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1.
冷泉碳酸盐岩是海底冷泉流体活动的重要标志,其地球化学特征记录了过去流体活动的信息。西藏岗巴地区晚白垩世沉积地层中发育有冷泉碳酸盐岩,为了探究其形成的流体来源及沉积环境,开展了野外观察、岩石学、矿物学、地球化学研究。该区岗巴剖面冷泉碳酸盐岩以结核状产于灰黑色页岩中,碳酸盐矿物主要为泥微晶方解石,含少量草莓状黄铁矿,δ13CV-PDB为-17.0‰~-7.2‰,表明碳源可能与甲烷渗漏冷泉活动有关。稀土元素分布模式呈中稀土富集特征,经La校正后显示无Ce异常,指示了冷泉碳酸盐岩形成于弱缺氧的沉积环境中。西藏岗巴地区碳酸盐岩结核的发现及其地质地球化学特征是该地区晚白垩世冷泉甲烷渗漏活动发育的有力证据,对古冷泉流体来源及沉积环境特征的探讨将为恢复古冷泉活动提供重要线索。 相似文献
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羌塘盆地南部双湖地区曲色组地层发育大量碳酸盐岩结核,这些结核多呈丘状、椭球状、透镜状、似层状、脉状、树枝状产出。其物质组分主要为泥微晶碳酸盐矿物,少量粘土矿物、石英及草莓状、半自形黄铁矿等。草莓状黄铁矿平均粒径在5.0μm左右,内部可见葵花状构造。发育凝块状、气孔状和渗漏孔等特殊构造。产双壳类、菊石类、蠕虫状或树枝状生物及超微生物化石,生物密度极高。碳同位素明显负偏,硫同位素则明显正偏,其特征与现代海底天然气水合物的渗漏、释放所形成的冷泉碳酸盐岩机理一致,因而推测为古代海底天然气渗漏喷发形成。大量海底天然气泉口的存在,可能表明羌塘盆地双湖地区早侏罗世大洋缺氧事件与海底天然气水合物喷发存在极大关联。 相似文献
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墨西哥湾GC238区冷泉碳酸盐岩的微结构与石化微生物特征 总被引：3，自引：0，他引：3
采于墨西哥湾GC238海底天然气渗漏区浅表层的冷泉碳酸盐岩呈结核状产出,由方解石微晶和胶结物及少量的黄铁矿构成。胶结物由直径为0.1～0.5m的方解石化的球体、卵形体、棒状体组成,充填于方解石晶体之间。冷泉碳酸盐岩结核下表面发育有由方解石化的球体、卵形体、棒状体组成的薄层,其中的一些球状集合体(约5m)断面显示发育有核和外壳的层圈结构。黄铁矿呈草莓状,也具有相似的层圈结构。这种层状结构与活体古细菌被硫酸盐还原细菌包裹的层圈结构相似。样品中所保存的球体、卵形体、棒状体及其所组成的层圈结构可能是石化的甲烷氧化古细菌和硫酸盐还原细菌。 相似文献
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采于墨西哥湾GC238海底天然气渗漏区浅表层的冷泉碳酸盐岩呈结核状产出,由方解石微晶和胶结物及少量的黄铁矿构成。胶结物由直径为0.1～0.5 m的方解石化的球体、卵形体、棒状体组成,充填于方解石晶体之间。冷泉碳酸盐岩结核下表面发育有由方解石化的球体、卵形体、棒状体组成的薄层,其中的一些球状集合体（约5 m）断面显示发育有核和外壳的层圈结构。黄铁矿呈草莓状,也具有相似的层圈结构。这种层状结构与活体古细菌被硫酸盐还原细菌包裹的层圈结构相似。样品中所保存的球体、卵形体、棒状体及其所组成的层圈结构可能是石化的甲烷氧化古细菌和硫酸盐还原细菌。 相似文献
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《地球化学》2017,(6)
冷泉碳酸盐岩是冷泉渗漏活动的重要产物之一,它记录了冷泉流体的来源、其活动演化特征和沉积环境等。通过对南海北部东沙海域Site3站位采集的三个烟囱状冷泉碳酸盐岩的矿物成分、碳氧同位素及碳酸盐岩中黄铁矿硫同位素的研究,确定了冷泉渗漏可能的流体来源,结合烟囱状碳酸盐岩独特的形貌特征,探讨了研究区冷泉流体的活动演化特征。烟囱A为环状,外环直径16 cm,中央流体通道直径5 cm;烟囱B呈底部直径8 cm的实心锥形;烟囱C也为环状,外环直径20 cm,中央流体通道直径12 cm。三个烟囱都具有较负的碳同位素组成(δ~(13)CVPDB值低至–55.7‰)和较正的氧同位素组成(δ~(18)OVPDB值高达5.4‰)特征。研究认为,甲烷是该海域冷泉渗漏流体的主要烃类来源,其中沉淀烟囱C的冷泉流体中很可能存在水合物分解释放流体的加入。三个烟囱状碳酸盐岩的外层相比于内层,普遍具有δ~(13)C值高、δ~(18)O值低、δ~(34)S值高的特征,认为这是由于烟囱状碳酸盐岩从外至内形成过程中沉积空间逐渐受到限制导致流体渗漏强度增强而造成的。综上所述,烟囱状冷泉碳酸盐岩因其独特的形态结构,是冷泉流体渗漏特征在时间和空间上变化的优良记录者。 相似文献
