Calc-Silicate Rocks in the Wollaston Lake Area, Saskatchewan

Abstract

The Hollaston Lake area is underlain by infracrustal rocks of the Daly Lake Group which constitutes the major part of the Hollaston Lake fold belt. Shape , greywacke , and arkose metamorphosed to the amphibolite facies of the Abukuma series form most of the. Group. In the Hollaston Lake area, the Hidden Bay formation of the Daly Lake Group consists of feldspathic quartzite and marble which occurs as layers bounded by calc-silicate rocks, hornblende biotite rock, and biotite gneiss. Important mineral assemblages in marble are: calcite-diopside-quartz; calcite-diopsioe-biotite:, calcitediopside- idocrase; calcite-dolomite-forsterite-phlogopite: dolomite: calcitesCdPo: Li i.:e-gtduui i.e+d i.op s i.de ; anci in ca.Lc-cs i Li ca t.e rOCKS are: dlopsldeplagioclase; diopside-idocrase; and scapolite-grandite-epidote-quartz. The rocks were metamorphosed to the middle to high amphibolite facies. Temperature ranges were from 600 to 725 C and pressure from 2 - 6 kb. Marbles were derived from slightly dolomitic limestone. Calc-silicate rocks are the result of metamorphic diffusion of CO2, and K20 from a calcareous-pelitic rock. The movement of these components was probably caused by the incompatibility of calcareous assemblages in the presence of mica-bearing assemblages at the amphibolite facies. Diffusion and redistribution of Ca and Mg cations within the calc-silicate rocks occurred to form large monomineralic segregations of diopside, plagioclase, tremolite, scapolite , and calcic+amphibole ,