Densities of Precambrian rocks of the Amisk Lake – Flin Flon area. A detailed study

Abstract

Densities were determined for 1855 fresh bedrock samples taken from an area of about 110 sq. miles (285 km2) in east-central Saskatchewan. Average results for the region are as follows[Formula: see text]In this area, density depends primarily on the mineral composition of the rocks because their porosity is insignificant. However, the mineral composition varies widely for many reasons. Metamorphism has resulted in significant changes in rock densities because some low density minerals such as bytownite are altered to high density minerals such as zoisite. Conversely, olivine and some pyroxene are changed to low density serpentine. The density measurements are used to indicate possible subdivisions of the Amisk Group of meta-volcanic rocks. As a result, certain areas are recommended for mineral prospecting.Evidence is presented to show that some basic intrusions have increased the density of their wall rocks by metamorphism.The Bouguer gravity field in this area is closely correlated with the densities of outcropping rocks. The shape and depth of some rock units are estimated from the gravity. All the outcropping rock units extend less than 5 km in depth and some are very shallow.