Sedimentary facies and regional tectonic significance of Cretaceous in the middle of Lanping Basin, Yunnan Province
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摘要: 云南兰坪盆地在白垩纪的演化为其喜马拉雅期的大规模成矿起到了铺垫作用。前人对该时期的沉积相分析较为笼统,一定程度上影响了对盆地演化、盆地性质及成矿方面的深入理解。在兰坪盆地中部开展了实测剖面和路线调查等工作,认为兰坪盆地的白垩系分为扇三角洲-湖泊和辫状河三角洲-残余河湖2个沉积体系,盆地性质应属断陷盆地。结合对特提斯洋演化过程的认识,认为早白垩世兰坪盆地继承了中侏罗世—晚侏罗世沉降的构造背景,早白垩世末中特提斯洋的闭合中断了盆地的沉降作用,晚白垩世新特提斯洋的北向俯冲导致了中生代兰坪盆地演化的终止。结合区域矿产资料,认为早白垩世成矿元素已有初步富集,并为喜马拉雅期成矿提供了必要的矿源层、建造水、运移通道及成矿定位空间。研究可为兰坪盆地的演化过程提供新的实证资料。Abstract: The evolution of Lanping Basin in Yunnan during the Cretaceous period paved the way for the large-scale mineralization of Himalayan period. The analysis of the sedimentary facies of this period by the predecessors was relatively general, which affected the comprehensive understanding of basin evolution, nature and mineralization, to some extent. The authors in this paper carried out the survey of geological section and route in the middle of the basin, and concluded that Cretaceous in Lanping Basin is a combination of fan delta-lake and braided river delta-remaining river-lake system, which makes the basin a fault basin. Combined with the evolution of Tethys, it is believed that the basin continued to inherit a Middle-Late Jurassic subsidence tectonic setting in Early Cretaceous. The closure of Meso-Tethys Ocean at the end of Early Cretaceous interrupted the settlement of the basin. The northward subduction of Neo-Tethys Ocean terminated the sedimentary evolution of Mesozoic Lanping Basin. Based on regional mineral data, it is believed that the early Cretaceous mineralization elements have been initially enriched, and provided necessary mineral source layers, formation water, migration channels, and mineralization positioning space for Himalayan mineralization. This research can provide new empirical data for the evolution process of Lanping Basin.
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Key words:
- Lanping Basin /
- Cretaceous strata /
- fan delta /
- braided river delta /
- regional tectonic evolution
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