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海底天然气渗漏系统微生物作用及冷泉碳酸盐岩的特征 总被引：18，自引：3，他引：18
海底天然气渗漏系统是全球海洋环境中广泛分布的自然现象。部分渗漏天然气通过细菌作用转变为二氧化碳,同时海水硫酸盐被还原为硫化氢, 与孔隙水中的钙和铁结合而沉淀冷泉碳酸盐岩。冷泉碳酸盐岩的常见矿物有微晶方解石、文石、白云石和黄铁矿。冷泉碳酸盐岩常发育一些特殊的组构, 如黄铁矿环带结核、溶蚀面、平底晶洞、凝块和向下生长的叠层石组构等。碳酸盐岩特别负的δ13C值指示碳来源于生物成因的甲烷, 而18O富集可能与天然气水合物的分解有关。冷泉碳酸盐岩中黄铁矿的δ34S值低于海水的, 这指示硫来源于微生物还原的海水硫。冷泉碳酸盐岩中的生物标志化合物及其极负的δ13C值指示微生物的生命代谢活动。 相似文献
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《地球化学》2017,(5)
对黔南泥盆系重晶石矿床的产出地质背景、矿床地质和同位素地球化学特征进行了综合分析,总结了重晶石矿床空间分布特征和成矿规律,指出了可能的成矿远景区。重晶石矿床空间展布形态及产出特征受北西向区域性深大断裂控制明显,矿体呈北西向沿褶皱或次级断裂分布。矿石结构、构造类型在乐纪矿段最为多样,包括纹层状、条带状、块状、碎屑状和角砾状构造,且矿体厚度最大,约10 m;向东部罗城矿段过渡,矿石构造类型主要以纹层状和块状构造为主,矿体厚度迅速减薄或尖灭。矿石S同位素组成从乐纪至罗城,δ~(34)S值由+68.4‰迅速降低至+27.6‰,指示乐纪地区相比罗城一带,可能处于更深水的局限环境,硫酸盐还原细菌作用更加强烈。重晶石矿体中与古甲烷渗漏事件有关的球状灰岩,其δ~(13)C值在乐纪矿段表现最负,为–10.27‰,罗城矿段灰岩δ~(13)C值逐渐偏正,达到+0.03‰,说明古甲烷渗漏活动在乐纪矿段表现更剧烈,强烈的渗漏事件为形成厚度约10 m的重晶石矿体提供了充足的物质保障。镇宁乐纪地区很可能是重晶石成矿的中心,向东部罗城一带过渡,逐渐远离成矿中心,成矿物质供应匮乏,不易形成具有经济价值的工业重晶石矿体。此外,应重视并加强乐纪以西地区重晶石找矿勘查工作,重点是寻找北西向断裂或褶皱构造发育地区,重晶石成矿条件相比更加优越,易在隐伏重晶石矿床找矿方面取得新突破。 相似文献
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新元古代晚期盖帽碳酸盐岩的成因与“雪球地球”的终结机制 总被引：5，自引：3，他引：5
新元古代晚期约635 Ma的地球发育了到达赤道附近的冰川作用，地质记录上表现为代表寒冷气候的冰期沉积杂砾岩，直接被代表温暖环境的碳酸盐岩层（常称盖帽碳酸盐岩）覆盖。由于盖帽碳酸盐岩奇特的岩石学和地球化学特征，引起了对其成因认识的巨大争论，提出了“雪球地球”和“甲烷渗漏”等假说。“雪球地球”假设可以解释一些令人困惑的地学现象，如低纬度和低海拔冰川沉积、盖帽碳酸盐岩、碳酸盐δ13C负漂移和条带状铁矿层等，但许多科学家对此提出了质疑。最近对盖帽碳酸盐岩的δ13C分析结果（最低达-41‰）、盖帽碳酸盐岩发育的类似现代冷泉碳酸盐岩沉积组构等似乎支持“甲烷渗漏”假说。 相似文献
