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1.
Xiugen Fu Jian Wang Yuhong Zeng Fuwen Tan Xinglei Feng 《Environmental Earth Sciences》2013,70(3):1125-1134
The Shengli River–Changshe Mountain oil shale zone represents a potentially large marine oil shale resource in China. With the aim of better understanding the geochemistry of trace elements in marine oil shale and its combustion residues, 40 raw samples, 27 oil shale combustion residues and 29 selected minerals from Changliang Mountain oil shale are studied for geochemical analyses. The contents of Se, Cd, Mo, As, Cs, Pb, Sr and U in the oil shale samples are enriched from 1.47 to 33.91 times as compared with the Clarke values, whereas the concentrations of other elements are slightly higher/lower than the respective worldwide means. The most enriched elements in oil shale combustion residues are Se, Cd, Mo, As and U with enrichment values from 4.78 to 50.92. Trace elements with high volatile behaviour such as As, Co, Ni, Sc, Sn and V occur predominantly in organic matter and/or sulphides. Other non-volatile or slightly volatile trace elements (e.g., Be, Bi, Cs, Cu, Ga, Hf, Li, Nb, Rb, Ta, Th, W, Zr and REEs) may occur mainly in original and relatively refractory minerals in raw oil shale. The potentially hazardous trace elements in Changliang Mountain oil shale include As, Cd, Mo and Se. Arsenic and Se are controlled mainly by Fe-bearing minerals (probably pyrite) in Changliang Mountain oil shale. Cadmium is present mainly in dolomite, while Mo occurs mainly in organic matter. 相似文献
2.
下扬子地区早古生代发育3套重要的深水相黑色岩系,分别为下寒武统荷塘组和黄柏岭组、上奥陶统五峰组、下志留统高家边组和相当层位的霞乡组。27件样品的微量和稀土元素分析结果显示：此3套黑色岩系具有Li、Be、Rb、Ba、Cs、W、Th、U、Cd、Bi、Pb等元素富集,Sc、Sr,Cr、Cu、Ga、Co、Ni等元素亏损,稀土元素总量较高,轻重稀土分异明显和具负Eu异常等壳源物质特征;微量不活动元素含量和比值特征的构造环境判别表明,下扬子地区早古生代黑色岩系构造环境为大陆岛弧和活动大陆边缘,兼具被动大陆边缘特征;母岩以上地壳的再旋回沉积物和后太古宙地层沉积物为主,部分为未分异的太古宙地壳和玄武岩成分,源岩性质主要为安山岩、英安岩和沉积岩;沉积环境为缺氧的半深海、深海环境。在上述研究基础上,对物源的来源进行了探讨,认为物源主要来自江南造山带。 相似文献
3.
Major and trace element composition of the Ordovician Obolus phosphorites and associated Dictyonema shales were determined by ICP-MS and chemical and microchemical elemental analyses. Relative to the phosphorites, the Dictyonema shales are substantially enriched in a variety of trace elements, except for As, Be, Co, Y, REE, Sr, and Pb. The Obolus phosphorites show enrichment of As, Bi, Hg, Mo, La, Y, Pb, and Sr and depletion of Ag, Ba, Be, Cd, Cr, Cu, Hf, Ni, Sc, Sn, U, V, Zn, and Zr relative to the world average phosphorite composition. The average trace element composition of the Dictyonema shales is close to the mean shale composition, except for higher contents of Mo, Hg, Pb, Se, Ta, Te, Th, V, and U and lower contents of Ba, Bi, Cd, Co, Re, Sr, and Zn. The results suggest that the change from phosphate sedimentation in aerated environments to anoxic carbonaceous sedimentation was accompanied by changes in the composition and concentration of trace elements in the sediment. Both facies show similar trends of trace element distribution indicative of the stability of the composition of seawater and terrigenous sediment input. 相似文献
4.
