阿尔金原特提斯洋闭合新证据——环形山高压基性麻粒岩研究

New Evidences for the Closure of the Altyn Proto-Tethys Ocean:A Case Study of High Pressure Basic Granulites from Ring Hills in the Altyn Mountains

为探讨阿尔金南缘新发现的高压岩石的成因及其地质意义，采用显微镜、电子探针及 LA-ICP-MS 等方法对岩石及其矿物、锆石原位微量元素、Lu-Hf同位素特征及同位素年龄进行分析。结果表明，岩石为高压基性麻粒岩，其原岩年龄为592±11～790±14Ma，变质年龄为508±6Ma，岩石在形成演化过程中曾受到地壳的混染。研究认为岩石形成于新元古代晚期Rodinia超大陆裂解期，随着威尔逊旋回的发展，原特堤斯洋形成，在500Ma左右发生板块的俯冲、碰撞及折返，形成环形山高压基性麻粒岩表明阿尔金原特堤斯洋在早奥陶世已经闭合。

In order to discuss the petrogenesis and geological significance of high pressure rocks newly discovered in south margin of the Altyn Mountains,a study on characteristics of rock and minerals,trace element characteristics of zircons by in-situ analysis,Lu-Hf isotope geochemistry and isotopic dating of the rock has been carried out by using microscope,e-lectron microprobe,LA-ICP-MS,and other methods in this paper.The results show that the rock is identified as a high pressure basic granulite,with ages of 592±1 1Ma-790±1 4Ma for its primary rocks,and age of 508±6Ma for its meta-morphism.The rock is contaminated with crustal materials in the formation process.With the combination of existing previ-ous research results,it is believed that the rock was formed after the late Neoproterozoic Rodinia supercontinent cracking period.With the development of the Wilson cycle,the Proto-Tethys Ocean was formed.The subduction,collision and ex-humation of the Altyn Proto-Tethys Ocean plate,occurred around 500Ma,resulted in the formation of high pressure basic granulites in ring hills,indicating that the Altyn Proto-Tethys Ocean was closed in Early Ordovician.