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Shigeyuki Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Provenance, tectonics and source weathering of modern fluvial sediments of the Brahmaputra–Jamuna River, Bangladesh: Inference from geochemistry
Journal of Geochemical Exploration, 2011Co-Authors: Mohammad Amir Hossain Bhuiyan, Samuel B. Dampare, M. Julleh Jalalur Rahman, Shigeyuki SuzukiAbstract:Abstract This present study describes the elemental geochemistry of fluvial sediments in the Kurigram (upstream) to Sirajganj–Tangail (downstream) section of the Brahmaputra–Jamuna River, Bangladesh, with the aim of evaluating their provenance, weathering and tectonic setting. Petrographically, the sediments are rich in quartz (68%), followed by feldspars (8.5%) and lithic grains (7%). The bulk sediment chemistry is influenced by grain size. Concentrations of TiO 2 , Fe 2 O 3 , MgO, K 2 O, P 2 O 5 , Rb, Nb, Cr, V, Y, and, Ce, Th and Ga slightly decrease with increasing SiO 2 /Al 2 O 3 and grain size, suggesting clay matrix control. In contrast, concentrations of CaO, Na 2 O, Sr and Pb increase with increasing SiO 2 /Al 2 O 3 and grain size, suggesting residence of these substances in feldspar. Decrease in Zr as grain size increases is likely controlled both by clay matrix and heavy minerals. In addition, heavy minerals' sorting also influences Ce, Th, Y and Cr abundances in some samples. The sediments are predominantly quartzose in composition with abundant low-grade metamorphic and sedimentary lithics, low feldspars and trace volcanic detritus, indicating a quartzose recycled orogen province as a source of the sediments. Discriminant diagrams together with immobile element ratio plots show that, the Brahmaputra–Jamuna River sediments are mostly derived from Rocks formed in an active continental margin. Moreover, the rare earth element ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate derivation of the sediments of Brahmaputra–Jamuna River from Felsic Rock sources of upper continental crust (UCC). The chemical indices of alteration suggest that Brahmaputra–Jamuna River sediments are chemically immature and experienced low chemical weathering effects. In the A–CN–K ternary diagram, most of the samples close to the plagioclase–K-feldspar join line and to the UCC plot, and in the field of various lithologies of Higher Himalayan Crystalline Series, suggesting that Rocks in these series are likely source Rocks. Therefore, the elemental geochemistry of the Brahmaputra–Jamuna River sediments is controlled mostly by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite > albite > quartz.
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Composition of Neogene shales from the Surma Group, Ben- gal Basin, Bangladesh: implications for provenance and tec-
2007Co-Authors: Shigeyuki SuzukiAbstract:The geochemical comp osition of the Neogene shales from the Surma Group in the Bengal Basin, Bangladesh encountered in pe- troleum exploration wells were analyzed by lithium me taborate/tetraborate fusion Inductively Coupled Plasma (ICP ) and Inductively Coupled Plasma Ma ss spectrom etry (ICP -MS). Geochemically, the me an ma jor elem ent comp osition of the Neogene shales is similar to that of the average shale with the ex- ception of the CaO content, which is lower here. The low CaO content (1.37 wt %) could be due to lower carbonate content. The Neogene shales are enriched with V, Cr, Co, Ni in comp ared to UC (Upper Crust. The RE E content (186-228) is higher than those of UC and NA SC but is in agreem ent with those of PAAS. The Eu/Eu* (~0.68), (La/Lu)cn (~0.43), La/Sc (~2.64), Th/Sc (~1.06), La/Co(~2.71), Th/Co (~1.08), and Cr/Th (~5.59) ratios as well as Chondrite-normalized REE patterns with flat HREE, LREE en- richme nt, and negative Eu anom aly indicate the derivation of the Neogene Surma Group shales from Felsic Rock sources. The geochemical characteristics suggest the active continental ma rgin setting for the Neogene Surma Group shales and preserve the signatures of recycled provenance field that have undergone significant weathering at the source areas.