This paper presents the results of eco-geochemical research on black rock series enriched in metallic elements in Pingli County,Shaanxi Province,which lies at the northern margin of the Yangtze Platform.There is a suite of bone coal-bearing black carbonaceous rocks in the Cambrian Donghe Formation throughout the region.Soils in Pingli contain high metallic elements derived from the bone coal and carbonaceous rocks.Edible plants growing in the soils contain high Se,Cu and Mo.Two case studies are documented.One is a black shale area with bone coal and Se enrichment,and the other is a black shale area with bone coal mine and copper mineralization.Eco-geochemical effects of metallic element-rich black shales on plants are reported in this paper. 相似文献
5.
贵州遵义寒武系底部黑色页岩中含Mo、Ni、U等重金属的富集层，它们一直被认为与热水沉积作用有关。本文通过对贵州遵义松林小竹一带的寒武系底部地层的系统的岩石、矿物、地球化学研究，认为遵义松林小竹一带寒武系底部黑色页岩中富含Mo、Ni、U等重金属层属于热液（水）喷流沉积，主要依据有：①含大量的黄铁矿、针镍矿、硫钼矿及较多的锑硫镍矿、黄铜矿、闪锌矿、重晶石、石英、石膏等矿物；②具有大量的同生砾屑，砾屑成分为黑色碳质体和碎屑状黄铁矿、针镍矿、硫钼矿等矿石，它们堆积成层状结构，碎屑呈被撕裂状、棱角状、熔蚀港湾状等结构，球状、脸盆状、枕头状等构造，它们类似海底喷流沉积；③硅同位素、锶同位素、Re／Os值、Th／Sc值、Th／U值都表明有深部物质加入；④黑色岩系中夹碳酸盐岩透镜体，碳同位素具有强烈负异常特征，表明有热液作用；⑤超强富集元素Mo、As、Se、Re和T1都属于典型的气相迁移元素，而钼是典型的高温气相迁移元素，暗示了可能存在火山射气作用；而强富集的Ni、U、Au、Ag、PGE元素组合是超基性岩浆活动的产物，表明有热液活动。研究发现在热液（水）喷流沉积形成的富集Mo、Ni、U等重金属硫化物层之上，产出丰度大、分异度低、含大型海绵类、双壳类、菌藻类和少量大型蠕虫化石的生物群，它的特征与现代太平洋海底热喷口附近的生物群类似，因此认为遵义小竹一带寒武系底部生物群属于与海底热喷口相关生物群，这一新发现对研究寒武纪生态和生物爆发具有重要意义。 相似文献
6.
黔北下寒武统黑色岩系的沉积环境与地球化学响应 总被引：2，自引：0，他引：2
下寒武统黑色岩系在我国华北、华南及塔里木盆地等广泛发育,但富有机质泥页岩的分布特征及其控制因素未有定论。本文对黔北地区下寒武统牛蹄塘组(及同时期地层)不同沉积相带典型剖面中的富有机质泥页岩及其上下层位进行了地球化学分析,识别出寒武纪早期不同沉积相带氧化还原环境的明显差异。台内凹陷相主要岩性为黑色页岩,底部为不等厚的薄层磷块岩和硅质岩或硅磷质结核,沉积的黑色页岩厚度大,有机质丰度高,V、Ni、Mo、U等微量元素显著富集,反映了贫氧-缺氧环境,以及短暂动态的硫化环境,Mo/TOC反映了其为局限盆地特征;上斜坡相为贫氧到氧化的沉积环境,但更多地是表现为氧化的沉积环境,其中牛蹄塘期存在局部的硫化环境,沉积的黑色页岩厚度小,但有机质丰度最高,V、Ni、Mo、U等微量元素的富集程度较低;盆地相为黑色硅质岩与富有机质的黑色硅质页岩间互沉积,同期沉积厚度较小,有机质丰度相对较低,V和U的富集程度大于台内凹陷相,而Ni和Mo的富集程度则低于台内凹陷相,指示了缺氧环境,期间伴随有贫氧和短暂的氧化环境存在,且可能存在局部的硫化环境,Mo/TOC反映了中等的局限程度。总的来说,黔北下寒武统黑色岩系的有机质丰度、厚度以及微量元素富集程度等特征主要受控于不同的氧化还原环境。 相似文献
7.
