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Marine Redox Conditions in the Early Cambrian Ocean: Insights from the Lower Cambrian Phosphorite deposits, South China

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Journal of Earth Science 2016年第2期27卷 282-296页

作者： Haifeng Fan Hanjie Wen Xiangkun Zhu State Key Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences institute of geology Chinese Academy of Geological Sciences

It is generally considered that a significant change in oceanic redox conditions occurred during the Ediacaran-Cambrian transition. However, there are currently two major conflicting views on the degree of oxygenation of deep water（oxic vs. ferruginous） during this interval. To date, the oxygenation conditions of the Early Cambrian ocean have not been well constrained. The oxygenation magnitude and mechanism of the Early Cambrian ocean could be critical to the significant biological evolution of the ＂Cambrian Explosion＂. To constrain the Early Cambrian oceanic redox environment, we conducted an integrated study on iron and sulfur isotopes and redox-sensitive elements（Mo, U, and V） of Lower Cambrian phosphorite deposits from two shallow sections（Meishucun and Gezhongwu） and a deeper water section（Zunyi） from the Yangtze Platform, South China. The near zero δ^（56）Fe values from the two shallow sections studied here reflect oxic conditions in the lower phosphorite deposition. An obvious positive shift in δ^（56）Fe and redox-sensitive element content was observed in the middle parts of the two shallow water sections, which might reflect loss of light iron by dissimilatory iron reduction during early diagenesis under suboxic shallow water in the platform. However, the highly positive δ^（56）Fe values in the deep section could reflect a lower oxidation degree of dissolved Fe（II） under anoxic deep water. The data suggest redox-stratified oceanic conditions during the Early Cambrian, in which completely oxygenated shallow water（platform） coexisted with anoxic deep water（slope）. We propose that prolonged upwelling of dissolved organic carbon（DOC）-, Fe（II）- and phosphorus-rich anoxic deep water in a redox-stratified ocean could have increased exchange with the open ocean, resulting in major phosphorite deposition in oxic-suboxic conditions. The progressive oxygenation of the ocean may have facilitated the Early Cambrian biotic diversification.

关键词： Early Cambrian redox-stratified ocean southern China iron isotope phosphorite.

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History of tectono-magmatic evolution in the Western Kunlun Orogen

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Science China Earth Sciences 1999年第6期42卷 604-619页

作者：毕华王中刚王元龙朱笑青 Open Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences institute of geology Chinese Academy of Sciences

Based on the statistical and analytical data on more than 170 isotopic ages published since the 1980s of magmatic rocks, metamorphic rocks, tectonites and ores from the Western Kunlun Orogen, and the characteristics of sedimentation, magmatism, metamorphism and tectonic activities in the region studied in conjunction with geological field investigations and necessary supplementary isotope data, five stages of tectono-magmatic evolution, i.e. Ar3-Pt 2 1 tectono-magmatic active stage (I), pt 2 2 stable stage (II), Pt 3 1 -p2 active stage (III), T1-T2 stable stage (IV), and T3-Q active stage (V) can be distinguished in the Western Kunlun Orogen. Moreover, the tectono-magmatic active style and general trend, the characteristics of tectonic settings, etc. of each stage and substage in the region studied are also discussed.

关键词： Western Kunlun Orogen isotopic age history of tectono-magmatic evolution.

