鄂西地区志留系纱帽组斑脱岩的发现及其锆石U-Pb年代学意义

发布时间：2018-07-05 06:38

本文选题：纱帽组 + 斑脱岩　；参考：《地质科技情报》2017年04期

【摘要】：扬子地台纱帽组的地质年代归属一直存在争议。鄂西地区纱帽组主体由砂泥岩组成,但在顶部出现一套夹生物屑灰岩透镜体的碎屑岩。在恩施地区纱帽组灰岩段之下发现了一套斑脱岩,通过对斑脱岩的锆石U-Pb测年,得到加权平均年龄为(424.5±6.4)Ma,由此认为纱帽组顶部的沉积时限为文洛克世。考虑到纱帽组下部为早志留世,综合分析认为纱帽组是一跨时代的地层单元。该层斑脱岩产于含生物屑灰岩团块或条带的岩性段的下部,因此认为以灰岩的出现作为文洛克统沉积的开始;同时,认为该层斑脱岩为加里东运动在华南活动的产物。
[Abstract]:The geochronology of the Yangzi floor yarn cap formation has always been controversial. The main body of the Shimao formation in western Hubei is composed of sand and mudstone, but there is a set of clastic rocks with bioclastic limestone lens on the top. A set of porphyry deformations was found under the limestone member of the Shimao formation in Enshi area. By zircon U-Pb dating of the porphyry, the weighted average age is (424.5 卤6.4) Ma. it is considered that the deposition time at the top of the Shimao formation is Wenloch. Considering that the lower part of the Yarn formation is early Silurian, it is considered that the Yarn formation is an intergenerational stratigraphic unit. The porphyry occurs in the lower part of the lithologic segment of the bioclastic limestone mass or belt, so the occurrence of limestone is considered as the beginning of the Wenloc sedimentary system, and it is considered that the porphyry is the product of the Caledonian movement in South China.
【作者单位】：湖北省地质调查院;
【基金】：中国地质调查局地质大调查项目(12120114066101);中国地质调查局“扬子工程湘西-鄂西成矿带神农架-花垣地区地质矿产调查”二级项目(DD20160029)
【分类号】：P534.43;P597.3

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