especially in complex terranes, and therefore provided new significant insights into the Lower Seve prograde evolution.
2783.
Cross-Property Relationship Between Electrical Resistivity and Elastic
Wave Velocity of Crustal Rocks From the Oman Drilling Project Hole GT3A:
Implications for in Situ Geophysical Properties of Oceanic Crust
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,
128
(6)
2023
Keywords:▾
electrical resistivity; elastic wave velocity; oceanic crust; crack;
Oman drilling Project; IODP hole 1256D
2782.
Country-wide exploration for graphite- and sulphide-rich black shales with airborne geophysics and petrophysical and geochemical studies
Journal of Geochemical Exploration,
244
2023
ISSN: 03756742
Publisher: Elsevier B.V.
Keywords:▾
Core drilling; Deposits; Electric conductivity; Geological surveys; Geophysics; Graphite; Infill drilling; Magnetic susceptibility; Oil shale; Sampling; Stratigraphy; Airborne geophysics; Black shales; Ferrimagnetics; Finland; Geophysical measurements; Greenschist; Monoclinics; Sample sets; Sulphide; Sulphide deposits; graphite; host rock; hydrocarbon exploration; hydrocarbon generation; petrography; shale; sulfide; Sulfur compounds
Abstract: ▾ Black shales host critical raw materials such as graphite and cobalt and occur in the vicinity of many types of sulphide deposits. We report the procedure for country-wide mapping of graphite- and sulphide-rich rocks and the chemical and petrophysical data of 319 samples we selected from sulphide occurrences and mines in Finland. Even though black shales are rarely outcropped in glaciated and deeply weathered terrains, they can be traced with geophysical surveys. In the Precambrian of Finland, where the metamorphic grade varies from greenschist to granulite facies, systematic airborne geophysical surveys revealed stratigraphy-related, coupled magnetic and electrically conductive patterns. Electrical conductivity was related to the graphite and sulphide contents, producing continuous and bending electromagnetic anomaly patterns. The magnetic anomalies, if present, resulted from ferrimagnetic monoclinic pyrrhotite. The petrophysical properties of black shales varied in our sample set. The densities were mainly between 2700 and 3000 kg/m3, with the mean density ~ 2800 kg/m3, where the amount of graphite had a reducing effect on density whereas sulphides increased it. The average magnetic susceptibilities were about 6000·10−6 (SI), but they showed wide variation, depending on the abundance of ferrimagnetic monoclinic pyrrhotite. The electrical conductivity of black shales appeared to be positively related to the abundance of monoclinic pyrrhotite. Conductivity variation, 1–105 1/Ωm was based on laboratory determinations of apparent resistivities. We correlated an airborne magnetic and electromagnetic survey with petrophysical and chemical data from altogether 319 drill core samples containing >1 % graphitic C and >1 % S. The samples were selected during 2009–2011 from 102 drill cores all over Finland except for the Talvivaara–Outokumpu region, which was studied during previous projects. The black-shale-hosted Talvivaara Ni–Zn–Co–Cu deposit is currently being mined. The maximum graphite concentration in the country-wide sample set was 34.3 %, and the median value was 5.7 %, a lower value than reported from the Talvivaara black-shale-hosted sulphide deposit (7.6 %). S, Co, Cu, Fe and Ni concentrations were also lower in our sample set on average than in the Talvivaara ore. However, the maximum concentration in our sample set was 397 mg/kg for Co, 0.36 % for Cu, 40.8 % for Fe and 0.28 % for Ni. The developed black shale mapping procedure can be directly applied in other parts of the world in terrains with greenschist to granulite facies regional metamorphism. Information on basic petrophysical properties, i.e., density, magnetic and electric properties, are needed to explain geophysical anomalies. If the metamorphic grade is lower than greenschist facies and there is no graphite, sulphides will increase the electromagnetic properties. If ferrimagnetic pyrrhotite exists, susceptibility increases, as well as remanence. The black shale database covering the whole of Finland is used not only in exploration and bedrock mapping, but also in regional planning and for environmental risk analyses, because sulphide-rich black shales may cause acid rock drainage when exposed to weathering and the quality of surface water and groundwater may suffer from black shale bedrock and glacial till. The scale limitations given by airborne geophysics may request detailed studies in selected sites. © 2022 The Author(s)
2781.
