东天山星星峡群变质岩熔融实验的初步结果

PRELIMINARY RESULTS OF EXPERIMENTAL MELTING ON METAMORPHIC ROCKS IN XINGXINGXIA GROUP OF EASTERN TIANSHAN MOUNTAINS, XINJIANG, CHINA

通过对东天山星星峡群中的中酸性黑云斜长片岩、酸性石英二长片岩及二者各占50％的混合物在2×10~2MPa,750℃、800℃、850℃、900℃,水充填条件下的熔融实验,首次同时获得了淬火玻璃的主要成分和部分稀土元素含量,熔体的硅含量增高并不是与稀土元素含量的增高同步,酸性及混合成分体系产生的熔体其稀土元素含量低于源岩;中酸性成分体系仅在特定的温度下,其熔体的稀土元素含量超过源岩;混合成分体系产生的熔体并不等于同等条件下两端元物质分别熔融产生的熔体的平均成分;通过对实际熔体稀土元素含量的理论模拟,提出使用新的分配系数及处理方法。

The main compositions and REE contents of quenched glasses are determined for the first time according to the results of the melting experiments under pressure of 200MPa and various temperatures (750℃ , 800℃ , 850℃ ,and 900℃) on intermediate-acidic biotite plagioclase schist, acidic monzonitic schist as well as mixture of each 50% of the two schists in Xingxingxia group of Eastern Tianshan Mountains, Xinjiang, China. The results show that the increase of silica and REE contents did not synchronize in the melts ; the REE contents of melts are lower than that of the original materials in the systems of acidic and mixture compositions; the REE contents of melts surpass that of the original materials in the system of intermediate-acidic composition only at special temperature; the melt compositions of mixture composition system are not equal to the average melt compositions produced in the intermediate-acidic and acidic composition systems respectively at the same conditions. The new partition coefficients and handling methods are proposed, based on the theoretical simulation calculations to REE contents of melts. Calculated partial melting degrees are identical with actual observations.