Time constraints for the closing of the Paleo-Asian Ocean in the   Northern Alxa Region: Evidence from Wuliji granites

doi:10.1007/s11430-012-4435-y

CORC > 北京大学 > 地球与空间科学学院

	Time constraints for the closing of the Paleo-Asian Ocean in the Northern Alxa Region: Evidence from Wuliji granites
	Zhang Wen ; Wu TaiRan ; Feng JiCheng ; Zheng RongGuo ; He YuanKai
刊名	science china earth sciences
	2013
关键词	Alxa Engger Us Qagan Qulu SIMS crust-mantle mixing volcanic arc post-collision PHANEROZOIC CRUSTAL GROWTH ND ISOTOPIC EVIDENCE INNER-MONGOLIA TECTONIC IMPLICATIONS TRACE-ELEMENT OROGENIC BELT GEODYNAMIC EVOLUTION ZIRCON STANDARDS NW CHINA ICP-MS
DOI	10.1007/s11430-012-4435-y
英文摘要	The Wuliji pluton in the Northern Alxa Region, Inner Mongolia, is the principal part of Shalazhashan Mountain. It belongs to the Zongnaishan-Shalazhashan Arc Zone, northwestern North China Plate, whose north is Engger Us Ophiolite Belt and south is Qagan Qulu Ophiolite Belt. The pluton was emplaced into Upper Carboniferous-Lower Permian Amushan Formation. According to the research about the original Carboniferous Amushan Formation, the lower and middle sections of the Carboniferous Amushan Formation consist of volcanic, clastic, and carbonate rocks, interpreted to represent the sedimentary association of a volcanic arc and back-arc basin; the upper section of the Amushan Formation is a molasse composed of silty shale, sandstone, gravel-bearing sandstone, and conglomerate. The Wuliji pluton consists mainly of biotite monzonitic granite, amphibole-bearing biotite monzonitic granite, and monzonitic granite. Geochemical analyses show that the pluton has both metaluminous and peraluminous characteristics, and on average has SiO2 > 70 wt%, Al2O3 > 14 wt%, and high contents of Na2O+K2O (8.5 wt%), which define a calc-alkaline series. In addition, REE patterns show enrichment of LREE and weak negative Eu anomalies (delta (Eu) = 0.3-1). Altogether, the samples are depleted in Nb, Ta, Ti, P, Sr, and Ba, and enriched in Rb, Th, and K. These geochemical traits are interpreted to reflect an arc component. A secondary ion mass spectrometry (SIMS) U-Pb zircon age of the biotite monzonitic Wuliji pluton in the Northern Alxa Region, Inner Mongolia, is 250.8 +/- 2.0 Ma (1 sigma). Samples have E > (Nd)(t) values between -0.1 and 1.3, which suggests that the granites were derived from mixing between the crust and mantle. Based on the SIMS age and geochemical characteristics, Wuliji granite is interpreted to be a post-collisional granite, the result of mantle-derived melt and assimilated juvenile arc crust. However, according to the newest international stratigraphic classification standard, the upper section of the Amushan Formation is Lower Permian in age, indicating that the back-arc basin had already closed in Early Permian. We conclude that the Paleo-Asian Ocean represented by the Engger Us Ophiolite Belt subducted southward in Late Carboniferous, at the same time that the trench-arc-basin system formed in the Northern Alxa Region. The Paleo-Asian Ocean was closed in Early Permian and the Northern Alxa Region entered a post-collisional period in the Late Permian, as indicated by the Wuliji granites. This suggests that the genesis of the Wuliji granites is consistent with the pluton emplacement at the upper crust, which occurred widely in the northern margin of the North China Plate in Late Carboniferous to Triassic.; Geosciences, Multidisciplinary; SCI(E); EI; 4; ARTICLE; 1; 153-164; 56
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155667]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Zhang Wen,Wu TaiRan,Feng JiCheng,et al. Time constraints for the closing of the Paleo-Asian Ocean in the Northern Alxa Region: Evidence from Wuliji granites[J]. science china earth sciences,2013.
APA	Zhang Wen,Wu TaiRan,Feng JiCheng,Zheng RongGuo,&He YuanKai.(2013).Time constraints for the closing of the Paleo-Asian Ocean in the Northern Alxa Region: Evidence from Wuliji granites.science china earth sciences.
MLA	Zhang Wen,et al."Time constraints for the closing of the Paleo-Asian Ocean in the Northern Alxa Region: Evidence from Wuliji granites".science china earth sciences (2013).