陕北三叠系上统延长油层中海绿石的发现及其初步研究

A DISCOVERY AND PRIMARY STUDY OF GLAUCONITE IN THE UPPER TRIASSIC YANCHANG OIL-BEARING SAND STONE IN NORTHERN SHAANXI

本文对陕北三叠系延长群延长油层中的海绿石——延长海绿石进行了分析研究。结果表明,延长海绿石的矿物学特征与一般海绿石相同,其扩展层含量19%,属于无序低钾云母型结构。碳同位素及微量元素分析表明,延长海绿石系陆相淡水-半咸水湖泊环境下的自生矿物,延长海绿石存在于湖泊三角洲前缘远沙坝或三角洲间湖湾的粉-细砂岩中,也常与自生黄铁矿共生,其形成时水深为50—100m。海绿石的存在指示着该处为弱还原环境,对于成油较为有利。因此,在陆相湖泊三角洲环境中,也应当建立海绿石地球化学相。

The glauconite described in this parper is collected from the core of Yaodian oil-bearing layer in Yan'an. The fine-grained feldspar-sand stones containing the glauconite belong to the upper Trassic Yanchang group. They are the main oilbearing sands of the Yanchang oil field. We call the glauconites 'Yanchang glauconite' here.The Yanchang glauconites are examined by means of electron probe, X-ray powder pattern, infrared absorption spectroscopy and laser Raman spectrometry.Analysis of stable isotopes indicates that the Yanchang glauconites were formed in he nonmarine enviroment, and the grain size distribution shows that the Yanchang glauconite-feldspar-sandstones were formed on the distal bars of the lake delta front or the lake bays between the deltas.Therefore, all the evidence above suggests that geochemical facies for the glauconites should have been built in the nonmarine or lake environment.