西大别南缘印支期吕王-高桥-永佳河构造混杂岩带的厘定及其构造意义  

Identification of Indosinian Tectonic Mélange Belt in West Dabie Orogenic Belt and Its Geological Significance

作　　者：徐扬 杨振宁[4] 邓新 王令占[1] 刘浩[1] 金鑫镖[1] 张维峰 魏运许[1] 彭练红[1] 黄海永[4] Xu Yang;Yang Zhenning;Deng Xin;Wang Lingzhan;Liu Hao;Jin Xinbiao;Zhang Weifeng;Wei Yunxu;Peng Lianhong;Huang Haiyong(Wuhan Center of China Geological Survey,Wuhan 430205,China;Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;College of Resources,Hebei GEO University,Shijiazhuang 030031,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [3]中国科学院广州地球化学研究所同位素地球化学国家重点实验室,广东广州510640 [4]河北地质大学资源学院,河北石家庄050031

出　　处：《地球科学》2021年第4期1173-1198,共26页Earth Science

基　　金：湖北省自然科学基金项目(No.2020CFB344);中国地质大学构造与油气资源教育部重点实验室开放基金项目(No.TPR-2019-07);同位素地球化学国家重点实验室开放-合作基金项目(No.SKLabIG-KF-18-13);中国地质调查局地调项目(No.DD20190050)。

摘　　要：在西大别造山带的区调工作中,新识别出一系列中元古代末-新元古代的岩石-构造单元,它们沿着吕王-高桥-永佳河一线展布,并构成一条NNW-SEE向展布的构造混杂岩带.该混杂岩带主要由超镁铁质-镁铁质岩、硅泥质岩、石英质岩、大理岩、含碳陆源碎屑岩、双峰式火山岩以及卷入其中的榴辉岩等多种变质岩块(片)共同组成,并赋存于一套遭受了强烈剪切变形的泥质片岩之中.混杂岩带内各岩块(片)的原岩年龄跨度较大(>4亿年),分别集中在1 200~1 100 Ma和800~700 Ma之间.锆石记录的变质年龄和云母的冷却年龄则主要集中在240~200 Ma之间.结合接触关系、岩性组合、年代学及地球化学数据的综合研究认为,混杂岩带的物质来源既包括中元古代末-新元古代早期的弧-弧后盆地系统的沉积岩-火山岩-侵入岩;也包括叠置其上的新元古代中-晚期大陆裂解期的沉积岩-火成岩.这些不同时代、不同性质岩石在三叠纪不同程度地卷入了华南陆块北缘向华北陆块之下的俯冲,而后快速折返,最终沿着区域上折返断裂(桃花-七角山断裂)就位于西大别造山带之中,形成一条包含高压-超高压变质岩的三叠纪构造混杂岩带.混杂岩带内新厘定的中元古代末弧-弧后岩浆-沉积事件,可与大洪山-黄陵庙湾同时期的地质事件对比,它们共同揭示扬子北缘曾经存在一条中元古代末-新元古代早期的俯冲岩浆带.Recently, a series of the Late Mesoproterozoic to Neoproterozoic tectonic blocks in the southern part of the West Dabie orogenic belt were identified by geological field mapping. These tectonic blocks are distributed along NNW-SSE trending fault,from the Lüwang in the west, to the Gaoqiao and Yongjiahe in the east, forming a tectonic mélange belt within the West Dabie orogenic belt. This tectonic mélange belt is composed of various metamorphic blocks, including ultramafic to mafic rock, silicapelitic rock, quartzose rock, marble, carbonaceous clastic rock, bimodal volcanic rock, and eclogites. The matrix mainly consists of mica schist with strong deformation. Their protolith ages have a wide range that cluster as two age populations including 1 200-1 000 Ma and 800-700 Ma. Moreover, the 240-200 Ma ages are also recorded by the metamorphic zircons. On the basis of contact relationship and lithological assemblages, as well as their geochronologic and geochemical data, it is proposed that the tectonic blocks in the Lüwang-Gaoqiao-Yongjiahe tectonic mélange have two different geotectonic affinities, including the Late Mesoproterozoic to Early Neoproterozoic arc to back-arc basin system, and Middle to Late Neoproterozoic continental rift system.These blocks may have been brought into a deep depth by the subduction of the South China block beneath North China block during the Triassic, followed by subsequent exhumation to the surface and emplacement along the Taohua-Qijiaoshan fault.Furthermore, considering the close temporal and spatial relationships, it is inferred that the Late Mesoproterozoic to Early Neoproterozoic arc to back arc basin system in this study extended westward to the 970-820 Ma Dahongshan arc to back arc basin and 1 100-1 000 Ma Miaowan ophiolite.

关 键 词：锆石U-Pb-Hf同位素 印支期构造混杂岩带 中元古代末岩块 扬子克拉通北缘 构造地质学 

分 类 号：P548[天文地球—构造地质学] P56[天文地球—地质学]