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Provenance of Lower Carboniferous Bauxite Deposits in Northern Guizhou,China:Constraints from Geochemistry and Detrital Zircon U-Pb Ages

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Journal of Earth Science 2021年第1期32卷 235-252页

作者： Guolin Xiong Wenchao Yu Yuansheng Du Shenfu Weng Dawei Pang Xusheng Deng Jintao Zhou State Key Laboratory of Biogeology and Environmental Geology School of Earth SciencesChina University of GeosciencesWuhan 430078China Innovation Center of Ore Resources Exploration Technology in the Region of Bedrock Ministry of Natural Resources of People's Republic of ChinaGuiyang 550004China Geological Party Guizhou Bureau of Geology and Mineral Exploration and DevelopmentZunyi 563099China Guizhou Geological Survey Guizhou Bureau of Geology and Mineral Exploration and DevelopmentGuiyang 550081China

The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province,China,are a Kazakhstan subtype of karst bauxite *** provenance of the Jiujialu Formation has long been debated,with uncertainty about the formation of the bauxite *** we report new geochemical data that indicate the affinity between the Lower-Middle Ordovician clastic rocks and argillaceous dolostones and the overlying Carboniferous bauxite deposits,all of which are characterized by high Al_(2)0_(3),K2_(O),and∑REE contents,flat post-Archean Australian shale(PAAS)-normalized REE patterns,and uniform immobile element ratios(TiO2/Al_(2)0_(3),Nb/TiO2,and Zr/TiO2).Their similar detrital zircon age distributions further indicate the link between the bauxite deposits and the clastic rocks and argillaceous *** age spectra of clastic rocks of the Lower Silurian Hanchiatien Formation in northern Guizhou match those of the bauxite deposits,with a maximum age peak at-980 Ma and other secondary age peaks,suggesting these clastic rocks may represent the provenance of the bauxite *** youngest detrital zircons(-445 Ma)occur only in the bauxite deposits and are probably sourced from K-bentonite beds of the Ordovician-Silurian *** analyses indicate that the source materials of the bauxite deposits in the Jiujialu Formation are of mixed provenance:Lower-Middle Ordovician aluminosilicate rocks and argillaceous dolostones of the underlying strata,and Lower Silurian clastic rocks and K-bentonite from adjacent areas.A comparison of Early Carboniferous bauxitic provenances in northern and central Guizhou indicates that paleotopography was the major factor controlling the provenance of these bauxite deposits.

关键词： weathering bauxitization karstification chemical weathering Jiujialu Formation

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The importance of non-carbonate mineral weathering as a soil formation mechanism within a karst weathering profile in the SPECTRA Critical Zone Observatory, Guizhou Province,China

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Acta Geochimica 2017年第3期36卷 566-571页

作者： Oliver W.Moore Heather L.Buss Sophie M.Green Man Liu Zhaoliang Song School of Earth Sciences University of Bristol Geography College of Life and Environmental SciencesUniversity of Exeter School of Water Resources and Environment China University of Geosciences (Beijing) Institute of the Surface-Earth System Science Research Tianjin University

Soil degradation, including rocky desertification,of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock(marls). Atmospheric inputs from dust were also detected.

关键词： Critical zone chemical weathering Karst Desertification Guizhou Province

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Geochemistry of core sediments from the southeastern Bay of Bengal:Inferences on weathering and early diagenetic changes

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Geoscience Frontiers 2021年第2期12卷 495-504页

作者： A.Prajith Abhishek Tyagi P.John Kurian National Centre for Polar and Ocean Research(NCPOR) Ministry of Earth Sciences(MoES)Headland SadaVasco-da-Gama403804GoaIndia

A sediment core(ABP24/05),collected at a water depth of 3520 m from the southeastern Bay of Bengal was studied to determine the change in chemical weathering during the last glacial to deglacial periods and the factors of sedimentary environment which controlled earliest diagenetic changes in the sediment after its *** ratios of K/Rb,Ti/Al and Zr/Rb during~45 to~18 cal kyr *** the core sediments may be attributed to the stronger physical erosion and turbidity currents activity during this *** might have brought a higher quantity of unaltered minerals to the study *** ratios of K/Rb,Zr/Rb,and Ti/Al and increase of SiO_(2)/TiO_(2),Rb/Al and Cs/Al from~18 cal kyr *** present may be indicating an increase in the rate of chemical weathering during this *** time of increased chemical weathering in the study area is consistent with deglaciation warming in the tropical Indian Ocean and strengthening of river runoff into the Andaman *** change during the interglacial period by increased solar insolation thereby strengthened the summer monsoon which might have led to intensified chemical weathering in the source region since~18 cal kyr *** low organic carbon(OC),high Mn/Al,Fe/Al and the Mn-oxides minerals precipitation indicate prevailing of oxic conditions during~11 cal kyr *** the core sediments,which is contradictory to suboxic conditions developed in the deep ocean sediments in the western Bay of Bengal and the equatorial Indian *** low terrigenous influx and export of less OC to the bottom sediments might have created a favorable condition for the formation of Mn-oxides in the study area during Holocene.

