The Seminoe Mountains greenstone belt in central Wyoming is a fragmented belt of Archean metamorphic rocks cropping out along the western flank of the Seminoe Mountains. The core of the Seminoes is formed by crystalline rock consisting of an ancient greenstone terrane of metamorphosed volcanic, sedimentary and plutonic rock intruded by Late Archean granodiorite. The metamorphic rocks include amphibolite, mica schist, serpentinite, ultramafic schist, metagreywacke, metapelite, and banded iron formation. The flanks of the Precambrian core are unconformably overlain by Phanerozoic sedimentary rock that form a spectacular steeply dipping precipice along the southern flank of the range.
The district is known for its iron ore and gold deposits, but also hosts some copper, silver, serpentine, asbestos, jasper, jade and leopard rock. Some previously unknown zones of anomalous lead and zinc associated with shear zones were detected during a mapping project by the author and pyrope garnets and chromian diopsides were recovered from nearby Tertiary paleoplacers. All of the kimberlitic indicator minerals tested to date have yielded diamond-stability (G10) geochemistry which is highly unusual. These are found along with detrital gold in the Kortes paleoplacer. The paleoplacer remains unexplored but could lead to discovery of a major diamond deposit and significant gold.
Quartz vein samples from the Seminoe Mountains containing VG (visible gold).
In 1981, while conducting reconnaissance in this area, the author recovered more than a dozen samples of quartz with visible gold. One assay of quartz without visible gold yielded 2.87 ounces per ton of gold, and a sample of banded iron formation assayed 1.15 ounces per ton of gold. This zone of mineralization occurs in a larger propylitically altered zone in metatholeiites (basalts), metakomatiites, and banded iron formation that likely hosts a large-tonnage, low-grade gold deposit with high grade quartz veins. Samples of altered metatholeiite from this zone contained anomalous gold.
As incredible as it seems - this deposit remains essentially unexplored to date (2009), yet it has excellent potential for diamonds and gold! Would you like to read more about this deposit? See our new gold book at CreateSpace and Amazon.