Hasil untuk "Petrology"

F. Pettijohn, P. E. Potter, R. Siever

Z. Moser, M. Guillong, C. Nathwani et al.

<p>Quantifying timescales and establishing robust eruption chronologies is critical for understanding the evolution and hazards of volcanic systems. U-Th disequilibrium dating on zircon is especially valuable for young and active systems (<span class="inline-formula">&lt;</span> 300 ka). However, there is no consensus on how to calculate U-Th crystallization ages. To address this, we applied an optimized LA-ICP-MS U-Th-Pb double-dating strategy that simultaneously retrieves U-Th and U-Pb ages from the same zircon ablation volume. This dating routine increases confidence in crystallization ages across 150–300 ka, where the resolution of either dating technique alone is limited. We applied this strategy to the Kos Plateau Tuff, which spans this critical interval, and compared U-Th model age calculation approaches against the well-established U-Pb age calculations. U-Th model ages calculated using the two endmember approaches, either using a constant melt composition or a constant zircon-melt U <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="527256ea34e0af356380afd605ccefc0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-8-63-2026-ie00001.svg" width="8pt" height="14pt" src="gchron-8-63-2026-ie00001.png"/></svg:svg></span></span> Th fractionation factor (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>f</mi><mrow><mi mathvariant="normal">U</mi><mspace width="0.125em" linebreak="nobreak"/><mo>/</mo><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">Th</mi></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4d883c16a0cdf82d81af5c13a1b78aeb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-8-63-2026-ie00002.svg" width="28pt" height="14pt" src="gchron-8-63-2026-ie00002.png"/></svg:svg></span></span>), yield similar age spectra when well-estimated values are used. In this context, it is essential to evaluate whether the measured groundmass glass or whole-rock composition truly reflects the zircon-forming melt. This can be assessed by comparison with the youngest isochron intercept on the secular equilibrium line, which provides an independent melt composition estimate. We also evaluated eruption age estimation methods using synthetic U-Th datasets, with increasing uncertainty toward older ages. Bayesian models, particularly those with uniform priors, consistently outperformed weighted mean methods in terms of accuracy and precision and are therefore recommended for eruption age estimates in volcanic U-Th zircon datasets.</p>

Mohammad Hossein Madadi, Masoumeh Kordi, Arezoo Abedi

Abstract The type and amount of distribution of evaporite minerals within reservoir rocks play important role in reservoir quality. This study focuses on thin section petrography, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, aqueous fluid inclusions microthermometry, and UV fluorescence microscopy of hydrocarbon fluid inclusions, to study the genesis of anhydrites within dolomite facies of the Oligocene-Miocene Asmari Formation, Zagros Basin. Petrographic studies of primary (dolomicrite) and secondary (dolosparite) dolomite-dominated facies of the Asmari Formation showed that the associated diagenetic anhydrites occurred in different morphological textures (forms) including poikilotopic, pervasive pore-filling, scattered pore-filling, fracture-filling, and vein cements, nodular and layered forms. Fluid inclusion studies of anhydrites revealed that the diagenetic anhydrites particularly within the dolomicrite facies were formed at an average temperature of 68.2 °C, and by mineralizing solutions with salinity of about 23.5 wt% NaCl. Indeed, in the dolomicrite facies, the anhydrites were associated with gypsum dewatering and/or direct anhydrite precipitation during eodiagenesis. In contrast, in the dolosparite facies, anhydrites were formed at an average temperature of 100.1 °C, and by mineralizing solutions with salinity of about 16.4 wt% NaCl. This latter condition was very likely related to the dolomitization processes including the creation of calcium-rich and magnesium-poor pore fluids with presence of sufficient sulfate ions during the mesodiagenesis. Occurrences of eugenic and mesogenic anhydrites within the dolomite facies were largely controlled the petrophysical parameters as well as the reservoir quality of the Asmari Formation.

Zharkov, Rafael V.

