The Study On Geochemical Characteristics And Tectonic Meaning Of Basic-Intermediate Dyke In The Bailingshan Rocks In The Eastern Tianshan,Xinjiang

The Jueluotage area of East Tianshan Mountain,is one of the important tectonic metallogenic belt in China.The intense magmatic activities in the late Paleozoic not only provide a material source for the mineralization,but also an important record of the geological tectonic evolution in the Tianshan Mountains.The Carboniferous magmatic activities is particularly widespread,but the formation environment remains controversial.This is a direct result of the of Tianshan tectonic system in the late Paleozoic evolution characteristics of views.The Bailingshan rocks display east-west zonation within the metallogenic belt,and were controlled by Aqikekuduke faults and the volcanic rocks from Dikaner Formation in its south and north respectively.The diabase-porphyrite and diorite-porphyrite are widely distributed in the Bailingshan rocks.The main direction of the veins is near east-west,north-east and north-west.The significance of the research on the veins is to understand the geological characteristics and formation environment of the basic-intermediate dyke in the study area To solve the tectonic background of the Carboniferous in the eastern Tianshan Mountains and to restore its tectonic evolution.The basic-intermediate dyke in the study area belong to calc alkaline series and high-potassium calc-alkaline series.Geochemical characteristics of the diabase-porphyrite's major elements show a good negative correlations between SiO₂ and the other oxides,but the positive correlation of Al₂O₃;the correlation between the major elements of the diorite-porphyrite is not very obvious,but it is negatively correlated first and then with positive correlation with the Al₂O₃.In the geochemical characteristics of trace elements and rare earth elements,the veins mainly show the relative selective enrichment of LILE?K?Rb?Ba ?LREE?,and the relative loss of HFSE?Ti?P?.The rocks showed REE enrichments and right-trending affinities,which light rare earth enrichment is higher than heavy rare earth.The diorite-porphyrite has a slight negative europium anomaly.Petrogenesis of the intermediate-basic dikes produced in the Bailingshan rocks should be derived from the Nb-rich basaltic magma formed by the upwelling of the mantle-derived material,and there is a limited crustal contamination in the process of magmatic ascending and evolution.Diabase-porphyrite and diorite-porphyrite have similar geochemical characteristics,which may explain the same magma source,suggesting that the causes of diorite-porphyrite is products of cogenetic Nb-rich basaltic magma evolution,but also by a certain degree of crustal contamination effect.The diabase-porphyrite and diorite-porphyrite veins in the Bailingshan rocks should be the product of the mantle-derived magmatic intrusion in the post-collision tensile stress background,combined with the diorite-porphyrite's U-Pb zircon ages 311 ± 5.8 Ma,it is presumed that the regional geology of the study area is at the end of the Carboniferous and Permian early in the post-collision collision extension and gradually evolves into the intraplate environment.