British Columbia Ministry of Energy, Mines and Natural Gas and Responsible for Housing
News | The Premier Online | Ministries & Organizations | Job Opportunities | Main Index

MINFILE Home page  ARIS Home page  MINFILE Search page  Property File Search
Help Help
File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  08-Jul-2015 by Karl A. Flower (KAF)

Summary Help Help

NMI
Name WEST REDONDA ISLAND Mining Division Vancouver
BCGS Map 092K026
Status Past Producer NTS Map 092K07W
Latitude 050º 17' 06'' UTM 10 (NAD 83)
Longitude 124º 57' 07'' Northing 5572141
Easting 360943
Commodities Limestone, Magnesium Deposit Types R09 : Limestone
Tectonic Belt Insular Terrane Wrangell
Capsule Geology

The West Redonda Island limestone occurrence is located approximately 1.2 kilometres west of Gloucester (George) Point on West Redonda Island.

At various locations along the Strait of Georgia, the 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 1920's and are exposed from sea level to greater than 200 metres elevation on the precipitous slope. It 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.

During 2007 through 2012, the area was prospected, sampled and mapped by H.T. Shearer. 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).

Bibliography
EMPR AR 1919-215; 1920-216; 1926-314
EMPR ASS RPT *29775, 33248, 33897
EMPR BULL 23, pp. 100,101; 40, pp. 92,93
EMPR OF 1987-13, pp. 50,51; 1992-18
GSC MAP 1386A
GSC MISC RPT *Bureau of Mines No. 811, 1944
GSC OF 480
CANMET REPORT 452, Vol.5, p. 162; 811, pp. 127,161-163
CIM BULL February 2008, Vol. 101, No. 1106

COPYRIGHT | DISCLAIMER | PRIVACY | ACCESSIBILITY