关键词： Bay of Bengal Trace elements chemical weathering Summer monsoon Mn-oxides

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Using computational fluid dynamic simulation with Flow-3D to reveal the origin of the mushroom stone in the Xiqiao Mountain of Guangdong, China

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Journal of Mountain Science 2022年第1期19卷 1-15页

作者： LI Jian-cheng WANG Wei ZHENG Yan-ming WEN Xiao-hao FENG Jing SHENG Li WANG Chen QIU Ming-kun Department of Geography Hanshan Normal UniversityChaozhou 521041China Geographic School South China Normal UniversityGuangzhou 510631China

Mushroom shaped rocks are not uncommon in nature, but their origin is often misunderstood because they can be formed by different natural forces. A huge mushroom stone in a stream valley of the Xiqiao Mountain of Guangdong,China is widely believed to be formed through the way of stream water erosion. However, the result of the simulation performed with Flow-3 D in this study indicates that the mushroom shape of the rock could not have been sculpted by the flowing water erosion because the simulation result contradicts that of the field investigations:(1) the sediment brought by upstream flowing water tends to be deposited on the leeward side of the flowing water preventing the rock on this side form being eroded, but the narrowest part of the rock bottom is exactly located on this side of the rock and(2) the stream flow should erode the bed sediment and produce high abrasion on the rock surface on the upstream and lateral sides of the rock,respectively, but no abrasion marks are found on the same sides of the rock. Subsequent geological analyses in this study provide evidence that the narrow bottom of the mushroom stone was resulted from chemical and physical weathering happening within the sediment that used to deposit on the lee side of the stone.

关键词： Mushroom Stone Computational fluid dynamics(CFD)model Mineralogical analysis chemical weathering Xiqiao Mountain happening

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Geochemistry of Sediments from a Subalpine Lake Sedimentary Succession in the Western Nanling Mountains,Southern China:Implications for Catchment weathering During the Last 15400 Years

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Chinese Geographical Science 2022年第3期32卷 537-548页

作者： WANG Bingxiang ZHONG Wei ZHU Chan OUYANG Jun WEI Zhiqiang SHANG Shengtan School of Geography Sciences South China Normal UniversityGuangzhou 510631China Guangdong Center for Marine Development Research Guangzhou 510220China Zhuhai Branch of State Key Laboratory of Earth Surface Processes and Resource Ecology Faculty of Geographical ScienceBeijing Normal UniversityZhuhaiGuangdong 519087China School of Earth Science and Engineering Sun Yat-sen UniversityZhuhai 519082China

In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the region of the western Nanling Mountains,*** climate of the study region was deeply controlled by the East Asian summer *** results indicate that,in the past 15400 yrs,the values of chemical index of alteration(CIA)ranged from 73.9%to 88.2%(mean:85.3%),suggested a medium and high intensity of chemical *** local exogenous clastic materials,which were derived from the weathered residues,played a key role in contributing towards the *** the climate-induced chemical weathering exerted strong influences on the geochemical features of weathered residues,the geochemical characteristics of the sediments were deeply impacted by climatic *** and warmer conditions would favor increased chemical weathering,resulting in more leaching of soluble and mobile elements(e.g.,Ba and Sr)and leaving the resistant and immobile elements(e.g.,Al and Ti)enriched in the weathered *** materials were then eroded and transported into the lake,and led to the sediments characterized by the characteristic of having depleted soluble *** contrast,dry and cold conditions would result in an opposite *** this sense,the geochemical records can serve as proxies to indicate changes of chemical weathering intensity,which were closely related to the evolution of summer monsoon.

