| Basis for focus area |
Porphyry molybdenum, minor Lithocap alunite in nearby alteration scars. The focus area encompasses of the Questa Mo porphyry deposit and the Log Cabin and Spring gulch resources. These deposits constitute a Climax-type porphyry cluster. Questa and Red River district boundaries from McLemore (2017). Molybdenum deposit at Questa and Mo resources at Log Cabin and Spring Gulch; REE, Re, W, Sn are potential byproducts. Rhenium is a potential byproduct. Alunite lithocap remnant in down-dropped fault block is too small to be potential alumina, potash, sulfuric acid, ± Ga resource. However, alteration scars from Questa eastward to Red River could have potential for alumina, potash, sulfuric acid, ± Ga. |
| Identified resources |
Identified molybdenum resource; historical production of molybdenum. |
| Production |
Peak Mo production at the Questa mine occurred in 1976 with 11.5 million lbs/yr. |
| Status |
Past mining. The Questa mine was declared a Superfund site in 2011; on June 2, 2014 Chevron declared the mine permanently closed. |
| Estimated resources |
Proven reserves at Questa (1999) of 16,344,898 tons of 0.343% MoS2 at a cutoff grade 0.25% MoS2 Probable reserves 47,198,409 tons of 0.315% MoS2 Possible reserves 3,223,000 tons of 0.369% MoS2 (McLemore, 2009). |
| Geologic maps |
Lipman and Reed (1989), scale 1:48,000; Meyer (1991), scale unknown. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. AVIRIS data (Livo and Clark, 2002). |
| Favorable rocks and structures |
High grade molybdenite ore occurs in andesite wallrocks in proximity to texturally variable silicic intrusions (Gaynor, Coleman and others, 2019) and in large magmatic-hydrothermal breccias near the andesite-porphyry contact. Alunite occurs in distal veins and alteration scars (areas of oxidizing sulfides exposed at the surface). |
| Deposits |
Questa mine (MRDS dep_id: 10198817; USMIN Site_ID: NM00018), Log Cabin prospect (MRDS dep_id: 10012900). |
| Evidence from mineral occurrences |
MRDS; USMIN; McLemore (2009). |
| Geochemical evidence |
Numerous references on geochemistry of igneous intrusions in area, summarized by McLemore and others (2009). Sparse cassiterite and scheelite mineralization observed in deep Questa Granite Porphyry. Late-stage beryl, rhodochrosite, ankerite, and fluorite veins occur throughout the deposit (J. Rosera, personal communication). Estimated 38 metric tons of Re (John and Taylor, 2016). |
| Geophysical evidence |
Silicic intrusions associated with the Questa porphyry deposit and its host batholith form a regional bouguer gravity low. However, a significant portion of the batholith was assembled after formation of the Questa Mo deposit, which complicates the relationship to gravity data (Gaynor, Rosera and Coleman, 2019). |
| Evidence from other sources |
The USGS conducted a large baseline study that focused on alteration scars upstream of the Questa mine. See Nordstrom (2008) for an overview. |
| Comments |
Questa mine is a superfund site. Alteration scars have larger potential for alunite and Ga then realized. Potential mineralized bodies have been delineated to the west of the Questa mine in the Log Cabin deposit, and east of the Questa mine in the Spring Gulch deposit (McLemore, 2009). |
| Cover thickness and description |
Molybdenite ore bodies range from the surface to a few thousand feet at depth, and generally plunge to the north parallel to Red River valley (Gaynor, Rosera and Coleman, 2019). |
| Authors |
Ryan D. Taylor, Albert H. Hofstra, Virginia T. McLemore, Joshua M. Rosera. |
| New data needs |
None requested at this time. |
| Geologic mapping and modeling needs |
None requested at this time. |
| Geophysical survey and modeling needs |
None requested at this time. |
| Digital elevation data needs |
Lidar complete. |
