Alteration and genesis of the Goldboro Meguma-hosted orogenic gold deposit, Goldboro, Nova Scotia, Canada

Szmihelsky, Marko (2022) Alteration and genesis of the Goldboro Meguma-hosted orogenic gold deposit, Goldboro, Nova Scotia, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Goldboro deposit (16,036,000 tonnes @ 3.78 g/t Indicated and Measured, 5,306,000 tonnes @ 4.68 g/t Inferred, 1,946,100 oz and 798,100 oz Au, respectively) is a Meguma-type orogenic gold deposit in Nova Scotia, Canada. Despite the economic importance of Meguma-type orogenic gold deposits, their origin, paragenesis, and hydrothermal footprint are not completely understood compared to other sediment-hosted orogenic gold districts (e.g., Victorian gold belt, Sukhoi Log). Deposits are hosted within folded metaturbidite successions that consist of repeating fining-upwards successions containing argillite and greywacke. Gold in the deposit is predominantly hosted within quartz veins that lie parallel to bedding, at the contacts between greywacke and mudstone. Four distinct vein generations exist at Goldboro: V1) foliated, bedding parallel, glassy quartz veins that are rich in sulfides, V2) foliated, bedding parallel and discordant milky white quartz veins with abundant arsenopyrite, V3) undeformed, tan, carbonate-rich veinlets, and V4) undeformed, albite+K-feldspar+chlorite+biotite+ilmenite veins. A broad halo of sericite alteration surrounds Goldboro (>100 m from the hinge line of the Upper Seal Harbour anticline) with more localized biotite, chlorite, and albite+sericite alteration. Biotite alteration occurs proximal to V1 and V4 veins (< 2 m), and albite+sericite and chlorite alteration are local to V4 veins (≤2 cm). V2 veins exhibit rare arsenopyrite alteration of the wall-rock, and V3 veins are not associated with any alteration. Lithogeochemistry and mineral chemistry were used to identify vectors towards mineralization by demonstrating chemical changes within the wall-rock mudstones resulting from fluid-rock interactions during vein-stage mineralization: 1) K₂O and 3K/Al changes reflect the intensity of K-related mica alteration; 2) mass increases in Fe₂O₃ and MgO were found to correlate to biotite and chlorite alteration; 3) mass increases in Na₂O and CaO correspond to albite alteration; 4) Rb, Ba, and Cs were found to be proxies for K₂O; and 5) Sr was identified as a proxy for CaO, and can be used to identify carbonates in V3 veinlets. Gold mineralization is predominantly hosted within V1, V2, and V4 veins as free gold and as cores and inclusions in arsenopyrite. Petrographic textures and mineral assemblages suggest that V4 veins are potentially magmatic-hydrothermal in origin. Vein and mineral parageneses suggest two main mineralizing events, providing evidence for gold remobilization and refocusing, as has been suggested by previous researchers in the Meguma zone.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/15452
Item ID: 15452
Additional Information: Includes bibliographical references.
Keywords: lithogeochemistry, alteration, orogenic gold, Meguma terrane, gold
Department(s): Science, Faculty of > Earth Sciences
Date: May 2022
Date Type: Submission
Library of Congress Subject Heading: Mineralogical chemistry--Nova Scotia--Goldboro; Gold compounds--Nova Scotia--Goldboro; Gold ores--Geology--Nova Scotia—Goldboro.

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