Geochronological constraints on the formation, setting and evolution of the Olympic Dam IOCG deposit and the Olympic IOCG Province, South Australia

AR Cherry
2019
The Olympic Dam Cu-U-Au-Ag deposit in the Olympic Cu-Au Province (Gawler Craton, South Australia) is unique in the iron oxide-copper-gold (IOCG) deposit class for its polymetallic tenor and size; it is one of the largest economic accumulations of metals in the world. The deposit is hosted within the Olympic Dam Breccia Complex (ODBC) within the Roxby Downs Granite. The breccia complex also contains clasts and domains of other lithologies, including surficial lithologies (bedded clastic facies
more » ... ed clastic facies and felsic volcanic rocks). The Olympic Dam deposit, along with the other deposits and prospects in the Olympic Province, was originally suggested to have developed entirely within a geologically brief magmatic-hydrothermal event at ca. 1590 Ma. However, recent work has suggested Olympic Dam has been episodically modified after 1590 Ma. This thesis aims to clarify aspects of the architecture and timing of events at Olympic Dam as well as the nearby Olympic Province primarily through application of geochronology as well as mineral chemistry and textural analyses. This aim is addressed through: (1) determining the timing and relationships of the surficial lithologies in the ODBC with the Roxby Downs Granite, (2) demonstrating that Olympic Dam was originally overlain by the U-prospective Pandurra Formation and (3) exploring the complex history of hydrothermal mineralisation in the nearby Acropolis prospect. New high-precision CA-TIMS geochronology has constrained the Roxby Downs Granite (1593.87 ± 0.21 Ma) to be slightly younger than felsic volcanic clasts (Gawler Range Volcanics -1594.73 ± 0.30 Ma) in the ODBC. The absence of older country rock fragments in the ODBC and shallow emplacement textures in the Roxby Downs Granite suggest the granite intruded already-present Gawler Range Volcanics. The age of tuffaceous mudstone intervals (1590.97 ± 0.58 Ma) in the bedded clastic facies indicates a basin was present at Olympic Dam and the bedded clastic facies were being deposited ca. 3 myr after emplacement of the Roxby Downs Grani [...]
doi:10.25959/100.00031443 fatcat:5fplisfjqrehdleqxhqa44w7i4