The tectonics and mineralisation of the Black Angel Pb/Zn deposit, central West Greenland

• Main Author: Carmichael, Andrew John
• Format: Thesis
• Language: English
• Published: Goldsmiths, University of London 1988
• Subjects: Greenland
• Online Access: https://research.gold.ac.uk/id/eprint/33732/; https://research.gold.ac.uk/id/eprint/33732/1/GOL_thesis_CarmichaelA_1988.pdf

The 13.5 M Tonne Black Angel Zn-Pb-A/J-Fe deposit at Marmorilik, West Greenland (71·10' N, 51· 045' W) consists of six massive, strata bound to discordant sulphide lenses hosted in poly-deformed, poly-metamorphosed evaporite bearing carbonates of the Early Proterozoic Upper Marmorilik Formation. This study is an analysis of the tectonics and mineralisation of the orebodies. The research programmed involved detailed and regional structural and stratigraphic mapping, section measuring, extensive underground mapping and sampling, logging of drill cores, detailed mineralogical and textural studies, and stable and lead isotopic analyses. The deposits occur within the Karrat Group supracrustal sequence of the Mid-Proterozoic (1860 -1680 ma. )Rinkian mobile belt, an upper greenschist to granulite facies terrain composed of Archean and Early Proterozoic tectono-stratigraphic units. Four deformation phases have been recognised within the supracrustal of the Marmorilik and Nukavsak Formations. Three penetrative phases have been assigned to the polyphase Rinkian event end are namely, D1 - an early recumbent nappe phase, D2 - a south verging fold and slide phase and D3 - a sinistral sheer event. Peak metamorphic conditions of upper greenschist facies in the mine area were attained after this deformation, which was succeeded by an extensional D4 deformation (Late Precambrian) associated with dolerite dyke intrusion. The mineralisation occurs as folded and boudinage massive sulphide lenses within a narrow, highly deformed. east-west trending mineralised corridor in the Marmorilik Formation carbonates. The ores consist of tectonised, metamorphosed and recrystalised medium to coarse grained sphalerite, galena, pyrite, pyrrhotite and chalcopyrite with subordinate tennantite and arsenopyrite. Primary void-fill (marcasite/early pyrite) textures occur in metamorphic pyrite grains. Intense shearing at the ore host rock contacts has produced discordant relationships and the inclusion of rafted calcites marble and pelitics clasts, ...