《International Geology Review》2012,54(3):305-326
In this article, we describe the geological features of the Ediacaran (upper Sinian), lower Cambrian and lower Silurian shale intervals in the Upper Yangtze Platform, South China, and report on the gas potential of 53 samples from these major marine shale formations. Reflected light microscopy, total organic carbon (TOC) measurement, Rock-Eval, carbon isotope ratio analysis, thermovaporization gas chromatography (Tvap-GC), and open pyrolysis gas chromatography (open py-GC) were used to characterize the organic matter. Measured TOC in this research is normally >2% and averages 5%. TOC contents are roughly positively correlated with increasing geological age, i.e. lower Silurian shales exhibit generally lower TOC contents than lower Cambrian shales, which in turn commonly have lower TOC contents than Ediacaran shales. Kerogen has evolved to the metagenesis stage, which was demonstrated by the abundant pyrobitumen on microphotographs, the high calculated vitrinite reflectance (Ro = 3%) via bitumen reflectance (Rb), as well as δ13 C of gas (methane) inclusions. Pyrolysates from Tvap-GC and open py-GC are quantitatively low and only light hydrocarbons were detected. The lower Silurian shale generally exhibits higher generation of hydrocarbon than the lower Cambrian and Ediacaran shale. Cooles’ method and Claypool’s equations were used to reconstruct the original TOC and Rock-Eval parameters of these overmature samples. Excellent original hydrocarbon generation was revealed in that the original TOC (TOCo) is between 5% and 23%, and original S1+S2 (S1o+S2o) is ranging from 29 to 215 mg HC/g rock. 相似文献
8.
Release of heavy metals during weathering of the Lower Cambrian Black Shales in western Hunan,China 总被引：8，自引：0，他引：8
Weathering of heavy metal enriched black shales may be one of the most important sources of environmental contamination in areas where black shales are distributed. Heavy metal release during weathering of the Lower Cambrian Black Shales (LCBS) in western Hunan, China, was investigated using traditional geochemical methods and the ICP-MS analytical technique. Concentrations of 16 heavy metals, 8 trace elements and P were measured for samples from selected weathering profiles at the Taiping vanadium ore mine (TP), the Matian phosphorous ore mine (MT), and Taojiang stone-coal mine (TJ). The results show that the bedrock at these three profiles is enriched with Sc, V, Cr, Co, Ni, Cu, Zn, Pb, Th, U, Mo, Cd, Sb, Tl, and P. Based on mass-balance calculation, the percentages of heavy metals released (in % loss) relative to immobile element Nb were estimated. The results show significant rates of release during weathering of: V, Cr, Co, Ni, Cu, Zn, U, Mo, Cd, Sn, Sb, and Tl for the TP profile; Sc, Cr, Mn, Co, Ni, Cu, Zn, Pb, Th, Cd, and Sn for the MT profile; and Sc, Mn, Co, Ni, Zn, Th, Cd, Sn, and Tl for the TJ profile. Among these heavy metals, Co, Ni, Zn, Cd, and Sn show very similar features of release from each of the three weathering profiles. The heavy metals released during weathering may affect the environment (especially topsoil and surface waters) and are possibly related to an observed high incidence of endemic diseases in the area. 相似文献
9.
