| Basis for focus area |
The focus area encompasses the Big Ben porphyry molybdenum resource; REE, Re, Sc, Sn, and W are potential byproducts. A 15 km buffer was applied to encompass undiscovered occurrences in adjacent areas. |
| Identified resources |
Identified molybdenum resources. |
| Production |
None. |
| Status |
Big Ben was drilled and mapped by the U.S. Bureau of Mines in the early 1940s (Herdlick, 1949) and drilled by ASARCO (eight holes in 1958-1959); and then extensively by AMAX in the 1970s. |
| Estimated resources |
Big Ben: 245 Mt at 0.092% Mo (Johnson, 1964); 376 Mt at 0.098% Mo (Gammons and others, 2020). |
| Geologic maps |
Witkind (1971), scale 1:62,500. |
| Geophysical data |
Inadequate Rank 3 aeromagnetic and Rank 5 aeroradiometric coverage. |
| Favorable rocks and structures |
The terrane is early Proterozoic metamorphic rocks intruded by Tertiary porphyries and breccia pipes; Big Ben is a silicified pipe (Worthington, 2007). Big Ben porphyry dated at 49.5 Ma (Rostad and others, 1978). |
| Deposits |
Big Ben Molybdenum (MRDS dep_id: 10096465). |
| Evidence from mineral occurrences |
MRDS; Herdlick (1949); Worthington (2007); Gammons and others (2020). |
| Geochemical evidence |
USBM drilling indicated a weighted average of 0.19 to 0.26% MoS2 in core samples (Herdlick, 1949). Molybdenite and molybdite occur with chalcopyrite, galena, fluorite, and quartz. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
Molybdenum resources identified at Big Ben. REE, Re, W, Sn are potential byproducts, but their enrichment has been inferred from the mineral system/deposit type table (Hofstra and Kreiner, 2020). |
| Cover thickness and description |
Exposed at the surface, mineralization followed down to 45 m. |
| Authors |
Ryan D. Taylor, Albert H. Hofstra, Joshua M. Rosera, Kaleb C. Scarberry. |
| New data needs |
Geologic mapping, geophysical, and geochemical surveys. |
| Geologic mapping and modeling needs |
None requested at this time. |
| Geophysical survey and modeling needs |
High resolution aeromagnetic and aeroradiometric coverage. |
| Digital elevation data needs |
Lidar planned over a small portion of focus area and is incomplete for the rest. |
