Geochemical Characteristics And Geological Significance Of Quartz-Diorite From The Area Of Karamaili In Eastern Junggar

Central Asian orogenic belt (CAOB) is one of the largest hyperplasia orogenic belts which is formed through a series of the inner arcs, arcs, hyperplasia of complex rock mass, and a small amount of land mass lateral accumulation in the evolutionary process of the Paleo-Asian Ocean in the phanerozoic, which is a large suture zone because of the Paleo-Asian Ocean closed.The Kalamaili orogenic belt is one of the key areas of Central Asia orogenic belt evolution, so that it is important geological significance to study the tectonic evolution.The quartz diorite which is on the northern side of the western of Kalamaili orogenic belt is research object in the article, through the comprehensive research of field geological survey, petrology, zircon U-Pb chronology, and trace elements, combining previous research achievements in the area, analyzing the early carboniferous quartz diorite petrogenesis and the tectonic evolution process of kalamaili orogenic belt, we obtained the following understanding:1. In Kalamaili the early carboniferous quartz diorite LA-ICP-MS zircon U-Pb ages distribute in 336 ±8 Ma-354±10 Ma, a weighted average of 346.7±3.3 Ma. Rock formed in The middle of early carboniferous.2. In Kalamaili early carboniferous quartz diorite have the characters of low potassium and low Mg, with high Si, Al, rich in alkali and Na, depleted K, rich in Ca and high Mg, narrow Mg# (Mg#= 45-48), low Ti etc. K, Pb are high. Nb, Ta, Ti, P are low, lower amount of rare earth elements (Z REE= 53.295×10-6), (La/Yb) N= 1.98-4.41, (Gd/Yb) N= 1.19-1.46, Eu is slight negative anomaly to no exception (σEu=0.86-1.00). it is result of spinel lherzolite-garnet phase, near the spinel lherzolite being replaced by subduction fluid, higher degree of partial melting (8%-18%), in the process of rising, it has the certain crystallization differentiation and assaults Jiangbasitao Formation in early carboniferous, formed in the collision tectonic environment,3. In the middle of the early carboniferous, the post-collision granites are extensive distribution in the study area, such as quartz diorite (346.7±3.3 Ma) and biotite quartz-syenite (345.7±4.0 Ma), states that in early middle carboniferous, the old oceanic basin that is represented by the ophiolite in western of the Kalamaili fault fossil basin had closed and entered the post-collision evolution stage.