CAJ | 학술논문

通过微量元素和稀土元素地球化学分析，对长江三峡地区陡山沱组层型剖面---田家园子剖面成冰系南沱组顶部和埃迪卡拉系陡山沱组下部102个岩石样品进行了地球化学研究。重点分析了氧化还原敏感元素（Zn，Co，U，Mo，Ni，V）的富集特征，并探讨其可能成因机制以及三峡地区成冰纪-埃迪卡拉纪转换时期的水体特征。结果表明：在南沱组顶部仅 Zn和 Co 富集；在盖帽白云岩下部，氧化还原敏感元素均富集，而在盖帽白云岩上部，除 Zn和 V 外，其他氧化还原敏感元素均亏损；在陡山沱组Ⅱ段下部，氧化还原敏感元素由最初的亏损，逐渐变为较稳定的富集。在陡山沱组下部，出现2次明显的富集峰值，分别出现在剖面的0.4m 处（盖帽白云岩中间）和6.5m处（陡山沱组Ⅱ段下部）。整个剖面大部分样品具有 Eu 的轻微正异常（Eu/Eu*＜1.6），而在剖面0.4m和6.5m处，Eu具有明显的正异常，结合稀土配分类型、Y/Ho值、La 异常、Ce 异常等指标，推测这2次异常均可能受到深海热液流的影响，而缺氧海水的上涌造成水体缺氧，导致这些元素出现富集峰值。U/Th、V/（V＋Ni）以及稀土元素指标综合指示，三峡地区南沱组顶部冰碛岩应为氧化环境下的沉积物；随着冰川消融，冰融淡水注入古海洋，陡山沱组盖帽碳酸盐的沉积受冰融淡水的影响，深部缺氧海水的上涌使沉积水体经历氧化-缺氧-氧化的转变，海水的分层性较强；而陡山沱组Ⅱ段下部沉积环境以分层性较弱的弱氧化环境为主。
통과미량원소화희토원소지구화학분석，대장강삼협지구두산타조층형부면---전가완자부면성빙계남타조정부화애적잡랍계두산타조하부102개암석양품진행료지구화학연구。중점분석료양화환원민감원소（Zn，Co，U，Mo，Ni，V）적부집특정，병탐토기가능성인궤제이급삼협지구성빙기-애적잡랍기전환시기적수체특정。결과표명：재남타조정부부 Zn화 Co 부집；재개모백운암하부，양화환원민감원소균부집，이재개모백운암상부，제 Zn화 V 외，기타양화환원민감원소균우손；재두산타조Ⅱ단하부，양화환원민감원소유최초적우손，축점변위교은정적부집。재두산타조하부，출현2차명현적부집봉치，분별출현재부면적0.4m 처（개모백운암중간）화6.5m처（두산타조Ⅱ단하부）。정개부면대부분양품구유 Eu 적경미정이상（Eu/Eu*＜1.6），이재부면0.4m화6.5m처，Eu구유명현적정이상，결합희토배분류형、Y/Ho치、La 이상、Ce 이상등지표，추측저2차이상균가능수도심해열액류적영향，이결양해수적상용조성수체결양，도치저사원소출현부집봉치。U/Th、V/（V＋Ni）이급희토원소지표종합지시，삼협지구남타조정부빙적암응위양화배경하적침적물；수착빙천소융，빙융담수주입고해양，두산타조개모탄산염적침적수빙융담수적영향，심부결양해수적상용사침적수체경력양화-결양-양화적전변，해수적분층성교강；이두산타조Ⅱ단하부침적배경이분층성교약적약양화배경위주。
Geochemical characteristics of trace elements and rare earth elements were analyzed on1 02 rock samples including tillites from the top of Nantuo Formation in Marinoan glaciation and carbonate from the lower part of Doushantuo Formation (cap carbonate of Member Ⅰ and lower part of Member Ⅱ) of Ediacaran in Tianjiayuanzi section,the stratotype section of Doushantuo Formation,in Yangtze Gorges area.Enrichment characteristics of redox-sensitive elements (RSEs)(Zn,Co,U,Mo,Ni and V) and its probable genetic mechanism and depositional water environment during the Cryogenian-Ediacaran tran-sition in Yangtze Gorges area were systemically researched.The results indicated that only Zn and Co were enriched in the Nantuo Formation,in the lower part of cap carbonate all RSEs changed to be enriched, while in the top of cap carbonate all RSEs were depleted except Zn and V.In the lower of Member Ⅱ of Doushantuo Formation,RSEs changed from depleted in the lower part to relatively stable in the upper.In the lower Doushantuo Formation,there were twice significant enrichments of RSEs.One happened in 0.4 m position of cap carbonate,and the other happened in 6.5 m position of the section (the lower part of Member Ⅱ of Doushantuo Formation ).Most of the rock samples had slightly positive Eu anomalies (Eu/Eu*<1.6),but two significant positive Eu anomalies happened at the same places with the two sig-nificant enrichments of RSEs.Combined with palaeoenvironmental proxies (REE distribution patterns, Y/Ho,Ce anomalies,and La anomalies)in Doushantuo Formation,it was suggested that both of the a-nomalies were derived primarily from hydrothermal fluids,and upwelling of anoxic water caused those ele-ments reach to peak.U/Th,V/(V+Ni)values and palaeoenvironmental proxies of REE suggested that the sedimentary environment during the top of Nantuo Formation was oxic on the whole,and with glacial ablation,deposition of cap carbonate was affected by melting ice water and sedimentary environment had endured an oxic-anoxic-oxic change with an increasing of the water column stratification.In the lower part of MemberⅡ of Doushantuo Formation,the depositional environment was mainly suboxic and with a weak water column stratification.