Quartz oxygen isotopes from Tick Hill area in Mount Isa Inlier: indication of a regional fluid overprint

Abstract

At the Tick Hill gold deposit, d18Oquartz data for the mineralised lithologies and surrounding rocks are similar and fall within a narrow range of 10.5–13.7‰ V-SMOW. The highly mineralised quartzofeldspathic mylonite has quartz d18O (d18Oquartz) values of 11.3–13.6‰, which are similar to values for the surrounding rocks both locally and regionally, i.e. d18Oquartz by itself does not provide a useful exploration tool. The d18Oquartz values from the Tick Hill area most likely reflect the late Isan hydrothermal overprint at 1525–1520Ma. The origin of the altering fluids is unclear, as the d18Oquartz values overlap with reported d18O values calculated for both metamorphic and igneous fluids. When combining the d18Oquartz results with d18Ocalcite results available from the literature, a temperature of 350–550 oC was calculated, which is consistent with observed alteration assemblages associated with gold mineralisation.