PRELIMINARY GEOLOGIC OBSERVATIONS OF THE VICTORIO MINING DISTRICT, LUNA COUNTY, NEW MEXICO

Three types of deposits occur in the Victorio district, west of Deming, New Mexico: carbonate-hosted lead-zinc replacement deposits, W-Be-Mo skarn/vein deposits, and porphyry-Mo deposits. The district was discovered in the late 1800’s and was in production until the 1950’s, primarily from the carbonate-hosted replacement deposits. The major metals extracted were Pb, Zn, Cu and minor Ag and Au. The relationship between the mineralization events for the 3 types of deposits is unknown at this time. There is geochemical evidence that the skarns and porphyry-Mo deposits may be related to the Victorio granite intrusion and that all 3 deposits formed during one mineralization event. However, it is possible there was more than one event. 40Ar/39Ar dating has been used to determine the ages, cooling history and possibly the timing of alteration and mineralization. The age dating results suggest there was an alteration event between 30 and 35 Ma. The Victorio Peak dactite yielded an age of ~30 Ma, which probably represents hydrothermal alteration. The age of the Victorio granite is dated at ~35 Ma. Preliminary observations of fluid inclusions show that there were at least three different types of fluids during and after the time of mineralization. Primary two-phase liquid-vapor inclusions are found throughout the district in various minerals in all rock types. Secondary inclusions with halite daughter minerals can be found in the skarn minerals. Secondary inclusions that contain liquid CO2 are primarily found in fluorite from the skarns and in quartz from the granite. A study of skarn mineral fluid inclusions determined the fluid homogenization temperature in wolframite to be 280-380°C and salinities of 5.4-8.9 eq. wt% NaCl. Quartz fluid inclusions had homogenization temperatures of 141-320°C and salinities of 1.3-10 eq. wt% NaCl.