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Petrochemical Characteristics and Timing of Middle Eocene Granitic Magmatism in Kooh-Shah, Lut Block, Eastern Iran

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Acta Geologica Sinica(English Edition) 2013年第4期87卷 1032-1044页

作者： Maryam ABDI M. H. KARIMPOUR Department of geology Ferdowsi University of Mashhad Research Center for ore deposit of Eastern Iran Ferdowsi University of Mashhad

The Kooh-Shah region located in a Tertiary volcanic-plutonic belt of the Lut Block in eastern Iran comprises several subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, which have intruded into volcanic rocks. The Kooh-Shah granitoid rocks are characterized by enrichment in large ion-lithophile elements （LILE： e.g. Sr, Ba, Rb） and depletion in high field-strength elements （HFSE： e.g. Nb, Ta, Ti）. The chondrite-normalized REE patterns are characterized by moderate LREE enrichment （La/Yb）N=6.01-10.01, medium-heavy REE enrichment, and absence of Eu anomalies. The Kooh-Shah intrusive rocks are metaluminous, shoshonitic with calc-alkaline affinity and high values of magnetic susceptibility, and classified as the magnetite-series of oxidant I-type granitoids. The age of Kooh-Shah granitoid rocks based on zircon U-Pb age dating is 39.7±0.7 Ma （=Middle Eocene） and the ranges of their initial 87Sr/86Sr and 143Nd/144Nd ratios are from 0.704812 to 0.704920 and 0.512579 to 0.512644, respectively, when recalculated to an age of 39 Ma. The initial ？Nd isotope values for the Kooh-Shah intrusive rocks range from -0.18 to 1.09. This geochemical data indicates that the Kooh-Shah granitoid rocks formed from depleted mantle in an island arc setting. The geochemical signature of the studied granitoid rocks represents a characteristic guide for future exploration of copper-gold porphyry-type deposits in the Lut block.

关键词： geochemistry igneous rocks granitoids magmatism Lut Block Iran

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Study of an Early Silurian–Early Permian paleo-weathering profile in Zunyi, north Guizhou Province, China

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Chinese Journal Of Geochemistry 2015年第4期34卷 558-578页

作者： Xiao-hui Xiong Jia-fei Xiao Rui-zhong Hu Yi Wang Jian Wang Xiu-gen Fu State Key Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Chinese Academy of Geological Sciences Chengdu institute of geology and Mineral Resources Nanjing institute of geology and Palaeontology Chinese Academy of Sciences

To understand and help settle the controversy around the living time of Pinnatiramosus qianensis Geng, a paleo-weathering profile situated in the town of Yongle near the city of Zunyi, north Guizhou Province, China, was analyzed. The profile formed during a break in sedimentation between the Early Silurian and the Early *** developed with a depth of several meters. The fossil plant P. qianensis Geng is present, but only in the lower portions(Layer 2) of the paleosol. Another plant with an irregularly branching system is found in Layers 2and 3. The distinct geochemical characteristics of the lower and upper portions of the Gaojiayan paleosol indicate a compound genesis. Its lower portions(Layers 1 and 2)resulted from in situ weathering of silty mudstone of the lower Silurian Hanjiadian Formation. The upper portions(Layer 3) are allochthonous. Transgression brought substantial concentrations K and Na, and led to K- and Naenrichment in the profile. Pumping of vascular plants and downward leaching enhanced the K enrichment in the middle portions. A superior preservation of P. qianensis Geng was observed in an exposure of Layer 2. Mass balance calculation indicates a great K enrichment related to bioaccumulation in the top of Layer 2 and a K loss in Layer3. Fossil plants(e.g., P. qianensis Geng) preserved in the paleosol are Permian rooting systems growing down into the lower Silurian rocks.

关键词：风化剖面早二叠世早志留世中国北方贵州省遵义市化石植物地球化学特征

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Mineralogy, Geochemistry, Fluid Inclusion and Oxygen Isotope Investigations of Epithermal Cu±Ag Veins of the Khur Area, Lut Block,Eastern Iran

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Acta Geologica Sinica(English Edition) 2018年第3期92卷 1139-1156页

作者： M.Javidi MOGHADDAM M.H.KARIMPOUR K.Ebrahimi NASRABADI M.R.Haidarian SHAHRI A.Malekzadeh SHAFAROUDI Department of geology Faculty of Science Ferdowsi University of Mashhad Research Center for ore deposit of Eastern Iran Ferdowsi University of Mashhad

