--> Abstract: Geology and Mineralization of the Seminoe Mountains Granite-Greenstone Belt, Wyoming, by W. D. Hausel; #91017 (1992).

Datapages, Inc.Print this page

ABSTRACT: Geology and Mineralization of the Seminoe Mountains Granite-Greenstone Belt, Wyoming

HAUSEL, W. DAN, Wyoming Geological Survey, Laramie, WY

The Seminoe Mountains form a Precambrian-cored Laramide uplift near the southern margin of the Wyoming craton. The core of the range consists of Archean age crystalline supracrustal (>2.7 Ga) rocks folded into a vertically plunging open fold intruded by granodiorite (>2.6 Ga).

The amphibolite grade supracrustal rocks are subdivided into three mappable units. The lowermost unit consists of 11,000 ft of mafic schists with minor ultramafic schist and metasedimentary rock. This unit is overlain by the Bradley Peak ultramafics, which consist of 1000 ft of ultramafic and mafic metavolcanic rock. These rocks include several mappable ultramafic flows that grade upward from a cumulate serpentinite flow bottom to a tremolite-talc-chlorite schist spinifex flow top. Compositions and textures indicate they are peridotitic and basaltic komatiites. The uppermost unit (informally named the Seminoe formation), consists of 4000 ft of metasedimentary rock, including metagreywacke, banded iron formation, and pelitic schist with minor amounts of mafic and ultramafic schist.

Mineral deposits in the Seminoe Mountains include extensive banded iron formation, narrow high-grade gold veins, localized copper-silver-gold veins, gold placers, serpentine, jade, leopard rock, and uncommon asbestos. Recently, anomalous zones of zinc and lead were identified in shears in the district, and pyrope garnet was recovered from a nearby placer.

 

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)