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Rock magnetic property of gravity core CSH1 from the northern Okinawa Trough and the effect of early diagenesis

Acta Oceanologica Sinica 2007年第5期26卷 54-65页

作者： GE Shulan SHI Xuefa WU Yonghua LEE Tehquei XIONG Yingqian SAITO Yoshiki Marine Sedimentation and Environmental Geology Key Laboratory of State Oceanic Administration First Institute of Oceanography State Oceanic Administration Qingdao 266061 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Institute of Earth Sciences Taipei China Geology Survey of Japan Tsukuba 306 - 8567 Japan

Detailed rock magnetic investigations were undertaken at 2 -4 cm interval for the gravity core CSHI （with a length of 17.36 m） from the northern Okinawa Trough. Time-scale of the core was constructed by two characteristic tephras and foraminferal assemblages, indicating an age of 50 ka for the bottom of the core. Except for three tephras and abrupt decrease in surface, there are little changes in all kinds of rock magnetic parameters that can be correlated to the climate change for the last 50 ka. Different from the common sediments, most S-ratios （S equals the negative ratio of IRM-0.3T to SIRM, which is an indicator of low coercivity content） of the sediments are smaller than 0. 9, which implies a substantial amount of magnetic minerals with high coercivity. The existence of iron sulphide （ greigite or pyrrhotite） is revealed by representative susceptibility - temperature curves showing 200 350 ℃ Curie temperature in addition to 580 ℃ of magnetite, and also by awful smell during heating and dark heating products. Both the occurrence of authigenic iron sulphide and quick decrease of magnetic parameters near the surface clearly show that sediments from Core CSHI have undergone early diagenesis. The featureless magnetic changes of the whole core except for three tephras mean that the post-depositonal alteration is so strong that most original signals have been destroyed. For the same reason, the organic matter in sediment and sulphate in pore water must have been consumed along with dissolution, precipitation of iron and manganese happening sequencially during the redox reaction series. Great caution must be taken when using these altered chemical parameters for the interpretation of climatic changes.

关键词： northern Okinawa Trough gravity core of CSHI rock magnetic property characteristic tephra early diagenesis

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early diagenesis of nurtrients (C, N, P and Si) stored in sediments of two reservoirs in southwestern China

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Acta Geochimica 2006年第S1期 161-162页

作者： Yuchun WANG1, Jun ZHU2, Congqiang LIU2 1 Dept. of Water Environment, China Institute of Water Resources and Hydropower Research, Beijing 100044, China 2 State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

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early Diagenetic Dolomite as a Potential Archive of Paleoredox Fluctuations in an early Tonian Marine Basin?

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Acta Geologica Sinica(English Edition) 2022年第2期96卷 607-620页

作者： KANG Junyao LI Chenqing DONG Lin XIAO Shuhai Key Laboratory of Orogenic Belts and Crustal Evolution MOEBeijing 100871China School of Earth and Space Sciences Peking UniversityBeijing 100871China Department of Geosciences Virginia TechBlacksburgVA 24060U.S.A.

The Tonian Period witnessed important environmental changes and critical evolutionary innovations. Published iron speciation data suggest a global redox transition of mid-depth seawaters from euxinic to ferruginous in early Tonian, but details of this transition remain unknown. This study explores Tonian stromatolitic carbonates as a possible archive of paleoenvironmental changes, through the investigation of dolomitic limestones and dolostones associated with stromatolites of the Weiji Formation in the Huaibei region of North China. Three types of dolomitization are recognized on the basis of petrographic and geochemical data. Type Ⅰ and Ⅱ dolomitization resulted in dolomitic limestones characterized by LREE depletions, MREE enrichments, positive yttrium anomalies, and a lack of europium anomalies, indicating early diagenetic dolomitization, possibly in the iron reduction zone and under the influence of bottom seawater. The lack of cerium anomalies in these carbonates suggests anoxia in shallow marine environments. The coexistence of ferroan/non-ferroan dolomite crystals and overgrowth bands is interpreted as possible evidence for rapid fluctuations between iron-rich and iron-depleted conditions in pore-waters or seawaters. In contrast, type Ⅲdolomitization resulted in pervasively dolomitized stromatolitic carbonates and likely represents late diagenetic processes. This study highlights the potential of early diagenetic dolomite as an archive for paleoenvironmental investigations.