Continental geological evidence for Solar System chaotic behavior in the Late Cretaceous
Bulletin of the Geological Society of America,
135
(3-4)
712 – 724
2023
ISSN: 00167606
Publisher: Geological Society of America
DOI:10.1130/B36340.1
Keywords:▾
China; Songliao Basin; Binary alloys; Earth (planet); Lead alloys; Orbits; Uranium alloys; Chaotic behaviour; High resolution; Lacustrine sequence; Late cretaceous; Magnetic reversal; Milankovitch cycle; Orbital parameters; Songliao basin; System solution; U-Pb ages; age determination; chaotic dynamics; Cretaceous; Earth; Mars; reconstruction; solar cycle; solar system; stratigraphy; uranium-lead dating; Stratigraphy
Abstract: ▾ The Earth’s geologic record of Milankovitch cycles closely tracks Solar System solutions for the past 50 million years. Prior to 50 million years ago (Ma), however, the solutions lose accuracy rapidly due to chaotic behavior of the Solar System. Here we reconstruct a 10.173 million year-long record from 82.358 Ma to 92.531 Ma of Earth’s orbital parameters from a continental lacustrine sequence in the Songliao Basin, China, constrained by four in situ high-resolution radioisotopic U-Pb ages and magnetic reversal stratigraphy. Analysis of thorium and ostracode shell abundance records from the Songliao Basin reveal evidence for two chaotic secular resonance transitions in the orbital motions of Earth and Mars from 85.2 Ma to 91.55 Ma. The evidence validates similar observations in western North American marine stratigraphy. A unique phasing between the observed orbital eccentricity and obliquity modulations may explain the anoxic events that occurred in both marine and continental environments during this time. Taken together, the continental and marine stratigraphic evidence demonstrates a strong global reach of Late Cretaceous Milankovitch cycles, and provides an important constraint on Solar System chaoticity and the calculation of accurate orbital solutions prior to 50 Ma. © 2022 Geological Society of America
2780.
Constraints on the Nd-isotopic composition and nature of the last major influx of magma into the Bushveld Complex
Contributions to Mineralogy and Petrology,
178
(3)
14
2023
2779.
Boron geochemistry reveals the evolution of Dead Sea brines
Earth and Planetary Science Letters,
622
2023
Keywords:▾
Budget control; Glacial geology; Infill drilling; Isotopes; Lakes; Seawater; Authigenic; Boron cycle; Boron isotope budget; Boron isotopes; Lacustrine authigenic aragonite; Pleistocene; Pleistocene lake lisan; Pliocene; Pliocene sedom lagoon; Seawater evolution; aragonite; authigenic mineral; boron; brine; concentration (composition); geochemistry; lacustrine environment; seawater; Boron
Abstract: ▾ Well-known for their geological and natural singularity, the Dead Sea brines evolved from a marine ingression of the Mediterranean during the Pliocene. Dead Sea brines are currently almost ten times more concentrated than seawater and have a unique chemical composition with high boron isotope values (δ11Bbrine = ∼57‰). However, little is known on how these values were attained and their underlaying driving processes. Here we use boron isotopes (δ11B) combined with B/Ca and B/Li of lacustrine authigenic aragonites from the deep basin drill-core ICDP 5017-1, and Ein Gedi and Masada profiles to reconstruct past brine conditions. Comparing reconstructed δ11Bbrine from two key periods of contrasting hydro-climatic regimes we find that the brines of the late Holocene Dead Sea were enriched in 11B (δ11Bbrine = ∼60‰) relative to its glacial precursor Lake Lisan (∼57‰). With the aid of boron cycle modelling, we quantify the main boron fluxes in the basin. We show that the post-glacial δ11Bbrine enrichment is best explained by overall reduction of freshwater inflow to the lake and coeval increase in 10B sink through boron co-precipitation in evaporitic deposits and boron loss in atmospheric water vapour, consistent with the onset of warmer and drier climate in the Eastern Mediterranean during the Holocene. On geological time scales, adsorption of 10B on clastic sediments has acted as an important 10B sink and can explain the evolution of the high δ11Bbrine values. © 2023 The Author(s)
2778.
