摘要
The Santanghu area is located on the northeastern margin of the Junggar Basin,northern Xinjiang,Northwest China.The Carboniferous volcanic rocks in this area are widely distributed in Kaokesaiergaishan,Santanghu,Daheishan and Naomaohu districts,which are located to the north of the Kalameili Fault.These rocks,sourced from a cognate magma,consist of basic,intermediate,and acidic lavas,and pyroclastic rock.The basic volcanic rocks are enriched with large-ion lithophile elements(LILE),but are relatively depleted in high field strength elements(HFSE),and have an obvious negative Nb-Ta-Ti anomaly.They were most probably derived from a depleted mantle source,and during their ascent,these magmas were not contaminated by the crustal material as they underwent magma crystallization differentiation.Based on the Carboniferous volcanic assemblage and geochemical data,it is apparent that the early Carboniferous volcanism occurred in a subduction-related tectonic setting.New LA-ICP-MS zircon U-Pb analyses constrain the age of the andesite within the volcanic rocks as the early Carboniferous(328.9-331.3 Ma).Combined with the regional geological record,comprehensive analysis of the isotope geochronological data indicates that the subduction of the Junggar Ocean predates the early Carboniferous,and that the Santanghu island arc magmatism was induced by the subduction of the Junggar Ocean in the Carboniferous.
The Santanghu area is located on the northeastern margin of the Junggar Basin, northern Xinjiang, Northwest China. The Car- boniferous volcanic rocks in this area are widely distributed in Kaokesaiergaishan, Santanghu, Daheishan and Naomaohu dis- tricts, which are located to the north of the Kalameili Fault. These rocks, sourced from a cognate magma, consist of basic, in- termediate, and acidic lavas, and pyroclastic rock. The basic volcanic rocks are enriched with large-ion lithophile elements （LILE）, but are relatively depleted in high field strength elements （HFSE）, and have an obvious negative Nb-Ta-Ti anomaly. They were most probably derived from a depleted mantle source, and during their ascent, these magmas were not contaminated by the crustal material as they underwent magma crystallization differentiation. Based on the Carboniferous volcanic assem- blage and geochemical data, it is apparent that the early Carboniferous volcanism occurred in a subduction-related tectonic set- ting. New LA-ICP-MS zircon U-Pb analyses constrain the age of the andesite within the volcanic rocks as the early Carbonif- erous （328.9-331.3 Ma）. Combined with the regional geological record, comprehensive analysis of the isotope geochronological data indicates that the subduction of the Junggar Ocean predates the early Carboniferous, and that the Santanghu island arc magmatism was induced by the subduction of the Junggar Ocean in the Carboniferous.
基金
supported by Land and Resources Survey Project of China(Grant No. 1212011085009)
the Sinopec Project "Study and Map Compilation for Structure,Lithofacies,and Paleogeography in Northwestern China" (Grant No. YPH08103)
National Natural Science Foundation of China (Grant No. 40802051)