关键词： redox early diagenesis rare earth elements dolomite Neoproterozoic North China

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Characteristics and distribution of low molecular weight organic acids in the sediment porewaters in Bosten Lake, China

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Journal of Environmental Sciences 2010年第3期22卷 328-337页

作者： Min Xiao Fengchang Wu Haiqing Liao Wen Li Xinqing Lee Rongsheng Huang State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of SciencesGuiyang 550002 China Graduate School of Chinese Academy of Sciences Beijing 100039 China Chinese Research Academy of Environmental Sciences Beijing 100012 China

The composition and vertical profiles of low molecular-weight organic acids （LMWOAs） and the contribution of them to dissolved organic matter （DOM） in sediment porewaters in Bosten Lake, Xinjiang, China were investigated. The results showed that total concentration of LMWOAs was up to 94.5 μmol/L and their proportion in DOM was 5.6%, suggesting that LMWOAs were important chemical components in DOM in lake sediment porewaters. Among the seven LMWOAs, pyruvic and acetic acid had the highest concentrations with 26.30 and 8.31 μmol/L, accounting for 51.4% and 14.92% of LMWOAs, respectively. Trifluoroacetic and sorbic acid had the lowest concentrations, indicating that the compositions of LMWOAs in relative reducing environments were largely different from those reported in glacier, atmosphere and soils. The concentrations of lactic, acetic, formic, sorbic and oxalic acid decreased with increasing depth, probably relating to stronger microbial activities in the initial stage of early diagenesis. Trifluoroacetic acid was mainly anthropogenic with its concentration, showing a diusive trend from the surface to bottom sediments. The concentrations of lactic acid and nitrate generally showed a consistent profile. The increasing concentration of pyruvic acid in the vertical profile was just opposite to that of sulfate, revealing a significant negative relationship between them. Oxalic acid remained constant except for an obvious peak at 6 cm depth. The results indicated the diversities in sources and behaviors for various LMWOAs during early diagenesis in sediments.

关键词： dissolved organic matter low molecular-weight organic acids sediment porewaters early diagenesis

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Distribution and accumulation of biogenic silica in the intertidal sediments of the Yangtze Estuary

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Journal of Environmental Sciences 2008年第5期20卷 543-550页

作者： HOU Lijun LIU Min XU Shiyuana YAN Huimin OU Dongni CHENG Shubo LIN Xiao State Key Laboratory of Estuarine and Coastal Research East China Normal University Shanghai 200062 China Key Laboratory of Geographical information Science of the Ministry of Education East China Normal University Shanghai 200062 China

Sedimentary biogenic silica is known to be an important parameter to understand biogeochemical processes and paleoenviromental records in estuarine and coastal ecosystems. Consequently, it is of great significance to investigate accumulation and distribution of biogenic silica in sediments. The two-step mild acid-mild alkaline extraction procedure was used to leach biogenic silica and its early diagenetic products in intertidal sediments of the Yangtze Estuary. The results showed that total biogenic silica （t-BSi） in the intertidal sediments varied from 237.7-419.4 μmol Si/g, while the mild acid leachable silica （Si-HCl） and the mild alkaline leachable silica （Si- Alk） were in the range of 25.1-72.9 μmol Si/g and 208.1-350.4 μmol Si/g, respectively. Significant correlations were observed for the grain size distributions of sediments and different biogenic silica pools in intertidal sediments. This confirms that grain size distribution can significantly affect biogenic silica contents in sediments. Close relationships of biogenic silica with organic carbon and nitrogen were also found, reflecting that there is a strong coupling between biogenic silica and organic matter biogeochemical cycles in the intertidal system of the Yangtze Estuary. Additionally, the early diagenetic changes of biogenic silica in sediments are discussed in the present study.

