内蒙古阿拉善右旗杭嘎勒晚二叠世闪长岩地球化学特征和LA-ICP-MS锆石U-Pb定年

阿拉善右旗杭嘎勒地区晚三叠闪长岩轻稀土元素明显富集,大部分具正Eu异常,显示I型花岗岩的特点。Rb、Sr、Hf富集,而Nb、P、Ti亏损,显示出与俯冲有关的侵入岩特征。在R1-R2图解上,大部分样品集中在碰撞前花岗岩区;在Nb-Y图解上,样品落在火山弧-同碰撞花岗岩区;在Rb-(Y+Nb)图解上,样品点落在火山弧花岗岩区;在Rb-Hf-Ta图解上,样品全部落在弧系统岩石区。LA-ICP-MS锆石U-Pb定年表明其年龄为(257.1±4.0)Ma。杭嘎勒晚二叠世闪长岩为碰撞前火山弧花岗岩,研究区在晚二叠世时属于活动大陆边缘的火山弧。

Geochemical Characteristics and LA-ICP-MS Zircon U-Pb Dating of the Late Permian Diorite in Hanggale,Alax Right Banner,Inner Mongolia

Late Permian diorite of Hanggale is characterized by enrichment of LREE, and positive Eu anomalies, implying an I-type granite. The accumulation of Rb, Sr, Hf elements and the depletion of Nb, P, Ti elements shows that such arc granite has features of intrusive rocks relating to subduction. In the R1-R2 diagram, most of the samples are concentrated in the pre-collision granite area. In the Nb-Y diagram, the samples fall into the area of the volcanic arc-syncollisional granite. In the Rb-（Y＋Nb） diagram, the samples lie in the area of volcanic arc granite. In the Rb-Hf-Ta diagram, the samples all fall into the arc system. LA-ICP-MS zircon U-Pb dating shows that its age is 257.1±4.0 Ma. The Late Permian diorite of Hanggale area was pre-collisional volcanic arc granite, and Hanggale area was a volcanic arc belonged to active continental margin in Late Permian.