Eastward extension of the Solonker Suture beneath the central Songliao Basin, NE China: Evidence from a deep seismic reflection profile
Gondwana Research,
119164 – 171
2023
2777.
Bayesian seismic travel-time cross-hole tomography in vertically transversely isotropic media
Journal of Applied Geophysics,
209
2023
ISSN: 09269851
Publisher: Elsevier B.V.
Keywords:▾
Gas hydrates; Markov processes; Monte Carlo methods; Recovery; Seismology; Uncertainty analysis, Algorithm approaches; Bayesian; Cross hole; Finite difference; Markov chain monte carlo samplings; Monte carlo; Monte carlo sampling algorithms; Seismic; Transversal isotropy; Transversely isotropic medias, Anisotropy, algorithm; Bayesian analysis; data inversion; data set; finite difference method; gas hydrate; Markov chain; model test; Monte Carlo analysis; seismic tomography; seismic velocity; seismic wave; transverse isotropy; travel time
Abstract: ▾ We apply a transdimensional, hierarchical Markov chain Monte Carlo sampling algorithm (McMC) for 2-D cross-hole travel-time tomography in transversely isotropic media with vertical symmetry axis. The McMC approach has several advantages compared to classical inversion approaches: It is a global search, the high number of tested models allows the statistical analysis including the calculation of a reference model as well as uncertainty estimation, no initial models or regularization parameters are needed, the amount of data noise is automatically determined, and the model parametrization is data dependent and self-adjusting. For the forward solution a FD Fast Marching method utilizing second-order Godunov schemes is used. The performance of the approach is first tested on synthetic datasets to evaluate the potential and possible limitation to recover anisotropic models. We have shown that the recovery of models described by 2 anisotropic parameters (Thomsen parameters) and the vertical velocity is possible for observation scenarios with good distribution of sources and receivers. For more realistic observational geometries (i.e. cross-hole experiments), the recovery of the 3 parameters is limited, but still possible for example for the elliptical anisotropic case (ε = δ) or regarding the horizontal velocity. Finally we applied the McMC approach to a well-studied real cross-hole data set from the MALLIK 2002 research program and compared the results with previous conventional inversions. © 2022
2776.
Authigenic minerals reflect microbial control on pore waters in a
ferruginous analogue
GEOCHEMICAL PERSPECTIVES LETTERS,
2820-26
2023
2775.
Authigenic mineralization in Surtsey basaltic tuff deposits at 50 years
after eruption
SCIENTIFIC REPORTS,
13
(1)
2023
2774.
Application of improved support vector machine in geochemical lithology identification
Earth Science Informatics,
16
(1)
205 – 220
2023
ISSN: 18650473
Publisher: Springer Science and Business Media Deutschland GmbH
Keywords:▾
China; Songliao Basin; geochemical method; identification method; lithology; logging (geophysics); machine learning; support vector machine; weight
Abstract: ▾ Lithology identification is an important task in oil and gas exploration. In recent years, machine learning methods have become a powerful tool for intelligent lithology identification. To address the redundancy of conventional logging data and unbalanced distribution among formation lithology classes due to the complexity of depositional environment and inhomogeneity of subsurface space, this paper investigates the affiliation-weighted one-to-one support vector machine (WOVOSVM) lithology identification method based on geochemical logging data. This method uses geochemical logging data, which can directly reflect the formation lithology information, as input, and achieves intelligent and accurate lithology classification under the calculation of WOVOSVM. In this study, Shahezi Formation of Songke 2 Well in Songliao Basin, China is taken as the experimental object, and two data sets with different distribution characteristics are selected as the input. Use WOVOSVM, Adaboost, random forest (RF) and traditional support vector machine (SVM) to identify lithology, and compare and analyze the results. The results are as follows: (1) Accuracy metrics of most of the four classification models were above 60%, indicating the geochemical logging data can effectively reflect the formation lithology information, which is a reliable indicator for the intelligent identification of logging lithology. (2) When the data set has a strong imbalance, the lithology recognition performance of WOVOSVM is better than other methods, the average value of accuracy metrics is more than 72%, F1 value is 8.77% to 14.56% higher than other models, especially in the small sample lithology category recognition, 70% of the samples are correctly classified. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
2773.
