Petrology And Geochemistry of The 1308 Lake Sill, Beechey Lake Area, District of Mackenzie, Northwest Territories

Abstract

<p> A gabbroic intrusion within the Goulburn group of sediments near the west margin of Bathurst trench was studied and mapped using a TV-1 scintillometer. Petrographic examination of the sill was carried out and geochemical whole rock and trace element data were obtained using X.R.F. methods. </p> <p> The 1308 Lake sill was injected conformably between the Western River (argillite/greywacke) and Burnside River (pink quartzite) units of the Goulburn group of sediments. The sill subsequently underwent minor fractional crystallization and differentiation. Generally the sill exhibits poor phase layering, but can be divided into six basic units. </p> 1) Upper Chilled Margin Gabbro 2) Leuco-Micro-Syenite Lens 3) Diabasic Gabbro 4) Pyroxene Granophyre 5) Diabasic Gabbro 6) Basal Sheared Chilled Margin Gabbro These units are evident in this section and are distinguishable both modally and texturally. In most cases, variations in the chemistry and norms reflect the units mapped in the field. Comparisons have been drawn and theories incorporated from other gabbroic intrusions to help explain some features of the 1308 Lake sill. </p>