Reconnaissance mineral and cathodoluminescence studies of gold occurrences in the Pogo-Black Mountain area, eastern interior Alaska, USA
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Abstract
The Pogo Au deposit is the largest of a number of gold occurrences in eastern interior Alaska, that occur along a broad trend from west of Pogo to Black Mountain. Some of these occurrences are hosted in amphibolite facies gneisses and others in mid-Cretaceous igneous rocks that intruded the older metamorphic rocks. All occurrences contain arsenopyrite and pyrite. Whole rock geochemical trends distinguish most metamorphic rock-hosted vein prospects (strong Bi-Te-Au correlations) and intrusion-hosted occurrences (weak As-Au correlations). Brecciated quartz veins in metamorphic rocks have paragentically late Bi-Te (±S) + Au that post-dates Fe-As sulphide deposition. High grade vein samples from the Tibbs Creek intrusion-hosted deposits contain pyrite and arsenopyrite, generally lack Bi-Te minerals, but can contain paragentically younger euhedral quartz, stibnite and carbonate. Cathodoluminescence studies of gold-rich samples indicate that quartz dissolution occurred during the syn- to post-tectonic Bi-Te-Au deposition, and the later stibnite event. In the case of metamorphic rock-hosted deposits (e.g., Pogo, Gray Lead), Bi-Te and gold deposition commonly occurs in microfractures within quartz veins; the limited quartz in these fractures have distinctive CL response. We propose that gold deposition is related to changes in P-T conditions rather than fluid-rock chemical reactions. Similar quartz dissolution textures affect the void-filling euhedral quartz before or during stibnite and carbonate mineralization in the high-grade Au samples from Blue Lead.
Suggested Citation
Graham, G.E., Marsh, E.E., Lowers, H.A., Taylor, R., 2023, Reconnaissance mineral and cathodoluminescence studies of gold occurrences in the Pogo-Black Mountain area, eastern interior Alaska, USA, in Proceedings of the 17th SGA biennial meeting, v. 2, Zurich, Switzerland, August 28 - September 1, 2023, p. 142-145.
Study Area
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Reconnaissance mineral and cathodoluminescence studies of gold occurrences in the Pogo-Black Mountain area, eastern interior Alaska, USA |
| Volume | 2 |
| Year Published | 2023 |
| Language | English |
| Publisher | Society for Geology Applied to Mineral Deposits |
| Contributing office(s) | Geology, Geophysics, and Geochemistry Science Center |
| Description | 4 p. |
| Larger Work Type | Book |
| Larger Work Subtype | Conference publication |
| Larger Work Title | Proceedings of the 17th SGA biennial meeting |
| First page | 142 |
| Last page | 145 |
| Conference Title | 17th Biennial SGA Meeting |
| Conference Location | Zurich, Switzerland |
| Conference Date | August 28 - September 1, 2023 |
| Country | United States |
| State | Alaska |
| Other Geospatial | Pogo-Black Mountains area |