Geology the of Old Cabin Creek Massif, Selwyn Basin, Yukon Territory

Abstract

<p>The Old Cabin Creek Massif is under lain by Hadrynian to Silurian basin facies strata intruded and altered by Cretaceous plutonic rocks. Exposures are typical of Selwyn Basin and Misry Creek Embayment lithologies.</p> <p>A 500 m package of upper Cambrian to lowermost Silurian submarine volcanics occur in the stratigraphy. Such volcanics are not uncommon in the Selwyn Basin, but thicknesses such as those exposed at the Old Cabin Creek Massif are unusual. The volcanic rocks are typically hyaloclastic breccias with lesser amounts of massive flows, pillowed flows, lapillituffs, epiclastics, sills and dikes. These rocks show evidence of intense low-temperature hydrothermal alteration. Olivine and pyroxene are pseudomorphed by hydrated phyllosilicates, guartz and carbonate. Unaltered amphiboles (hornblende?) were seen in one sample.</p> <p>Chemical analysis and petrologic examination suggest they are tholeiitic basalts.</p> <p>Correlation of upper Proterozoic and lower Paleozoic strata is enhanced by the use of trace fossils. The "Grit Unit" is divided into a Hadrynian "Lower" member and a lower Cambrian "Upper" member. Oldhamia is recognized only in Cambrian strata.</p> <p>A late Mesozoic tectonic event emplaced northwest-trending overturned and upright isoclinal folds, open folds and thrust faults in all stratigraphy. In addition a klippe derived from the west repeats Cambro-Ordovician litologies on "Wenchless Ridge".</p> <p>Most of the study area has been hornfelsed and block faulted by the instusion of more than one Cretaceous granodiorite pluton.</p> <p>Gold values up to 9650 ppb were found in thin arsenopyrite veins at the lower contact of the volcanics. They are thought to have been derived from the intrusive and not the volcanics. The potential for other mineralization to be hosted at the Old Cabin Creek Massif is high.</p>