GEOLOGY OF THE STURGEON LAKE-01 KIMBERLITE BLOCK, SASKATCHEWAN

The Sturgeon Lake 01 body was the first kimberlite discovered in Saska tchewan. It was found by heavy mineral sampling and shown to be diamon diferous, but not economic. The body is a glacially transported megabl ock of crater-facies volcaniclastic kimberlite that is at least 200 m by 125 m by 40 m in size. The block, which is 98 Ma in age, occurs wit hin 100 m of glacial sediments that overlie Cretaceous bedrock shale. Marine shale of a similar age occurs adjacent to the kimberlite and ap pears to represent a separate glacial block(s) at least 110 m by 90 m by 16 m in size. The kimberlite is typical of Group 1, containing two generations of olivine, macrocrysts of ilmenite, gar net, spinel and m ica together with groundmass mica, spinel, perovskite, apatite, carbon ate and serpentine. Texturally, the kimberlites are subaerial pyroclas tic airfall lapilli tuffs and coarse ash composed mainly of juvenile l apilli and single grains of olivine. The juvenile lapilli have amoeboi d shapes and are vesicular; a feature which is similar to the kimberli tes at Sturgeon Lake 02 and Fort a la Come, but unusual compared to ot her kimberlites worldwide. This suggests that the Sturgeon Lake 01 kim berlites formed by different emplacement processes to most documented kimberlites; probably by Hawaiian- and Strombolian-style eruptions inf illing maar-like craters with no associated diatreme as proposed for t he Fort a la Corne province. Copyright (C) 1996 Canadian Institute of Mining, Metallurgy and Petroleum.