摘要
本文采用ＧＣ＿ＭＳ、ＩＣＰ＿ＭＳ、形态硫分析、硫同位素、物相分析等方法综合研究了湘西晚震旦世－早寒武世黑色岩系的地球化学特征和形成条件。湘西黑色岩系以富有机质为特征，其来源为藻、菌类生物，形成于缺氧环境。缺氧标志包括有机碳、黄铁矿含量、硫同位素、稀土元素的分布、δＵ、ＤＯＰ和生物标志物等参数。在黑色页岩中富集Ｖ、Ｎｉ、Ｍｏ等微量元素，并在局部地区形成具有工业价值的矿床。研究认为，生物、有机质对一些元素的吸收、络合作用是黑色岩系中富集多种元素的主要原因。稀土元素的分布和硫同位素的组成表明湘西黑色岩系形成于缺氧的陆架边缘浅海环境，海底热液活动为其提供了丰富的物质来源。
This paper deals with the formation conditions of black shales based on such analytical techniques as ICP_MS, GC_MS, isotope, organic carbon, element facies and micropetrology. Studies show that the Upper Sinian_Lower Cambrian black shales were formed in an anoxic environment, and the organic sources were algae and fungi (Thallophyta). The paper points out five geochemical indicators of anoxic environment. The organic matter, especially lipids, can be well preserved in an anoxic environment. Black shale is also an indicator of the oceanic anoxic event. During the slow degradation of organism, the organic matter absorbed and combined many elements. At the early diagenetic stage, the organic matter was decomposed, and some elements were remobilized. Hence the elements exhibit multi_stage enrichment and varied forms. The key factor is the adsorption of organism and the combination with the organic matter. The strata of Ni_Mo, coal stone, barite and phosphorite deposits are controlled by the change of sea level, and the ore_bearing sets are developed in the transgressive series and condensed sections. The black shales are characterized by high content of Ni, Mo and Mn, lower total REE, comparative enrichment of HREE, and negative Ce anomaly. Geochemical and REE features indicate that black shales were deposited in an epeiric sea environment.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
1999年第1期26-39,共14页
Acta Petrologica et Mineralogica
基金
国家自然科学基金
关键词
黑色岩系
地球化学
缺氧环境
有机质
湘西
页岩
black shales
geochemistry
organic matter
anoxic environmlent
western Hunan
