桐柏造山带兵马寺冲花岗岩年代学及岩石成因研究  

Geochronology and Petrogenesis of the Bingmasichong Granitic Pluton in the Tongbai Orogen

作　　者：辛成辉 张菲菲[1] 王亦凡 高宏森 XIN Chenghui;ZHANG Feifei;WANG Yifan;GAO Hongsen(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,Shaanxi,China)

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,陕西西安710069

出　　处：《大地构造与成矿学》2024年第4期899-910,共12页Geotectonica et Metallogenia

基　　金：国家自然科学基金面上项目(41872236、42172235)资助。

摘　　要：桐柏造山带早古生代花岗岩对于恢复该地区早古生代弧盆格局和构造背景具有重要意义。本文对桐柏造山带东段侵入二郎坪群的兵马寺冲花岗岩进行系统的锆石U-Pb年代学、原位Hf同位素,全岩主微量元素、Sr-Nd同位素地球化学研究。LA-ICP-MS锆石U-Pb定年结果显示,兵马寺冲花岗岩的结晶年龄为436.7±2.8 Ma;其具有高的SiO_(2)、Na_(2)O和低的K_(2)O、TiO_(2)含量,富集Rb、Th和Ba等大离子亲石元素,亏损Nb、Ta等高场强元素。兵马寺冲花岗岩全岩ε_(Nd)(t)值为3.7~4.7和锆石ε_(Hf)(t)值为11.3~16.1,具有年轻的Hf二阶段模式年龄(tDM2(Hf)=402~643 Ma),暗示源区中地幔组分的贡献较大,推测其可能来源于新生地壳的部分熔融。信阳地区~437 Ma花岗质岩浆活动与该时期大洋的俯冲事件有关。The Early Paleozoic granites of the Tongbai orogen are of great significance in establishing the regional tectonic framework.To achieve a better understanding of the orogeny in the Tongbai orogen,this paper reports new zircon U-Pb geochronological and Hf isotopic and whole-rock elemental and Sr-Nd isotopic results for the Bingmasichong granitic pluton.LA-ICP-MS zircon U-Pb dating yielded an age of 436.7±2.8 Ma.The granites are characterized by high SiO_(2) and Na_(2)O and low K_(2)O and TiO_(2) contents;they are enriched in Rb,Th,and Ba and depleted in high field strength elements such as Nb,Ta,and Ti.The high whole rock ε_(Nd)(t)(3.7-4.7)and zircon ε_(Hf)(t)(11.3-16.1)values,as well as the young two-stage Hf model ages(tDM2=402-643 Ma),suggest that mantle components were involved in the magmatic sources.Therefore,we propose that the Bingmasichong pluton originated from the partial melting of juvenile oceanic crust.The ca.437 Ma granitic magmatism in the Xinyang area of the Tongbai orogen is related to subduction of the Shangdan Ocean.

关 键 词：桐柏造山带 二郎坪群 兵马寺冲花岗岩 早古生代 地球化学 年代学 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]