南阿尔金晚泥盆世构造体制转换:来自索尔库里二长花岗岩年代学和地球化学的制约

对阿尔金索尔库里地区二长花岗岩进行了 LA-ICP-MS锆石U-Pb定年及全岩主量、微量和稀土元素测试,结果表明二长花岗岩结晶年龄为(377.5±1.6)Ma和(377.4±2.1)Ma;具有高硅(SiO2=72.55％～76.41％)和高碱(K2O+Na2O=7.32％～8.59％)、正常的铝含量(A/CNK=0.9...

Late Devonian Tectonic Transition in South Altyn Tagh: Constraints from Geochronology and Geochemistry of the Suoerkuli Monzogranite

Whole-rock major, rare earth and trace element compositions, as well as LA-ICP-MS zircon U-Pb ages of monzogranites from Suoerkuli in the Altyn Orogen are newly presented. LA-ICP-MS zircon U-Pb dating indicates that the monzogranites were formed at (377.5±1.6) Ma and (377.4±2.1) Ma. Geochemically, the rocks are characterized by relatively high Si (72.55%-76.41%) and total alkaline (K₂O+Na₂O=7.32%-8.59%), normal aluminum saturation index (A/CNK=0.92-1.08), and high TFeO/MgO (2.57-6.47), suggesting that the rocks are high-K calc-alkaline. These rocks have relatively high LREEs and remarkable negative Eu anomalies. Furthermore, they are enriched in elements of Rb, Th, Y, Zr, Hf and depleted in Ba, Sr, P, Ti. According to the geochemical characteristics, it is suggested that the monzogranites are classified as A1-type. The monzogranites were likely generated by the fractionation of the parental magma, which was produced by the partial melting of felsic crustal rocks led by mantle-derived material underplating. Based on the regional geological investigations and spatial-temporal distribution of the igneous rocks, we considered that the monzogranite was emplaced in an intraplate extensional environment, and generated in the transition from post-orogenic to intraplate tectonic regime in the Late Devonian.