The Characteristics And Genetic Significance Of Dahalajunshan Volcanic Rocks In Tekesi West Tianshan Mountains

In this paper,to the west of the Turks Tianshan Carboniferous igneous Great Sahara Junshan group for the study.Field geological survey,Turks Carboniferous igneous Great Sahara Junshan group carried out a detailed petrology,geochemistry,zircon U-Pb dating of a series of work aimed at identifying the type of rock,rock its combination of spatial and temporal distribution;Discussion and analysis of magmatic activity in the area and the volcanic rocks in the study area for the systematic study and preliminary study of its genesis as.Carboniferous Great Sahara Junshan group is mainly distributed in the West Tianshan Mountains and the surrounding land mass,its lower Silurian strata or old unconformity contact Ake Sark on their set of parallel unconformity.Its lithology complex,multi-terrigenous clastic rocks interbedded or associated.Combination of volcanic basalt,andesite,rhyolite and andesite,rhyolite composition,of which the most developed andesite.Belong to calc-alkaline basalts and island arc tholeiitic basalts,Pacific Sodium class quality,tectonic island arc center close to the ocean on one side,with its south Nalati Late Devonian Early Carboniferous intrusive rocks composed of volcanic arc,with ancient Asian ocean northward subduction of the product.Early and Middle Carboniferous a shallow littoral sedimentary strata and Moto salad Bayingou a ditch a Late Devonian?Erie northern margin of landmass?Early Carboniferous presence ophiolite belt,due to the large group with Sahara Junshan symbiosis,which indicates active continental margin tectonic environment is therefore essential that the formation of Carboniferous volcanic rocks in the northern margin of the Ili land during the Carboniferous to late Devonian subduction Devonian early Carboniferous in a north south Tianshan ocean basin.In the area by volcanic magma rising crustal contamination to some extent,the sample display for many years-potassium series,this type of potassium reflects the importance of matrix in the continental crust magmatic activity status.High content of rare earth elements,light rare earth content is more than heavy rare earth elements.As can be seen from the diagram trace element geochemistry of these rocks formed in a continental island arc.Specifically as follows:First,according to lithological Great Sahara army volcanic rocks,the spatial distribution,lithologic characteristics can be divided into upper and lower two.Within the region,the overlying Akshak group?C₁a?and Great Sahara group Junshan angular unconformity,Great Sahara Junshan group is not clear.Secondly,we found in abundance in the Early Carboniferous lower Carboniferous fossil Akshak group,which is a large group of Sahara Junshan overburden,presumably after the formation of the Carboniferous era of big Sahara Junshan group.On the other hand,Rb-Sr isotopic age test samples from rhyolite Great Sahara Junshan group performed to measure the age of 337Ma?note that the data is consistent with the later---Alexander West Sahara army volcanic rocks Geochemistry characteristics and geological significance?,during the early Carboniferous.Third,from the Great Sahara Petrochemical characteristics of military volcanic rocks can be drawn as a calc-alkaline series mainly to the main pyroclastic rocks,as well as a small amount of alkaline volcanic rocks in which the neutral and basic lava lava often poor Ti02?<1.2%?,intermediate volcanic rocks is relatively small,with mainly acidic volcanic rocks.Preliminary evidence can be large volcanic rocks Sahara army has continental margin arc volcanic features.Which also REE and trace element characteristics indicate that this area has a volcanic island arc and continental margin arc characteristics.Fourth,the sum available,Yili is a relatively mature plot of land,which determines the large Sahara army volcanic rocks tectonic setting.Yili Lot found ancient Precambrian strata in the vicinity of the Turks,this research in the Department of the Great Wall Nalati Nanshan exposed ancient rocks Nalati group having stable continental crust,from that point,Yili land for a continental nature of the land,therefore Great Sahara Junshan group is formed in the margin area of volcanic arc environment.