Geochemical Characteristics And Tectonic Environment Of Carboniferous Volcanic Rock In The Yamansu Volcanic Arc Of East Tianshan Mountains

Jueluotage orogenic belt is exposed a lot of the Carboniferous volcanic rocks in different tectonic environment, Its geochemical characteristics is of great significance to explore the tectonic environment evolution of Jueluotage. This article make study of early carboniferous Yamansu volcanic rock and late carboniferous Tugutubulake volcanic rock of main elements, trace elements and Sr, Nd isotopes characteristics in Yamansu volcanic island-arc. The studies have shown that the volcanic rocks of Yamansu tectonic belt is abundance of LREE and Ba, Th, U, Sr and other LILE, Loss of HREE and Ta, Nb, P, Ti et.al HFSE, combining with high Al2O3 and low MgO、Ti O2 in main elements and the instruction significance of the ratio of La/Sm and Ba/La in trace element, the volcanic rocks show that it possess the geochemical characteristics of volcanic island arc in subduction zone. The Sr, Nd isotopes show that the parent magma derived from the metasomatic enriched lithospheric mantle wedge, at the same time, it shows a similar loss of MORB characteristics, it is common characteristics of many magmatic rocks in central Asia orogenic belt. In combination with regional geological background research, the author think Yamansu volcanic island arc belt for the early carboniferous period gradually forming Marine immature island arc, in gradually evolved into the continental more mature island arc in late Carboniferous period, it reveals the evolution of the land and sea tectonic environment, and according to the characteristics of space and time distribution of volcanic rocks, it illustrates with Yamansu arc belt was formed in late Paleozoic, it is the result of the Tuha ocean fracture subduction stage and island arc system collision splicing stage. At the same time, At the same time, the time and space distribution features of magmatic activity reveals the characteristics of the earth’s crust from the old new and north to south gradually thickening in south belt in Carboniferous period, it provides the important evidence of the Tuha ancient ocean fracture southward subduction polarity in the carboniferous period.