Stable isotope and fluid inclusion investigations of epithermal vein and porphyry molybdenum ineralization in the Rico mining district

The Rico mining district, western San Juan Mountains, Colorado, contains epithermal vein deposits, carbonate replacement deposits, and a large zone of porphyry-style molybde-num mineralization. Historically, the vein and replacement deposits have produced signifi-cant amounts of silver, lead, and zinc, with minor gold and copper. All the mineralization formed nearly contemporaneously about 5 m.y. ago. The veins and replacement deposits occur in Paleozoic and Mesozoic sedimentary rocks that have been uplifted into the Rico dome, which is cored by a horst of Precambrian greenstone and quartzite. The porphyry molybdenum ineralization (40 million tons of 0.31 % Mo) is 1,500 m beneath the surface in the east end of the district and consists of stockwork veining in Precambrian quartzite and greenstone and in Pennsylvanian sedimentary rocks. The epithermal veins occur above and peripheral to the porphyry mineralization. Widespread high silica, alaskite porphyry dikes were also emplaced at the same time as the porphyry mineralization and are probably related to the source intrusion for the molybdenum mineralization and the heat source for the hydrothermal system that produced the epithermal and replacement deposits. Flui