华南地区不同时代硅质岩地球化学特征及地质意义

Geochemical Characteristics for Siliceous Rocks of Different Ages in South China and Their Geological Significance

我国华南地区前寒武系至二叠系地层广泛发育硅质岩,开展不同时代硅质岩地球化学特征及成因研究对华南地区构造演化具有重要意义。基于华南地区前寒武系至二叠系硅质岩主量及稀土元素分析数据,结合岩石学、古生物等资料,对华南地区元古代和古生代7个层系中硅质岩开展了对比分析及成因探讨。结果表明:(1)震旦纪时期,华南地区硅质岩沉积于远洋盆地,热源受南华裂谷等张裂事件影响;(2)寒武纪时期,华南地区硅质岩沉积于远洋盆地和大陆边缘过渡带,热源受到地壳张裂作用影响;(3)奥陶纪—志留纪时期,华南地区硅质岩沉积于大陆边缘环境,热源与地壳的张裂作用有关;(4)泥盆纪时期,华南地区硅质岩沉积于海盆环境,热源与广西运动造成火山活动有关;(5)石炭纪时期,华南地区硅质岩沉积于海盆环境,热源与地壳张裂作用有关;(6)二叠纪时期,华南地区硅质岩沉积于海盆环境,热源与峨眉山地幔柱活动有关。震旦纪—二叠纪时期,华南地区与构造运动相伴生的热液活动为硅质岩形成提供了充足的硅源,是该地区硅质岩形成的主要控制因素,且硅质岩清晰记录了华南地区震旦纪—二叠纪时期古气候、古环境和古构造特征及其演化。

Chert is widely developed in the Precambrian to Permian strata in South China,The geochemical characteristics and genesis of siliceous rocks in different ages are of great significance to the tectonic evolution in South China.Based on the data of the former Cambrian and Permian siliceous rocks and the rare earth elements in South China,combined with petrological and palaeontological data,a comparative analysis of geochemistry and the causes of the siliceous rocks in the Mesoproterozoic and Paleozoic were conducted.The results show：（1） During the Sinian period,siliceous rocks in South China were deposited in oceanic basins,and the heat source was affected by the South China Rift and other events;（2） During the Cambrian period,siliceous rocks in South China were deposited in the oceanic basins and continental margin transition zones,and the heat source was affected by the crustal cracking;（3） During the Ordovician-Silurian period,siliceous rocks in South China were deposited in the continental margins,and the heat source was related to the crustal action;（4） During the Devonian period,siliceous rocks in South China were deposited in the basin environment,and the heat source was related to the volcanic activities caused by the Guangxi Movement;（5） During the Carboniferous period,siliceous rocks in south China were deposited in the basin environment,and the heat source was related to the crustal cracking;（6） During the Permian period,siliceous rocks in South China were deposited in the basin environment,and the heat source was related to the activity of the mantle plume in Mount Emei.During the Sinian-Permian period,the hydrothermal activity associated with tectonic movement in South China provided a sufficient source of siliceous rocks,which was the main controlling factor of the formation of siliceous rocks in this area,and the siliceous rocks clearly recorded the paleoclimatic,paleoenvironment and palaeotectonic characteristics and evolution of the Sinian-Permian period in South China.