Analysis On Tectonic-Magmatic Evolution Characteristics Of Carboniferous-Early Permian In Barkol Mountain Of East Tianshan

The predecessors had been many studied on the crustal structure and tectonic evolutionof East Tianshan area，However，there was considerable controversy about Late Paleozoictectonic evolution in Bogda and Harlik. Barkol Mountain areas is located in the transfer partsof the Bogda Mountain and Harlik Mountain, It did not a detailed research, only inferredstudy from the east and west sides. Through two thematic projects, the author worked forthetwo years in Barkol Mountain and its surrounding areas. Based on the extensive collectionof previous studies results, combining with field research, and sample analysis and datacompilation indoor, There is a comprehensive analysis and discussion about the tectonic-magmatic evolution process of Carboniferous-Early Permian in Barkol Mountain of easternTianshan Mountain. The detailed contents are as follows:Deposition construction, rock assemblages, depositional environment, Magmatic activityand rock geochemistry etc were comprehensively analyzed in the study area. The resultsshow that Carboniferous strata in the study area is a Marina-shallow marine sedimentary andvolcanic rock assemblages, and has a number of regression and transgression, a clearrelationship between sedimentary and volcanic rocks, volcanic activity have a big changes inthe strength, volcanic rocks is typical rift bimodal volcanic rocks. Early Carboniferous basaltand rhyolite belong to the same genetic type of rock, basalt derives from a depleted mantle,and associated rhyolite is the product of fractional crystallization of basaltic magma. LateCarboniferous basalt and rhyolite belong to different genetic types of rocks, basalt derivesfrom a depleted mantle, and suffers from the contamination of crustal material, rhyolite fromthe product the magma heat generated by basaltic magma underplating to remelting of crustalmaterial. In study area, the characteristics of basalt and rhyolite are different from thesurrounding area.Carboniferous in the study area is oblique subduction of the ancient Asian oceanic crustto the earlier Junggar-Turpan-Hami continental block, lateral tearing force produced drawsland mass to form Rift Valley, the time of Rift Valley formation and evolution is a very short.Barkol Mountain in Early Carboniferous began the evolution of rift stage, mainly rhyolite and dacite, basalt less, rift in Late Carboniferous began closing, its development and evolutionhas a direct relationship of oceanic crust subduction and plate collision in the northernXinjiang region. Oceanic crust subduction and plate collision course interact withmantle-derived magma, resulting in a unique coastal-shallow marine facies tectonicenvironment of Carboniferous in the study area of the, and tectonic-magmatic evolution andrift formation process are unique.The intrusion of mafic dikes in study area is before the extrusion environment in theregion, in the latter experiences overheating fluid alteration，The time of intrusion ispost-collisional stage in Late Carboniferous-Early Permian, associate with the large scalemantle-derived magmatism of Early Permian in northern Xinjiang region. In post-collisionalstage, under crustal extension caused by mantle-derived magma rise, depleted mantle magmainvades surface along early mid-acidic rock fissures, in the process of magma ascent sufferssome contamination from crustal material.