新疆阿尔泰花岗岩类源区物质的定量模拟

QUANTITATIVE MODELLING OF SOURCE ROCKS FOR GRANITOIDS IN THE ALTAI MTS., XINJIANG UYGUR AUTONOMOUS REGION, CHINA

对产出于阿尔泰、额尔齐斯、乌化古三条构造-岩浆带上的六个典型岩体进行了源区岩石化学组成和初始熔体部分熔融程度的定量模拟。模拟结果表明:六个岩体的ε_(Sr)~t值多介于0-120之间,源区岩石多为地幔物质与陆壳物质的混合源,地壳柱中成熟陆壳所占比例较少,反映了中亚型地洼区在地壳化学结构上的一个重要特征.从北往南,ε_(Sr)~t值与壳源锶所占百分率逐渐减小,反映了从地槽造山带核心部位往边缘部位往边缘部位,地壳柱中成熟陆壳所占比例逐渐减小。初始熔浆部分熔融程度温度、压力呈正消长关系。

Based on investigation of geological and tectonic development history and granitoid geology, six typical granitoid plutons are selected from the Altai Mt., Altai Mt. front and the Wulungu tectono-magmatic belts and their source rocks are modelled on their chemical compositions and the partial fusion extent of their initial melts. The average ε_(Sr)~t values of the six plutons change from 0 to 120 and their source rocks are mostly a mixture of the mantle material and the crust one. This demonstrates that the mature continental crust is low in proportion in the crust column, which may be one of the most important characteristics of the Central-Asia type activated region in its crust chemical structure. Furthermore, ε_(Sr)~t values and the continental crust-derived materials become lower progressively from north to south, which displays that the mature continental crust becomes lower in proportion in the crust column from the core of the Altai Palaeozoic gcosyncline orogen to its margin. Finally, a positive correlation is observed between the partial fusion extent and the petrogenetic temperature and pressure.