重庆城口地区下寒武统黑色岩系元素地球化学特征及其成因
摘要
地区广泛发育有下寒武统。利用ICP-MS方法系统分析重庆城口地区下寒武统黑色岩系中多金属富集层、炭质粉砂岩以及硅质岩样品的微量元素、稀土元素组成。研究结果表明稀土总量为111.41×10-6~184.13×10-6,平均为138.83×10-6,相对其他地区黑色岩系较低;LREE/HREE=2.49~3.44,LREE相对富集,HREE亏损;δCe=0.39~0.46,Ce呈明显负异常;δEu=0.84~1.10,Eu异常不明显。δCe,δU,V/Cr,Ni/Cr,V/(V+Ni)表明该区黑色岩系形成于缺氧环境;稀土元素地球化学特征及其相关图解、Cr,Sb,As,Bi的富集以及U/Th等反映本区黑色岩系非正常海水沉积产物,明显受热水沉积的影响,同时还存在火山活动的影响,火山活动可能为热水活动提供了动力及物质成分。
The black rock series of Lower Cambrian are well developed in Chengkou district,Chongqing.ICP-MS techniques was used to analyze trace element contents in Lower Cambrian black rock series,including cherts,black siltstones and multi-elements concentrated layers.Compared to northern Guizhou and northwestern Hunan,the REE in these rocks is very low with the value ranging from 111.41×10-6 to 184.13×10-6,averaging 138.83×10-6.LREE/HREE ratios vary from 2.49 to 3.44,indicating that LREE is relative abundant.δCe values range from 0.39 to 0.46,showing almost negative anomaly,and the δEu shows unconspicuous anomaly,with the value between 0.84 and 1.10.The indicators of δCe,δU,V/Cr,Ni/Cr and V/(V+Ni) demonstrated that these black rock series formed in the anoxic environment.REE geochemical characteristics and their diagrams,high enrichments of Cr,Sb,As,Bi and U/Th ratios indicated that black rock series mainly formed by hydrothermal deposition.Meanwhile,the petrogenesis of black rock series was associated with volcanism,which provided the composition and dynamics to the hydrothermal activity.
The black rock series of Lower Cambrian are well developed in Chengkou district,Chongqing.ICP-MS techniques was used to analyze trace element contents in Lower Cambrian black rock series,including cherts,black siltstones and multi-elements concentrated layers.Compared to northern Guizhou and northwestern Hunan,the REE in these rocks is very low with the value ranging from 111.41×10-6 to 184.13×10-6,averaging 138.83×10-6.LREE/HREE ratios vary from 2.49 to 3.44,indicating that LREE is relative abundant.δCe values range from 0.39 to 0.46,showing almost negative anomaly,and the δEu shows unconspicuous anomaly,with the value between 0.84 and 1.10.The indicators of δCe,δU,V/Cr,Ni/Cr and V/(V+Ni) demonstrated that these black rock series formed in the anoxic environment.REE geochemical characteristics and their diagrams,high enrichments of Cr,Sb,As,Bi and U/Th ratios indicated that black rock series mainly formed by hydrothermal deposition.Meanwhile,the petrogenesis of black rock series was associated with volcanism,which provided the composition and dynamics to the hydrothermal activity.
引文
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[21]王立社,侯俊富,张复新,等.北秦岭庙湾组黑色岩系稀土元素地球化学特征及其成因意义[J].地球学报,2010,31:73-82.
[22]Marchig V,Gundlach H,Moller P,et al.Some geochemical indicators for discrimination beyween diagenetic and hydrothermal metallifer-ous sediments[J].Marine Geology,1982,50:241-256.
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[26]Rona P A.Criteria for recognition of hydrothermal mineral deposits in oceanic crust[J].Economic Geology,1978,73:135-160.
[27]Hogdahl O T,Melson S,Bowen V T.Neutron activation analysis of lanthanide elements in seawater[J].Advances in Chemistry,1968,73:308-325.
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[29]夏邦栋,钟立荣,方中,等.下扬子区早二叠世孤峰组层状硅质岩成因[J].地质学报,1995,69:125-137.
[30]罗泰义,张欢,李晓彪,等.遵义牛蹄塘组黑色岩系中多金属富集层的主要矿化特征[J].矿物学报,2003,23:296-302.
[31]Coveney R M,Chen N S.Ni-Mo-PGE-Au-rich ores in Chinese black shales and speculations on possible analogues in the United States[J].Mineralium Deposita,1991,26:83-88.
[2]冯彩霞,刘燊,胡瑞忠,等.遵义下寒武统富硒黑色岩系地球化学:成因和硒富集机理[J].地球科学-中国地质大学学报,2010,35:947-958.
[3]范德廉,杨秀珍,王连芳,等.某地下寒武纪含镍钼多元素黑色页岩的岩石学及地球化学特点[J].地球化学,1973,3:143-160.