关键词： lacustrine sediments chemical weathering asian summer monsoon last deglacial western Nanling Mountains China

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Non-climate environmental factors matter to Holocene dynamics of soil organic carbon and nitrogen in an alpine permafrost wetland,Qinghai‒Tibet Plateau

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Advances in Climate Change Research 2023年第2期14卷 213-225页

作者： Qing-Feng WANG Hui-Jun JIN Cui-Cui MU Xiao-Dong WU Lin ZHAO Qing-Bai WU State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Civil Engineering Northeast China Observatory and Research Station of Permafrost Geo-Environment(Ministry of Education)Institute of ColdRegions Engineering and EnvironmentNortheast Forestry UniversityHarbin 150040China Key Laboratory of Western China's Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesObservation and Research Station on Eco-Environment of Frozen Ground in the Qilian MountainsLanzhou UniversityLanzhou 730000China Cryosphere Research Station on the Qinghai‒Tibet Plateau State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 101408China School of Geographical Sciences Nanjing University of Information Science&TechnologyNanjing 210044China

Studies on the responses of soil organic carbon(SOC)and nitrogen dynamics to Holocene climate and environment in permafrost peatlands and/or wetlands might serve as analogues for future scenarios,and they can help predict the fate of the frozen SOC and nitrogen under a warming *** date,little is known about these issues on the Qinghai‒Tibet Plateau(QTP).Here,we investigated the accumulations of SOC and nitrogen in a permafrost wetland on the northeastern QTP,and analyzed their links with Holocene climatic and environmental *** order to do so,we studied grain size,soil organic matter,SOC,and nitrogen contents,bulk density,geochemical parameters,and the accelerator mass spectrometry(AMS)^(14)C dating of the 216-cm-deep wetland *** and nitrogen contents revealed a general uptrend over last 7300 *** stocks for depths of 0-100 and 0-200 cm were 50.1 and 79.0 kgC m^(-2),respectively,and nitrogen stocks for the same depths were 4.3 and 6.6 kgN m^(-2),***,a cooling and drying trend for regional climate over last 7300 years was inferred from the declining chemical weathering and humidity ***,SOC and nitrogen accumulated rapidly in 1110e720 BP,while apparent accumulation rates of SOC and nitrogen were much lower during the other periods of the last 7300 ***,we proposed a probable conceptual framework for the concordant development of syngenetic permafrost and SOC and nitrogen accumulations in alpine permafrost *** indicates that,apart from controls of climate,non-climate environmental factors,such as dust deposition and site hydrology,matter to SOC and nitrogen accumulations in permafrost *** emphasized that environmental changes driven by climate change have important impacts on SOC and nitrogen accumulations in alpine permafrost *** study could provide data support for regional and global estimates of SOC and nitrogen pools and for global models on carbon‒climate interactions

关键词： Syngenetic permafrost in alpine wetland Soil organic carbon pool Nitrogen accumulation chemical weathering Dust deposition Holocene

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Paleo-Environment Reconstruction of the Middle Permian Lucaogou Formation,Southeastern Junggar Basin,NW China:Implications for the Mechanism of Organic Matter Enrichment in Ancient Lake

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Journal of Earth Science 2022年第4期33卷 963-976页

作者： Dawei Cheng Chuanmin Zhou Zhijie Zhang Xuanjun Yuan Yinhe Liu Xingyu Chen Research Institute of Petroleum Exploration and Development PetroChinaBeijing 100083China School of Earth and Space Sciences Peking UniversityBeijing 100871China

The Middle Permian Lucaogou Formation is the source rock and the main oil shale producing formation in the southeastern Junggar *** study focused on the Lucaogou Formation exposed in two outcrop sections on the northern flank of the Bogda Mountain,namely the Jingjingzigou and Dalongkou ***,we present integrated analysis of the sedimentology,major and trace elements,mineral components and total organic carbon *** paleo-environment was reconstructed including provenance,redox conditions,paleo-salinity,chemical weathering intensity and primary organic matter *** results showed that the upper and lower units were deposited in distinct depositional environments with different organic matter accumulation *** lower unit was characterized by low lake level,dry climate,fresh-brackish and well-oxygenated *** during the deposition of the upper unit the lake level rose,climate turned wetter and the bottom water became less oxidized and much *** mechanism of the organic matter accumulation is different for these two *** preserved organic matters were mainly controlled by the primary productivity in the lower unit and by the redox conditions in the upper unit.

关键词： trace element redox condition paleosalinity primary productivity chemical weathering

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Sources of dissolved inorganic carbon in rivers from the Changbaishan area, an active volcanic zone in North Eastern China

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Acta Geochimica 2017年第3期36卷 410-415页

作者： Xue Bai Benjamin Chetelat Yilong Song Institute of Surface-Earth System Science Tianjin University 92 Weijin Road Tianjin 300072 China School of Environmental Engineering Tianjin University 92 Weijin Road Tianjin 300072 China

