| The study area is located in Lvchun, which is situated in the southern part of the Yunnan-Guizhou Plateau and the southwest of Three Rivers tectonic belt with the southwest margin of the Yangtze plate junction, belongs to the southern section of the Jinsha River-Ailao Mountain orogenic belt. Since the1950s, domestic and foreign experts and scholars have done a lot of research of this orogenic belt, and achieved great results, but the study is limited to the middle and north segment of the orogenic belt, the southern section of the relatively low.Duo to the influence of the large scale structure-magma repeatedly invaded, uplift and erosion and Mesozoic sedimentary basins material mixed and cover, the Paleo-Tethys (suture zone) in the area of the surface outcrop characteristics are not significantly,lacking of the knowledge about the presence of the suture zone or not, open ocean basin closed basin-range coupling process and sedimentary response and so difficult observation, the suture zone tectonic units (ophiolite melange zone, island arc, etc.), material composition, fabric,and nature, what is short of support for the suture zone in the area extending basic evidence.Therefore,the study of presence or absence of Lvchun island arc belt not only provides the geological basis for extension southeast segment jinsha River-Ailao Mountain orogenic belt, but also to orogen evolution of the area, lithosphere group structure, dynamics, and regional metallogenic regularity of great theoretical and practical significance.Based on the regional geological survey and comprehensive research project, making use of the predecessors research results about the region and its neighboring area, using modern plate tectonics, orogenic belt and continental dynamics research of new theory and technical methods to systematically analyzes and summarizes the basic geological studies, closely combined with route geology survey and mapping and indoor comprehensive study work, according to the "Li Xian River structure-magmatic belt" and Lanping-Simao foreland basin magmatic rocks, composition and characteristics of detrital zircon chronology of the basin as the research object and focus, which the structure, sedimentary tectonics and magmatism in Lvchun regional of the southern section of Jinsha River-Ailao Mountain orogenic belt, combined with the domestic and foreign subduction collision orogenic belt and the new research results of island arc belt; Using the characteristics of tectonic deformation and tectonic units of the comparative to analysis with the surrounding tectonic units and clarify its relationships, preliminarily discusses its subduction, collision model; Further clarify sanjiang arc basin system in the area of time-space distribution, formation and evolution of it Subduction and collision model preliminary discussion, for in green in the spring of orogenic belt of east tethys tectonic evolution process provides the basis.Lvchun island arc magmatic rocks distribute brokenly in the Ailaoshan Lixianjiang tectonic-magmatic rock band what between the Anling-Jiujia fault and the Ailaoshan-Lixianjiang fault, which in the form of the (small) rock strains and apophyses. The main rock types is the acidic intrusive rocks with a small amount of extrusive rock. Rock trace elements-tectonic discrimination diagrams and cation parameters characteristic R1-R2diagram, most of the investment point falls on the same collision (S type) and its near the granite, individual rock cast in the plate collision and orogenic uplift after collision stage after the reporting period; REE chondrite-normalized distribution patterns showed enrichment of the rightist, total rare earth has features of late tend to concentrate, and light, the presence of heavy rare earth elements fractionation or insignificant Rock trace element the LILE variation, magmatic unit of the relationship between the causes and the evolution of non-product of the crust-mantle magma differentiation Zircon U-Pb isotopic geochronology feature analysis (260±1.7Ma～266±1.5Ma) formed in the Late Permian, combined with the regional tectonic evolution characteristics and rock geochemical analysis, Description Lvchun region " Ailaoshan tectonic magmatic belt " in the late Permian period belong to the island arc environment.Lanping-Simao arc foreland basin-Late Permian unequal thickness to the development of carbonate and clastic rocks interbedded folder volcano-pyroclastic rocks (tuff, andesite, etc.) is characterized by Triassic and developed carbonate and terrigenous-fine-grained clastic rocks interaction is characterized by deposition. The ba liu group, the wai gu chun group, the sandstone debris and the mai chu qing group of conglomerate composition and deposition facies and paleocurrent reveal that the sediments from the eastern orogenic volcanic arc. Combined Permian the yang ba zhai group, Triassic the wai gu chun group, the mai chu qing group geochronology of detrital zircons from the measured age range Distribution and Variation Characteristics reveal Lvchun Island arc volcanic rocks of Early Permian collision stage of the product.According to the research geological actual, response and tectonic setting of back-arc basin sediments, combined with regional data comprehensive analysis can be summarized geological evolution of the study area is divided into three important stages of evolution:the intracontinental rift valley (trap)-ocean basin formation and expansion stage; ocean basin subduction-continental arc collision stage; continent-continent collision and extrusion orogenic stage. |
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