For the first time in the history of mud volcano research on Sakhalin Island, remote video surveillance methods were used to monitor the activity of Main Pugachev mud volcano (central part of Sakhalin Island) and record its eruption process in the winter. As a result, a unique video footage of the eruption of the Western field of Main Pugachev mud volcano was obtained, allowing to trace the stages of its next activation. The eruption of the mud volcano, recorded on January 15, 2025, began rapidly at 6:15 p.m. (local time), without any noticeable precursors. The main explosions occurred during the first 30 minutes, the intensity of explosions in the first minutes of the eruption was 1–3 seconds, and the height of the mud mass ejections reached 10–12 m. At 6:17 p.m., an explosion in the form of a directed blast was observed; the mud mass was ejected at an angle of approximately 45° to a distance of about 20 m. According to preliminary visual data, this eruption is characterized as typical of Main Pugachev mud volcano. With a mud field diameter of more than 50 m and an average thickness of 0.5–0.7 m, the volume of the mud mass was at least 1000 m3. During the eruption, no activation was observed on other fields of the Pugachev group of mud volcanoes.

Md. Shakil Rahaman, Md. Ashraful Islam

Abstract Greenhouse gases pose a significant threat to life on Earth by trapping infrared radiation, leading to global warming. In Bangladesh, carbon dioxide (CO2) emissions have surged by 40% from 2000 to 2020, primarily from the power industry and process sector, making CO2 the most significant contributor to the country's greenhouse gas inventory. One promising mitigation strategy is the integration of CO2 sequestration with enhanced gas recovery (CO2-EGR-CCUS) in depleted gas reservoirs. This study presents a reservoir simulation-based investigation using CMG software to evaluate the dual objective of maximizing CO2 storage and recovering residual methane. A comprehensive sensitivity analysis was also performed to assess the impact of well placement, injection rate, and injection pressure on CO2 injectivity and methane recovery. Among the tested scenarios, staggered well placement with an injection rate of 47 MMSCF/D at 4700 psi yielded the highest gas recovery factor of 4.52%, recovering 1.3 BCF of methane from a depleted gas reservoir with a Gas Initially in Place of 28.8 BCF. The abandoned gas rate was 0.1 × 10⁶ SCF/day, and residual gas saturation was 0.1. The cumulative CO2 injection reached 3.82 × 1012 SCF, with 1.36 × 1012 SCF securely stored under a fracture pressure limit of 6000 psi, as determined using the Pennebaker Correlation. Notably, the project demonstrates a CO2 capture potential equivalent to 1.24% of Bangladesh’s total annual CO2 emissions. Staggered well placement also achieved the highest sweep efficiency (12.27%), outperforming linear and five-spot patterns by 3.19% and 2.41%, respectively. These findings highlight the feasibility of combining CO2 storage with enhanced methane recovery as a scalable and sustainable strategy for carbon management in Bangladesh. The study contributes valuable insights into optimizing CCUS operations under site-specific geological and operational constraints.

Zhengzhen An, Yue Zhao, Yue Zhao et al.

This study focuses on understanding the fractal characteristics and controlling factors of micropore structures within organic-rich shale of the Cambrian Shuijingtuo Formation in the Yichang area of Hubei Province. Mineralogy, petrology, and organogeochemical characteristics were confirmed through comprehensive testing methods, including whole-rock X-ray diffraction and organic geochemical analyses. Additional experiments included low-temperature carbon dioxide adsorption, low-temperature nitrogen adsorption, and high-pressure mercury injection. Fractal dimensions of micropores, mesopores, and macropores were calculated using the V-S, FHH, and MENGER sponge models, respectively. Results indicate that the Cambrian Shuijingtuo Formation represents a typical deposit from an alkaline water body, resulting in high-calcareous shale. Fractal dimensions were as follows: micropores (D1) ranged from 2.1138 to 2.3475 (average 2.2342), mesopores (D2) ranged from 2.5327 to 2.7162 (average 2.6171), and macropores (D3) ranged from 2.7361 to 2.9316 (average 2.82905). Correlations were observed between total organic carbon (TOC) content and Ro with D1 and D2 (positive) and D3 (negative). Shale pore volume and specific surface area exhibited positive correlations with D1 and D2 but negative correlations with D3. High bio-deposited silica positively influenced micropore and mesopore development, while clay mineral compaction and dehydration transformations favored macropore development. Carbonate minerals primarily contributed to regular macropores, with complex correlations involving fractal dimensions D1, D2, and D3. The research results provide theoretical support for analyzing pore fractal characteristics of shallow old Marine shale reservoirs and the prediction and development plan of high-quality reservoirs of the Shuijingtuo Formation in the Yichang area.

