Mayville Lithium Project

Lithium in the Bird River Greenstone Belt Manitoba Canada

The Bird River Greenstone Belt in southeastern Manitoba hosts several pegmatite belts including the world famous Bernic Lake pegmatite and the producing Tanco Mine. The Tanco Mine has produced lithium, tantalum and cesium products since 1968. It was purchased by Sinomine Resources, a Chinese company for US $130 million in 2019.

Left: Arial view of the Tanco Mine. Mining has centered on the world class Bernic Lake pegmatite

There are a number of pegmatite fields in the Bird River Greenstone area in addition to Bernic Lake. There has been intermittent exploration activity in the belt since the 1950’s. With the recent rise of lithium prices there has been new activity in the area.

Above: Claims held in the north arm of the Bird River Greenstone Belt

Above: Location of Tanco Mine and Makwa and Mayville base metal deposits in the Bird River Greenstone Belt, Manitoba.

Grid Metals has been exploring the area for base metals since 2006 and has defined a NI 43-101 resource of nickel-copper-PGM-cobalt at Makwa and a NI43-101 resource of copper-nickel-PGM at Mayville. Both deposits are open pit. Grid subsequently acquired mining claims from Tantalum Mining Corporation of Canada which included a historical resource of lithium from two pegmatites. The pegmatites are part of the Donner Lake Pegmatite field.

Above: Mayville Property held by Grid Metals showing Mayville Cu-Ni-PGM deposit and area of known pegmatites

Mayville Lithium Property

There are four known pegmatites on the property ( see map inset ). The pegmatites discovered to date in the Donner Lake area have all been spodumene ( lithium ) bearing. The Main Dyke is an example of an Albite Spodumene subtype with most of the pegmatite mass spodumene bearing. Drilling in 1955 on the Main Dyke ( 30 holes and Northwest Dyke 4 holes ) was completed forming the basis of the historical resource. The historical resource was estimated at 3.95 million tons at a grade of 1.28% Li2O. ( Source Manitoba Mineral Inventory File #229. Resources are historical in nature and not NI 43-101 compliant. Mustang does not consider the historical resource estimate as a current resource estimate and is not relying on the historical resource estimate as a current resource estimate until such time as a Qualified Person has reviewed and confirmed the data)

Drilling by Grid in 2018 drill tested the Main Dyke over a strike length of 775 meters. Results were consistent with the historical drill results. Grid also assayed for tantalum, cesium and rubidium.

Drill HoleFrom (m)To (m)Interval(m)   Li2O  (%) Cs2O (%)Rb2O (%) Ta (ppm) Fe (%)
MLI-18-0114.6818.483.80 0.13
MLI-18-02 36.7539.63 2.881.60.030.32120.30.28
MLI-18-04148.04 151.833.791.40.030.33108.40.16
MLI-18-0681.2483.92.661.8 0.030.30143.10.17
MLI-18-07 75.5078.883.381.8 0.030.42174.20.10

Note: results are believed to approximate true width.

Above: Long section of the Main Dyke drilling by Grid in 2018. The deposit is open to depth.

Grid sampling of a trenched area at the Northwest Dyke showed a pegmatite dyke highly enriched in Li2O with grab values over 3%.  


Next exploration steps are to drill the Main Dyke along strike to the south and to greater depth and drill the Northwest and West Dykes to test their potential. Geological mapping and geochemistry have proven effective in pegmatite exploration in the Donner Lake area with geochemical results showing a strong correlation to the known dykes. The geological contact to the northwest is the prime target for discovery of additional pegmatites.  Grid is targeting a mineable resource of lithium and rare metals in the Donner Lake area.

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