甘肃西秦岭舟曲憨班花岗岩体的单颗粒锆石U-Pb年龄及地质意义

在 1:25万武都幅区域地质调查中对西秦岭憨班花岗岩体进行了调查研究,通过高 精度单颗粒锆石 U-Pb同位素测年,获得 ²⁰⁶ Pb/²³⁸ U表面年龄统计权重平均值分别为: 205±1 Ma 和212±1.4 Ma,属印支晚期。岩石化学和地球化学特征表明,憨班岩体属高钾钙碱性系列,在Rb-Yb+Nb和Nb-Y图解中,样品均投在火山弧花岗岩＋同碰撞花岗岩区。憨班岩体形成于陆陆碰撞造山阶段后期,可能形成于加厚地壳的部分熔融。

Single-grain zircon U-Pb ages and geological significance of the Hanban granite from Zhouqu(Gansu) in the west Qinling orogenic belt

Petrological and geochemical characteristics as well as formation ages of the Hanban granitic pluton has been investigated during the regional geological survey(scale 1:250 000)in Wudu,west Qinling Mountains.High-precision single-grain zircon U-Pb dating results yielded weighted average ages of 205±1 Ma and 212±1.4 Ma for fine-to middle-grained granodiorite and porphyritic adamellite in the Hanban pluton,respectively,indicating that the pluton was formed in the late Indosinian.The Hanban granitic rocks are high-K calc-alkaline in major elements and are plotted in the field of volcanic arc and syn-collisional granite in the Rb-Yb+Nb and Nb-Y plots.It is proposed that the Hanban pluton was formed by partial melting of thickened crust in the late stage of continent-continent collision.