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...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.展开更多
基金suppor ted by the“973”programme of China(Grant No.2001CB409801)filiale of the Turpan-Hami oil field.
文摘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.