贵州开阳白马洞铀矿化岩层地球化学特征 总被引：2，自引：0，他引：2
贵州开阳白马洞铀矿是重要的蚀变型铀矿,通过对白马洞清虚洞组黑色蚀变岩及白云岩风化红粘土和寒武系牛蹄塘组黑色页岩的常量元素、微量元素和稀土元素组成的分析研究,发现铀元素含量与Re、Se、Pb、Cu、As、Sb、Tl、Zn、Ni、Mo、Co、S含量为正相关关系,铀含量高,则Re、Se、Pb、Cu、As、Sb、Tl、Zn、Ni、Mo、Co、S含量也高,其中As、Co、Mo、Ni、Re、Tl、Zn、S具有显著的正相关性,而且地表土壤中Se、V、Mo 等元素的富集是铀矿找矿的主要标志之一。根据白马洞清虚洞组、寒武系牛蹄塘组黑色页岩、灯影组硅化白云岩的稀土元素配分模式分析,硒富集和铀矿化矿源层不仅是牛蹄塘组黑色页岩,可能有更深部的矿源存在。认为硒富集区是铀矿找矿远景区域;古代炼汞矿渣富集铀矿,值得开发利用和治理。 相似文献
10.
赣西北下寒武统黑色岩系,是一套重要的铀等金属的含矿岩系,其中观音堂组碳硅泥岩是典型的黑色岩石类型。运用地球化学方法,对这套灰黑色泥质岩的元素地球化学及古环境演变特征进行了研究。研究结果表明:该碳硅泥岩黏土类矿物含量55%～59%,SiO_2,Al_2O_3,Fe_2O_3,K_2O,MgO平均含量分别为69.47%,11.39%,3.32%,2.76%,1.57%;化学成分表现为高硅低铝低钾低镁特征,有机碳平均含量5.82%,属富碳黑色岩系。对比中国东部泥质岩,其Ni、V、U、Ba、Cd、In、Tl、Se、W、Mo、Cu、Zn、Au、Ag、As、Sb等元素有相对富集的特点。从碳硅泥岩层的上部到下部,SiO_2、Na_2O、Ni、Mo含量逐渐增高,Al_2O_3、K_2O、TiO_2、H_2O^-、LOI、Cr、Th、Ba、Ga、Li、Be、Rb、Sc、Sn、Bi、Cu、Pb、Zn、Ag、REE则显示逐渐降低趋势。主量或微量元素的判别参数或图解显示,碳硅泥岩的物源以陆源碎屑岩为主,是在一个沉积速率较小、且较稳定的深水还原环境下沉积的,从早期到晚期,物源区呈现风化作用逐渐增强、气候环境越来越湿润、盆地水质越来越淡化的趋势。 相似文献
11.
The Ilgin lignite field can be subdivided into the Haramiköy and Kurugöl areas which are separated by an area of basement and a fault. The lignite-bearing sequence consists mainly of fluvial and lacustrine Neogene deposits. The Ilgin lignite, averaging 8 m (up to 25 m) thick, is blackish brown and dark brown in colour. The lignite contains abundant brown wood, plant remains and white gastropod shells. Samples have an average of 38.9% moisture on an as-received basis and a mean of 3.9% total sulphur on an air-dried basis. Geochemical analysis, using an ICP-MS, was undertaken. Thirteen lignite core samples from three boreholes drilled in the Kurugöl area were ashed at 750°C. The average trace element contents of the lignite show a higher concentration of U (average 43 ppm) when compared to the range for most coals in the world, while the others (Ti, P, Sc, Be, Mn, Co, Cu, Zn, Ga, As, Rb, Sr, Zr, Nb, Mo, Cs, Ba, Y, Ta, W, Tl, Pb, Bi, Th, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu) agree with the global ranges. The Ilgin lignite is identified as of Middle Miocene (Middle Serravallian) age and occurs within lacustrine sediments deposited under subtropical climatic conditions. 相似文献
12.
