Murray Brook Polymetallic VHMS Deposit, Bathurst, New Brunswick
Garth Graves, Consulting Geologist
The Bathurst Mining Camp is one of Canada's major mining districts for volcanic-hosted, polymetallic, massive sulphide ‘VHMS’ deposits. The deposits form part of a Middle Ordovician arc and back arc system on the Gondwanan continental margin. The camp hosts 25 massive sulphide deposits and more than 140 massive sulphide occurrences, most of which were discovered during the 1950's. Ten deposits within the Bathurst Mining Camp have been brought into production; currently the only producer is the Caribou Mine.
The Murray Brook deposit is located along the north-west margin of the Bathurst Mining Camp and is hosted by fine-grained sedimentary rocks of the Ordovician Mount Brittain Formation (470 Ma). The latter is in the lower part of the California Lake Group which is predominantly composed of felsic tuffs and flows, and basalt flows. The massive sulphide body is enveloped by a narrow chlorite-sericite alteration zone. It was discovered by Kennco Exploration Ltd. in 1956 during a drill program following-up anomalous Cu, Pb and Zn in stream silt samples and prospecting that located mineralized float. Kennco drilled 63 holes into the deposit and estimated a resource of 23 million tonnes with an average grade of 0.44% Cu, 0.86 % Pb, 1.95% Zn and 31.2 g/t Ag. (Davies, 1966; not NI 43-101 compliant).
Further exploration was carried out by various companies on the massive sulphide deposit and the overlying precious metal-rich gossan from 1970 until 1989 at which time NovaGold Resources Ltd. began mining the gossan. Between 1989 and 1992, NovaGold mined 2.7 Mt of the gold-enriched gossan cap and recovered 45,000 ounces of gold and 315,000 ounces of silver.
The property was acquired by Murray Brook Minerals Inc. in 2006 which subsequently optioned the property in 2010 to Votorantim Metals Canada Ltd. which in turn entered into a joint venture agreement with El Nino Ventures Inc. by way of a pre-existing agreement. From 2010 to 2012 the JV completed a 30,000 metre drill program designed to enable a NI 43-101 compliant resource estimate for the massive sulphide body.
In January 2013, P&E Mining Consultants Inc. (P&E) tabled a NI 43-101 compliant resource estimate based on VMC’s drill results. The measured + indicated open-pit accessible sulphide resource is 17,884,000 tonnes with average grades of 2.73% Zn, 0.47% Cu, 0.99% Pb, 41.7 g/t Ag, and 0.59g/t Au. Metallurgical testing performed by RPC Science and Engineering of Fredericton, NB produced encouraging recoveries of 89% zinc. Further work with a pilot plant using larger samples will be required to define optimal recoveries of all metals. A Preliminary Economic Evaluation completed by P&E in July 2015 resulted in an estimated NPV of $96.4 million at a 5% Discount Rate yielding an IRR of 11.4% with a stand-alone mill.
Ongoing exploration has defined drill targets along strike from the Murray Brook deposit in similar stratigraphy utilizing soil geochemistry, airborne mag-EM and ground gravity surveys.
Garth Graves is a professional geologist with more than 35 years of experience in the national and international mineral exploration industry. He has specialized in grass roots exploration and project generation for precious and base metal deposits as well as managing advanced projects through the resource definition stage. Garth’s experience includes base metal and gold exploration programs in eastern Canada, uranium in northern Saskatchewan and porphyry and epithermal systems throughout Latin America including Chile, Ecuador, Argentina, Bolivia, Peru, Mexico and the Dominican Republic. Recent positions include that of senior geologist for Xstrata Zinc responsible for direction of base metal exploration in the Bathurst Mining Camp; exploration manager for Cornerstone Ecuador SA based in Cuenca, Ecuador; and senior geologist for Votorantim Metals Canada Inc. responsible for management of the resource definition of the 20 Mt Murray Brook massive sulfide Zn, Pb, Ag, Cu, Au deposit in the Bathurst Mining Camp that consisted of a 30,000 meter drill program and completion of the Preliminary Economic Assessment (PEA).