A one-million-year isotope record from siderites formed in modern ferruginous sediments
Bulletin of the Geological Society of America,
135
(1-2)
504 – 522
2023
ISSN: 00167606
Publisher: Geological Society of America
DOI:10.1130/B36211.1
Keywords:▾
Greater Sunda Islands; Lake Towuti; Malili Lakes; South Sulawesi; Sulawesi; Sunda Isles; Biogeochemistry; Deposition; Geology; Iron; Iron ores; Isotopes; Organic compounds; Oxygen; Sediments; Water; Biogenics; Bottom water; Diagenetics; Geological timescales; Iron isotopes; Isotope record; Isotope signatures; Pore waters; Water columns; δ13C; carbon isotope; depositional environment; iron; isotopic composition; oxygen; oxygenation; Precambrian; sediment chemistry; sediment-water interface; siderite; Lakes
Abstract: ▾ Ancient iron formations hold important records of environmental conditions during the Precambrian eons. Reconstructions of past oceanic systems require investigation of modern ferruginous analogs to disentangle water column and diagenetic signals recorded in iron-bearing minerals. We analyzed oxygen, iron, and carbon isotopes in siderite, a ferrous carbonate phase commonly used as an environmental proxy, from a 100-m-long record spanning a 1 Ma depositional history in ferruginous Lake Towuti, Indonesia. Combining bulk sediment and pore water geochemistry, we traced processes controlling siderite isotope signatures. We show that siderite oxygen isotope compositions (δ18O) reflect in-lake hydrological and depositional conditions. Low iron isotope values (δ56Fe) record water column oxygenation events over geological timescales, with minor diagenetic partitioning of Fe isotopes by microbial iron reduction after deposition. The carbon isotope compositions (δ13C) reflect the incorporation of biogenic HCO3 –, which is consistent with sediment organic matter remineralization lasting over ca. 200 ka after burial. Positive δ13C excursions indicate an increased production of biogenic methane that escaped the sediment during low lake levels. Diffusion across the sediment–water interface during initial formation of siderites tends to align the isotope signatures of bottom waters to those of pore waters. As microbial reduction of ferric iron and oxidation of organic matter proceed and saturate pore water conditions with respect to siderite, overgrowth on nuclei partially mutes the environmental signal inherited from past bottom waters over ca. 1 Ma. Because high depositional fluxes of ferric iron and organic matter in early oceans would have promoted similar microbial processes in ferruginous deposits prior to lithification, the environmental record contained in siderite grains can successively integrate depositional and early diagenetic signals over short geological timescales. © 2022 Geological Society of America
2772.
A neotropical perspective on the uniqueness of the Holocene among interglacials
Nature Communications,
14
(1)
2023
2771.
3-D imaging of the Balmuccia peridotite body (Ivrea-Verbano zone,
NW-Italy) using controlled source seismic data
GEOPHYSICAL JOURNAL INTERNATIONAL,
234
(3)
1985-1998
2023
Keywords:▾
Europe; Controlled source seismology; Seismic tomography; Continental
tectonics: compressional; Crustal structure
2770.