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Geochemistry of sandstones from the Miocene Surma Group, Bengal Basin, Bangladesh: Implications for Provenance, tectonic setting and weathering
GEOCHEMICAL JOURNAL, 2007Co-Authors: M. Julleh Jalalur Rahman, Shigeyuki SuzukiAbstract:Twenty six sandstone samples from six wells penetrating the Miocene Surma Group in the Bengal Basin, Bangladesh, were analyzed by lithium metaborate/tetraborate fusion Inductively Coupled Plasma (ICP) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and by petrographic microscope. The framework grains of the Surma Group sandstones are rich in quartz followed by lithic grains, feldspar and mica (predominantly white mica). The sandstones are dominantly quartzolithic and quartzose one in composition with abundant low-grade metamorphic, sedimentary lithics, low feldspars and little volcanic detritus, indicating that the sands were derived from a quartzose recycled orogen province. The Surma Group sandstones have moderate to high SiO2 contents (64-85%; on average 77%), TiO2 concentrations averaging 0.5%, Al2O3 contents of about 8.4%, and Fe2O3 (total Fe as Fe2O3) + MgO content of around 4.5%. Compared to the average sandstone value, the Surma Group sandstones are depleted in CaO (2.36%) and enriched in Al2O3, Fe2O3 and Na2O. Geochemically, the sandstones are classified mainly as litharenites. The Chemical Index of Alteration (CIA) values for the Miocene Surma Group sandstones vary from 53 to 65 with an average of 59, indicating low to moderate weathering of the source areas. The average CIA value (59) is a little above than that (50) of the upper continental crust. The shales from the Miocene Surma Group show higher CIA (∼70-78) values, indicating significant weathering in the source. The geochemical characteristics suggest an active continental margin to passive margin setting for the Surma Group sandstones, and preserve the signatures of a recycled provenance. The Eu/Eu* (∼0.69), (La/Lu)cn (∼10.07), La/Sc (∼3.98), Th/Sc (∼1.44), La/Co (∼3.84), Th/Co (∼1.40), and Cr/Th (∼9.48) ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate derivation of the Surma Group sandstones from Felsic Rock sources.
Susan L Brantley - One of the best experts on this subject based on the ideXlab platform.
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Where fast weathering creates thin regolith and slow weathering creates thick regolith
Earth Surface Processes and Landforms, 2012Co-Authors: Ekaterina Bazilevskaya, Marina I. Lebedeva, Milan J. Pavich, Dilworth Y Parkinson, Gernot Rother, David R Cole, Susan L BrantleyAbstract:Weathering disaggregates Rock into regolith – the fractured or granular earth material that sustains life on the continental land surface. Here, we investigate what controls the depth of regolith formed on ridges of two Rock compositions with similar initial porosities in Virginia (USA). A priori, we predicted that the regolith on diabase would be thicker than on granite because the dominant mineral (feldspar) in the diabase weathers faster than its granitic counterpart. However, weathering advanced 20× deeper into the granite than the diabase. The 20 × -thicker regolith is attributed mainly to connected micron-sized pores, microfractures formed around oxidizing biotite at 20 m depth, and the lower iron (Fe) content in the Felsic Rock. Such porosity allows pervasive advection and deep oxidation in the granite. These observations may explain why regolith worldwide is thicker on Felsic compared to mafic Rock under similar conditions. To understand regolith formation will require better understanding of such deep oxidation reactions and how they impact fluid flow during weathering. Copyright © 2012 John Wiley & Sons, Ltd.
Yanxin Wang - One of the best experts on this subject based on the ideXlab platform.
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Geochemical controls on magnesium and its speciation in various types of geothermal waters from typical Felsic-Rock-hosted hydrothermal systems in China
Geothermics, 2019Co-Authors: Qinghai Guo, Mingliang Liu, Li Luo, Ketao Yan, Wei Guo, Weide Yan, Yanxin WangAbstract:Abstract Magnesium is usually a major constituent in natural water but very likely to be depleted in high-temperature geothermal waters hosted by Felsic-Rocks. In the presented study, the Yunnan-Sichuan-Tibet Geothermal Province (YST) in China was selected as the study area for comprehensively investigating the geochemistry of magnesium in geothermal waters with a wide variety of pH, temperature and chemical composition. As expected, the acid geothermal waters have much higher magnesium concentrations than the neutral waters equilibrated with reservoir minerals to a higher degree. The primary alteration minerals controlling the concentrations of magnesium in neutral to alkaline geothermal waters are chlorites and saponites, as indicated by the evidence from Mg/H2 - SiO2 activity plots, calculation of saturation indices, and simulation of water-minerals reactions. It is noted that the complexation of magnesium with major anions in geothermal water also has a non-negligible effect on its total magnesium concentration because it increases the solubility of important magnesium-bearing minerals. Environmental temperature, solution pH, and salinity are the principal factors affecting the complexation between magnesium and these common anions. This is the first systematic study on the magnesium geochemistry of the hydrothermal systems in the sole high-temperature geothermal region (YST) in mainland China.