Paul-Desire Ndjigui, Estelle Huguette O. Ngono, Soureiyatou Fadil-Djenabou

Petrological data of the recent alluvial sediments from the Ngaye River watershed in the Northern Cameroon were used in order to infer their origin with the probable source rocks as gneisses, amphibolites, and granites; and to investigate the occurrence of precious metals like Gold and Platinum Group Elements (Au-PGE). The Ngaye River watershed is located in the Adamawa plateau from the Adamawa-Yade Domain (AYD) in the Central Cameroon, Central Africa. This region is characterized by two contrasted seasons which induce a savanna vegetation cover with gallery forests along the rivers. The field works were done during the dry season. During this season, several whole fractions of sediments were sampled at six vertical lithological sequences along the right terrace of the Ngaye Rivers. The selection of samples was linked to their grain size and color. To better understand the origin of sediments, twenty-one rock samples (gneisses, amphibolites, and granites) were also collected. The grain size distribution was done using the Robinson's standard Pipetting Method. Thin sections were done for the determination of mineral assemblages and textural features of rocks using Leica DM 750P optic microscope. Mineralogical compositions of sediments were obtained using the X-ray diffraction (XRD) instrument. The major elements data were determined using the X-ray Fluorescence spectrometry (XRF). The Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to obtain the concentrations of trace elements including rare earth elements and Au-PGE. The investigation of Au-PGE was done only in amphibolites as well as in the concentrate heavy minerals (160–100 µm) from sediments of lithological sequence A. Data of this paper are further presented and discussed in Ndjigui et al. [1].

Enze WANG, Tonglou GUO, Bo LIU et al.

In this work, the Permian Longtan marine-continental transitional shale in the southeast of Sichuan Basin was taken as study object. Through petrology and geochemical analysis, lithofacies types of the marine-continental transitional shale were classified, key controlling factors of physical properties and gas content of the different shale lithofacies were analyzed. The research results show that the Longtan Formation marine-continental transitional shale in the study area has four types of lithofacies, namely, organic-lean calcareous shale, organic-lean mixed shale, organic-lean argillaceous shale, and organic-rich argillaceous shale, among which the organic-rich argillaceous shale is the most favorable lithofacies of the study area. The pore types of different lithofacies vary significantly and the clay mineral-related pore is the dominant type of the pore system in the study area. The main controlling factor of the physical properties is clay mineral content, and the most important factor affecting gas content is TOC content. Compared with marine shale, the marine-continental transitional shale has low average values, wide distribution range, and strong heterogeneity in TOC content, porosity, and pore structure parameters, but still contains some favorable layers with high physical properties and gas contents. The organic-rich clay shale deposited in tidal flat-lagoon system is most likely to form shale gas sweet spots, so it should be paid more attention in shale gas exploration.

Antonio G. Checa, Carmen Salas, Francisco M. Varela-Feria et al.

Abstract The external surface microornament of the glass scallops Catillopecten natalyae and malyutinae is made by calcitic spiny projections consisting of a stem that later divides into three equally spaced and inclined branches (here called aerials). C. natalyae contains larger and smaller aerials, whereas C. malyutinae only secreted aerials of the second type. A remarkable feature is that aerials within each type are fairly similar in size and shape and highly co-oriented, thus constituting a most sophisticated microornament. We demonstrate that aerials are single crystals whose morphology is strongly controlled by the crystallography, with the stem being parallel to the c-axis of calcite, and the branches extending along the edges of the {104} calcite rhombohedron. They grow epitaxially onto the foliated prisms of the outer shell layer. The co-orientation of the prisms explains that of the aerials. We have developed a model in which every aerial grows within a periostracal pouch. When this pouch reaches the growth margin, the mantle initiates the production of the aerial. Nevertheless, later growth of the aerial is remote, i.e. far from the contact with the mantle. We show how such an extremely sophisticated microornament has a morphology and co-orientation which are determined by crystal growth.

Franziska Keller, Olivier Bachmann, Nobuo Geshi et al.

