An ophiolitic tectonic melange first discovered in Huashan area, south margin of Qinling Orogenic Belt, and its tectonic implications

On the basis of the synthetic studies of geology and geochemistry, an ophio litic tectonic melange was discovered in Sanligang-Sanyang area, the wester n part of Xiangfan-Guangji fault, the south margin of the Qinling; Orogenic Belt. It is composed of different tectonic blocks with different lithologi cal features and ages, mainly including the Huashan ophiolite blocks, Xiaof u Island-are volcanic blocks, pelagic sediments, fore-are volcanic-sediment ary system, and the massif of the basement and the covering strata of the Y angtze Block. These massifs were emplaced in the western part of Xiangfan-G uangji fault, the boundary between the Qinling Orogenic Belt and Yangtze Bl ock, contacting each other by a shear zone or chaotic matrix. The character istics of geochemistry indicate that the basalts of the Huashan ophiolite a re similar to mid-oceanic ridge basalts (MORB) formed in an initial oceanic basin, and the Xiaofu volcanic rocks are formed in a tectonic setting of i sland are. The ophiolitic tectonic melange is the Fragments of subduction w edge, which implies that there has been an oceanic basin between Qinling Bl ock and Yangtze Block.