北大别木子店石榴辉石岩的麻粒岩相退变质作用

GRANULITE-FACIES RETROGRADE METAMORPHISM OF GARNET PYROXENITE IN MUZIDIAN,NORTHERN DABIE MOUNTAINS

详细的岩相学、矿物化学、岩石化学和变质作用温压条件计算表明 ,大别变质地体北部角闪二辉麻粒岩是石榴辉石岩在其抬升过程中经历麻粒岩相退变质作用的产物 ,峰期变质作用至少是发生在高压榴辉岩相条件下 ,而且地温梯度较低 .石榴辉石岩的退变质作用 p -t轨迹以早期的近等温降压、中期的近等压升温和晚期的降温降压为特征 .这一结果表明北大别变质地体的峰期变质作用并非仅达麻粒岩相 .

The detailed investigation into the amphibole two_pyroxene granulite in the north of Dabie metamorphic terrain in terms of petrography, mineral chemistry, petrochemistry, and estimated p_t conditions for metamorphism indicates that this rock is a product of the garnet pyroxenite that experienced the granulite_facies retrograde metamorphism during its uplift. The peak metamorphism occurred at least in the high_pressure eclogite facies at a lower temperature gradient. The retrograde metamorphism p_t path of the garnet pyroxenite was characterized by the near isothermal decompression in the early stage, the near isobaric temperature rise in the middle stage and the temperature fall and decompression in the late stage. These features suggest that the p_t conditions of peak metamorphism in the northern Dabie terrain are higher than that of granulite facies.