伟晶岩侵位深度与伟晶岩成岩成矿的温度、压力相联系,它间接地影响着岩浆演化的热历史和成矿物质的迁移、富集、沉淀过程。本文选取新疆阿尔泰山脉代表性4条二叠纪伟晶岩、5条三叠纪伟晶岩,开展伟晶岩早期结构带及晚期石英核中石英矿物捕获的含液体CO_2流体包裹体(B型)显微测温学研究。卡鲁安805、806、807号脉中石英-钠长石-锂辉石带中石英/锂辉石矿物捕获的B型流体包裹体显示与熔体-流体包裹体(A2型)共生的特征,指示其形成于岩浆-热液过渡阶段体系,其他伟晶岩早期结构带中B型流体包裹体呈负晶型,孤立状分布,与熔体包裹体(A1型)共生,指示其具有岩浆成因特征。三叠纪伟晶岩早期结构带中B型流体包裹体的盐度为2.20%~3.89%,均一温度为400~581℃,计算的捕获流体压力为235~308 MPa,对应的侵位深度为8.4~11.0 km。而二叠纪伟晶岩早期结构带中B型流体包裹体的盐度为4.62%~6.54%,均一温度为430~580℃,捕获的流体压力为319~406 MPa,对应的侵位深度为11.4~14.5 km。研究结果表明,三叠纪伟晶岩侵位深度明显不同于二叠纪伟晶岩侵位深度。三叠纪伟晶岩侵位相对较浅,并显示复杂矿化类型,如卡鲁安805、806、807号脉的Li矿化,柯鲁木特112号脉的Li-Be-Nb-Ta矿化以及可可托海3号脉的Li-Be-Nb-Ta-Cs-Rb-Hf矿化,指示侵位较浅的伟晶岩很可能更有利于岩浆分异演化以及成矿作用发生。
The invasion depth, commonly, has close relation to temperature and pressure of diagenesis and mineralization of pegmatite, which indirectly influences the thermal history of magmatic evolution and influences the processes of migration, enrichment and precipitation of metallogenetic materials. In this work, 4 Permian pegmatites and 5 Triassic pegmatites were selected for conducting the microthermometry of type-B fluid inclusions which were captured by quartz in the early and late textural zones of pegmatites and were aqueous carbon dioxide fluid inclusions. The type-B fluid inclusions in Kaluan ore district(805, 806, and 807) which were captured by quartz/spodumeneare generally syngenetic with melt-fluid inclusions(type-A2), indicating that they formed from magma-hydrotherm system. Whereas, the type-B fluid inclusions in the early textural zones of other pegmatites are negative crystal shape, isolated, generally syngenetic with melt inclusions(type-A1), indicating magmatic genesis. The salinity value of type-B fluid inclusion ranges from 2.20% to 3.89%Na Cleqv; the total homogenization temperature ranges from 400 to 581℃ in the early textural zones of Triassic pegmatites, and the calculated pressure ranges from 235 to 308 MPa, corresponding to emplacement depth within the limits of 8.4 to 11.0 km. Whereas, type-B fluid inclusions in the early textural zones of Permian pegmatites manifested that their salinity values are within the range of 4.62% to 6.54%Na Cleqv; total homogenization temperature ranges between 430 and 580℃, and the calculated pressure ranges from 319 to 406 MPa, which corresponds to emplacement depth within the limits of 11.4 to 14.5 km. The results suggest that there is an obvious discrepancy of emplacement depth between the two periods. Triassic pegmatites have a shallower depth and are more fertile and more complex than that of the Permian, such as Li-mineralization in Kaluan ore district(805, 806, and 807), Li-Be-Nb-Ta-mineralization in Kelumute112, and Li-Be-Nb-Ta-C-Rb-Hf