Metallogenic, tectonic and geochemical evolution of the Cape Ray fault zone with emphasis on electrum mineralization

• Main Author: Wilton, Derek Harold Clement
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1983
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/6798/; https://research.library.mun.ca/6798/1/DerekHaroldClementWilton.pdf; https://research.library.mun.ca/6798/3/DerekHaroldClementWilton.pdf

The Cape Ray Fault Zone is host to two electrum/base metal sulphide-bearing quartz vein deposits. The deposits occur within an alaskitic granite (the Windowglass Hill Granite) and an intermixed graphite/ chlorite/ sericite schist unit (part of the Windsor Point Group). This study was initiated to determine the origin of these two deposits, but the metallogenesis could not be ascertained until the tectonic and lithogeochemical framework of the entire region was understood. -- The Cape Ray Fault cuts through an area of tectonic complexity in southwestern Newfoundland. The fault occurs within the Windsor Point Group, a northeasterly-striking, intermixed sequence of felsic and mafic pyroclastic/volcaniclastic and associated sedimentary rocks, which is centrally located between a tonalitic terrane to the northwest (the Cape Ray Granite) and an amphibolite facies gneiss unit, with synkinematic granite, to the southeast (the Port aux Basques Complex). The tonalite contains isolated metagabbroic remnants of an ophiolite sequence (the Long Range Mafic/Ultramafic Complex). The Windsor Point Group contains tonalitic fragments in the ignimbritic rhyolite at its base, and is in tectonic contact with the gneiss unit, wherein the gneiss is extensively retrogressed. The Windowglass Hill Granite intrude the Windsor Point Group in the northeastern part of the zone. Both sides of the fault zone were intruded by post-tectonic granites (the Strawberry Granite on the northwestern side and Isle aux Morts Brook Granite on the southeast). -- Geochronological determinations indicate that the tonalitic terrane is Ordovician in age, the Windsor Point Group and Windowglass Hill Granite are late Devonian, and the Strawberry/Isle aux Morts Brook Granites are early Carboniferous. -- Isograds defined in the Windsor Point Group indicate that metamorphic grade increases from lower to upper greenschist facies towards the SE, and that pressures are rather low. Within the Port aux Basques Complex metamorphic isograds record amphibolite facies ...