| 桂西南晚古生代深水相地层序列及沉积演化 |
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| 引用本文： | 史晓颖,侯宇安,帅开业.桂西南晚古生代深水相地层序列及沉积演化[J].地学前缘,2006,13(6):153-170. |
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| 作者姓名： | 史晓颖 侯宇安 帅开业 |
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| 作者单位： | 1. 中国地质大学(北京)地球科学与资源学院,北京,100083;中国地质大学,地质过程与矿产资源国家重点实验室,北京,100083
2. 中国地质大学(北京)地球科学与资源学院,北京,100083 |
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| 基金项目： | 国家自然科学基金;教育部优秀团队基金 |
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| 摘 要： | 右江盆地晚古生代沉积由浅水陆棚、地台边缘—斜坡、孤立碳酸盐岩台地和深水盆地4种主要的沉积类型组成,自北向南呈现由浅到深的规律性分布。深水区地层以含锰粘土岩、硅质岩、滑塌角砾灰岩和普遍发育玄武岩为重要特征,与盆地边缘差别显著。以斜坡相区生物地层控制良好的层序地层和重要事件为桥梁,建立了深水区地层序列、主要的海平面变化旋回及其与不同相区的年代地层对比关系。深水区岩浆活动可识别D1晚期—D2早期、D3晚期—C1早期、C2中期—P1早期以及P3—T1早期4个幕式活跃期;以洋岛型玄武岩(OIB)为主,滇—桂—越边境地区具洋岛—洋脊型(MORB)过渡特征。枕状玄武岩主要集中在C1早期、C2中期—P1早期和T1早期三个时段,其中C2—P1玄武岩厚度最大、分布最广。研究表明右江盆地是晚古生代发育于扬子与印支地块间的小洋盆,属东特提斯多岛洋的一部分。其沉积演化经历了浅水陆表海盆地(D1)、深水裂谷盆地(D2—D3)、扩张洋盆(C1—P2)、收缩洋盆(P3—T2早期)、残余盆地(T2晚期—T3早期)五个阶段。盆地西南缘可能属印支地块的北部边缘,而盆地北部属扬子地块的西南缘。
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| 关 键 词： | 右江盆地 深水沉积 晚古生代地层序列 岩浆活动幕 盆地演化 构造古地理 |
| 文章编号： | 1005-2321（2006）06-0153-18 |
| 收稿时间： | 2006-05-10 |
| 修稿时间： | 2006-06-10 |
Late Paleozoic deep-water stratigraphic succession in central Youjiang basin: constraints on basin evolution |
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| SHI Xiao-ying,HOU Yu'an,SHUAI Kai-ye.Late Paleozoic deep-water stratigraphic succession in central Youjiang basin: constraints on basin evolution[J].Earth Science Frontiers,2006,13(6):153-170. |
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| Authors: | SHI Xiao-ying HOU Yu'an SHUAI Kai-ye |
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| Institution: | 1. School of Earth Sciences and Resources, China University of Geosciences , Beijing 100083,China; 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences , Beij in g 100083,China |
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| Abstract: | The Youjiang basin is situated on the SW margin of the Yangtze platform, southwest China, and is one of the important potential oil-gas basins in southern China. The depositional environment of Late Paleozoic sediments can be summarized as four major types: 1)shallow shelf, 2)platform margin to slope, 3)isolated carbonate platform, and 4)deep-water basin. In the above order, these depositional environments have a north to south spatial arrangement, thereby suggesting a marginal sea to oceanic basin framework. In the central parts of the basin, the Upper Paleozoic is characterized by chert, manganese claystone, and pillow basalt, a succession that is quite distinct from that at basin margins. Using the sequence stratigraphy and events recognized in the slope belt, a multi-folded stratigraphic system for the deep-water basin and its correlation has been set up. The study shows that in the deep-water areas, OIB alkaline basalt predominates, with tholeiite mainly concentrated in the SW part of the basin. Around Yunnan-Guangxi-Vietnam border areas, however, some of the basalts show a geochemistry that is transitional between OIB and MORB. Four magmatic episodes are recognized as follows:1)late Early to early Middle Devonian; 2)middle Late Devonian to Early Carboniferous; 3)middle Late Carboniferous to Early Permian; and 4)Late Permian to Early Triassic. Pillow basalt occurs in the last three episodes, of which the third one has largest thickness and most extensive occurrence. On the basis of our study we propose that the Youjiang basin originated as a small oceanic basin between the Yangtz and Indochina blocks. This small oceanic basin was an eastward branch of the eastern Paleotethys along Changning-Menglian belt, in southwest China. In a broader view, this constitutes a part of the archipelago in eastern Paleotethys. The stratigraphic architecture further suggests that the Youjiang basin evolved through five stages:1)shallow epeiric basin (late D_ 1 -early D_ 2 ); 2)rift basin (middle D_ 2 -D_ 3 ); 3)rapidly expanding oceanic basin (C_ 1 -P_ 2 ); 4)contracting oceanic basin (P_ 3 -early T_ 2 ); and , 5)remnant basin (middle T_ 2 -early T_ 3 ). Our study supports that, paleogeographically, the southwestern part of the basin may belong to the northern margin of the Indochina block, while the northern part may form southwestern margin of the Yangtz plate. |
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| Keywords: | Youjiang basin deep-water sediments Late Paleozoic stratigraphy magmatism episodes basin e- volution tectono-paleogeography |
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