Monazite chemistry as an exploration tool for Cloncurry-style iron oxide–copper–gold deposits

Geochemical exploration criteria for relatively light rare earth element (LREE)-enriched iron oxide–copper–gold (IOCG) deposits have been tested and are applicable across multiple Proterozoic terranes in eastern Australia. The criteria were established using monazite from E1 (Cloncurry District, Queensland) and compared to existing data from Prominent Hill and Carrapateena (Gawler Craton, South Australia) and are effective in rare earth element (REE)-rich deposits. The criteria use La, Ce and Nd chemistry in combination with Th and Y, where La + Ce > 65 wt%, Nd < 12.5 wt%, and Y and Th are both <1 wt%. However, the criteria are not as effective in REE-poor deposits such as Osborne and SWAN (Cloncurry District). For these deposits, other trends in the monazite REEs, such as changing Y and Dy contents, are better to use, which can discriminate between mineralization-associated hydrothermal monazite that formed at low temperatures (low Y and Dy) from metamorphic monazite that formed at high temperatures and are not associated with mineralization (high Y and Dy). In metamorphosed terranes like the Cloncurry District, where metamorphism is well constrained, chemical and temperature information using monazite chemistry can give information on the formation conditions of monazite, potentially hinting at a nearby IOCG system.