Geochronological constraints on the geological history and gold mineralization in the Tick Hill region, Mt Isa Inlier

Abstract

The Tick Hill Gold deposit in the southern Mary Kathleen Domain of the Mount Isa Inlier is hosted in a strongly deformed, Paleoproterozoic volcano-sedimentary sequence intruded by pre- and syn-tectonic granites. Igneous rocks and quartzite from the Tick Hill region were dated to constrain the age of the lithologies, deformation events, and gold mineralization. LA-ICP-MS, U-Pb zircon ages for these rocks, together with field relationships, confirm the presence of: (1) 1855–1850 granite belonging to the Kalkadoon Supersuite at ∼10 km and ∼4 km west of Tick Hill, respectively; (2) 1790–1770 Ma early syn-tectonic granite along the contact zone between mapped Argylla Formation and the Kalkadoon Supersuite west of Tick Hill, and later syn-tectonic leucogranite within the immediate vicinity of Tick Hill, including the host rocks to gold mineralization; and (3) late-tectonic, 1525–1520 Ma pegmatite and associated hydrothermal activity in the Tick Hill area that resulted in the mobilization of gold. Quartzite ridges in the hanging wall and footwall of the orebody provided contrasting results, with the youngest zircon population groupings at ca. 1781 Ma and 1841 Ma, respectively. Textural evidence suggests that much of the hanging wall quartzite is probably metasomatic in origin, and the ca. 1781 Ma age group, which was derived from mostly prismatic, euhedral zircon, reflects the age of a heavily silicified quartzofeldspathic gneiss. Thus, the age of the youngest detrital zircon group, ca. 1841 Ma, constrains the maximum age of the sequence at Tick Hill. Field evidence suggests that the 1790–1770 Ma granites intruded into the sedimentary sequence that hosts gold mineralization, indicating that the supracrustal rocks are at least ca. 1790 Ma in age and should not be grouped as Corella Formation. These sediments were affected by intense shearing and upright folding between 1790 Ma and 1770 Ma and younger normal faulting and metasomatism around 1525–1520 Ma. Early gold was introduced during D1 peak metamorphism at 1790–1770 Ma while the later mineralizing events involved the new introduction of gold or the remobilization of pre-existing older gold around 1525–1520 Ma. One of the major outcomes of this study is that the old schist zones in the south Mary Kathleen Domain are prospective for gold mineralization.