扬子地区典型剖面二叠系不同沉积相地球化学特征

对扬子地区2个典型剖面即四川广元上寺剖面和贵州罗甸纳水剖面二叠系系统采样,在沉积相研究的基础上,对华南二叠系碳酸盐岩地层不同沉积相地球化学特征进行了分析。研究表明:Co、Ba、V、Rb等具有指相意义的元素,在越靠近深水环境,Co、Ba、V、Rb平均丰度越高,而w(Sr)/w(Ba)值从开阔台地相到盆地相整体有降低趋势。贵州罗甸纳水剖面为斜坡沉积背景的典型剖面,从台地前斜坡相→陆棚相→斜坡相→盆地相,w(ΣREE)值逐渐增大,且各相带稀土元素配分模式存在明显的Ce异常。四川广元上寺剖面二叠系浅海陆棚相下部和盆地相地层中平均残余有机碳丰度大于1.5%,说明这2个沉积相带可能为该地区优质烃源岩发育相带,该剖面二叠系显示从开阔台地相到盆地相具有有机质逐渐富集的特点。

Geochemical Characteristics of Different Facies of Permian Typical Sections in the Yangtze Region

The geochemical characteristics of the different facies of Permian carbonate formation have been analyzed based on the study two typical sections in the Yangtze region, Shangsi section of Guangyuan area in Sichuan Province and Nashui section of Luodian area in Guizhou Province. The results indicate: (1)The average contents of Co,Ba,V,Rb showing distinct marks for depositional facies become higher toward deep marine environments, but Sr/Ba ratio decreases from platform facies to basin facies. (2)In the Luodian profile, the typical section of the slope deposit background, total REE (∑REE) increases gradually from fore-platform, outershelf, slope to basin facies, with obvious Ce anomaly in REE patterns of every facies. (3)The average contents of residual organic matter of the lower shallow sea shelf facies and basin facies in Shangsi section of Guangyuan area are more than 1.5%, suggesting that both facies could be the developing area of good quality hydrocarbons. Shangsi section also exhibits a chracteristics of progressive enrichment of the organic matter from the open platform to the basin.