中国南方扬子地区下寒武统黑色页岩分布广泛,主要由黑色页岩、黑色白云质页岩,黑色粉砂质页岩和黑色硅质页岩等组成;并伴生有较厚的磷块岩矿床、钒矿床和镍、钼多元素硫化物矿床。对黑色页岩岩石学特征、元素地球化学特征进行系统研究,并详细分析微量元素的富集成因,结果表明：黑色页岩主要形成于静水还原的浅海-半深海缓坡环境,层状元素富集带为沉积成因,海底热流体提供了丰富物质来源。总体上,Co、Be、Mn、Ga等元素含量较低;Cu、V、Ni、Mo等元素的含量较高,多数超过北美页岩平均值;以Ni、Mo为主的多元素富集层通常位于磷块岩之上,以黑色页岩、黑色白云质页岩中的硫化物和硫酸盐矿物为主要载体,其中有机碳（TOC）含量可达12.2%以上,远高于其他元素富集层,随着页岩内硅质成分增加,Ni、Mo、Fe、Co等元素含量明显降低;以V为主的多元素主要赋存于黑色硅质页岩中的水云母,与页岩内硅质成分具有较好的正相关关系;黑色页岩中稀土元素含量为(76.22~290.67)×10-6,轻重稀土比值LREE/HREE介于1.21~4.22,说明轻稀土更为富集,Sr/Ba值为0.04~0.34,δEu正异常,且北美页岩标准化配分曲线呈现平缓左倾,为沉积过程中存在海底热水流体提供了进一步证据。 相似文献
13.
In western Victoria, a widespread stratiform style of gold enrichment in Palaeozoic black mudstone and chert—clearly different from the classic mesothermal quartz vein deposits of the Victorian goldfields—has been confirmed by whole-rock geochemistry and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). This enrichment pre-dates compaction, deformation and low-grade metamorphism of the sedimentary host-rocks, and therefore possibly developed diagenetically during slow deposition of the thin carbonaceous black mudstone beds and the thinner layers of chert. These paired strata have been documented at many locations in three regional outcrop areas of chevron-folded Cambrian and Lower Ordovician metasediments in the Stawell and Bendigo Zones, where they are interbedded with quartz-rich turbidites. The layers were named ‘indicators’ by the early miners, who found locally rich nuggety gold deposits at intersections between these layers and mesothermal quartz veins. Gold is present in euhedral pyrite crystals in both black shale and chert. LA-ICPMS analysis of individual pyrite crystals in the indicator beds shows that pyrite is enriched in Au, As, Sb, Se, Te and Bi. The Au content of pyrite varies from 0.03 to 2.69 ppm with a mean of 0.58 ppm and shows a positive correlation with As, which varies from 1000 to 6000 ppm. Many pyrite crystals show enrichment of gold in their cores and depletion in their rims, confirming the likely syngenetic or syndiagenetic accumulation of gold during pyrite formation in the sediments. Prior to regional metamorphism, folding and faulting, the many indicator strata in the outcrop areas were parts of an extensive marine sequence of Late Cambrian and Early Ordovician age. The former primary source of this mineralisation is considered to have been one or more contemporaneously exhalative submarine hydrothermal systems. Thus, the older Palaeozoic sediments of the western Lachlan Fold Belt were significantly enriched in syngenetic gold in the Early Palaeozoic, at least 40 million years before emplacement of the quartz – gold vein deposits of the goldfields. 相似文献
14.
Raimundo Jiménez Ballesta Paz Conde Bueno Juan A. Martin Rubi Rosario Garcia Giménez 《Central European Journal of Geosciences》2010,2(4):441-454
To evaluate trace element soil contamination, geochemical baseline contents and reference values need to be established. Pedo-geochemical baseline levels of trace elements in 72 soil samples of 24 soil profiles from the Mediterranean, Castilla La Mancha, are assessed and soil quality reference values are calculated. Reference value contents (in mg kg?1) were: Sc 50.8; V 123.2; Cr 113.4; Co 20.8; Ni 42.6; Cu 27.0; Zn 86.5; Ga 26.7; Ge 1.3; As 16.7; Se 1.4; Br 20.1; Rb 234.7; Sr 1868.4; Y 38.3; Zr 413.1; Nb 18.7; Mo 2.0; Ag 7.8; Cd 4.4; Sn 8.7; Sb 5.7; I 25.4; Cs 14.2; Ba 1049.3; La 348.4; Ce 97.9; Nd 40.1; Sm 10.7; Yb 4.2; Hf 10.0; Ta 4.0; W 5.5; Tl 2.3; Pb 44.2; Bi 2.2; Th 21.6; U 10.3. The contents obtained for some elements are below or close to the detection limit: Co, Ge, Se, Mo, Ag, Cd, Sb, Yb, Hf, Ta, W, Tl and Bi. The element content ranges (the maximum value minus the minimum value) are: Sc 55.0, V 196.0, Cr 346.0, Co 64.4, Ni 188.7, Cu 49.5, Zn 102.3, Ga 28.7, Ge 1.5, As 26.4, Se 0.9, Br 33.0 Rb 432.7, Sr 3372.6, Y 39.8, Zr 523.2, Nb 59.7, Mo 3.9, Ag 10.1, Cd 1.8, Sn 75.2, Sb 9.9, I 68.0, Cs 17.6, Ba 1394.9, La 51.3, Ce 93.5, Nd 52.5, Sm 11.2, Yb 4.2, Hf 11.3, Ta 6.3, W 5.2, Tl 2.1, Pb 96.4, Bi 3.0, Th 24.4, U 16.4 (in mg kg?1). The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination. 相似文献
15.