The Aso-4 caldera-forming event (86.4 ± 1.1 ka, VEI-8) is the second largest volcanic eruption Earth experienced in the past 100 ka. The ignimbrite sheets produced during this event are some of the first ever described compositionally zoned pyroclastic flow deposits exhibiting clear compositional, mineralogical and thermal gradients with stratigraphic position. Large quantities of the deposits are composed of crystal-poor, highly evolved juvenile pumices, while late-erupted pyroclastic flows are in many cases dominated by crystal-rich and less silicic scoria. These petrological gradients in the Aso-4 deposits have been linked to extensive magma mixing of two compositionally distinct magmas in a complex upper crustal reservoir. However, new studies on several other zoned ignimbrites suggest that magma mixing alone is not sufficient to fully explain such strong compositional gradients in the deposits. These gradients are expected to be dominantly caused by the recharge-induced reactivation of extracted melt caps and their complementary cumulate in the upper crust. Here, we investigate bulk rock and matrix glass data with detailed analyses of mineral chemistry in order to re-evaluate the Aso-4 deposits in light of these latest developments. Reverse chemical zoning in phenocrysts, Sr enrichment in euhedral rims of plagioclase and the presence of mafic minerals (clinopyroxene, olivine) indicate recharge of hot, mafic magmas shortly prior to eruption, inducing a mixing signature. However, the marked enrichment in some elements in bulk-rock analyses and the presence of highly evolved minerals (some in the form of glomerocrysts) in the late-erupted, crystal-rich units, provide clear evidence for crystal accumulation in these scoria. Mass balance modeling of P2O5, Sr and SiO2 supports the extraction of melt-rich lenses within an upper crustal mush zone, leaving a partly cumulative evolved crystal residue. We therefore propose an origin of the compositionally zoned Aso-4 ignimbrite largely by erupting a heterogeneous upper crustal reservoir, consisting of crystal-poor rhyodacitic melt caps within its associated cumulate mush. This complex reservoir was reactivated by mafic recharge shortly prior to eruption, imparting an additional mixing signature to the deposits.

Monire Sakhdari , Mehrdad Behzadi, Mohammad Yazdi et al.

