江南造山带西段四堡群的沉积地质特征和构造属性探讨

A Discussion on Sedimentary Characteristics and Structural Properties of the Sibao Group in the West Segment of the Jiangnan Orogenic Belt

华南四堡群是江南造山带的重要组成部分,是认识江南造山带弧沟体系的重要"窗口"。四堡群沉积地质学研究表明:1四堡群在黔东南地区总体构成一向上变浅的沉积序列:尧等组为深海-半深海相沉积;河村组浅海—滨岸相沉积。四堡群在桂北地区总体上也为一向上变浅的沉积序列:文通组为深海-半深海相沉积;鱼西组为浊积岩相沉积;2桂北地区四堡群碎屑岩系的29组沙纹层理(鲍马序列c段)的玫瑰花图解表明,古流向总体指向南,证明物源在其北侧;3四堡群砂岩骨架颗粒统计结果表明,其物源构造属性为岩浆弧;4基于以上研究,推测四堡群沉积于弧前盆地。

The Sibao Group in South China is an important part of the Jiangnan Oregenic Belt, it＇s a ＂window＂ to recognize Jiang Oregenic Belt＇ s trench--arc system, we use sedimentology to study its prototype basin and tectonic paleogeographic pattern. Based on these works, we have five following understanding：（1） The Sibao Group, in Southeast of Guizhou, is an upward-shallowing sequence. Yaodeng Formation is deep sea--bathyal mudstone and turbidite; The upper of Hecun Formation is neritic clastic, the lower of Hecun Formation is shore facies. Sibao Group, in north of Guilin, are turbidite facies, and the Bouma sequence are developed. （2） The rose diagram of inclined bedding in clastic of Sibao Group, in north of Guilin, show that paleocurrent direction Pointing to the south, the provenance is from the north. （3） Statistical results of skeleton particles show that the tectonic feature of the provenance of Sibao Group is Magmatc Arc. （4） Based on the above findings, we suggest that the tectonic environment of Sibao Group＇ cIastic rocks is forearc basin.