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Meguma Terrane - Goldenville, Caribou, Moose River, Beaver Dam, Tangier, Leipsigate, Cochrane Hill |
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Nova Scotia, Canada |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Meguma Terrane gold province is located ~80 km NE of the city of Halifax in Nova Scotia, eastern Canada (#Location: Caribou Gold Mines - 45° 3' 39"N, 62° 56' 20"W).
It contains several classic examples of turbidite-hosted mesothermal/orogenic gold deposits among over 300 gold occurrences and deposits hosted by the Cambro-Ordovician Meguma group rocks in southern Nova Scotia.
Historic production is believed to have totalled around 47 tonnes of gold, extracted largely in the 19th and early 20th centuries. The principal mines or clusters of mines were Goldenville district (6.5 t Au - the largest); Caribou mine (2.8 t Au); Moose River district - Touquoy zone (6 Mt @ 2 g/t Au - remaining resource); Beaver Dam, Tangier, Leipsigate, Cochrane Hill, Brookfield and Rawdon districts.
Nova Scotia is divided geologically into two distinct parts, the Avalon Terrane to the north and the Meguma Terrane to the south. The two terrane are separated by the east-west trending Minas Geofracture (commonly referred to as the Cobequid-Chedabucto Fault System). Docking of the two terranes was accompanied by major sinistral, transcurrent motion along this fault, followed by minor dextral movement. Overlying Devono-Carboniferous sediments, which are common on both sides of the Minas Geofracture, stitch these two terranes together (Schenk, 1995).
The Meguma Terrane is a 480 x 120 km (maximum width) wedge of Lower Palaeozoic metasedimentary rocks that were folded into long east-west trending, doubly plunging folds and regionally metamorphosed to greenschist and amphibolite facies during the Devonian, Acadian Orogeny (ca 400 Ma). These meta-sediments were then intruded by voluminous Devonian per-aluminous granitoids (ca 375 Ma) and were subsequently overlain by carbonate and clastic sedimentary rocks and evaporates of the Horton and Windsor Groups respectively.
The Meguma Group comprises two formations:
i). The Cambrian Goldenville Formation - a lower, sand-dominated flysch sequence that is >6.7 km thick, with no exposed base. In detail it is composed of massive, thick-bedded greywacke that is dark gray (carbonaceous) to light gray (calcareous) in colour.Ê The thick coarser beds are commonly separated by thin shaly horizons that may either be chloritic or very carbonaceous.Ê This formation grades upwards through manganese-rich strata into a basal unit of very carbonaceous sulphidic black slate.
i). The Halifax Formation - an upper shaly flysch which is up to 11.8 km thick and consists of about 75 % black carbonaceous sulphidic slate and 25% thinly (~10 cm) bedded to cross-laminated meta-siltstone.
The Meguma Group rocks are variably deformed into upright gently to moderately doubly-plunging folds with multiple cleavages. The strata are metamorphosed from greenschist to amphibolite facies and are subsequently intruded by the around 375 Ma per-aluminous granites (described above) and minor mafic intrusions.
The gold deposits can be divided into three main types: i). high grade (approximately 15 g/t Au) narrow gold-bearing quartz veins; ii). low-grade (0.5 to 4 g/t Au) slate/argillite hosted; and iii). low-grade meta-sandstone hosted veining.
Almost all of the historic production has come from the high-grade veins within 200 m of surface. A variety of vein types occur although most of the gold produced came from bedding concordant, stockwork and fissure veins. Envelopes of disseminated low-grade gold, with minor electrum and associated intermetallic compounds and metal alloys have recently been recognized in association with the high grade veins.
Concordant, auriferous quartz veins, which include bedding-parallel and stratabound geometries are located within or immediately below the upper margins of incompetent, impermeable argillite horizons in the Goldenville Formation. Many of the districts are located on the steeper, sometimes overturned limbs of anticlinal folds or in parasitic second order structures on the limbs of larger folds, with the auriferous veins are localised either on, or near, the crests of regional anticlinal domes.
Concordant and discordant, gold-bearing veins occur throughout the Meguma Group, although most of the recorded production has been recovered from the eastern part of the Meguma Terrane.Ê Gold deposits are present throughout the total exposed stratigraphy of the Goldenville Group and in a minor way, into the overlying Halifax Formation. Most of the districts occur within greenschist facies rocks and east of the South Mountain Batholith. However, several significant districts are within amphibolite grade metamorphic rocks that are spatially associated with numerous Devonian-Carboniferous granitic intrusions in the easternmost part of the province.
Most of the gold deposits and occurrences are associated with thicker than normal, interstratified slate and meta-siltstone within the Goldenville Formation. Within these gold districts, the fine-grained lithologies are variably argillaceous, silty, carbon-rich and sulphidic with abundant pyrrhotite and arsenopyrite with pervasive carbonate alteration.
The most recent source geological information used to prepare this decription was dated: 2000.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Caribou Gold Mines
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Selected References:
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Morelli R M, Creaser R A, Selby D, Kontak D J and Horne R J, 2005 - Rhenium-Osmium Geochronology of Arsenopyrite in Meguma Group Gold Deposits, Meguma Terrane, Nova Scotia, Canada: Evidence for Multiple Gold-Mineralizing Events: in Econ. Geol. v100 pp 1229-1242
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Ryan R J and Smith P K 1998 - A review of the mesothermal gold deposits of the Meguma Group, Nova Scotia, Canada: in Ore Geology Reviews v13 pp 153-183
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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