大别山宿松变质带~1.38 Ga花岗质岩浆作用的厘定及其对Columbia超大陆裂解的启示  

The Finding of~1.38 Ga Granitic Magmatism from the Susong Metamorphic Zone in the Dabie Orogen and Its Implications for the Breakup of the Columbia Supercontinent

作　　者：杨阳 刘贻灿[1] 李远 YANG Yang;LIU Yican;LI Yuan(State Key Laboratory of Lithospheric and Environmental Coevolution,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui,China)

机构地区：[1]岩石圈演化与环境演变全国重点实验室,中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《大地构造与成矿学》2024年第5期1078-1089,共12页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42372059,42072059)资助。

摘　　要：宿松变质带位于大别碰撞造山带的南部,是一个相对低级变质的构造岩石单元,然而,却具有复杂的岩石组成和成因,并发育了被构造肢解、破碎的新太古代、古元古代和新元古代的变质岩石地层单位及相关的变质火成岩,为研究前寒武纪超大陆的聚合与裂解在研究区的响应提供了极其重要的对象和靶区。但是,研究区乃至扬子北缘都缺乏中元古代的火成岩。本文通过对宿松变质带北浴地区花岗片麻岩的岩石学、元素地球化学和锆石U-Pb年代学等方面的综合研究,首次发现研究区存在中元古代的花岗质岩石,其形成时代为~1.38Ga。全岩主微量元素地球化学特征及高的Zr饱和温度(875℃)表明,该类岩石的原岩属于板内A型花岗岩,形成于大陆裂解构造环境,是Columbia超大陆裂解在研究区的岩石学响应。结合已查明的~2.0Ga岩浆作用及相关盆地沉积,证明扬子北缘宿松变质带中原“宿松群”的部分岩石属于Columbia超大陆的一部分。The Susong metamorphic zone is a relatively low-grade metamorphic lithotectonic unit,located in the southern part of the Dabie collisional orogen.However,this unit has complex rock compositions with a variety of genesis,and retains the broken metamorphosed lithostratigraphic units of the Late Archean,Paleoproterozoic,and Neoproterozoic,as well as the related meta-igneous rocks,thus providing an extremely important target for studying the response of the assembly and breakup of the Precambrian supercontinent in the area.However,Mesoproterozoic igneous rocks are absent from the northern margin of the Yangtze Block.Based on an integrated study of petrology,element geochemistry,and zircon U-Pb geochronology of the granitic gneiss from the Susong metamorphic zone at Beiyu,a Mesoproterozoic granitic rock with an emplacement age of ca.1.38 Ga was discovered for the first time in the region,which defines a Mesoproterozoic magmatic event.The whole-rock major and trace element characteristics as well as high Zr-saturation temperatures(875)indicate℃that the protoliths of the rocks belong to intraplate A-type granites and formed in the tectonic environment of continental rifting in response to the breakup of the Columbia supercontinent in this region.Therefore,combined with the identified ca.2.0 Ga magmatism and related basin sedimentation,it is suggested that some rocks of the“Susong Group”in the Susong metamorphic zone on the northern margin of the Yangtze Block belong to a component of the Columbia supercontinent.

关 键 词：花岗岩 中元古代 Columbia超大陆 裂解 宿松变质带 

分 类 号：P597[天文地球—地球化学]