미국 뉴멕시코주 Questa 몰리브덴 반암형 광상의 유체포유물 연구

초록

Molybdenite is the main Mo mineral in the Questa deposit. Molybdenite precipitation occurs in the early hydrothermal-assisted breccias matrix (MHBX), and in the postdating stockwork quartz veinlests (STW). Contribution of Mo tonnages in MHBX is around 30-40% and STW is around 60-70%. We conducted combined microthermometry and LA-ICP-MS microanalysis in the several brine inclusion assemblages of the Questa porphyry Mo deposits, USA to study a molybdenite deposition in the Climax-type porphyry Mo deposit. Plenty of S in the fluid inclusions adequate to precipitate molybdenite were found in the fluid inclusions. Molybdenite might be precipitated in the tight temperature range of 350 - 450 °C in Questa. Cesium concentrations in the hydrothermal fluids increase from the early-stage hydrothermal breccias (MHBX) to the crosscutting later-stage stockwork veinlets (STW) indicating that a fractional crystallization in the causative magma would enrich Mo and promoting molybdenite precipitation in the magmatic-hydrothermal system of Questa deposit.