秦岭造山带南缘早古生代基性火山岩地球化学特征及其大地构造意义

秦岭造山带南缘早古生代基性火山岩元素地球化学特征，显示其形成于大陆板块内部构造环境，岩石稀土总量高，稀土分布模式为轻稀土强烈富集型，微量元素分布模式类似于大陆溢流玄武岩，综合主元素，微量元素地球化学研究认为，南秦岭造山带南部边缘的早古生代基性火山岩为板内伸展－初始裂谷环境的拉斑质大陆玄武岩，区域对比表明，南秦岭与扬子陆块之间的早古生代晚期是大陆板伸展裂陷环境，这种伸展扩张的动力学体制始于早古生代初

GEOCHEMISTRY OF THE CALEDONIAN BASIC VOLCANIC ROCKS IN THE SOUTH MARGIN OF QINLING OROGENIC BELT AND THEIR TECTONIC IMPLICATIONS

The geochemistry of basic volcanic rocks in the south margin of Qinling Orogenic Belt (SMQOB) suggests that they were formed in an intraplate tectonic setting.The REE distribution patterns show these rocks strongly enriched in LREE with higher REE, and their trace elements geochemistry is similar to that of continental flood basalt. All above evidences suggest that the Caledonian basic volcanic rocks in SMQOB were tholeiitic basalts formed in an intraplate spreading-initial rift tectonic setting. The study of regional geology implies that there was an intraplate spreading-rift tectonic setting between South Qinling Block and Yangtz Block in Caledonian epoch,and the dynamic mechanism of spreading in this district was begun in early Caledonian and then the intraplate spreading-initial rifts were formed in late Caledonian.The Mianlue-Huashan limited oceanic basin was formed in Devonian for the reasons of the spreading of paleo-Tethys and geodynamics in deep mantle, and the Qinling microplate was separated from the northern part of the Yangtz plate.