Introduction Gold deposits formed during mountain-building processes in Phanerozoic terranes that formed in metamorphic environment have a great dispensation in the world (Goldfarb et al., 2001). They constitute an economically important type of gold mineralization called orogenic gold deposits (Groves et al., 2003). The Sanandaj-Sirjan zone is one of the most important areas for orogenic gold exploration and it hosts several orogenic gold deposits (Aliyari et al., 2012). This zone is characterized by regionally metamorphosed and deformed Paleozoic and Mesozoic sedimentary, volcanic and volcanoclastic rocks under green schist and amphibolite facies conditions. (Rashidnejad-Omran, 2001; Abdollahi et al., 2009; Kouhestani et al., 2014(. The Godar Sorkh area is locatedin the central part of the Sanandaj-Sirjan zone, 20km southwest of the Muteh region. The rocks sequence of the Godar Sorkh area comprise of the volcano-sedimentary rocks of the greenschist complex with Paleozoic age rock units intruded by basic and felsic dikes. These country rocks are affected by a NW-SE-trending shear zone and are highly deformed. Rock units illustrate ductile-brittle to brittle shear zones and had been under poly-phase metamorphism. In other words, Godar Sorkh has the most similarity with orogenic gold. Methods In this study after field observations, rock samples were collected from mineralized and altered zones that included 26 thin sections, 47 polished sections and 10 polished thin sections which were prepared for petrography, mineralization and alteration studies, 10 samples were prepared for XRD analyses, 21 samples were analyzed for Au content by the Fire Assay method and 21 samples were analyzed by the ICP-MS method for REE and trace element amounts in the Iran Minerals Research and Processing Center, and 9 samples were selected for XRF analyses in the Kansaran Binaloud laboratory. According to the petrographic studies and the results of chemical analysis 7 polished double sections were selected to determine the amount of gold and other elements by electron-microprobe analysis. Discussion and Results The rocks sequence of the Godar Sorkh area comprise of greenschists complexes including limestone, dolomitic, marbles, micaschists, black schist, greenschist, intercalations of quartzite, calc schist, phyllites and slate, metamorphosed under greenschist facies grade. These units are considered to belong to the Paleozoic age. Rock unites have been intruded by basic and felsic dikes. Rock assemblages are characterized by several phases of deformation and generation of various fabrics and structures. Gold mineralization occurs in ductile and brittle shear zones, along N45W trending and controlled by structures. The main alterations are sericitization, carbonization, chloritization, silicification and sulphidization. Ore-mineralogical paragenesis mainly includes pyrite and locally chalcopyrite, arsenopyrite, covellite, sphalerite, galena and Fe Oxide-Hydroxide secondary minerals such as goethite, hematite and limonite. The results show that the maximum grade of gold in the mineralization zone has been reported to be 9.9 ppm and the average value of gold in the area is about 0.3 ppm. The microscopic studies show native gold minerals in the range of 15 to 30 micrometers. Also, electron-microprobe analysis indicates Au in the lattice of sulfide minerals. Based on geochemical studies, rocks have characteristics peraluminous range and the granodiorite intrusion belongs to S type granitoids. LREE are enriched. Controlling parameters for mineral concentration in Godar Sorkh area are shear zone. Therefore, regarding the development of Paleozoic metavolcanic-sedimentary sequences and the formation of multistage extensional structures including the normal faults, and fractures, texture and structure investigation, mineral paragenesis, alteration and geochemistry, gold mineralization in the Godar Sorkh area can be classified as orogenic gold mineralization. Acknowledgement This study has been supported by the Shahid Beheshti University of Tehran, Iran. The authors would like to thank IMPASCO Company for help and cooperation in the completion of this research study. We also thank the support of the Iran National Science Foundation (INSF). References Abdollahi, M.J., Karimpour, M.H., Kheradmand, A. and Zarasvandi, A.R., 2009. Stable isotopes (O, H, and S) in the Muteh gold deposit, Golpaygan area, Iran. Natural Resources Research, 18(2): 137–151. https://doi.org/10.1007/s11053-009-9103-3 Aliyari, F., Rastad, E. and Mohajjel, M., 2012. Gold Deposits in the Sanandaj–Sirjan Zone: Orogenic Gold Deposits or Intrusion‐Related Gold Systems. Resource Geology, 62(3): 296–315. https://doi.org/10.1111/j.1751-3928.2012.00196.x Goldfarb, R.J., Groves, D.I. and Gardoll, S., 2001. Orogenic gold and geologic time: a global synthesis. Ore Geology Reviews, 18(1–2): 1–75. https://doi.org/10.1016/S0169-1368(01)00016-6 Groves, D.I., Goldfarb, R.J., Robert, F. and Hart, C.J.R., 2003. Gold deposits in metamorphic belts: overview of current understanding, outstanding problems, future research and exploration significance. Economic Geology, 98(1): 1–29. https://doi.org/10.2113/gsecongeo.98.1.1 Kouhestani, H., Rashidnejad-Omran, N., Rastad, E., Mohajjel, M., Goldfarb, R.J. and Ghaderi, M., 2014. Orogenic gold mineralization at the Chah Bagh deposit, Muteh gold district, Iran. Journal of Asian Earth Sciences, 91: 89–106. https://doi.org/10.1016/j.jseaes.2014.04.027 Rashidnejad-Omran N., 2001. Petrology and geochemistry of metavolcanosedimentary and plutonic rocks of Muteh region (South Delidjan) with special view to genesis of gold mineralization, Ph.D. Thesis. Tarbiat Modares University, Tehran, Iran, 436 pp. (in Persian)

