内蒙古科右中旗两类基性岩的年代学、地球化学及其构造意义

兴蒙造山带东段晚古生代构造演化存在争议，基性岩浆作用是构造演化过程中的良好地质记录. 对贺根山缝合带东段内蒙古科右中旗构造混杂岩带内的杜尔基基性岩和甲哈达基性岩进行了系统的地质特征、岩相学、年代学和地球化学研究. 杜尔基基性岩岩性为枕状玄武岩和辉绿岩，辉绿岩锆石LA-ICP-MS U-Pb年龄为348.3±2.6 Ma，为低钾拉斑玄武系列，相对富集LILE，亏损Nb、Ta等高场强元素. 甲哈达基性岩岩性主要为玄武岩，锆石U-Pb年龄为317.6±3.0 Ma，为钙碱性系列，同样具有HFSE亏损和LILE富集的特点，与杜尔基基性岩相比更加富集LILE和LREE. 结合贺根山缝合带早石炭世蛇绿岩及洋内俯冲作用的研究成果，认为从杜尔基基性岩到甲哈达基性岩的演化，可能指示了古亚洲洋东段早-晚石炭世洋内俯冲的渐进过程，洋内弧从不成熟向逐渐成熟演化. 

Geochronology and Geochemistry of Two Types of Basic Rocks in Horqin Right Middle Banner,Inner Mongolia and Their Tectonic Significances

The Late Paleozoic tectonic evolution in the eastern Xing-Meng orogenic belt is controversial,and the basic magmatism is a good geological record in the process of tectonic evolution.In this paper,the geological features,petrography,geochronology and geochemistry of the two newly identified basic rocks(Duerji basic rocks and Jiahada basic rocks)in the Horqin Right Middle Banner area of Inner Mongolia,eastern Hegenshan suture zone,are systematically studied.Both types of mafic rocks are structurally located in the tectonic melange zone.The Duerji mafic rocks are pillow basalt and diabase,and LA-ICP-MS U-Pb of zircon from diabase is 348.3±2.6 Ma.They are tholeiites and their geochemistry is characterized by low Ti and high Mg.LILE is relatively enriched and HFSE is relatively depleted.The mafic rocks in Jiahada are basalts,and the zircon U-Pb age is 317.6±3.0 Ma.The geochemistry is calc-alkaline series,and they are characterized by HFSE depletion and LILE enrichment compared with the Duerji mafic rocks.They are more abundant in LILE and LREE.Based on the research results of Early Carboniferous ophiolites and intracontinental subduction in Hegenshan suture zone,the evolution from Duerji mafic rocks to Jiahada mafic rocks may indicate the progressive process of Early-Late Carboniferous intra-oceanic subduction in the eastern part of the Paleo-Asian Ocean,characterized by the evolution of intra-oceanic arc from immature to mature.