钦-杭结合带在中生代构造转折事件以前的板块构造机制  

Plate tectonism of Qinzhou Bay-Hangzhou Bay juncture orogenic belt (South China)before Mesozoic tectonic transition event

作　　者：曾长育[1,2] 周永章[3,2] 郑义[3,2] 虞鹏鹏[3,2] 牛佳[3,2] 梁锦[3,2] 

机构地区：[1]广西地质调查院,广西南宁530023 [2]广东省地质过程与矿产资源探查重点实验室,广东广州510275 [3]中山大学地球科学与地质工程学院,广东广州510275

出　　处：《地学前缘》2015年第2期54-63,共10页Earth Science Frontiers

基　　金：中国地质调查局项目(1212011085412;12120113067600);国家自然科学基金项目(41273040)

摘　　要：钦州湾—杭州湾结合带是位于扬子与华夏两大古陆块中间的巨型构造结合带,在演化成西太平洋活动大陆边缘之前,经历了多期次的构造-岩浆事件。扬子和华夏板块于新元古代通过四堡造山运动（1 000~880 Ma）沿江山—绍兴断裂,经赣东北、湘中至钦州湾地区发生碰撞-拼合事件,拼合界线大致位于钦州湾—杭州湾结合带内,形成＂两陆夹一盆＂的主要格局。后碰撞过程经历了造山后岩浆活动和大陆拉张裂解两个过程,在结合带形成广阔的拉张盆地,加里东期（460~410 Ma）以及印支期（250~200 Ma）发生的碰撞-拼合事件导致扬子和华夏地块多次再造,引发强烈的构造-岩浆活动,并形成了华南统一的沉积环境。受西太平洋板块俯冲影响,华南地区中生代构造转折事件（125~140 Ma）使华南地区主要构造背景由碰撞挤压调整为岩石圈减薄,成为华南最重要的岩浆活动和成矿期。根据内部结构的不均一性和演化历史差异,钦州湾—杭州湾结合带可分为北段、中段和南段3段。其中,中段与传统南岭大体一致;北段为南岭以北地区,即绍兴—江山—萍乡一带;南段为南岭以南地区,大致与云开隆起—十万大山盆地相当。年代学和地球化学研究显示,在云开地块西缘的一系列变质基性岩、超基性岩和变质基性火山岩形成于新元古代洋中脊（MORB）或者岛弧（ITA）特征的构造环境,最近在岑溪一带发现形成于加里东期（441 Ma）的变质火山岩同样具有MORB型地球化学特征。在十万大山两侧发现早中生代的酸性火山岩和流纹岩具有典型岛弧型火山岩地球化学特征。可见结合带南段曾经存在古老洋壳,先后经历了新元古代、加里东期和印支期的碰撞造山事件,与北段演化历史具有一致性。The Oinzhou Bay （Q）-Hangzhou Bay （H） juncture orogenic belt is a giant suture separating Yangtze Block from Cathaysia Block in South China. Before involving into the Western Pacific active continental margin, it underwent several stages of regional-scale teetono-magmatism events. Assembly-collision had taken place between Yangtze Block and Cathaysia Block during the Neoproterozoic Sibao orogeny （1000 - 880 Ma）, with suture spreading from the Jiangshan- Shaoxing Fault, through northeastern Jiangxi Province and eastern Hunan Province, to the Qinzhou Bay of Guangxi Province. Post-collision process included post-orogeny magmatism stage and extension-break up stage, with broad extensional basin between Yangtze and Cathaysia Blocks. During the Silurian （460 - 410 Ma） and the Indosinian （250 - 200 Ma）, Yangtze Block and Cathaysia Block reassembled, leading to the regional-scale tectono magmatism and the united depositional environment in South China. Affected by the West Pacific subduction, the transformation of tectonic regime during the Late Jurassic （125 - 140 Ma） in South China turned the tectonic setting from compression to lithosphere thinning, arousing intensive magmatism and mineralization. Three segments, the northern, the middle and the southern, may be distinguished by the geological variation and are divided roughly at latitudes 24° and 27° north. The middle section is overlapped with the traditional Nanling Belt the northern section is roughly coincident with the Shaoxing-Jiangshan-Pingxiang zone; and the southern section with the Yunkai-Shiwandashan Mountainous zone. Chronological and chemical studies show that meta-mafic and ultramafic rocks found in the western Yunkai massif were formed in the Neoproterozoic and display MORB or ITA characteristics. The Caledonian meta-volcanic rocks in the Cenxi area display the same MORB chemical characteristics. The Early Mesozoic felsic volcanics and rhyolite in the both sides of Shiwandashan Mountains also display geochemical characteristics

关 键 词：板块构造机制 中生代构造转折事件 钦-杭结合带 华夏地块 扬子地块 岛弧俯冲环境 

分 类 号：P542.4[天文地球—构造地质学]