S. Kawagucci, S. Kawagucci, Y. Matsui et al.

<p>Isotope fractionation factors associated with various biogeochemical processes are important in ensuring the reliable use of isotope tracers in biogeosciences at large. Methane is a key component of the subsurface biosphere and a notable greenhouse gas, making the accurate evaluation of methane cycles, including microbial methanotrophy, imperative. Although the isotope fractionation factors associated with methanotrophy have been examined under various conditions, the dual-isotope fractionation factors of aerobic methanotrophy in oxic seawater remain unclear. Here, we investigated hydrogen and carbon isotope ratios of methane as well as the relevant biogeochemical parameters and microbial community compositions in hydrothermal plumes in the Okinawa Trough. Methanotrophs were found to be abundant in plumes above the Hatoma Knoll vent site, and we succeeded in simultaneously determining hydrogen and carbon isotope fractionation factors associated with the aerobic oxidation of methane (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi mathvariant="italic">ε</mi><mi mathvariant="normal">H</mi></msup><mo>=</mo><mn mathvariant="normal">49.4</mn><mo>±</mo><mn mathvariant="normal">5.0</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="75pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e3301306102c79229517cc5ca8b2b34e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-5351-2021-ie00001.svg" width="75pt" height="14pt" src="bg-18-5351-2021-ie00001.png"/></svg:svg></span></span> ‰, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi mathvariant="italic">ε</mi><mi mathvariant="normal">C</mi></msup><mo>=</mo><mn mathvariant="normal">5.2</mn><mo>±</mo><mn mathvariant="normal">0.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="69pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="614175b12e2a893551c9454f5cd3150c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-5351-2021-ie00002.svg" width="69pt" height="14pt" src="bg-18-5351-2021-ie00002.png"/></svg:svg></span></span> ‰) – the former being the first of its kind ever reported. This <span class="inline-formula"><i>ε</i>^H</span> value is comparable with values reported from terrestrial ecosystems but clearly lower than those from aerobic and anaerobic methanotroph enrichment cultures, as well as incubations of methanotrophic isolates. The covariation factor between <span class="inline-formula"><i>δ</i>¹³</span>C<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="c5c95d00c3681b9285a64c8d98939405"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-5351-2021-ie00003.svg" width="17pt" height="10pt" src="bg-18-5351-2021-ie00003.png"/></svg:svg></span></span> and <span class="inline-formula"><i>δ</i></span>D<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="a19c4ac9a18bb1a1d8e665b47b75604a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-5351-2021-ie00004.svg" width="17pt" height="10pt" src="bg-18-5351-2021-ie00004.png"/></svg:svg></span></span>, <span class="inline-formula">Λ</span> (9.4 or 8.8 determined using two different methods), was consistent with those from methanotrophic isolate incubations. These values are valuable for understanding dynamics of methane cycling in the marine realm, and future applications of the approach to other habitats with methanotrophic activity will help reveal whether the small <span class="inline-formula"><i>ε</i>^H</span> value observed is a ubiquitous feature across all marine systems.</p>

Akash Talapatra

Abstract Coal seams, particularly deep unmineable coal reservoirs, are the most important geological desirable formations to store CO2 for mitigating the emissions of greenhouse gas. An advantage of this process is that a huge quantity of CO2 can be sequestrated and stored at relatively low pressure, which will reduce the amount of storage cost required for creating additional platform to store it. The study on CO2 storage in coal seam to enhance coal bed methane (ECBM) recovery has drawn a lot of attention for its worldwide suitability and acceptability and has been conducted since two decades in many coalmines. This article focuses on the coal seam properties related to CO2 adsorption/desorption, coal swelling/shrinkage, diffusion, porosity and permeability changes, thermodynamic/thermochemical process, flue gas injection, etc. Here, the performance analysis of both CO2 storage and ECBM recovery process in coal matrixes is investigated based on the numerical simulation. In this study, a one-dimensional mathematical model of defining mass balances is used to interpret the gas flow and the gas sorption and describe a geomechanical relationship for determining the porosity and the permeability alteration at the time of gas injection. Vital insights are inspected by considering the relevant gas flow dynamics during the displacement and the influences of coal swelling and shrinkage on the ECBM operation. In particular, pure CO2 causes more displacement that is more efficient in terms of total CH4 recovery, whereas the addition of N2 to the mixture assists to make quicker way of the initial methane recovery. However, this study will support future research aspirants working on the same topic by providing a clear conception and limitation about this study.

Upendra Singh Yadav, Harinandan Kumar, Vishnu Roy et al.

Abstract The establishment of oil production well is becoming a challenge with the increasing demand for energy. The fulfillment of energy need requires large production of oil and gas as it is a primary source of energy. EOR is also important because of the enhancement in oil production from thirty percent to more than fifty percent. The chemical EOR is one of the techniques for the increment in oil production. Chemical flooding using water-soluble polymers like partially hydrolyzed polyacrylamide (PHPA) has been industrially used as an EOR technique. The paper deals with the effect of nano-silica particles on viscosity as well as the shear rate of the polymer solution. The change in viscosity, as well as shear rate, was studied at variable concentrations of the nano particles in the different concentrations of PHPA solution. Mutual correlation between viscosity and other parameters like temperature, shear rate, salinity, nanoparticle concentration, and polymer concentration was established using the statistical method.

