MINERAL CHEMISTRY AND GENESIS OF SAPPHIRINE-BEARING GRANULITES: A REVIEW

摘要

Sapphirine usually considered an uncommon rock-forming mineral, is being found with increasing frequency in granulite and amphibolite facies rocks, calc-silicate skarns, quartzites and xenoliths (both continental as well as oceanic environment). It is a metamorphic mineral that forms usually in the deeper crust in rocks with distinctive bulk compositions, specially those with high concentrations of Mg and Al. Sapphirine-bearing granulites are very useful in deducing the metamorphic conditions of the lower crust because sapphirine extends over a wide range of pressure-temperature conditions, as documented in experimental and theoretical investigations. Further, it preserves the earlier history in the form of symplectites, coronas and other reaction textures. It contains number of refractory phases which act as relics and serves as an indicator of metamorphic past. Several hypotheses suggested for the genesis of sapphirine-bearing rocks by different workers have been critically discussed and reviewed in the present communication.