Lithofacies Paleogeographic Constraints of Southwestern Boundary between Yangtze and Cathaysian Plates in Caledonian
Lithofacies Paleogeographic Constraints of Southwestern Boundary between Yangtze and Cathaysian Plates in Caledonian
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发表时间：
2006
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通讯作者：
Pan Luo-zhong
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作者：
Pan Luo-zhong
定量的岩相古地理分析可以为不同大地构造单元的边界提供约束。采用“单因素分析多因素综合成图”的方法，结合古水流方向、沉积特征等多方面资料，对桂东北地区加里东岩相古地理进行了定量研究。新元古代以来，整个研究区沿着荔浦断裂裂解成两个不同的盆地。在荔浦断裂西北侧(桂北、桂东北)，加里东盆地由深海盆地演化为被动大陆边缘盆地，坡度向东南倾斜，古水流方向由西北向东南。陆源碎屑沉积来自西北方向。而在荔浦断裂东南侧(桂东)，加里东盆地长期为活动的陆坡环境，奥陶纪最终演化为陆架-沿海环境。坡度向西北倾斜，古水流方向由东南向西北。陆源碎屑沉积来自东南方向。这些都表明它们属于不同的古地理系统。也就是说，桂北和桂东北的盆地属于扬子板块，而桂东的盆地属于华夏板块。岩相古地理证据表明，荔浦断裂是一条分隔加里东期两个地体的裂隙。
Quantitative lithofacies palaeogeographic analysis can provide constraints to the boundary of different geotectonic units. By means of the method of "single factor analysis multifactor comprehensive mapping", integrating several aspects of data such as palaeo-current directions and sedimentary charateristics, a quantitative study is made on the Caledonian lithofacies palaeogeography of NE Guangxi. Since the Neoproterozoic, the whole research area cracked into two different basins along the Lipu fault. On the NW side of the Lipu fault (N and NE Guangxi), The Caledonian basin evolved from deep-sea basin to passive continent margin basin.Its slope dipped to the southeast, and palaeo-current directions were from northwest to southeast. The terrigenous detrital sediments were derived from the northwest. However, on the SE side of the Lipu fault (E Guangxi), the Caledonian basin had long been an active continent slope environment, and eventually evolved into a continental-shelf-coastal environment in the Ordovician. The slope dipped to the northwest, and the palaeo-current directions were from southeast to northwest. The terrigenous detrital sediments were derived from southeast. All these indicate that they belonged to different palaeogeographic systems. That is, the basin in northern and northeastern Guangxi belonged to the Yangtze plate, while the basin in eastern Guangxi belonged to the Cathaysian plate. The proof of lithofacies paleogeography suggests that the Lipu Fault is a dividing fracture which separates two terrains in the Caledonian.