G. Sarthou, P. Lherminier, E. P. Achterberg et al.

<p>The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this special issue (<a href="https://www.biogeosciences.net/special_issue900.html" target="_blank">https://www.biogeosciences.net/special_issue900.html</a>), results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 18 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.</p>

Kun Wang, Tongshan Wang, Zecheng Wang et al.

The Meso-Neoproterozoic strata are wildly distributed in North China Craton (NCC), of which Changchengian strata are most widely developed. Taking Changchengian strata in south margin of NCC as the study object, and combined with comprehensive analysis of isotopic chronology and petrology, it can be concluded that the Xiong'er rift is a plume rift which responds to breakup of Columbia supercontinent. Seismic data shows that Changchengian rifts are developed in the Qinshui Basin and the southern part of Ordos Basin covered by Phanerozoic strata, respectively are large-scale graben rifts and half-graben rifts. Aero magnetic data indicates that a NE-trending rift is developed in the west of the Xiong'er rift, and the Qinshui Basin rift is the extension of the north branch of the Xiong'er rift. The filling process of Changchengian rifts can be divided into four stages: the early rifting stage developing thick andesitic volcanic rocks, the late rifting stage developing large suite of coarse clastic sedimentary rocks, the depression stage developing fine clastic rocks, and the epeiric sea stage developing carbonate rocks. The dark argillaceous rocks are developed in Cuizhuang Formation and Chenjiajian Formation during the depression stage, and the black shale in Cuizhuang Formation is the effective source rocks. The bitume is filled in fractures of dolomite in Luoyukou Formation, as well as dissolution pores and large caves in Longjiayuan Formation. The argillaceous sandstone and muddy limestone of Lower Cambrian is the effective cap rocks, which can form an potential accumulation assemblage of Changchengian strata with underlying source rocks of Cuizhuang Formation and reservoirs of Luoyu Group, and this assemblage may be still effective at present. Keywords: Changchengian, Xiong'er rift, Ordos Basin, Qinshui Basin, Filling sequence, Hydrocarbon geological conditions, Accumulation assemblage

Massimiliano Tirone, Jan Sessing

The complex process of melting in the Earth's interior is studied by combining a multiphase numerical flow model with the program AlphaMELTS which provides a petrological description based on thermodynamic principles. The objective is to address the fundamental question of the effect of the mantle and melt dynamics on the composition and abundance of the melt and the residual solid. The conceptual idea is based on a 1-D description of the melting process that develops along an ideal vertical column where local chemical equilibrium is assumed to apply at some level in space and time. By coupling together the transport model and the chemical thermodynamic model, the evolution of the melting process can be described in terms of melt distribution, temperature, pressure and solid and melt velocities but also variation of melt and residual solid composition and mineralogical abundance at any depth over time. In this first installment of a series of three contributions, a two-phase flow model (melt and solid assemblage) is developed under the assumption of complete local equilibrium between melt and a peridotitic mantle (dynamic equilibrium melting, DEM). The solid mantle is also assumed to be completely dry. The present study addresses some but not all the potential factors affecting the melting process. The influence of permeability and viscosity of the solid matrix are considered in some detail. The essential features of the dynamic model and how it is interfaced with AlphaMELTS are clearly outlined. A detailed and explicit description of the numerical procedure should make this type of numerical models less obscure. The general observation that can be made from the outcome of several simulations carried out for this work is that the melt composition varies with depth, however the melt abundance not necessarily always increases moving upwards. When a quasi-steady state condition is achieved, that is when melt abundance does not varies significantly with time, the melt and solid composition approach the composition that is found from a dynamic batch melting model which assumes the velocities of melt and residual solid to be the same. Time dependent melt fluctuations can be observed under certain conditions. In this case the composition of the melt that reaches the top side of the model (exit point) may vary to some extent. A consistent result of the model under various conditions is that the volume of the first melt that arrives at the exit point is substantially larger than any later melt output. The analogy with large magma emplacements associated to continental break-up or formation of oceanic plateaus seems to suggest that these events are the direct consequence of a dynamic two-phase flow process. Even though chemical equilibrium between melt and the residual solid is imposed locally in space, bulk composition of the whole system (solid+melt) varies with depth and may also vary with time, mainly as the result of the changes of the melt abundance. Potential factors that can influence the melting process such as bulk composition, temperature and mantle upwelling velocity at the top boundary (passive flow) or bottom boundary (active flow) should be addressed more systematically before the DEM model in this study and the dynamic fractional melting (DFM) model that will be introduced in the second installment can be applied to interpret real petrological data. Complete data files of most of the simulations and four animations are available following the data repository link provided in the Supplementary Material.

