利用岩石地球化学特征判断西秦岭寒武系含矿硅岩建造的沉积环境  

Judging the Sedimentary Environment of the Silicalite Formation on the Chemical Characteristics of Rocks in Western Qinling

作　　者：刘家军[1,2,3,4] 刘建明[1,2,3,4] 郑明华[1,2,3,4] 周渝峰 顾雪祥 张斌[1,2,3,4] 林丽 周德安 

机构地区：[1]中国科学院地球化学研究所 [2]中国科学院矿物资源探查研究中心 [3]成都理工学院矿床地质研究所 [4]核工部北京地质研究院

出　　处：《沉积学报》1998年第4期42-49,共8页Acta Sedimentologica Sinica

基　　金：国家自然科学基金;中国-奥地利国际合作项目;国家自然科学基金;中国博士后科学基金

摘　　要：西秦岭寒武系硅岩建造是拉尔玛、邛莫金矿床和牙相金矿点的赋矿岩系。其主要由炭质硅岩和炭质板岩组成。其中的含矿硅岩构造十分丰富，有块状、条带状、层纹状、多孔状和同生角砾状等。硅岩单层厚度一般为３０～２００ｍ。其主要成分除ＳｉＯ２（平均含量９５３０％）外，其它氧化物含量能达１％者仅有ＦｅＯ、Ｆｅ２Ｏ３和Ｐ２Ｏ５，且ＦｅＯ／Ｆｅ２Ｏ３比值大于１，而Ｓｒ／Ｂａ比值小于１。硅岩建造中有机炭含量相当高，一般为（０１２～８１４）％，高者达２２％。硅岩中稀土以总量低（３２９×１０－６～１００×１０－６）、铈亏损为特征。硅岩建造中沉积黄铁矿的δ３４Ｓ值变化在１０‰～＋４６．９‰之间。硅岩的δ３０Ｓｉ值主要变化在＋０４‰～＋０．８‰之间。硅岩建造的上述特点反映其主要是在深海—半深海环境下形成的。The Cambrian silicalite formation,composed of black chert and black slate,is the host rock of Laerma and Qiongmo gold deposits in western Qinling.The ore bearing chert is characterized by bedded,laminated,massive and pseudobrecciated structures which change regularly in space.The thickness of a chert bed generally varies from 30 to 200 meters.Host elements are simple and concentrated in the chert.Besides SiO 2(95.30 % on average),only FeO,Fe 2O 3 and P 2O 5 reach or are more than 1.0%.The ratios of FeO/Fe 2O 3 in all chert samples are mainly greater than 1,but the ratios of Sr/Ba are less than 1.The organic carbon concentrations of silicalite formation range mostly from 0.12% to 8.14%,the highest concentration being 22%.REEs(rare earth elements) are characterized by a low total content (ranging between 3.29×10 -6 and 100×10 -6 ),negative Ce anormal and a gradually increasing NASC—normalized value with increasing atomic number of REEs.The δ 30 Si values of the chert in the area range mainly from +0.4‰ to 0.8‰.All the geochemical characteristics of the silicalite formation manifest that the silicalite formation deposited in the deep and half-deep sea environment.

关 键 词：硅岩建造 沉积环境 西秦岭 岩石地球化学 

分 类 号：P588.244[天文地球—岩石学]