我国中上扬子地区下古生界黑色页岩是震旦系、二叠系大中型气田的重要烃源岩,同时其自身也具有形成页岩气藏的巨大潜力。初步研究表明,中上扬子地区下古生界有利页岩气层主要发育在下震旦统陡山沱组、下寒武统筇竹寺组、上奥陶统五峰组和下志留统龙马溪组,这些层位的黑色页岩厚度、有机碳含量、以及Ro值等各项参数均符合形成页岩气藏的特征,是今后页岩气勘探的潜力地层。 相似文献
16.
Xiugen Fu Jian Wang Wenbin Chen Xinglei Feng Dong Wang Chunyan Song Shengqiang Zeng 《Geological Journal》2016,51(3):443-454
The early Jurassic black shales are the most important source rocks in the Qiangtang Basin, Tibet. These black shales may provide a useful example for understanding the sedimentary conditions during the early Jurassic in the eastern Tethys. Thirty‐two black‐shale samples were collected from the Qiangtang Basin to reconstruct the depositional environments during the early Jurassic in the eastern Tethys. The palaeoclimate index Σ(Fe + Mn + Cr + Ni + V + Co)/Σ(Ca + Mg + Sr + Ba + K + Na) varies between 0.58 and 1.14, together with low Sr/Ba (0.20–0.60) and Sr/Cu (1.68–7.88) ratios, indicating a warm humid to semi‐humid climatic condition during black‐shale deposition. The early Jurassic black shales exhibit slight Ce anomalies (0.89–0.94) and Mn enrichment (EF = 1.2), suggesting a slightly oxic depositional environment. The conditions of the sedimentary water system during black‐shale deposition were apparently brackish as evidenced by middle B/Ga (3.96–5.73) and Th/U (3.96–6.51) ratios. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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18.
The radiation of macroscopic animals in the Early Cambrian, commonly be called as ‘Cambrian explosion’, had a close relationship with Earth oxygenation. These macrofossils are widely preserved within the Early Cambrian in the northern and western Yangtze Craton. In order to show the casual relationship between animal evolution and Earth redox environment, Mo content and isotopic composition analyses have been conducted on dolomites of the Tianzhushan Formation and the black shales of the Shuijingtuo Formation from the lowermost Cambrian profile in the eastern Huangling dome, northern Yangtze Craton. The calcitic dolostones from the Tianzhushan Formation display lower concentrations of Mo contents (0.055–0.666 ppm) than that of the black silty shales from the Shuijingtuo Formation (6.0–172 ppm). This magnitude difference is most likely related to the different lithologies due to Mo enrichment in shales. The Mo isotope values (δ98/95Mo) of the calcitic dolostones for the Tianzhushan Formation vary from −0.73‰ to 0.41‰. In comparison, the black sandy shales from the Shuijingtuo Formation exhibit δ98/95Mo of −1.04–1.84‰, including 5 samples from the earliest Shuijingtuo Formation displaying systematically higher δ98/95Mo values (0.09–1.84‰) than those of the other 5 samples from upper layers (δ98/95Mo = −1.04 to −0.19‰). These geochemical data suggest that the redox environment of the early Cambrian is fluctuating, and the peak oxygenation of the ocean had already reached a level similar to modern environments. According to the Mo concentrations and δ98/95Mo data, the sedimentary succession can be divided into five intervals, which are closely correlated to the episodic evolution of early life in the Cambrian. Together with the available published data from other profiles in the Yangtze Craton, our new data reveal that the higher oxidation environment had a positive effect on the evolution of early life. 相似文献
19.