Major elements and carbon isotopes of dissolved inorganic carbon(DIC)have been measured in the waters of Changbaishan mountain,a volcanic area in northeastern China,between June and September 2016 to decipher the origin of the CO_2 involved in chemical weathering *** variations of major elements ratios measured in water samples can be explained by a change of the chemical composition of the volcanic rocks between the volcanic cone(trachytes)and the basaltic shield as evidenced by the variations in the composition of these ***,DIC results from the neutralization of CO_2 by silicate *** concentrations vary from 0.3 to 2.5 mmol/L and carbon isotopic compositions of DIC measured in rivers vary from-14.2‰to 3.5‰.At a first order,the DIC transported by rivers is derived from the chemical weathering’s consumption of CO_2 with a magmatic origin,enriched in^(13)C(-5%)and biogenic soil CO_2 with lower isotopic *** highest δ^(13)C values likely result from C isotopes fractionation during CO_2 degassing in rivers.A mass balance based on carbon isotopes suggest that the contribution of magmatic CO_2 varied from less than 20%to more than 70%.Uncertainties in this calculation associated with CO_2 degassing in rivers are difficult to quantify,and the consequence of CO_2 degassing would be an overestimation of the contribution of DIC derived from the neutralization of magmatic CO_2 by silicate rocks.

关键词： Carbon isotopes Dissolved inorganic carbon Rivers chemical weathering Changbaishan Active volcanic zone

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Coupling between the Cenozoic west Pacific subduction initiation and decreases of atmospheric carbon dioxides

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Acta Geochimica 2023年第3期42卷 387-392页

作者： Guozhi Xie Fanfan Tian Kun Wang Yuanyuan Xiao Tianyu Chen Weidong Sun Center of Deep Sea Research Institute of OceanologyChinese Academy of SciencesQingdao 266071China Deep-Sea Multidisciplinary Research Center Laoshan LaboratoryQingdao 266237China University of Chinese Academy of Sciences Beijing 100049China CAS Key Laboratory of Marine Geology and Environment Ocean Mega-Science CenterInstitute of OceanologyChinese Academy of SciencesQingdao 266071China State Key Lab Mineral Deposits Research School of Earth Science and EngineerNanjing UniversityNanjing 210023China

At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from~51 to 34 *** cause of this phenomenon is still not well *** this study,we demonstrate that the initiation of Cenozoic west Pacific plate subduction,triggered by the hard collision in the Tibetan Plateau,occurred at approximately 51 Ma,coinciding with the tipping *** water depths of the Pacific subduction zones are mostly below the carbonate compensation depths,while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate ***,more volcanic ashes erupted from the west Pacific subduction zones,which consume CO_(2).The average annual west Pacific volvano eruption is 1.11 km~3,which is higher than previous *** amount of annual CO_(2)absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global *** propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO_(2)concentration.

关键词： Subduction initiation in the west Pacific Collision of the Neo-Tethys Volcano eruption rates Cenozoic CO_(2)declining Carbonate compensation depths chemical weathering

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Is the Cape Stone Forest in Shantou City formed by wave erosion? A comparison of the pedestal rocks on the coasts and the mountains of Queshi in eastern Guangdong, China

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Journal of Mountain Science 2024年第5期21卷 1447-1463页

作者： CHEN Min WANG Wei School of Geography South China Normal UniversityGuangzhou 510631China

Cape Stone Forest is a group of granite rock pillars(pedestal rocks) towering over Shilin Lake, on the southern shore of Shantou Bay in eastern Guangdong, China. The rock pillars were previously identified as sea stacks because they have marine notch-like concave sidewalls at their base, and more importantly, the lake is immediately adjacent to the bay, which is exposed to the open sea. However, rock pillars similar in shape and size can also be found at the top of Queshi Mountain, which is only about 300 meters northwest of the lake and about 85 meters above sea level. Therefore, the marine origin of Cape Stone Forest is seriously questioned. In this study, 3D imagery and drone technology were used to collect data in the investigations without direct manual measurements in the water or on the mountain. It shows that the concave sidewalls of the rock pillars in the lake and on the mountains occur at different heights and are exposed to different directions, while a natural sea stack on Mayu Island at the mouth of Shantou Bay has a horizontal notch parallel to the sea level, although the granite rock of the sea stack is the same as that of the lake and the mountains. The eastern side of the island, where the sea stack is located, is exposed to the open sea but blocks large waves for the rock pillars in the lake. Therefore, the origin of Cape Stone Forest cannot be explained by wave-based mechanisms. The only satisfactory explanation that takes into account all the field evidence is that the narrow rock pillars of the lake and mountain were formed by chemical weathering that penetrated closely the spaced joints of the granite rock, and the notch-like concave sidewalls were formed by more effective chemical weathering at the base of the pillars.

关键词： Pedestal rock Granite Closely spaced joints Wave erosion chemical weathering

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