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File Created: 17-Apr-91 by George Owsiacki(GO)
Last Edit:  17-Apr-91 by George Owsiacki(GO)

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NMI
Name MOUNT ASSINIBOINE Mining Division Golden
BCGS Map 082J082
Status Prospect NTS Map 082J13E
Latitude 50º 49' 26" N UTM 11 (NAD 83)
Longitude 115º 38' 51" W Northing 5631113
Easting 595261
Commodities Magnesite Deposit Types E09 : Sparry magnesite
Tectonic Belt Foreland Terrane Ancestral North America
Capsule Geology

The Mount Assiniboine occurrence area is underlain by carbonate, shale and phyllitic rocks of Middle Cambrian age which have been metamorphosed and uplifted into an anticlinal form. This anticlinal feature has its central axis located in the valley of Assiniboine Creek. West of this axis, the rocks dip from 5 to 35 degrees southwest and strike northwest from 310 to 355 degrees. East of the axis, the rocks are essentially flat-lying. The entire property is underlain at shallow depth by the Main Ranges thrust fault along which the rocks have moved eastward several kilometres.

Two distinct types of dolomite of the Middle Cambrian Cathedral Formation occur on the property. A "granola" textured dolomite is host to the magnesite mineralization and is generally underlain and sometimes enclosed by a tight, crystalline, sometimes argillaceous dolomite. The host rock which contains the magnesite mineralization is a very coarse-grained, recrystallized dolomite which occurs as massive, tan coloured, resistant outcrops. Magnesite mineralization in outcrop exposures is recognized by its extreme hardness, white colour, massive appearance and the presence of large rhombic crystals of dolomite spar with minor pyrite.

Two areas of significant buildup of coarse-grained magnesite- bearing dolomite were identified. The best area occurs in a cirque occupied by Eon Creek where 274 metres of Cathedral Formation hosts a 104 metre thick zone of rock which assays a high of 28.88 per cent MgO. The second area may represent the updip continuation of the Baymag orebody (082JNW001) to the south. The Cathedral Formation reaches a maximum thickness of 186 metres and contains 101 metres of favourable magnesite-bearing rock which assays a high of 43.07 per cent MgO (Assessment Report 19092).

Bibliography
EMPR ASS RPT 18203, *19092
EMPR OF 1992-14
GSC OF 634

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