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- Title
Paleoproterozoic gold deposits in the Bald Hill and Coyote areas, Western Tanami, Western Australia.
- Authors
David Huston; James Anderson; Terrence Mernagh
- Abstract
Abstract?? Significant gold deposits in the western Tanami region of Western Australia include deposits in the Bald Hill and Coyote areas. The ca. 1,864?Ma Bald Hill sequence of turbiditic and mafic volcanic rocks hosts the Kookaburra and Sandpiper deposits and a number of smaller prospects. The ca. 1,835?Ma turbiditic Killi Killi Formation hosts the Coyote deposit and several nearby prospects. The Kookaburra deposit forms as a saddle reef within a syncline, and the Sandpiper deposit is localized within graphitic metasedimentary rocks along a limb of an anticline. Gold in these deposits is hosted by anastomosing quartz?(?pyrite?arsenopyrite) veins within quartz?sericite schist with disseminated arsenopyrite, pyrite, and marcasite (after pyrrhotite). Based on relative timing relationships with structural elements, the auriferous veins are interpreted to have been emplaced before or during the ca. 1,835?1,825?Ma Tanami Orogeny (regional D1). Gold deposition is thought to have been caused by pressure drops associated with saddle reef formation (Kookaburra) and chemical reactions with graphitic rocks (Sandpiper). The Coyote deposit, the largest in the western Tanami region, consists of a number of ore lenses localized along the limbs of the Coyote Anticline, which formed during the Tanami Orogeny. The largest lenses are associated with the Gonzalez Fault, which is located along the steeply dipping southern limb of this fold. Gold was introduced at ca. 1,790?Ma into dilatant zones that formed in local perturbations along this fault during later reactivation (regional D5) towards the end of a period of granite emplacement. Gold is associated with quartz?chlorite?pyrite?(arsenopyrite?galena?sphalerite) veins with narrow (<?5?mm) chloritic selvages. A quartz?muscovite?biotite?K?feldspar?(tourmaline?actinolite?arsenopyrite) assemblage, which is interpreted to relate to granite emplacement, overprints the regional greenschist facies metamorphic assemblage. The mineralogical similarity between this overprinting assemblage and the vein assemblage suggests that the auriferous veins at the Coyote deposit are associated with the granite-related metamorphic?metasomatic assemblage. Gold deposition is thought to have been caused by pressure drops within dilatant zones.
- Subjects
WESTERN Australia; PROTEROZOIC paleoecology; GOLD mining; VOLCANIC ash, tuff, etc.
- Publication
Mineralium Deposita, 2007, Vol 42, Issue 1, p127
- ISSN
0026-4598
- Publication type
Article