Syntectonic vein formation in the Rundle Thrust sheet near Canmore, Alberta

Abstract

Syntectonic veins provide a record of both pore/connate and meteoric fluids present during emplacement of the Rundle Thrust sheet near Canmore, Alberta. Comparison of §180 values of host rocks (-11.39 to -3.34%0 VPDB) and veins reveals that veins are depleted to varying degrees with respect to corresponding host rocks. Moderately 18OdepIeted veins (S18O values > -13%o VPDB), that are mineralogically-controlled by host rocks, are interpreted as having formed in a rock-dominated closed system with a connate fluid source. Conversely, a water-dominated open system with a meteoric fluid source is characterized by calcite veins (regardless of host rock mineralogy) with S18O values < -13%o VPDB. Quadrupole mass spectrometry lends support to this interpretation, with fluid inclusion contents in closed system veins containing varying amounts of CO2, CH4 and H2S (in addition to water), as influenced by the respective host rock. Regardless of the host rock, open system vein fluid inclusions are water-rich.