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acid hot springs discharged from the rehai hydrothermal system of the tengchong volcanic area china formed via magmatic fluid absorption or geothermal steam heating
Bulletin of Volcanology, 2014Co-Authors: Jiexiang Li, Xiaobo Zhang, Yanxin WangAbstract:Across mainland China, Tengchong is geothermally unique because both magmatic-hydrothermal systems and late Cenozoic volcanic activities have been observed there. Rehai, located in the Tengchong volcanic area, is the only hydrothermal system in mainland China discharging acid springs with very low pH values. Two types of acid geothermal waters were identified: one is sulfate waters with low chloride concentrations and pH levels as low as around 2; the other has slightly higher chloride concentrations and is marked with diversified hydrochemical types. Both types of acid springs at Rehai are immature waters and far from being equilibrated with a thermodynamically stable mineral assemblage comprising albite, K–feldspar, muscovite, and clinochlore characteristic for Felsic Rock-hosted reservoirs. In contrast to those neutral chloride springs at Rehai that are formed via boiling, conductive cooling or mixing with cold groundwaters of a parent geothermal liquid (PGL), the sulfate-rich acid waters discharged from the Diretiyan area, the Dagunguo area, and the Shizitou Spring of Rehai are essentially locally perched groundwaters heated by H2S-rich steam separated from deep geothermal fluid. The acidity of these waters originates from the oxidation of H2S in near-surface environment. In contrast, the acid waters with higher chloride concentrations are the results of mixing between steam-heated waters and neutral chloride waters. The geochemical geneses of the Rehai geothermal springs inferred based on stable hydrogen and oxygen isotopes are generally identical. Unlike active volcanic areas across the world, there is a lack of acid waters at Rehai formed through partial neutralization of magmatic fluid, possibly owing to the comparatively deep-seated magma chamber there (no less than 7 km deep).
M. Julleh Jalalur Rahman - One of the best experts on this subject based on the ideXlab platform.
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Provenance, tectonics and source weathering of modern fluvial sediments of the Brahmaputra–Jamuna River, Bangladesh: Inference from geochemistry
Journal of Geochemical Exploration, 2011Co-Authors: Mohammad Amir Hossain Bhuiyan, Samuel B. Dampare, M. Julleh Jalalur Rahman, Shigeyuki SuzukiAbstract:Abstract This present study describes the elemental geochemistry of fluvial sediments in the Kurigram (upstream) to Sirajganj–Tangail (downstream) section of the Brahmaputra–Jamuna River, Bangladesh, with the aim of evaluating their provenance, weathering and tectonic setting. Petrographically, the sediments are rich in quartz (68%), followed by feldspars (8.5%) and lithic grains (7%). The bulk sediment chemistry is influenced by grain size. Concentrations of TiO 2 , Fe 2 O 3 , MgO, K 2 O, P 2 O 5 , Rb, Nb, Cr, V, Y, and, Ce, Th and Ga slightly decrease with increasing SiO 2 /Al 2 O 3 and grain size, suggesting clay matrix control. In contrast, concentrations of CaO, Na 2 O, Sr and Pb increase with increasing SiO 2 /Al 2 O 3 and grain size, suggesting residence of these substances in feldspar. Decrease in Zr as grain size increases is likely controlled both by clay matrix and heavy minerals. In addition, heavy minerals' sorting also influences Ce, Th, Y and Cr abundances in some samples. The sediments are predominantly quartzose in composition with abundant low-grade metamorphic and sedimentary lithics, low feldspars and trace volcanic detritus, indicating a quartzose recycled orogen province as a source of the sediments. Discriminant diagrams together with immobile element ratio plots show that, the Brahmaputra–Jamuna River sediments are mostly derived from Rocks formed in an active continental margin. Moreover, the rare earth element ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate derivation of the sediments of Brahmaputra–Jamuna River from Felsic Rock sources of upper continental crust (UCC). The chemical indices of alteration suggest that Brahmaputra–Jamuna River sediments are chemically immature and experienced low chemical weathering effects. In the A–CN–K ternary diagram, most of the samples close to the plagioclase–K-feldspar join line and to the UCC plot, and in the field of various lithologies of Higher Himalayan Crystalline Series, suggesting that Rocks in these series are likely source Rocks. Therefore, the elemental geochemistry of the Brahmaputra–Jamuna River sediments is controlled mostly by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite > albite > quartz.