Millennial hydrological variability in the continental northern Neotropics during Marine Isotope Stages (MISs) 3-2 (59-15 cal ka BP) inferred from sediments of Lake Petén Itzá, Guatemala
Climate of the Past,
19
(7)
1409 – 1434
2023
Keywords:▾
Atlantic Ocean; Atlantic Ocean (Tropical); Guatemala [Central America]; Lake Peten Itza; Pacific Ocean; Pacific Ocean (Equatorial); Peten; Atlantic Multidecadal Oscillation; atmospheric convection; climate conditions; climate variation; hydrological change; intertropical convergence zone; lacustrine deposit; marine isotope stage; Neotropical Region; overturn; paleoclimate; primary production; redox conditions; sediment core
Abstract: ▾ Lake Petén Itzá (Guatemala) possesses one of the longest lacustrine sediment records in the northern Neotropics, which enabled study of paleoclimate variability in the region during the last ∼400000 years. We used geochemical (Ti, Ca/(Ti+Fe) and Mn/Fe) and mineralogical (carbonates, gypsum, quartz, clay) data from sediment core PI-2 to infer past changes in runoff, lake evaporation, organic matter sources and redox conditions in the water column, caused by hydrological changes in the northern Neotropics during Marine Isotope Stages (MISs) 3-2. From 59 to 39 cal ka BP climate conditions were relatively wet, and the lake was marked by higher primary productivity and anoxic bottom waters. This wet environment was interrupted for two periods of possible low water level at 52 and 46 cal ka BP, when our data suggest higher evaporation, high terrestrial organic matter input and persistent oxic conditions. Between 39 and 23 cal ka BP, evaporation and input of terrestrial organic matter increased considerably, lake level declined, and lake bottom waters generally became oxic. These conditions reversed during the Last Glacial Maximum (23.5-18.0 cal ka BP), when runoff and lake productivity increased, and rising lake level caused bottom waters to again become anoxic. Comparison of our hydrologic proxy data with sea surface temperature anomalies between the eastern Pacific and the Caribbean suggests that changes in the intensity of the Caribbean Low-Level Jet (CLLJ) may have influenced long-term changes in runoff during MISs 3-2. Higher intensity of the CLLJ during the onset of MIS 3 and the LGM might have led to greater runoff into the lake, whereas the MIS 3-2 transition experienced a weaker CLLJ and consequently less runoff. A refined, high-resolution age-depth model for the PI-2 sediment core enabled us to identify millennial-scale Greenland interstadials (GIs) 14-2, Greenland stadials (GSs) 14-2 and Heinrich stadials (HSs) 5-1. In general, HSs and GSs were characterized by drier conditions. In contrast to GSs and HSs, GIs were characterized by greater runoff and overall wetter conditions, with the most pronounced GI peaks between 40 and 30 cal ka BP. Whereas GSs 9, 8, 7 and 6 began with abrupt increases in evaporation and ended with gradual increases in humidity, GSs 11 and 10 showed reversed patterns. The Lake Petén Itzá paleohydrology record, along with other regional paleoclimate records, led us to conclude that shifts in the position of the Intertropical Convergence Zone (ITCZ) altered moisture delivery to the lake on millennial timescales. During GSs and HSs, high evaporation from Petén Itzá (dry climate conditions) was associated with a more southerly position of the ITCZ, whereas wetter GIs prevailed during a more northerly ITCZ position. Although abrupt millennial-scale shifts in ITCZ and hydroclimate between GSs/HSs and GIs can be linked to instabilities in the Atlantic Meridional Overturning Circulation (AMOC), longer-term changes were additionally influenced by changes in atmospheric convection linked to modulations of the CLLJ in response to ΔSST between the equatorial Pacific and tropical Atlantic. © 2023 Rodrigo Martínez-Abarca et al.
2769.
Early Diagenesis in the Lacustrine Ostracods from the Songliao Basin 91.35 Million Years Ago and Its Geological Implications
Minerals,
13
(1)
2023
2768.
An astronomical time scale for the Early Cretaceous continental strata in the Songliao Basin, Northeastern China (in Chinese with English abstract); [松辽盆地松科2井早白垩世沙河子组天文年代标尺]
Quaternary Sciences,
43
(6)
1573-1583
2023
2767.
Effect of Pressure Perturbations on CO2 Degassing in a Mofette System: The Case of Hartoušov, Czech Republic
Geosciences (Switzerland),
13
(1)
2023
ISSN: 20763263
Publisher: MDPI
Abstract: ▾ Mofettes are gas emission sites where high concentrations of CO2 ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of the Eger Graben, is a key site to study interactions between fluids and swarm earthquakes. The mofette field (10 mofettes within an area of 100 m × 500 m and three wells of 28, 108, and 239 m depth) is characterized by high CO2 emission rates (up to 100 t/d) and helium signatures with (3He/4He)c up to 5.8 Ra, indicating mantle origin. We compiled geological, geophysical, geochemical, and isotopic data to describe the mofette system. Fluids in the Cheb basin are mixtures between shallow groundwater and brine (>40 g/L at a depth of 235 m) located at the deepest parts of the basin fillings. Overpressured CO2-rich mineral waters are trapped below the mudstones and clays of the sealing Cypris formation. Drilling through this sealing layer led to blow-outs in different compartments of the basin. Pressure transients were observed related to natural disturbances as well as human activities. External (rain) and internal (earthquakes) events can cause pressure transients in the fluid system within hours or several days, lasting from days to years and leading to changes in gas flux rates. The 2014 earthquake swarm triggered an estimated excess release of 175,000 tons of CO2 during the following four years. Pressure oscillations were observed at a wellhead lasting 24 h with increasing amplitudes (from 10 to 40 kPa) and increasing frequencies reaching five cycles per hour. These oscillations are described for the first time as a potential natural analog to a two-phase pipe–relief valve system known from industrial applications. © 2022 by the authors.
