关键词: 姑婆山, 暗色包体, 锡石, 榍石, 锆石, 岩浆混合

Abstract:

       In the middle part of Nanling Range there is an early Yanshanian (Jurassic) A-type granite belt. The Guposhan granite
batholith  is well known by  its mafic microgranular enclaves  (MME).  In order  to study  the mineralogical evidence of magma
mixing and the relationship between basic magma and tin-mineralization, we studied and compared the compositions of accessory minerals  in  the granite and MME by using elecron microprobe. We  firstly confirmed  the appearance of subhedral cassiterite of magmatic origin  in cleavages of mafic minerals  in MME. We also  found  that  the zircon and  titanite  in MME show a  rapid crystallization evidence after  the basic magma emplacement. Particularly,   consistent with  the  tin enrichment during  the granite evolution, the late-stage titanite from the granite has higher tin contents than the early-stage one. However, the MME titanite has just the opposite evolution trend in the aspect of tin contents, which is the result of rapid crystallization.

Key words: Guposhan, mafic microgranular enclaves (MME), cassiterite, titanite, zircon, magma mixing