| Since the Cenozoic,the collision and compression between the Indian plate and the Asian plate have formed the Qinghai Tibet Plateau with the largest scale and the highest altitude on the earth.The Qinghai Tibet Plateau is formed by the collage of many different blocks(the main body of the plateau includes Himalayas,Lhasa,Qiangtang and Songpan Ganzi blocks as well as Jinsha River,Bangong Lake Nujiang and Yarlung Zangbo Suture Zone).It is a natural laboratory to study the continental collision and its dynamic mechanism,the formation and evolution of the lithosphere,and constantly breeds new academic views and theoretical breakthroughs.Bange Basin and Lunpola Basin in the middle of Qinghai Tibet Plateau are located in the north of Lhasa massif and in the middle of Bangong Lake Nujiang suture zone between Qiangtang and Lhasa massif.They are typical representatives of a series of continental basins distributed on the Bangong Lake Nujiang suture zone.The huge thick Cenozoic strata deposited in the basin record a lot of information about plateau uplift and geomorphic evolution.According to the basin mountain coupling relationship,based on the Cenozoic stratigraphic chronology framework,this paper mainly studies the Cenozoic zircon U-Pb age provenance of Lunpola-Bange Basins,combined with the sedimentary facies,paleocurrent analysis and previous research results,restores the Cenozoic provenance change history of the basin,discusses the formation and evolution of the Cenozoic Basin and the process of structural uplift around the basin The following knowledge is obtained:1.The Cenozoic strata of the Lunpola Basin mainly include fan delta facies,shore shallow lake facies and semi deep lake deep lake facies.In the Eocene,the sedimentary area of the basin gradually expanded,and the sediment is mainly lake facies.In the Oligocene,the area of the lake basin gradually decreased,and the fan Delta and alluvial fan environment gradually changed from shore shallow lake environment.In Miocene,the lake basin area was faulted again and the lake waterbecame deeper,and the deep lake semi deep lake deposition developed.2.The Lunpola Bange Basin experienced at least three provenance changes in the Cenozoic: the U-Pb age of zircon in the Pliocene early Oligocene(before 30 Ma,the middle part of Niubao formation)is mainly 75-160 and 190-290 Ma,and the dominant peak is 350-720 Ma,and the provenance is mainly from Lhasa terrane;the age component of 75-160 Ma in the Oligocene(30-22 Ma,the upper part of Niubao formation)is suddenly reduced,while that of 190-320,720-1000 The components of1600-2000 and 2080-2640 Ma increased,and the source came from Lhasa terrane,and the material of Qiangtang terrane increased;since Miocene(Dingqinghu formation),the components of 75-160 Ma and 720-1000 Ma increased,and the source came from Qiangtang and Lhasa terrane,and the Qiangtang terrane was the main one.3.Tectonic activities in the middle of the Eocene(>38Ma)Plateau mainly led to the uplift of Lhasa terrane and the formation of Lunpola Bange Basin,which began to accept the deposition of Niubao formation;tectonic activities in the middle of the plateau in the early Oligocene(around 30Ma)led to the intensification of the uplift of Qiangtang terrane and the transformation of the basin's uplifting sedimentary environment from lake facies to water alluvial environment;tectonic uplift activities in the middle of the plateau from late Oligocene to early Miocene The movement resulted in the rapid uplift of Lhasa and Qiangtang terranes and the rapid transformation of Lunpola Bange basin from alluvial environment to semi deep lake facies. |
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