2766.
In-situ physical and elastic properties of Archaean basement granitoids
in the Koyna seismogenic zone, western India from 3 km downhole
geophysical well logs: Implications for water percolation at depth
TECTONOPHYSICS,
848
2023
Keywords:▾
Fault zone; Downhole geophysical logs; Recurrent earthquakes; Scientific
drilling; Koyna; India
2765.
Milankovitch cycle identification of Denglouku Formation
in Songliao Basin and its paleoclimate significance (in Chinese with English abstract); [松科3井下白垩统登娄库组米兰科维奇旋回识别及其古气候意义]
Sedimentary Geology and Tethyan Geology
2023
2764.
Enrichment of rare methanogenic Archaea shows their important ecological role in natural high-CO2 terrestrial subsurface environments
Frontiers in Microbiology,
14
2023
2763.
Magmatism during the continent - ocean transition
EARTH AND PLANETARY SCIENCE LETTERS,
614
2023
Keywords:▾
rifting; East Africa; Afar Stratoid Series; magmatism
2762.
Joint passive seismic imaging based on surface wave inversion and reflection wavefield retrieval: A case study in the sedimentary basin areas adjacent to Well Songke-2
Journal of Applied Geophysics,
208
2023
ISSN: 09269851
Publisher: Elsevier B.V.
Keywords:▾
China; Songliao Basin; Acoustic noise; Cost effectiveness; Sedimentology; Seismic prospecting; Seismic response; Shear waves; Signal to noise ratio; Surface waves; Underground structures; Wave energy conversion; Wave propagation; Ambient noise; Ambient noise seismic interferometry; Geological interpretation; High-mode surface wave inversion; Higher mode; Sedimentary basin; Sedimentary basin geological interpretation; Seismic interferometries; Songliao basin; Surface wave inversion; Well songke-2; ambient noise; sedimentary basin; seismic reflection; seismic wave; surface wave; wave field; Seismic waves
Abstract: ▾ Owing to their cost-effectiveness, environmental friendliness, and high-efficiency, passive seismic methods are widely used in geophysical exploration. However, field passive seismic data suffer from low signal-to-noise ratio, as well as the fact that different types of seismic waves are naturally mixed together, which can affect the accuracy of subsurface imaging results and the subsequent geological interpretation. In this paper, we demonstrate that these problems can be addressed and present a case study on passive seismic detection in sedimentary basin areas adjacent to Well Songke-2 in Songliao Basin. To obtain accurate and reliable imaging results of the sedimentary strata, a detailed practical scheme is proposed, where fundamental and higher mode surface wave dispersion curves are inverted for obtaining the near-surface S-wave velocity profile, and the body wave component of ambient noise is utilized to retrieve the reflection wavefield information. The obtained profiles from surface wave inversion and reflection wavefield retrieval illustrate similar underground structures. The marker boundaries T2 (1.5 s) and T4 (2.1 s) are well demonstrated, and a low velocity stratum (0.4 s) is detected at a shallow depth of around 400–600 m. Further, the results are highly consistent with the data obtained from borehole logging of Well Songke-2 and the deep reflection seismic profile adjacent to this area, which indicates that the surface wave and body wave in passive seismic data can be utilized together to contribute to a detailed and accurate subsurface imaging and interpretation. Overall, this study investigated and validated the reliability and accuracy of the combination use of passive seismic methods for geological structure exploration, which can further boost their applications for geological interpretation in sedimentary basin areas. © 2022 Elsevier B.V.
2761.
