Basalt from Permian Haerjiawu formation in Xiemisitai Mountain of Xinjiang is located in the northwestern margin of Junggar Basin.Xiemisitai Mountain is a key part of Central Asia orogenic which is the intersection of Siberia plate,Kazakhstan plate and Tarim plate.Haerjiawu formation basalt is gray vesicular or amygdaloidal basalt,which belongs to the medium and low potassium andesite-basalt.Zircon U-Pb age is (298.2±4.7) Ma,which is formed in the early Permian.The basalt is enriched in LILE,such as Ba,Th,K,Sr and HFSE,such as Nb,Ta are relatively depleted.Zr and Hf are slightly enriched.And the overall abundance of incompatible elementsis relatively lower,reflecting the geochemical characteristics related with continental subduction zone magmatism.The Haerjiawu formation basalt is formed in the orogenic environment.It suggests that the basalt occurs in intracontinental subduction environment related to the subduction zone,which is appeared in post orogenic extensional background.%新疆谢米斯台山中段二叠纪哈尔加乌组玄武岩处于准噶尔盆地西北缘,是西伯利亚板块、哈萨克斯坦板块和塔里木板块交汇处的中亚增生造山带关键部位,哈尔加乌组玄武岩为青灰色气孔或杏仁状玄武岩,属中低钾安山玄武岩,锆石年龄为(298.2±4.7) Ma,属早二叠世.该玄武岩大离子亲石元素Ba,Th,K,Sr相对富集,高场强元素Nb,Ta相对亏损,Zr,Hf轻微富集,不相容元素丰度整体相对较低,反映与俯冲带相关的大陆岩浆作用的地球化学特征.哈尔加乌组玄武岩以板内大陆环境为主,并形成于活动造山环境,推测该玄武岩形成于与俯冲带有关的碰撞后陆内环境,且出现在俯冲造山期后的伸展背景下.
展开▼
