Rb/Sr dating of rocks from the Wollaston Lake Belt, Saskatchewan

Abstract

Rb and Sr measurements on rocks of the Wollaston Lake fold belt in Saskatchewan indicate a major metamorphic resetting of most of the whole-rock Rb/Sr systems, particularly in the arkosic units, associated with the Hudsonian orogeny and dated at 1850 m.y. (λ = 1.39 × 10−11 y−1).Some of the so-called 'young' granites in the area appear to be primary intrusives of that age, but others contain clear evidence of containing older material. A tentative age of 2650 m.y. for the Archean granites is suggested on the basis of three samples that appear to have retained their original Rb/Sr ratios. Two quartzite samples suggest an Archean age of about 2360 m.y. for the sediments in the area although the data are inconclusive. A late metamorphism is well dated at 1730 m.y. by a mineral isochron and by ratios in remobilized material along the edge of the Johnson River batholith.