The Khur metallogenic district is located in a volcanic-plutonic belt in the central Lut Block(central eastern Iran). Mineralization occurs in Middle Eocene andesitic tuff and along four main vein systems trending northwest-southeast(Shurk, Mir-e-Khash, Shikasteh Sabz and Ghar-e-Kaftar veins).Microscopic studies reveal that the veins contain bornite, chalcocite, pyrite, tennantite together with minor sphalerite and chalcopyrite as hypogene minerals and chalcocite, digenite, covellite, valleriite,malachite, azurite, atacamite, hematite, and goethite as supergene minerals. The ore bodies are accompanied by narrow but intensely developed wall rock alterations of argillization, carbonatization and silicification. Copper content reaches 6.5, 2.4, 4.2 and 5% in Mir-e-Khash, Shikasteh Sabz, Ghar-eKaftar and Shurk, respectively. Microthermometric measurements of quartz-and calcite-hosted fluid inclusions indicate that the mineralization might be derived from a moderately saline hydrothermal fluid at temperatures between 175-316℃. Calculated δO values of water in equilibrium with quartz and calcite for Khur veins suggest that the fluid might have had a magmatic source, but theO-depletion was developed through mixing with meteoric water. Copper deposition in Khur veins is believed to have been largely caused by mixing, although wall rock reactions may also have occurred. The Khur veins are classified as volcanic-subvolcanic hydrothermal-related vein deposits.

关键词： fluid inclusion oxygen isotopes Khur veins Lut Block Iran

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Magmatic systems of large continental igneous provinces

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Geoscience Frontiers 2017年第4期8卷 621-640页

作者： E.Sharkov M.Bogina A.Chistyakov institute of geology of ore deposits PetrographyMineralogy and Geochemistry RAS

Large igneous provinces（LIPs） formed by mantle superplume events have irreversibly changed their composition in the geological evolution of the Earth from high-Mg melts（during Archean and early Paleoproterozoic） to Phanerozoic-type geochemically enriched Fe-Ti basalts and picrites at 2.3 *** propose that this upheaval could be related to the change in the source and nature of the mantle superplumes of different *** first generation plumes were derived from the depleted mantle,whereas the second generation（thermochemical） originated from the core-mantle boundary（CMB）.This study mainly focuses on the second（Phanerozoic） type of LIPs,as exemplified by the midPaleoproterozoic Jatulian-Ludicovian LIP in the Fennoscandian Shield,the Permian-Triassic Siberian LIP,and the late Cenozoic flood basalts of *** latter LIP contains mantle xenoliths represented by green and black *** xenoliths are fragments of cooled upper margins of the mantle plume heads,above zones of adiabatic melting,and provide information about composition of the plume material and processes in the plume *** on the previous studies on the composition of the mantle xenoliths in within-plate basalts around the world,it is inferred that the heads of the mantle（thermochemical） plumes are made up of moderately depleted spinel peridotites（mainly lherzolites）and geochemically-enriched intergranular fluid/***,it is presumed that the plume heads intrude the mafic lower crust and reach up to the bottom of the upper crust at depths-20 *** generation of two major types of mantle-derived magmas（alkali and tholeiitic basalts） was previously attributed to the processes related to different PT-parameters in the adiabatic melting zone whereas this study relates to the fluid regime in the plume *** is also suggested that a newly-formed melt can occur on different sides of a critical plane of silica undersaturation and can acquire either alkalic or tholeiitic composition de

关键词： Magmatic systems LIP Mantle plume Paleoproterozoic Mantle xenoliths Basalts

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Geochemistry of Rare Earth Elements in Lamprophyres in Laowangzhai Gold orefield, Yunnan Province

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Journal of Rare Earths 2000年第1期18卷 62-68页

