Feature of Mayonerbuo Ophiolitic Melange Subduction Reenterant Collage Position in Altay Orogenic Belt

The Lower Carboniferous Jiangbasitao formation in south margin of Altay Mountains is actually oceanic crust metamorphic rocks, constituted by basalt, gabbro and minor silicalite, and mixed Precambrian basement residual block. The oceanic crust components are embedded in accretionary complexes, which can be divided into seven slices; the formation of the tectonic wedge is the result of repeated pulsed advance of subduction; slide melange was found in the lower part of the accretionary wedge. The oceanic crust with amphibolite facies metamorphism experienced retrograde metamorphism; under the microscope, it is observed that pyroxene was transferred into actinolite and epidote plagioclase metasomatic, indicating the retrogressive metamorphism evolution from amphibolite facies and greenschist facies. The remnants of oceanic crust subduction was carried up by the obduction, with a subduction and reentrant collage, and formed the SSZ ophiolitic melange with arc volcanic rocks. Features of ophiolite melange accretionary complex demonstrate the oceanic crust subduction from south to north, and record the evolution characteristics of Paleo-Asian Ocean in late Early Paleozoic era.