西秦岭太白地区岩湾－鹦鸽咀蛇绿混杂岩的地质特征及形成时代

Geological features and SHRIMP U-Pb zircon age of the Yanwan-Yinggezui ophiolitic mélange in the Taibai area, West Qinling, China

摘要: 岩湾－鹦鸽咀蛇绿混杂岩是秦岭商丹蛇绿混杂岩带的重要组成部分，由变质基性火山岩（玄武岩）、蛇纹岩、变辉长岩、硅质岩、变复理石（云母石英片岩）等构造岩块组成。其中变基性火山岩具有N-MORB的地球化学特征，安山岩具有与俯冲作用密切相关的岛弧火山岩的性质。玄武岩的锆石SHRIMP U-Pb年龄为483Ma±13Ma，与天水关子镇和丹凤蛇绿混杂岩的时代相一致。对岩湾－鹦鸽咀蛇绿混杂岩的岩石组成和形成时代进行研究，可为进一步探讨商丹蛇绿混杂岩带和秦岭造山带的增生造山作用提供重要证据。

Abstract: The Yanwan-Yinggezui ophiolitic mélange in the West Qinling orogenic belt is an important component part of the Shangdan ophiolitic mélange. It is composed of tectonic blocks of metabasic volcanic rocks (basalt), serpentinite, metagabbro, cherts and meta-flysch (mica-quartz schist), of which basalt blocks have the geochemical features of N-MORB and andesite is subduction-related island-arc rocks. The zircon SHRIMP U-Pb age of basalt is 483±13 Ma, which agrees with the age of the Guanzizhen and Danfeng ophiolitic mélanges. The study of the composition and age of the Yanwan-Yinggezui ophiolitic mélange can provide important geological evidences for a further study of the evolution of the Shangdan ophiolitic mélange and accretionary orogeny of the Qinling orogenic belt.