华南东段加里东期花岗岩类形成构造背景探讨  

Discussions on the tectonic setting of Caledonian granitoids in the eastern segment of South China

作　　者：张芳荣[1,2] 舒良树[1] 王德滋[1] 于津海[1] 沈渭洲[1] 

机构地区：[1]南京大学地球科学与工程学院,江苏南京210093 [2]江西省地质调查研究院,江西南昌330030

出　　处：《地学前缘》2009年第1期248-260,共13页Earth Science Frontiers

基　　金：国家自然科学基金项目(40634022,40572118);教育部博士点基金项目(20060284008)

摘　　要：根据近年对区域地质调查取得的认识和前人的研究成果,研究了华南东段加里东期花岗岩类的地质产状、分布规律、形成时代以及Nd、Sr同位素特征;结合研究区超镁铁质-镁铁质岩及火山岩的形成时代、震旦纪—奥陶纪的沉积环境、加里东期构造事件的构造变形特征,对加里东期花岗岩类的形成背景进行了探讨。结果表明,加里东期花岗岩类形成于410～460Ma,大部分岩体属于S型花岗岩,岩浆来源于地壳物质的部分熔融;极少数为I型花岗岩,有幔源物质参与。研究区在早古生代不存在与俯冲有关的弧火山岩,也不存在大面积的早古生代I型花岗岩,震旦纪—奥陶纪地层主要形成于浅海环境。研究提出,加里东期花岗岩类主体形成于板内构造环境。Based on our newly first-hand data obtained recently from regional geological survey and previous research results, we have analyzed in detail the geological features, distribution, forming ages and Nd-Sr isotopic characteristics of Caledonian granitoids in the eastern segment of South China. The tectonic setting forming Caledonian granitoids were discussed, which includes the ages of ultramafic-mafic rocks and volcanic rocks that outcrop in the study areas, the deposited environment of sedimentary rocks during the Sinian-Ordovician period, and deformation patterns of the Caledonian structures. Results suggest that the Caledonian granitoids were mainly formed between 410-460 Ma corresponding to the period from the Middle Ordovician to the Early Devonian. Geochemically, most of granitoids belong to the S-type that their magma were derived from the partial fusion of continental crust, but a few granitoids show characteristics of type Ⅰ granitoids that the magma conrains mantle materials. There is neither a large-scale Caledonian type Ⅰ granitoids that were related to plate subduction, nor the synchronous island arc-type volcanic rocks in the study area; the sedimentary environment during the Sinian-Ordovician period is mainly a shallow sea and partly a bathyal one. We propose that the tectonic setting forming Caledonian granitoids mainly belongs to intraplate tectonic environment.

关 键 词：花岗岩类 地质特征 构造背景 加里东期 华南东段 

分 类 号：P588.12[天文地球—岩石学]