湖南及邻区志留纪兰多弗里世鲁丹期至埃隆期岩相古地理及加里东期板块构造演化  

Rhuddanian—Aeronian(Llandovery, Silurian) lithofacies palaeogeography of Hunan Province and its adjacent region and Caledonian plate tectonic evolution

作　　者：王根贤[1] 陈必河 郑正福 周超 WANG Genxian;CHEN Bihe;ZHENG Zhengfu;ZHOU Chao(Hunan Institute of Geology,Changsha,410007;Hunan Geological Survey,Changsha,410116)

机构地区：[1]湖南省地质科学研究院,长沙410007 [2]湖南省地质调查院,长沙410116

出　　处：《地质论评》2021年第6期1557-1585,共29页Geological Review

基　　金：中国地质调查局大调查项目“湖南花垣—锦和地区寒武纪—奥陶纪岩相古地理与铅锌矿成矿关系研究”(编号:资[2010]矿评01-13-10)的成果。

摘　　要：湖南兰多弗里世鲁丹期岩相古地理格局以桃江—白马山—苗儿山一线为界,其南东为华夏洋壳板块兰多弗里统鲁丹阶周家溪组陆屑浊积深水盆地相,陆屑来自更南东的湘中南褶皱山地,其北西为扬子陆壳板块兰多弗里统鲁丹阶龙马溪组沉积洋盆,南东后缘是上陆棚相,北西前缘是下陆棚相,陆屑都由南东湘中南褶皱山地提供。至兰多弗里世埃隆期岩相古地理发生巨变:龙马溪组顶部Coronograptus cyphus笔石带末即大约440.8±1.2 Ma时,发生华夏洋壳板块向扬子陆壳板块俯冲碰撞事件,华夏洋壳板块周家溪组本身褶皱造山为华夏褶皱山地,华夏洋壳板块洋盆关闭。同时华夏洋壳板块以A型俯冲形式下插到扬子陆壳板块之下,并使扬子陆壳板块南东前缘崛起形成加里东期雪峰造山带。后者将扬子陆壳板块南东前缘牵引、挠曲和凹陷成华夏洋壳板块弧后前陆盆地,小河坝组是该弧后前陆盆地的沉积盖层,陆屑都由南东的雪峰造山带提供。该弧后前陆盆地沉积了三角洲相—滨海相的小河坝组,向北东、北西和南西方向相变为台地相石牛栏组,再向北西陕南紫阳相变为盆地相斑鸠关组。小河坝组两次采集的重砂样均出现蓝闪石,它是蓝闪石片岩标志矿物,蓝闪石片岩是确认加里东期华夏洋壳板块与扬子陆壳板块俯冲碰撞及形成雪峰造山带的判别标志。As to the Lunmachian paleogeography in the Llandovery, the Taojiang—Baimashan—Yuechengling is the boundary between the Cathaysia Oceanic Crust Block to the southeast and the the Yangtze Continental Crust Block to the northwest. The Cathaysia Oceanic Crust Block was characterized by a deep-water turbidite basin consisting of the Llandovery Rhuddanian(i.e., the Zhoujiaxi Formation), of which clastic sediments would have fed by the central Hunan fold mountains further southeast. The Yangtze Continental Crust Block was a sedimentory oceanic basin composed of the Longmaxi Formation. The distant edge to the southeast was in an upper continental shelf environment and the margin to the northwest was the lower continental shelf ones. The fold mountains in south—central Hunan would have supplied most of detrital materials to basins. The Siaohopan lithofacies and paleogeography were obviously different from the past. The subduction—collision of the Cathaysia Block with the Yangtze Block took place at the end of the D. triangulates graplite zone time, ca. 440.8±1.2 Ma. The orogenesis of the Zhoujiaxi Formation(in the Cathaysia Block) itself created the Cathaysia fold mountains, resulting in the closure of the Cathaysia Ocean Basin. At the same time the Cathaysia Block wedged beneath the Yangtze Block by the A-type subduction, leading to the uplift of the Caledonian Xuefeng Orogenic Belt along the southeast margin of the Yangtz Block on a large scale. The Xuefeng Mountain, as a tectonic load, resulted in the formation of a retroarc foreland basin of the Cathaysia Ocean Crust Block in the new southeast margin of the Yangtze Block. The Siaohopan Formation was the cover of the retroarc foreland basin. Its terrigenous material supply would have derived from the Xuefeng Orogenic Belt. The Siaohopa Formation was comprised mainly of delta-facies deposits in southeast distant edge and littoral-facies deposits in northwest margin. The Siaohopan Formation graded into a platform facies stratigraphic unit of the Shiniulan Format

关 键 词：板块构造 加里东期板块俯冲碰撞 华夏褶皱山地 雪峰造山带 弧后前陆盆地 华南洋 生物地层 岩相古地理 志留纪 兰多弗里世 湖南 

分 类 号：P612[天文地球—矿床学]