地质学报2018，Vol.92Issue(2)：378-394,17.
扬子板块西北缘热水沉积硅质岩稀土元素配分模式的影响因素
Factors Influencing the REE Distribution Patterns of Hydrothermal Sedimentary Cherts in the Northwestern Margin of Yangtze Block
摘要
Abstract
In this study,we carried out an REE geochemical study of lower-middle Silurian organic-rich bedded cherts and underlying Sinian volcanic rocks in the regions of northern Ruoergai (Zoig(e)) County in Sichuan and Diebu (T(e)wo) County in Gansu,central China.The aim of this study was to understand the origin of rare earth elements in hydrothermal cherts and factors affecting REE patterns,and establish a corresponding model.28 samples of cherts from one drilling core and two profiles were studied using petrographic analysis,scanning electron microscopy (SEM) analysis,major and rare earth element analyses.14 samples of volcanic rocks from one profile were investigated using major elements and REE analyses.Petrographic and SEM analyses of black hydrothermal cherts show that the black cherts have typical features of deposition structure and weak late-stage metamorphism.The TAS diagram of lower Sinian volcanic rocks suggests that they are dominantly felsic volcanic rock,with minor being mafic volcanic rocks.Combined with previous results,comparison analysis of underlying Sinian volcanic rocks and overlying middle-early Silurian hydrothermal siliceous rock draw the following conclusions.(1) Tensional tectonic setting is an essential dynamic factor for formation of hydrothermal chert,REEs of which mainly derived from hydrothermal fluids,ancient seawater (mixed in continental matters).(2) Relative abundances of the REEs in hydrothermal cherts have a threshold,below which LREEs' distribution pattern is consistent with that of hydrothermal fluids while HREEs' distribution patterns consistent with that of underlying volcanic rocks;and above which LREEs' distribution presents the characters of mixing of hydrothermal fluid with ancient water (terrestrial material).The LREE patterns of hydrothermal cherts are consistent with that of upper crust,while HREE patterns are consistent with that of underlying volcanic rocks.Therefore,hydrothermal chert deposited in a certain condition can indicate paleodepositional structure environment.关键词
热水沉积硅质岩/稀土元素/来源/影响因素/古构造环境Key words
Hydrothermal chert/REE/Sources/Influence factors/Paleodeposition setting引用本文复制引用
张岩,漆富成,陈文,叶会寿..扬子板块西北缘热水沉积硅质岩稀土元素配分模式的影响因素[J].地质学报,2018,92(2):378-394,17.基金项目
本文为国家基金委基础科学中心项目(编号 41688103)、国家自然基金面上项目(编号 41573049、41473053)、中国黑色岩系非常规铀资源矿集区成矿条件分析及资源预测评价(编号 201493)、湘中地区黑色岩系非常规铀资源调查及远景评价(编号 201768)、中国地质科学院基本科研业务费项目(编号 YYWF201707)共同资助的成果. （编号 41688103）
