Bulletin 009

Bulletin 009

BUL 009

Sedimentary Magnetite Deposits of the Crowsnest Pass Region, Southwestern Alberta

Author(s) Mellon, G.B. Date 1961-01-01

Low-grade, titaniferous magnetite deposits of sedimentary origin are present at widely scattered localities in the folded Foothills belt of southwestern Alberta. The individual deposits are thin and lensing, forming a locally developed, iron-rich zone at the top of the basal sandstone member of the Upper Cretaceous Belly River formation.

The iron-rich rocks are composed of black finely laminated, very fine-rained, magnetite-rich beds up to three feet thick, interbedded with dark green fine-grained, calcareous sandstones composed of quartz, feldspar, fine-grained rock fragments, and clastic dolomite. The rocks are well cemented by authigenic chlorite and calcite. The ithologic and fossil assemblages admitted with the magnetite- bearing sandstones suggest that they were concentrated as placer deposits along the margin of an ancient shoreline complex formed during the eastward regression of the late Cretaceous Colorado sea.

The average Fe203 content of 60 randomly elected sample from 17 localities is 29 per cent, distributed among magnetite, chlorite, and ilmenite. The average TiO2 content of the samples is about 3.5 per cent, distributed among titaniferous magnetite, ilmenite, anatase, and leucoxene. The rocks are unsuitable for treatment by conventional beneficiation and smelting processes because of their high titanium and chlorite content, and fine grain size.

The richest deposits are located north of Burmis in the Crowsnest Pass, and near DungarvanCreek, south of Pincher Creek. At both localities the rocks have been complexly faulted andfolded, limiting the volume of ore that can be recovered by strip-mining. Reserve of potential ironore grading between 20 and 30 per cent Fe are tentatively estimated at less than two million tonsin the Burmis area, and less than six million tons in the Dungarvan Creek area.

Mellon, G.B. (1961): Sedimentary magnetite deposits of the Crowsnest Pass region, southwestern Alberta; Research Council of Alberta, RCA/AGS Bulletin 09, 108 p.