作者：黄智龙肖化云许成刘丛强 Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

Lamprophyres, widely distributed in the Laowangzhai gold orefield, Yunnan province, China, and closely related to gold mineralization in time and space, can be distinguished into three kinds: the fresh (weakly altered ), the altered, and the mineralized lamprophyres. These lamprophyres in the orefield are similar in the range of BEE contents and REE patterns, but definitely different in parameters of LRE/HRE, NLa/Yb etc. The geochemistry of REE in fresh lamprophyre shows flat the rock is a product of different partial melting of the enriched mantle. Calculation results of mass balance of REE activity regularity in the process of alteration and mineralization of the lalnprophyres in the orefield shows that the altering fluids and mineralizing fluids contain REE, and these fluids are mainly [he products of mantle degassing and magma degassing during the lamprophyric magmatism.

关键词： rare earths lamprophyre geochemistry laowangzhai gold orefield

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Role of nitrogen and oxygen in emission of Si quantum dots formed by pulse laser

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Chinese Physics B 2010年第9期19卷 590-594页

作者：黄伟其刘家兴蔡成兰吕泉刘世荣秦朝建 institute of Nanophotonic Physics Guizhou University State Key Laboratory of ore deposit Geochemistry Institute of GeochemistryChinese Academy of Sciences

Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence （PL） emission with the stimulated emission observed at about 700 nm. It is difficult to distinguish between the photoluminescence peaks emitted from samples prepared in different atmospheres. The reason for the appearance of similar peaks may be the similar distribution of the localised states in the gap for different samples when silicon dangling bonds of quantum dots are passivated by nitrogen or oxygen. It is revealed that both the kind and the density of passivated bonds on quantum dot surface prepared in oxygen or nitrogen have a strong influence on the enhancement of PL emission.

关键词： nitrogen and oxygen quantum dots stimulated emission localised states

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Geochemical Characteristics of Rare Earth Elements in Gejiu Tin Polymetallic deposits, Yunnan Province, China

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Journal of Rare Earths 2004年第5期22卷 714-720页

作者：贾润幸方维萱赫英高振敏李红阳 Key Laboratory of Continental Dynamics of the Ministry of Education Department of Geology Northwest University Xi'an 710069 China Open Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

In order to get a better understanding of metallogeny, the geochemical characteristics of REE and trace element for Gejiu tin polymetallic deposits were studied by comparing concentrations of REE and trace elements in different type ores and rocks, including skarn-type ore, bedded-type ore, vein-type ore, altered granite, country rocks. Results of this study indicated that the metallogenic matters for different type ores in the study area might be derived from the same origin source, which may be mainly related to granitic activities. Furthermore, there are some differences in concentrations of REE in different ores due to their different depositional mechanism during that time. LREE concentrations were enriched relatively in the vein-type ores and the bedded-type ores with relatively low total REE concentrations, whereas total REE concentrations were higher in the skarn-type ores with LREE and HREE concentrations in wide variation ranges.

关键词： geochemistry of REE tin polymetallic deposit in origin Gejiu rare earths

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REE characteristics of the Fanshan alunite deposit in Zhejiang Province, China

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Chinese Journal Of Geochemistry 2006年第4期25卷 365-372页

作者：何玉良张乾邵树勋朱笑青祝朝辉王大鹏 Key Laboratory of ore deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences

REE geochemistry data from the Fanshan alunite deposit indicated that its ore-forming materials came chiefly from the country rocks, with δCe>0 for alunite ores. According to the differences in δEu,the alunite ores were divided into three types: weak negative Eu anomaly, weak positive Eu anomaly and remarkable positive Eu anomaly. The phenomena of Ce-enrichment in the ores indicated that the Fanshan alunite deposit was formed in an oxidizing environment. Variations in fO2 are corresponding to those in δEu: Eu anomaly varies from negative to positive with increasing fO2 . And two other important factors may impact the occurrence of Eu anomalies: the contents of alkaline feldspar and the protolith structure in the mineralization period.

关键词： REE特性火山作用浙江地球物理学

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