Iron-mediated anaerobic ammonium oxidation recorded in the early Archean
ferruginous ocean
GEOBIOLOGY,
21
(3)
277-289
2023
Keywords:▾
ammonium oxidation; biogeochemistry; Buck Reef Chert; Feammox;
ferruginous ocean; nitrogen isotopes; Paleoarchean
Abstract: ▾ The nitrogen isotopic composition of organic matter is controlled by metabolic activity and redox speciation and has therefore largely been used to uncover the early evolution of life and ocean oxygenation. Specifically, positive delta N-15 values found in well-preserved sedimentary rocks are often interpreted as reflecting the stability of a nitrate pool sustained by water column partial oxygenation. This study adds much-needed data to the sparse Paleoarchean record, providing carbon and nitrogen concentrations and isotopic compositions for more than fifty samples from the 3.4 Ga Buck Reef Chert sedimentary deposit (BRC, Barberton Greenstone Belt). In the overall anoxic and ferruginous conditions of the BRC depositional environment, these samples yield positive delta N-15 values up to +6.1% . We argue that without a stable pool of nitrates, these values are best explained by non-quantitative oxidation of ammonium via the Feammox pathway, a metabolic co-cycling between iron and nitrogen through the oxidation of ammonium in the presence of iron oxides. Our data contribute to the understanding of how the nitrogen cycle operated under reducing, anoxic, and ferruginous conditions, which are relevant to most of the Archean. Most importantly, they invite to carefully consider the meaning of positive delta N-15 signatures in Archean sediments.
2760.
Insights into organic metagenesis using Raman spectroscopy and high resolution mass spectrometry: A case study of the Shahezi formation, deep Songliao basin, China
International Journal of Coal Geology,
265
2023
ISSN: 01665162
Publisher: Elsevier B.V.
Keywords:▾
China; Songliao Basin; Aromatic compounds; Energy resources; Mass spectrometry; Organic lasers; Petroleum deposits; Raman spectroscopy; Reflection; Fourier transform ion cyclotron resonance mass spectrometry; Fourier-transform ion cyclotron resonance mass spectrometry; Laser Raman; Laser Raman spectroscopy; Maturity parameters; Raman parameters; Shahezi formations; Songliao basin; Source rocks; Vitrinite reflectance; Fourier transform; hydrocarbon resource; lithostratigraphy; mass spectrometry; organic compound; organic matter; Raman spectroscopy; source rock; vitrinite reflectance; Thermodynamic stability
Abstract: ▾ The maturity of sedimentary organic matter is a key parameter for evaluating oil and gas resources. Existing maturity indicators have different evaluation principles and application scopes. This study investigated samples of high to overmature lacustrine source rocks (Ro = 1.33%–4.24%) from the deep Shahezi formation in the Songliao basin, including the zone of catagenesis and metagenesis. Various methods, including vitrinite reflectance, Tmax, laser Raman spectroscopy, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to evaluate the samples' maturity. Through laser Raman analysis of representative samples from the Shahezi formation, most laser Raman parameters showed an inflection point or reversal when the thermal evolution of deep source rocks in the Shahezi formation reaches a certain stage. The variation trend of some Raman parameters and Ro has strong regularity (1.33% < Ro < 3.52%). Based on FT-ICR MS, this research analyzed the relative content and molecular composition of polycyclic and heterocyclic aromatic compounds in soluble organic matter of lake source rock samples and comparison samples (marine shale). Quantitative maturity evaluation of organic matter was performed by converting the signal intensity of each compound. The fitting results of maturity parameter based on FT-ICR MS and Tmax indicated that the maturity parameter of the samples have high coefficient of correlations with maturity in the vitrinite reflectance (Ro) range of 1.33%–2.5% and the Tmax range of 420 °C–600 °C. The maturity parameter values decreased as Ro exceeded 2.5% and Tmax exceeded 600 °C. These findings are attributed to the thermal stability of organic compounds and the formation of pyrobitumen and graphite. The parameters of laser Raman spectroscopy also confirmed the growth of aromatic rings reflected by the maturity parameters of FT-ICR MS. These two methods revealed the structural changes of organic matter in the thermal evolution process from multiple perspectives and provided insights for the maturity evaluation of deep source rocks. © 2022