Petrogenesis of the Xuanwoling mafic–ultramafic intrusion in the northeastern Tarim Block(Northwest China)  

作　　者：Zhao-De Xia Chang-Yi Jiang Ming-Zhe Xia 

机构地区：[1]School of Earth Science and Resources, Chang’an University [2]Jiang Key Laboratory of Western China’s Mineral Resources and Geological Engineering of Ministry of Education, Chang’an University

出　　处：《Chinese Journal Of Geochemistry》2015年第1期69-84,共16页中国地球化学学报

基　　金：supported by the Nationa Natural Science Foundation of China (Grant No. 4130207,41102045);the Fundamental Research Funds for the Central Universities (2014G1271066);China Regional Geological Survey (12120113043100)

摘　　要：Beishan Terrane, located in the northeast of the Tarim Block, in northwest China, has developed a 500-km long and 100-km wide belt of Permian mafic–ultramafic intrusions One of these mafic–ultramafic intrusions, the Xuanwoling Intrusion, is composed of dunite, troctolite, olivine gabbros and gabbros, with cumulate texture and rhythmic layering The crystallization sequence is olivine ? spinel ? plagio clase ? pyroxene, indicating that the crystallization pressure is lower than 0.5–0.8 GPa and that the intrusion has undergone variable degrees of crustal contamination, increasing from dunite to gabbros. The olivines found in the Xuanwoling Intrusion have high Fo values(up to 90), suggesting a primary magma with a high composition of mg. It is likely that this high-mg magma was produced at extremely high temperatures(1,330–1,350 °C), and as a result, Nd–Sr isotopic compositions similar to oceanic island basalts are found in the Xuanwoling Intrusion, which we propose arose from the mantle plume.Beishan Terrane, located in the northeast of the Tarim Block, in northwest China, has developed a 500-kin long and 100-km wide belt of Permian mafic-ultramafic intrusions. One of these mafic-ultramafic intrusions, the Xuanwoling Intrusion, is composed of dunite, troctolite, olivine gabbros, and gabbros, with cumulate texture and rhythmic layering. The crystallization sequence is olivine ＋ spinel ＋ plagio- clase→pyroxene, indicating that the crystallization pressure is lower than 0.5-0.8 GPa and that the intrusion has undergone variable degrees of crustal contamination, increasing from dunite to gabbros. The olivines found in the Xuanwoling Intrusion have high Fo values （up to 90）, suggesting a primary magma with a high composition of mg. It is likely that this high-rag magma was produced at extremely high temperatures （1,330-1,350℃）, and as a result, Nd-Sr isotopic compositions similar to oceanic island basalts are found in the Xuanwoling Intrusion, which we propose arose from the mantle plume.

关 键 词：中国西北地区 超镁铁质 东北部 塔里木盆地 侵入 ND-SR同位素 成因 纯橄榄岩 

分 类 号：P588.12[天文地球—岩石学]