摘要
The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological study of the basalts developed in the basins reveals that theformation period is Permain (293—266 Ma). From geochemical comparison of the basalts, theSantanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE,reflecting that the source region is influenced by the subducted components related to subduction ofthe ancient oceanic crust and characterized with ''lagged arc volcanic rocks''. In contrast, theTurpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basaltsformed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formationperiod of the ophiolite and ophiolite melange zones and regional magmatic activities occurring onthe post-orogenic extensional background in northern Xinjiang, it can be inferred from thesegeochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghubasins is closely related to the regional extension after the continent-continent collisionalorogeny. The basalts of the two basins came from different sources on the post-orogenic extensionalbackground of the similar basin-forming dynamics. Although the settings are all intracontinentalrift, the source for the Santanghu basalts is obviously subjected to the metasomatism of thesubducted components, implying the existence of the previous subduction.
The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoic re-worked intracontinental basins that superposed on the folded basement of the Paleozoic orogenic belt. 40Ar/39Ar geochronological study of the basalts developed in the basins reveals that the formation period is Permain (293—266 Ma). From geochemical comparison of the basalts, the Santanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE, reflecting that the source region is influenced by the subducted components related to subduction of the ancient oceanic crust and characterized with “lagged arc volcanic rocks”. In contrast, the Turpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basalts formed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formation period of the ophiolite and ophiolite mélange zones and regional magmatic activities occurring on the post-orogenic extensional back-ground in northern Xinjiang, it can be inferred from these geochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghu basins is closely related to the regional ex-tension after the continent-continent collisional orogeny. The basalts of the two basins came from different sources on the post-orogenic extensional background of the similar basin-forming dynamics. Although the settings are all intracontinental rift, the source for the Santanghu basalts is obviously subjected to the metasomatism of the subducted components, implying the existence of the previous subduction.
作者
ZHOU Dingwu1,2, LIU Yiqun1,2, XING Xiujuan1, HAO Jianrong1, DONG Yunpeng1 & OUYANG Zhengjian1 1. Key Laboratory of Continental Dynamics, Ministry of Education, Northwest University
Department of Geology, Northwest University, Xi’an 710069, China
2. Geoinformation Science & Engineering College, SDUST, Qingdao 266510, China
