黑海西北部冷泉碳酸盐岩的沉积岩石学特征及氧化还原条件的稀土元素地球化学示踪

现代地质 ›› 2008, Vol. 22 ›› Issue (3): 390-396.

黑海西北部冷泉碳酸盐岩的沉积岩石学特征及氧化还原条件的稀土元素地球化学示踪

冯东^1,2, 陈多福¹

1中国科学院广州地球化学研究所边缘海地质重点实验室，广东广州 510640； 2. 中国科学院研究生院，北京 100049

收稿日期:2008-01-05 修回日期:2008-02-24 出版日期:2008-03-20 发布日期:2008-03-20
作者简介:冯东，男，博士研究生，1980年出生，地球化学专业，主要从事冷泉碳酸盐岩及天然气水合物研究。
基金资助:
中国科学院海洋地质与环境重点实验室开放基金项目（MGE2007KG05）；国家杰出青年基金项目（40725011）；NSFC-广东联合基金项目（U0733003）

Petrographic Characterization and Rare Earth Elements as Geochemical Tracers for Redox Condition of Seep Carbonates from Northwestern Black Sea

FENG Dong^1,2, CHEN Duo-fu¹

1Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,
Guangzhou，Guangdong510640, China;
2Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Received:2008-01-05 Revised:2008-02-24 Online:2008-03-20 Published:2008-03-20

摘要/Abstract

摘要：

黑海西北部罗马尼亚大陆架（水深120 m）和乌克兰陆坡（水深190 m）发育冷泉碳酸盐岩结壳。XRD测试表明此结壳主要由高镁方解石和文石组成。结壳中与渗漏系统微生物活动有关的凝块和葡萄状文石等特殊的沉积组构非常发育。冷泉碳酸盐岩酸可溶部分（碳酸盐岩相矿物）的稀土元素含量很低（0.068×10^-6~2.817×10^-6），稀土元素页岩标准化配分模式显示罗马尼亚大陆架冷泉碳酸盐岩具有明显的Ce负异常，乌克兰陆坡冷泉碳酸盐岩具Ce的正异常，表明它们是分别在氧化和还原环境中沉积的。稀土元素和V、Cd和U等微量元素的含量在泥晶中最高，亮晶中最低，可能反映成岩过程对元素含量有控制作用。

关键词: 冷泉碳酸盐岩, 生物组构, 稀土元素, 地球化学示踪, 氧化还原环境, 黑海, XRD

Abstract:

Seep carbonate crusts described here were collected on the Romanian (RO)shelf(120 m water depth)and Ukrainian(UKR)slope(190 m water depth)of the Black Sea. X-ray diffraction investigations show that high-Mg-calcite and aragonite are the dominant minerals. Peloids and botryoidal aragonite in the carbonate crust suggest a genesis induced by bacterial metabolism at the seep sites. The content of rare earth elements(REE)of the 5% HNO_³treated solution of the carbonates are very low(0.068×10-6 to 2.817×10-6).The shale-normalized REE patterns of RO carbonate show significantly negative Ce anomalies, while that of UKR carbonate shows no Ce anomalies, indicating that RO and UKR seep carbonates were deposited in oxic and anoxic environments, respectively. The contents of REE and trace elements(e.g.V, Cd and U)are highest in microcrystalline, lowest in sparite, and intermediate in microspar, suggesting that the elements concentration of seep carbonate is a function of diagenesis. 

Key words: seep carbonate, biogenic fabrics, rare earth element, geochemical tracer, redox condition, Black Sea, X-ray diffraction

中图分类号:

P74
P588.2

冯东, 陈多福. 黑海西北部冷泉碳酸盐岩的沉积岩石学特征及氧化还原条件的稀土元素地球化学示踪[J]. 现代地质, 2008, 22(3): 390-396.

FENG Dong, CHEN Duo-fu. Petrographic Characterization and Rare Earth Elements as Geochemical Tracers for Redox Condition of Seep Carbonates from Northwestern Black Sea[J]. Geoscience, 2008, 22(3): 390-396.

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