关键词： biogenic silica early diagenesis intertidal flats the Yangtze Estuary

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Pyrite Formation in Organic-rich Clay, Calcitic and Coal-Forming Environments

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Acta Geologica Sinica(English Edition) 2006年第4期80卷 574-588页

作者： Gordana DEVI Petar PFENDT Branimir JOVANIEVI Zoran POPOVIC Center of Chemistry IChTM Njego(s|ˇ)eva 1211000 BelgradeSerbia Center of Chemistry IChTM Njego(s|ˇ)eva 1211000 BelgradeSerbia Faculty of ChemistryUniversity of BelgradePOB 15811001 BelgradeSerbia Ministry of Science and Environmental Protection Department of Geology BelgradeSerbia

The early diagenetic characteristics of pyrite formation processes in a Miocene freshwater sequence of mixed sediments （coal fragments in clays, sandstones or shales） alternating with continuous brown coal layers was investigated. Based on abundant minerals, the following main sedimentary environments were distinguished： the illite-montmorillonitic （I-M）, calcitic （Ct） and coal-forming environment （CL）. For these hydrogeochemically differing environments the effects of limiting factors on the pyrite formation process （availability of sulphate and Fe, amount of organic matter and participation of organic sulphur） were assessed by correlation analysis. Significant differences in the effects of these limiting factors in the particular environments were observed. These differences were explained taking in account the different oxidative activity, Fe-complex and surface complex forming properties of humic substances in dependence of pH of environment and the abundance of sorptionally active clay minerals. In environments having a relatively low pH and containing clay minerals （I-M- and CL-environments） the oxidative activity of humic substances （Hs） on pyrite precursors was greatly prevented however pyrite formation depended on reactive Fe availability as the consequence of complex formation. On the contrary, in environments with a relatively high pH, as it was the calcitic, the oxidative activity of Hs was greatly enhanced, thus oxidizing the sulfur precursors of pyrite. The oxidation degree of organic matter was probably also a consequence of the differing activity of the humic electron-acceptors.

关键词： early diagenesis pyrite formation humic electron-acceptors calcitic environment illitemontmorillonitic environment coal mixed sediments

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Magnetic properties of Holocene core ZK9 in the subaqueous Yangtze delta and their mechanisms and implications

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Frontiers of Earth Science 2013年第3期7卷 331-340页

作者： Yan LIU Zhongfa HE Zhanghua WANG Department of Geography East China Normal University Shanghai 200062 China Shanghai Geological Survey Shanghai 200072 China State Key Laboratory of Estuarine and Coastal Research Shanghai 200062 China

We measured the magnetic properties of core ZK9 from the subaqueous Yangtze delta to examine the mechanisms and possibility of using magnetic proxies for the sedimentary environmental evolution controlled by the Holocene sea level. The results showed that low values of most magnetic parameters occurred and pyrite formed in the estuarine sediments during c. 10.5-8.4 cal ka BE reflecting the predominant early diagenesis in a tidaldominated depositional environment when the sea level rose rapidly. Sharp increases in the values of χARM （susceptibility of Anhysteresis Remanent Magnetisation）, χARM/χ, χARM/SIRM （Saturation Isothermal Remnant Magnetisation） and HIRM （Hard Isothermal Remnant Magnetisation） occurred immediately above the transitional zone from estuarine to deltaic system of c. 8.4--5.9 cal ka BP, which imply accumulation of single-domain magnetite and anti-ferromagnetic minerals. These magnetic properties indicate the enhanced freshwater processes at the core site as a result of the relatively stable sea level and the associated delta progradation since c. 5.9 cal ka BP. Therefore, magnetic proxies Of χARM and HIRM are useful to identify the maximum flooding surface. In addition, the intertidal-subtidal sediment of c. 13.2-10.5 cal ka BP had high values of χ, SIRM and HIRM, reflecting the features of a coastal environment. The sharp decline of the above parameters from c. 10.5 cal ka BP indicates possibly an event of rapid sea level rise.

