Zircon saturation temperatures of Yangba granodiorite and mafic microgranular enclaves in northern margin of Yangtze Block and its significance

Assessing temperatures of magma that solidified to form plutonic rocks is notoriously problematic,because of:①scarcity of appropriate mineral pairs with temperature-sensitive exchange reaction and ② reequilibration during cooling. Zircon saturation thermometry provide a simple and robust means of estimating magma temperatures,because solubility of zircon is extremely sensitive to temperature.But in most cases,only weakly sensitive to other factors. Yangba pluton located in Yangba town,southern Kangxian,Gansu Province,NW China. In this paper,we calculate the zircon saturation temperatures for Yangba granodiorite and mafic microg ranular enclaves to inverse the temperature in magma source. The result indicated that the zircon saturation temperatures for host granodiorite range in 762～773℃,the average is 769℃,and the zircon saturation temperatures for mafic microg ranular enclaves range in 752～770℃,the average is 760℃.The temperatures suggested that Yangba granodiorites are derived from partial melting of thickened lower crust whichis in low temperature(770℃)with the participation of fluid which richin volatiles,and the fluid was possibly the results of gas discharge of mantle-derived magmas during early stage of underplating.