攀枝花-西昌古裂谷晚古生代的演化

文章分６个阶段重塑了晚古生代攀枝花－西昌古裂谷的演化，认为它属地台区不成熟的小规模裂谷，是大陆边缘地区发生张裂及深部物质上涌的结果

TECTONIC EVOLUTION OF PANZHIHUA XICHANG PALEORIFT DURING LATE PALAEOZOIC

Panzhihua Xichang paleorift which is situated on the Kangdian Paleozoic Block Rise in the west part of Yangtze fault block developed from deep to shallow during Late Paleozoic. It could be divided into six stages. (1)Pre rifting:an uplifted platform area during Early Paleozoic, rifting occurred against a background of sinking; (2)Initial rifting (Early Devonian): marked by platinum and palladium bearing ultramafic plutons; (3) Rifting (Middle Devonian Carboniferous): with vanadium and titanium bearing layered mafic ultramafic intrusions;(4)Relative compression:accompanied with alkalic and acidic intrusions; (5)Rift valley(Permian): eruption of Emeishan basalt and (6)Closure and inversion: with intrusion and eruption of acidic and alkalic rocks. Synthesizing the data of stratigraphy, isotope geology,petrology, sedimentology, ore deposits and structure geology, three paleotectonic maps have been compiled, which reconstruct the rift development and reveal its space configurations. The paleorift might developed on a platform. The fills were mainly bimodal magmatites. The magmatic evolution seems comparable with Oslo paleorift. It might show a tendency of the southern part earlier in a single belt, and the western part earlier as the region concerned. Correspondingly, the geochemistry features of Emeishan basalt might change from intraplate westwards to continental margin. Along the west boundary fracture of the Kangdian Block Rise,there might be the Yanyuan Lijiang pericontinental rift; west further, the Ganzi Litang sea floor rift. The tectonic pattern might reflect an Atlantic type continental margin. The rift mechanism should be tension and taphrogenesis plus upwelling of the deep materials, instead of plate subduction.