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Geochemistry of sandstones from the Miocene Surma Group, Bengal Basin, Bangladesh: Implications for Provenance, tectonic setting and weathering
GEOCHEMICAL JOURNAL, 2007Co-Authors: M. Julleh Jalalur Rahman, Shigeyuki SuzukiAbstract:Twenty six sandstone samples from six wells penetrating the Miocene Surma Group in the Bengal Basin, Bangladesh, were analyzed by lithium metaborate/tetraborate fusion Inductively Coupled Plasma (ICP) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and by petrographic microscope. The framework grains of the Surma Group sandstones are rich in quartz followed by lithic grains, feldspar and mica (predominantly white mica). The sandstones are dominantly quartzolithic and quartzose one in composition with abundant low-grade metamorphic, sedimentary lithics, low feldspars and little volcanic detritus, indicating that the sands were derived from a quartzose recycled orogen province. The Surma Group sandstones have moderate to high SiO2 contents (64-85%; on average 77%), TiO2 concentrations averaging 0.5%, Al2O3 contents of about 8.4%, and Fe2O3 (total Fe as Fe2O3) + MgO content of around 4.5%. Compared to the average sandstone value, the Surma Group sandstones are depleted in CaO (2.36%) and enriched in Al2O3, Fe2O3 and Na2O. Geochemically, the sandstones are classified mainly as litharenites. The Chemical Index of Alteration (CIA) values for the Miocene Surma Group sandstones vary from 53 to 65 with an average of 59, indicating low to moderate weathering of the source areas. The average CIA value (59) is a little above than that (50) of the upper continental crust. The shales from the Miocene Surma Group show higher CIA (∼70-78) values, indicating significant weathering in the source. The geochemical characteristics suggest an active continental margin to passive margin setting for the Surma Group sandstones, and preserve the signatures of a recycled provenance. The Eu/Eu* (∼0.69), (La/Lu)cn (∼10.07), La/Sc (∼3.98), Th/Sc (∼1.44), La/Co (∼3.84), Th/Co (∼1.40), and Cr/Th (∼9.48) ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate derivation of the Surma Group sandstones from Felsic Rock sources.
Toshio Mizuta - One of the best experts on this subject based on the ideXlab platform.
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An experimental study on Felsic Rock–artificial seawater interaction: implications for hydrothermal alteration and sulfate formation in the Kuroko mining area of Japan
Mineralium Deposita, 2005Co-Authors: Yasumasa Ogawa, Naotatsu Shikazono, Daizo Ishiyama, Hinako Sato, Toshio MizutaAbstract:Experimental studies on the interactions between artificial seawater (ASW) and fresh rhyolite, perlite and weakly altered dacitic tuff containing a small amount of smectite suggest changing cation transfer during smectite-forming processes. Initially, dissolution of K from the Rocks accompanies incorporation of Mg and Ca from ASW during both earlier (devitrification stage) and later smectite formation, whereas Ca incorporated with early smectite formation redissolves with progressive reaction. Barium mobility increases toward the later smectite-forming reactions. Therefore, the large amounts of barite, anhydrite and gypsum in Kuroko ore deposits are considered to have precipitated from hydrothermal solutions derived from the interaction with previously altered Felsic Rocks during late smectite formation, rather than by the reaction with fresh Felsic Rocks.
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an experimental study on Felsic Rock artificial seawater interaction implications for hydrothermal alteration and sulfate formation in the kuroko mining area of japan
Mineralium Deposita, 2005Co-Authors: Yasumasa Ogawa, Naotatsu Shikazono, Daizo Ishiyama, Hinako Sato, Toshio MizutaAbstract:Experimental studies on the interactions between artificial seawater (ASW) and fresh rhyolite, perlite and weakly altered dacitic tuff containing a small amount of smectite suggest changing cation transfer during smectite-forming processes. Initially, dissolution of K from the Rocks accompanies incorporation of Mg and Ca from ASW during both earlier (devitrification stage) and later smectite formation, whereas Ca incorporated with early smectite formation redissolves with progressive reaction. Barium mobility increases toward the later smectite-forming reactions. Therefore, the large amounts of barite, anhydrite and gypsum in Kuroko ore deposits are considered to have precipitated from hydrothermal solutions derived from the interaction with previously altered Felsic Rocks during late smectite formation, rather than by the reaction with fresh Felsic Rocks.