[4]罗泰义,宁兴贤,罗远良,等.重庆城口地区早寒武系黑色岩系研究:铂族元素成矿潜力评价[J].矿物学报,2007,27:287-301.
[5]李晓彪,罗远良,罗泰义,等.重庆城口地区早前寒武统黑色岩系研究:巴山组硅质岩中PGE异常的地球化学研究[J].矿物学报,2007a,27:315-324.
[6]李晓彪,罗远良,罗泰义,等.重庆城口地区早前寒武统黑色岩系研究:早寒武世硅质岩的沉积环境研究[J].矿物学报,2007b,27:302-314.
[7]杨文光,林丽,朱丽东,等.重庆城口黑色岩系中铂矿的分子古生物学特征研究[J].成都理工大学学报(自然科学版),2004,31:457-460.
[8]Qi L,Hu J,Gregorie D C.Determination of trace elements in granites by inductively coupled plasma mass spectrometry[J].Talanta,2000,51:507-513.
[9]黎彤.地壳元素丰度的若干统计特征[J].地质与勘探,1992,28:1-7.
[10]陈德潜,陈刚.实用稀土元素地球化学[M].北京:冶金工业出版社,1996.
[11]Sun S S,McDonough W F.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes.Mag-matism in the ocean basins[A].In:Saunders A D,Norry M J eds,Geological Society Special Publication[C].London,1989,42:313-345.
[12]赵瞻,谢渊,刘建清,等.渝东南及周边早寒武世黑色岩系岩石地球化学特征及其成因[J].矿物岩石,2010,30:79-85.
[13]杨剑,易发成,刘涛.黔北黑色岩系稀土元素地球化学特征及成因意义[J].地质科学,2005,41(1):84-94.
[14]李胜荣,高振敏.湘黔地区牛蹄塘组黑色岩系稀土特征-兼论海相热水沉积岩稀土模式[J].矿物学报,1995,15(2):225-229.
[15]杨兴莲,朱茂炎,赵元龙,等.黔东震旦系—下寒武统黑色岩系稀土元素地球化学特征[J].地质论评,2008,54:3-15.
[16]徐晓春,王文俊,熊亚平,等.安徽石台早寒武世黑色岩系稀土元素地球化学特征及其地质意义[J].岩石矿物学杂志,2009,28:118-128.
[17]Morad S,Felitsyn S.Identification of primary Ce-anomaly signatures in fossil biogenic apatite:implication for the Cambrian oceanic anoxiaand phosphogenesis[J].Sedimentary Geology,2001,143:259-264.
[18]Jones B,Manning A C.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones[J].Chemical Geology,1994,111:111-129.
[19]Wignall P B.Black shales[M].Oxford:Clarendon Press,1994.
[20]钱建民,李海亭,徐岳行,等.扬子地台东南缘黑色岩系(荷塘组)地球化学研究[J].矿物岩石,2010,30:95-102.
[21]王立社,侯俊富,张复新,等.北秦岭庙湾组黑色岩系稀土元素地球化学特征及其成因意义[J].地球学报,2010,31:73-82.
[22]Marchig V,Gundlach H,Moller P,et al.Some geochemical indicators for discrimination beyween diagenetic and hydrothermal metallifer-ous sediments[J].Marine Geology,1982,50:241-256.
[23]Toth J R.Deposition of submarine crusts rich in manganese and iron[J].Geological Society of America Bulletin,1980,91:244-254.
[24]Smith P A,Cronan D S.The geochemistry of metaliferous sediments and waters associated with shallow submarine hydrothermal activity(Santorini,Aegean Sea)[J].Chemical Geology,1983,39:241-262.
[25]Peter J M,Scott S D.Mineralogy,composition,and fluid-inclusion microthermometry of seafloor hydrothermal deposits in the southerntrough of Guatmas basin,gulf of California[J].Canadian Mineralogist,1988,26:567-587.
[26]Rona P A.Criteria for recognition of hydrothermal mineral deposits in oceanic crust[J].Economic Geology,1978,73:135-160.
[27]Hogdahl O T,Melson S,Bowen V T.Neutron activation analysis of lanthanide elements in seawater[J].Advances in Chemistry,1968,73:308-325.
[28]Allegre C J,Minster J F.Quantitative models of trace element behavior in magmatic processes[J].Earth and Planetary Science Letters,1978,38:1-25.
[29]夏邦栋,钟立荣,方中,等.下扬子区早二叠世孤峰组层状硅质岩成因[J].地质学报,1995,69:125-137.
[30]罗泰义,张欢,李晓彪,等.遵义牛蹄塘组黑色岩系中多金属富集层的主要矿化特征[J].矿物学报,2003,23:296-302.
[31]Coveney R M,Chen N S.Ni-Mo-PGE-Au-rich ores in Chinese black shales and speculations on possible analogues in the United States[J].Mineralium Deposita,1991,26:83-88.
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