2013 Volume 47 Issue 3 Pages 309-319
Ore-forming fluid trapped in vein quartz as fluid inclusions from tungsten ore at the Takatori mine was extracted by a crush-leach technique. The trace metal content and isotopic composition (δ7Li and 87Sr/86Sr ratio) of inclusion fluids were measured. Although quartz single crystals can host fluid inclusions associated with different generations, careful selection of analytical samples made it possible to separate the temporal mineralization stages. We succeeded in reconstructing the evolution of the ore-forming fluid from the results of chemical analyses. δ7Li values of the ore-forming fluid were between -2.6 and +7.9‰, gradually increasing in the later stages. The early-stage fluid characterized by low δ7Li values was derived from magma with a meta-sedimentary source (S-type granite). During precipitation of Li-bearing minerals, the δ7Li value of the ore-forming fluid became larger. The initial 87Sr/86Sr ratio of early-stage ore-forming fluid was 0.7202 to 0.7276, suggesting that the fluid responsible for tungsten mineralization was derived from S-type magma, and this magma had a different origin from the granitic rocks widely distributed in the mining area.