关键词： magnetic properties early diagenesis maximum flooding surface sea level Yangtze delta Holocene

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The bio-barite in witherite deposits from Southern Qinling and its significance

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Progress in Natural Science:Materials International 2004年第10期14卷 49-55+98页

作者： Lv Zhicheng 1,2 ,LIU Congqiang 2 ,LIU Jiajun 2 and WU Fengchang 2 (1.Development and Research Center,China Geological Survey,Beijing100037,China 2.Institute of Geochemistry,Chinese Acade-my of Sciences,Guiyang550002,China) China Geol Survey Ctr Res & Dev Beijing 100037 Peoples R China Chinese Acad Sci Inst Geochem Guiyang 550002 Peoples R China

Being stratiform or stratoid,the Huangboshuwan witherite deposit at Zhiyang and the Wenyuhe witherite-barite deposit at Zhushan occur in the lower Lower Cambrian siliceous rocks and the orebodies are remarkably controlled by lithological character and pet-rography.Carbon and oxygen isotopic studies of witherite,barytocalcite and calcite have shown that the carbon,involved in the formation of these minerals,was derived largely from organic carbon resultant from degradation,polycondensation and dehydroxylation of bio-organic matter in sediments at the early stage of diagenesis.Extensive occurrence of bio-barite strongly evidenced that Ba 2+ was concentrated and settled down in the form of bio-barite on the seafloor as a result of biological processes,thereafter forming the initially enriched orebodies of barium deposits.The witherite was metasomatic products of bio-barite under the action of sulfate-reducing bacteria and organic and inor-ganic reduction.

关键词： bio-barite carbon and oxygen isotopes early diagenesis witherite deposits

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Carbon, oxygen and boron isotopic studies of Huangbai-shuwan witherite deposit at Ziyang and Wenyuhe witherite deposit at Zhushan

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Science China Earth Sciences 2003年第12期 1273-1291页

作者：吕志成刘丛强刘家军赵志琦 Jilin University Changchun 130026 China The State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sci-ences Guiyang 550002 China Open Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China The State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sci-ences Guiyang 550002 China Open Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

Being stratiform or stratoid, the Huangbaishuwan witherite deposit at Ziyang and the Wenyuhe witherite-barite deposit at Zhushan occur in the lower Lower Cambrian siliceous rocks and the orebodies are remarkably controlled by lithological character and petrography. Boron, carbon and oxygen isotopic studies of witherite, barytocalcite and calcite have shown that the car-bon, involved in the formation of these minerals, was derived mainly from hydrocarbons and bio-genetic gases resulting from degradation, polycondensation and dehydroxylation of bio-organic matter in sediments at the early stage of diagenesis; the boron was a mixture of boron in pore wa-ter and that released in the process of degradation of organic matter, with a minor amount of boron from cycling brines in the deep interior of the basin. Boron, carbon and oxygen isotopic studies unanimously demonstrated that witherite was precipitated in this sort of organic carbon-rich pore water medium during the early stage of diagenesis. Extensive occurrence of biodetritus and clastic texture in witherite ores strongly evidenced that Ba2+ was concentrated and settled down in the form of bio-barite on the seafloor as a result of biological processes, thereafter forming the initially enriched orebodies of barium deposits. Biological processes in seawater and early diagenesis in sediments are the major ore-forming mechanisms of witherite deposits in the region studied.

关键词： witherite deposit boron isotope carbon and oxygen isotopes early diagenesis bio-barite.

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