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扬子克拉通秭归地区震旦系陡山沱组第四段黑色泥页岩中广泛发育具明显δ13C负异常的碳酸盐岩结核,其是否与古甲烷天然气水合物渗漏有关值得深入研究.对该碳酸盐岩结核开展的沉积结构构造、岩相学和地球化学研究表明,碳酸盐岩结核具典型韵律环带结构,普遍发育有亮晶球体结构、草莓状黄铁矿,以及与渗漏系统有关的凝块组构,δ13C具明显负异常(-5.65‰~-6.76‰),U、Mo元素强烈富集(UEF=8~26,MoEF=99~320),Y/Ho比值为31.05~37.31,稀土配分型式为平缓左倾,主微量元素K、Sc、V、Cr、Co、Ni、Rb、Sr、Ba、Th、U和Mo等总体显示为缺氧-硫化环境,与冷泉碳酸盐岩的形成环境和特征一致.碳酸盐岩结核环带SiO2、MgO、CaO、CO2等地球化学元素含量呈阶段性连续增减变化,显示碳酸盐岩结核形成经历了初始形成、成岩-交代、成岩后改造3个连续演化阶段.据此,提出碳酸盐岩结核是新元古代末噶斯奇厄斯冰期(582~551 Ma)结束温度回暖,黑色泥页岩中低温封存固态天然气水合物发生分解释放和成岩-交代形成的冷泉碳酸盐岩结核,也是古天然气水合物存在的重要地质记录和标志,这一新认识为华南扬子克拉通在震旦系和下古生界沉积盖层中寻找页岩气(甲烷天然气)储集层位提供了重要地质依据. 相似文献
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S. Viswanathan K. Surya Prakash Rao B. Mahabaleswar 《Journal of the Geological Society of India》2013,82(6):621-627
Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours. 相似文献
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奥地利安东帕有限公司 《岩矿测试》2009,28(3):306-306
最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提 相似文献
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E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others. 相似文献
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Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance. 相似文献
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Alexander E. C. Broberg J. S. Kehren A. R. Graziani M. M. Turri W. L. 《Environmental Geology》1993,22(4):353-361
Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×106 1 of partially treated effluent and about 600 m3 of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes. 相似文献
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Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA 总被引：1，自引：0，他引：1
The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources. 相似文献
19.
滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床. 相似文献
20.
岩石密度和超高压岩石折返速率 总被引：1，自引：3，他引：1
在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。 相似文献