| The radial Whistle Offset structure strikes northeast off the northeastern corner of the Sudbury Igneous Complex, intruding Archean gneisses, granites, gabbros, and Matachewan diabase dykes. The Whistle Offset contains Footwall Breccia, an in situ impact breccia with composition reflecting the Archean footwall rocks, and three "quartz dioritic" phases, which are generally granodioritic in composition.; The Leucocratic Quartz Diorite intruded the offset structure first, and represents the most primary composition of the impact melt sheet. Common disequilibrium textures such as stellate amphibole, granophyric intergrowths, and elongate fluorapatite with axial melt inclusions and irregular REE zoning reflect rapid crystallization induced by volatile loss through change of pressure associated with readjustment of the crater. A second pulse of Inclusion Quartz Diorite intruded, and through local irregular heating, pods of Quartz Diorite developed within this magma. Disequilibruim textures in these rocks indicate a second crater readjustment, inducing crystallization.; Chlorine-rich fluids hydrothermally remobilized Cu and PGE, precipitating these metals as veins in areas of low pressure, permeability and constricted flow, and creating hydrous alteration halos in the host rocks. |
