滇桂个旧-那坡三叠纪沉积盆地原型盆地与构造-古地理属于发育在大陆地壳之上的弧后裂谷盆地.该弧后裂谷盆地具有明显三向物源特征,一是靠近康滇和屏马古陆块附近,发育浅水碎屑岩相序,属于大陆蚀源岩区形成的沉积组合.二是云南个旧地区以中三叠统个旧组碳酸盐岩为代表的沉积组序,主体以陆缘海盆内源沉积为主,属于大陆边缘裂谷盆地热沉降形成的沉积组合.三是三叠纪来自沉积盆地底源,地幔热物质源区的海相火山岩；海底热水同生沉积-交代作用形成的热水沉积岩等沉积组合.来自深部地幔热物质源区的海相火山岩,包括碱性苦橄岩类、碱性玄武岩类和酸性凝灰岩,并伴随凝缩段中凝灰质硅质岩、硅质岩、深水硅质岩和锰碳酸盐岩等火山-热水沉积岩组合.因受地幔热点控制,形成了个旧-那坡三叠纪弧后裂谷盆地,这种三向物源特征与弧后盆地双向物源明显不同.在盆地演化历史上,该沉积盆地经历了扬子地块陆缘石炭纪伸展盆地、二叠纪陆缘裂谷盆地与三叠纪弧后裂谷盆地三个主要演化阶段.三叠纪弧后裂谷盆地动力学特征为张剪性伸展作用,受大陆侧向挤压收缩体制控制而发生萎缩封闭.在垂向沉积相序列上三层结构为“下细夹火山岩、中变粗后变细且发育碱性苦橄岩和碱性玄武岩、上粗含煤”.垂向成矿序列结构为“下部为银锑铅锌矿、中部为锡铜多金属矿、上部为锰-银铅锌矿,顶部为煤矿”.%The Gejiu superlarge tin-copper polymetallic deposit, located in southeastern Yunnan Province in China, consists of few separate ore fields, for instance, the Malage, Songshujiao, Gaosong, Laochang and Kafang ore fields. This article focused on the study of lithofacies sequence of sedimentary rocks, volcanic rocks, and volcanic sedimentary rocks in the Gejiu superlarge tin-copper polymetallic deposit, as well as the western Guangxi Zhuang Autonomous Region. The tectonic lithofacies analysis and reconstruction of tectonic and palo-geographical location for the prototype basin were used to better understand dynamics of Triassic back-arc rift basin and its metallogenic sequence in Gejiu of Yunnan Province to Napo of Guangxi Zhuang Autonomous Region.This study revealed that the prototype basin for the Triassic sedimentary basin from the Gejiu of Yunnan Province to the western part of Guangxi Zhuang Autonomous Region might be the back-arc rift basin, and its tectonic palo-geographic location could be developed on the basement of continental crust on the southern-western margin of the Yangtze Block. This basin were filled up by sediments from three-direction source areas, I. E. , First, lithofacies sequence of shallow clastic rocks developed on the margin of the Kangdian-Pingma ( Northern Viet Nam) palo-massif, which the sequence can be classified into clastic sedimentary associations from the source area of the palo-massif. Secondly, carbonate lithofacies of the Middle Triassic Gejiu Group in Gejiu area of Yunnan Province could belong to sedimentation of in-basin source area on sea-basin on the continental margin, which the sedimentary sequence and association could be related to the rifted-basin thermosaging on the continental margin. Thirdly, the Triassic hot-material of mantle derived from the deep part of the basin basement erupted into the basin and volcanic rocks were formed in the basin. At the same time, hot water syn-sedimentation and syn-metasomatism in sea-bed might produce marine altered rocks and hydrothermal sedimentary rocks. Furthermore, marine volcanic rocks derived from the hot-material of mantle origin include alkaline picrite, alkaline basalt, and acid tuffs, accompied by tuffous chert, chert, abyssal chert, and Mn-bearing carbonated rocks.Tectonic dynamics of this basin could be the Carboniferous extensional basin on the continental margin of the Yangtze Block. Then, the basin was changed into a rifted basin on the continental margin. The Triassic back-arc rift basin on the continental margin might be formed by extrusive rocks of upwelling hot mantle plume, and its dynamics could be shear-extensional tectonic dynamics. The vertical lithofacies sequences are filled by the lower parts which are fine-grained sedimentary rocks interbedding with marine volcanic rocks, the middle parts which are from coarsening-upward sequence to fining-upward sequence with alkaline picrite and alkaline basalt, and the upper parts which are coarsening-upward sequence bearing coal seams.Metallogenic sequence in the Triassic back-arc rift basin is typified by Ag-Sb-Pb-Zn ores hosed in the lower parts, Sn-Cu-polymetallic ores hosted in the middle part, Mn-Ag-Pb-Zn ores hosted in the upper part, and coal seam at the top layer.
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