Total organic carbon content (TOC), trace element and platinum-group element (PGE) concentrations were determined in the black shales of the Lower Cambrian Niutitang Formation in the Nayong area, Guizhou Province, South China, in order to study the polymetallic Ni–Mo–PGE mineralization. The results demonstrate that numerous elements are enriched in the polymetallic ores compared to those of the nearby black shale, particularly Ni, Mo, Zn, TOC and total PGE, which can reach up to 7.03 wt.%, 8.49 wt.%, 11.7 wt.%, 11.5 wt.% and 943 ppb, respectively. The elemental enrichment distribution patterns are similar to those in the Zunyi and Zhangjiajie areas except that the Nayong location is exceptionally enriched in Zn. Whereas positive correlations are observed between the ore elements of the polymetallic ores, no such correlations are observed in the black shale. These positively correlated metallic elements are classified into three groups: Co–Ni–Cu–PGE, Zn–Cd–Pb and Mo–Tl–TOC. The geological and geochemical features of these elements suggest that Proterozoic and Early Palaeozoic mafic and ultramafic rocks, dolomites and/or Pb–Zn deposits of the Neoproterozoic Dengying Formation and seawater could be the principal sources for Co–Ni–Cu–PGE, Zn–Cd–Pb, and Mo–Tl–TOC, respectively. Furthermore, the chondrite-normalized patterns of PGEs with Pd/Pt, Pd/Ir and Pt/Ir indicate that PGE enrichment of the polymetallic ores is most likely related to hydrothermal processes associated with the mafic rocks. In contrast, PGE enrichment in the black shale resembles that of the marine oil shale with terrigenous and seawater contributions. Our investigations of TOC, trace elements and PGE geochemistry suggest that multiple sources along with submarine hydrothermal and biological contributions might be responsible for the formation of the polymetallic Ni–Mo–PGE mineralization in the black shales of the Lower Cambrian Niutitang Formation across southern China. 相似文献
20.
Accumulation and sources of heavy metals in urban topsoils: a case study from the city of Xuzhou, China 总被引：8，自引：0，他引：8
The knowledge of the variability, the anthropogenic versus natural origin and corresponding environmental risk for potentially harmful elements in urban topsoils is of importance to assess human impact. The aims of the present study were: (1) to assess the distribution of heavy metals (Sn, Li, Ga, Ba, Fe, Mn, Co, Be, Ti, Al, Hg, Cr, Sb, As, Bi, Pd, Pt, Au, Ni, Cd, Zn, Cu, Pb, Se, Mo, Sc and Ag) in urban environment; (2) to discriminate natural and anthropogenic contributions; and (3) to identify possible sources of pollution. Multivariate statistic approaches (principal component analysis and cluster analysis) were adopted for data treatment, allowing the identification of three main factors controlling the heavy metal variability in Xuzhou urban topsoils. Results demonstrate that Hg, Cr, Sb, As, Bi, Pd, Pt, Au, Ni, Cd, Br, Zn, Cu, S, Pb, Se, Mo, Sc and Ag could be inferred to be tracers of anthropogenic pollution, whereas Al, Ti, Ga, Li, V, Co, Pt, Mn and Be were interpreted to be mainly inherited from parent materials. Iron, Ba, Sn, Pd and Br were interpreted to be affected by mixed sources. 相似文献