Geochronology Research On The Structure-magma-mineralization Events Taking Place In Tianshan And Adjacent Areas In Paleozoic Era

We study the times of the tectonic,the magma and mineralization events since the Paleozoic in Tianshan and adjacent areas(the range roughly from N 40°to N 46°,China).The Paleozoic tectonic evolution mechanism of this area was discussed by the analysis of the tectonic settings of magma activity and mineralization activity.In the recent ten years,several "305" and "973" projects have been finished and some are under performing,many progresses about petrology,geotectonic,ore deposit have been made.It is very necessary to summarize the exist results systematically for finding out the relationship among the structure, the magma,the mineralization events and the evolution of these events.Therefore the exist results of the structure,the magma and the mineralization events were collected,analyzed and summarized here. Furthermore,we analyse the thrust-slip and strike-slip events taking place in Eastern Tianshan according to their ages measured by the precise ⁴⁰Ar/³⁹Ar dating,and determined their active times and the forming ages of the shear-type gold deposits.The progress from this paper as follows:(1) The geological meaning of several types of ⁴⁰Ar/³⁹Ar age spectra was discussed.In addition,the ⁴⁰Ar/³⁹Ar age spectrum of the sericite from the gold deposit in Eastern Tianshan shear zone show a little disturbed,indicating that the shear tectonic events took place after the gold deposit.(2) We summarized the ages of the tectonic events in this area and study the nappe and the strike-slip event of East-TianShan using ⁴⁰Ar/³⁹Ar method.Therefore,we further understand the Paleozoic tectonic evolution in Tianshan and adjacent areas.(3) The Geochronology results from the magmatic rocks in study area show that the features of the acid magmatism in Paleozoic are that the ages of the rocks became younger from the eastern to the western and from the northern to the southern.This suggests that the matching of the Tarim plate and the Siberia plate began from the east to the west and from the north to the south gradually.(4) The ages from the tin deposits show that the times of the tin deposits located in the western Xinjiang became younger from the north to the south,reflecting the matching of the Kazakhstan plate and the Junggar firstly,and then with Yili plate.(5) The forming ages of the shear zone gold deposits in East Tianshan are determined by the precise ⁴⁰Ar/³⁹Ar analysis.The results show that the age of the gold deposit become younger from the west to the east gradually,indicating the differential uplifting of the East Tianshan area from the west to the east.(6) A new way to discriminate the tectonic setting of alkaline rocks was established,and the tectonic setting of the rocks from the northern margin of Tarim basin and north-eastern margin of Junggar basin were discriminated by this way.The results show that the alkaline rocks in the northern margin of the Tarim basin formed under the extending environment and the alkaline rocks in the north-eastern margin of the Junggar basin formed under the extension environment caused by the strike-slip.(7) A new point about the mechanism of the large-scale extension in Late Carboniferous - Early Permian in study area is presented that this large-scale extension is caused by the intrusion of asthenosphere mantle.