B. N. Orcutt, M. Bergenthal, T. Freudenthal et al.

IODP Expedition 357 utilized seabed drills for the first time in the history of the ocean drilling program, with the aim of collecting intact sequences of shallow mantle core from the Atlantis Massif to examine serpentinization processes and the deep biosphere. This novel drilling approach required the development of a new remote seafloor system for delivering synthetic tracers during drilling to assess for possible sample contamination. Here, we describe this new tracer delivery system, assess the performance of the system during the expedition, provide an overview of the quality of the core samples collected for deep biosphere investigations based on tracer concentrations, and make recommendations for future applications of the system.

Gregor Kovačič, Nataša Ravbar

Prispevek obravnava kartiranje onesnaževalcev podtalnice na alpski kraški planoti Velika planina. Kljub temu, da na planoti ni stalne poselitve, je kakovost vode v izvirih pod planoto ogrožena zaradi športne, turistične in živinorejske aktivnosti na planoti. V izvirih so že zabeležili onesnaženje, kar kaže na pomanjkljivosti upravljanja s pitno vodo tudi na neposeljenih območjih alpskega krasa, ki so sicer z vidika varovanja zelo primerna za zaščito.    The present paper presents the hazard mapping of groundwater on the Velika planina alpine karst plateau. There are no permanent residents on the plateau. Nevertheless, some serious hazards to the quality of the respective karst springs are arising from sports, tourist and farming activities. Some pollution has been already recorded in springs, showing the shortcomings of drinking water management also in uninhabited alpine karst areas, which are ordinarily very favourable for water protection.

Janja Kogovšek

Podane so osnovne fi zikalno-kemične značilnosti voda v zaledju Malenščice in povezave, ki jih nakazujejo. Dolomitna voda Cerkniščice odteka predvsem v Rak v Rakovem Škocjanu, Kotliči pa kažejo na povezavo s Svinjsko jamo in Malo Karlovico. Rak na ponoru predstavlja ob zelo nizkih vodostajih pretežno vodo Kotličev s Ca/Mg okoli 3,5 in z najnižjo vrednostjo 2,2 ob najnižjih vodostajih, ko v Svinjsko jamo ponika le Cerkniščica, kar se kasneje odrazi tudi v Malenščici. Ob visokih vodostajih v ponor odteka mešanica Raka in Kotličev s Ca/Mg okoli 4. Dotok voda iz doline Pivke označuje višje razmerje Ca/Mg in večje vrednosti pokazateljev onesnaženja, medtem ko označujejo infi ltracijsko vodo iz slabo prepustnega dela Javornikov vrednosti Ca/Mg okoli 5. Zaradi zapletenosti sistema ostaja še vrsta odprtih vprašanj, ki bi jih lahko pojasnile le dodatne raziskave.   Basic physico-chemical properties of waters within the area of Malenščica are given, and so are the connections that they indicate. Dolomitic water of the Cerkniščica mostly fl ows into the Rak in Rakov Škocjan valley, while Kotliči springs show the connection with Svinjska jama (cave) and Mala Karlovica. When water levels are low the Rak river at its swallowhole mostly comprises waters from Kotliči, with Ca/Mg about 3, 5 and the lowest value 2,2 when the water levels are the lowest, when only the Cerkniščica sinks into Svinjska jama; this later reflects also in the water of the Malenščica. When water levels are high, the mixture of Rak and Kotliči fl ows into the swallowhole, and Ca/Mg is about 4. The infl ux of waters from Pivka Valley is designated by higher ratio of Ca/Mg and higher values of pollution indicators, when the infi ltration water from poorly conductive part of Javorniki is designated by Ca/Mg values about 5. Due to the complexity of the system there are still some unanswered questions left which can only be answered by carrying out additional researches.