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为了解定边地区石英次生加大的硅质来源,对定边地区数十口井的岩心进行薄片观察。在阴极发光镜下,定边地区山西组地层具如下鲜明特征:(1)整个地层以岩屑砂岩和岩屑石英砂岩为主,且地层中的石英颗粒之间含有大量高岭石和方解石;(2)大多数石英颗粒发生交代现象,其颗粒边缘表现的参差不齐;(3)地层中含有一定数量的云母、千枚岩等铝硅酸盐矿物,但是缺少长石;(4)在较深的层段,颗粒之间的压溶现象普遍发育,一部分颗粒发育缝合线,有些颗粒甚至发生破裂。这些特征反映了该地区石英次生加大的硅质最主要来源于长石的溶解和火山物质的蚀变,其次来源于石英颗粒之间的压溶,最后有少量来源于其它铝硅酸盐矿物的溶解和粘土矿物之间的转化。
In order to understand the source of siliceous secondary quartz in Dingbian area, the cores of dozens of wells in Dingbian area were observed. Under the cathode luminescence microscope, the strata of Shanxi Formation in Dingbian area have the following distinctive features: (1) The whole strata are dominated by lithic sandstone and lithic quartz sandstone, and there are a large amount of kaolinite and calcite between the quartz grains in the strata; 2) the majority of quartz particles occurred substitution phenomenon, the grain edge of the uneven performance; (3) the formation contains a certain amount of mica, phyllite and other aluminosilicate minerals, but the lack of feldspar; (4) Deep layers, the pressure solution between the particles generally developed, some of the particles developed sutures, and even some particles rupture. These characteristics reflect that the quartz secondary growth of quartz in this region is mainly due to the dissolution of feldspar and the volcanic alteration, followed by the pressure dissolution between quartz grains, and finally a small amount of silicas derived from other aluminosilicates Dissolution of minerals and conversion between clay minerals.