Origin of gold bearing hematitc breccias at the Lake George Antimony Mine, Western New Brunswick

Abstract

The Lake George Antimony deposit is located in southwestern New Brunswick. The main Au-Sb mineralization is hosted in stock-work veining emplaced into the Kingsclear Group metasedimentary rocks. These veins are believed to be spatially and temporally related to a granodiorite intrusion. To the east, northeast and southeast lies an hematite breccia and alteration zone. Previous studies indicate that this zone is coeval with but not related to, the Au-Sb mineralization event. This study proposes that this zone was formed from Carboniferous faulting, at epithermal to surface depths. The ---.. breccias are divided into three groups, hematite, carbonate-hematite and carbonate-quartz types. Hematite breccias are defined by a dominantly hematite matrix with angular to chemically corroded clasts. Carbonate-hematite type breccias consisting of a wide variety of textures from jigsaw patterns to rotated, rounded, clast supported and collapse. Carbonate-quartz type breccias have a varying abundances of carbonate and quartz, with highly chemically altered clasts. All three breccias are produced from localized faulting, indicating tectonic comminution, fluid assisted, and corrosive wear mechanisms. Carbonate-hematite breccias, also have wear abrasion, collapse, and impact mechanisms, which are produced by stronger and more continuous faulting. Gold, Sb, and other metals are enriched in carbonate-hematite and carbonate-quartz breccia types. This enrichment is likely related to mobilized Sb-Au from the Sb-Au-quartz carbonate veins at the Lake George deposit. Gold appears to be correlated with arsenopyrite or pyrite abundance and deposited on surfaces of iron oxides, iron hydoxides, and Mn oxides.These minerals may have been produced from near surface meteoric water circulation reacted with weathered product.