A temporal framework for the Carrapateena Iron Oxide Copper-Gold (IOCG) deposit, Eastern Gawler Craton, South Australia

Abstract

The Carrapateena Iron Oxide Copper-Gold (IOCG) deposit is located on the eastern margin of the Gawler Craton, approximately ∼475 km NE of Adelaide, South Australia. The deposit is hosted within a granite belonging to the Donington Suite and contains various polylithic breccias and intrusive volcanic units. Multiple stages of alteration/mineralisation are present throughout the deposit, which includes: (1) pre-mineralisation alteration; (2) hematite I; (3) Cu-Au mineralisation; (4) hematite II & REE mineralisation; (5) uranium mineralisation; (6) post-mineralisation alteration/veining. In order to establish a temporal framework, multi-mineral U–Pb geochronology was conducted on a variety of lithologies throughout the deposit and across multiple stages of alteration/mineralisation. Zircons from the host granite are predominantly discordant, with two concordant analyses from two samples producing 207Pb/206Pb ages of ca. 1880–1861 Ma, consistent with the emplacement of the Donington Suite (1860–1850 Ma). Apatite U–Pb geochronology performed on the granite-bearing samples produced ages of ca. 1775–1767 Ma, indicating the presence of a moderate temperature (≥350 °C) thermal event approximately 100 Ma after the crystallisation of the host rock. Zircon U–Pb geochronology conducted on a porphyritic volcanic unit and two polylithic breccia samples produce bi-modal age populations at ca. 1880–1860 Ma & ca. 1590 Ma. The ca. 1880–1860 Ma age reflects zircons inherited from the host granite, while the younger ca. 1590 Ma population represents the crystallisation age of the porphyritic volcanic unit and the maximum formation age of the polylithic breccias. U–Pb geochronology conducted on apatite, hematite and xenotime associated with various stages of mineralisation produce ages of ca. 1585 Ma, consistent with a major Fe-Cu-Au metallogenic event throughout the Gawler Craton. U–Pb geochronology performed on uraninite, apatite located within a late vein, and “vuggy” hematite records a second hydrothermal event from ca. 600–500 Ma, reflecting a period of minor deformation and deposit-wide fluid circulation.