The West Redonda Island limestone occurrence is located approximately 1.2 kilometres west of Gloucester (George) Point on West Redonda Island.
Regionally, the area is underlain by dioritic and granodioritic intrusive rocks of the Jurassic to Cretaceous Coast Plutonic Complex. Age dating from the southern part of West Redonda Island indicates 111 to 113 million years by potassium-argon from biotite and hornblende (Geological Survey of Canada Open File 480). Locally, highly metamorphosed greenstone and limestone of unknown group, formation or age are found in diorite. The strata strikes north with a dip of 65 degrees east.
At various locations along the Strait of Georgia, granitic intrusions of the Coast Plutonic Complex contain carbonate inclusions or roof pendants. The carbonates are generally of limited size and belong to the Permian Marble Canyon Formation and/or the Upper Triassic Quatsino Formation.
Locally, a carbonate deposit (mainly limestone) approximately 40 metres wide and at least 135 metres high is exposed along the shore approximately 100 metres northwest of the west corner of Lot 3439. Other smaller occurrences are exposed less than a kilometre west and northwest of Lot 3439.
The main limestones to the east were quarried in the 1920s and are exposed from sea level to greater than 200 metres elevation on the precipitous slope. The limestone is bounded by a green intrusive rock, which is in turn enclosed by a light-coloured hornblende granite. The limestone is white and grey, medium- to coarse-grained with a locally mottled texture. A shear-related lamination occurs within a section of white limestone.
Brucite occurs within zones as 1- to 3-millimetre granules, particularly in the eastern margin of the limestone, where it constitutes approximately 30 per cent of the rock. Brucite grains have a concentric structure and most are surrounded by white dolomite within a calcite matrix. Tiny rounded serpentine grains constitute the main impurity, although much of the brucitic limestone is free of it. On land, brucite alters to white hydromagnesite, which readily dissolves and leaves a typically pitted surface. Brucitic limestone exposed to seawater is prone to having the calcite groundmass dissolved, leaving brucite standing out in relief.
In 1944, Goudge collected Sample 23 across the entire width of the quarry, including the brucitic and non-brucitic limestone. Sample 23A was collected across approximately 6 metres of brucitic limestone:
------------------------------------------------------------------- MgO CaO Fe2O3 Al2O3 SiO2 CO2 Water + 105 C Sample 23 9.22 46.27 0.32 0.22 1.28 39.94 2.94 Sample 23A 20.50 37.21 0.18 0.05 0.48 34.60 6.48 -------------------------------------------------------------------- |
The MgO/CaO ratio indicates that the composition of brucite-bearing carbonate is equivalent to dolomite.
In 2007, seven samples, totalling 161.4 kilograms, assayed between 4.7 and 7.2 per cent magnesium oxide with an average of 83.3 per cent calcium carbonate and 2.45 per cent silicon dioxide (Assessment Report 29775).
In 2014, a single rock sample from the main quarry area yielded 59.46 per cent calcium and 2.65 per cent magnesium (Assessment Report 35109).
Work History
The limestone occurrence was first identified in the late 1800s or early 1900s. In 1920, the quarry was operated by the Nickson Construction Company limited and 7666 tonnes of limestone rock was mined and shipped. The quarry was reported to be still active in 1926.
During 2007 through 2014, Homegold Resources Ltd. conducted minor programs of prospecting, rock sampling and geological mapping on the area as the West Redonda property.
