Evolution and tectonic setting of the Paleoproterozoic Granites-Tanami Orogen, Western Australia / Leon Bagas

2010

[Truncated abstract]...Precambrian terrains in Australia are located west of the Phanerozoic "Tasmanides" and consist of the West Australian Craton (WAC), newly defined Central Australian Craton (CAC), North Australian Craton (NAC), and South Australian Craton (SAC). The largely concealed CAC is situated north of the Paterson Orogen and south of the newly defined Willowra Lineament and Willowra Gravity Ridge (or tectonic zone). The lineament is located along the southern margin of the Willowra Gravity Ridge and the northern margin of a magnetic low that extends southeast from the Western Australian coast across the northern part of the Arunta Orogen to Queensland. Gold mineralization appears to be generally concentrated around, or within 50 km of, the Willowra Lineament, which bisects the "Aileron Province" of the Arunta Orogen and has undergone significant reactivation during Paleozoic deformation. Elsewhere, the Proterozoic Paterson Orogen separates the WAC from the CAC and the Arunta Orogen from the SAC, the ca. 1300-1100 Ma Albany-Fraser Orogen separates the WAC and SAC, and the ca. 1080 Ma Pinjarra Orogen forms the western margin of the WAC. Proterozoic rocks in Australia host considerable mineral resources, some of which are amongst the largest in the world (e.g. Olympic Dam Fe-Cu-Au-U, McArthur River- Mount Isa Zn-Pb-Ag, and Telfer Au). These include Paleoproterozoic gold deposits that are not well documented, mainly because the tectonic setting for these largely obscured terranes remains poorly understood, such as the Granites-Tanami Orogen. Furthermore, multiply deformed metamorphosed rocks that have undergone a complex geological history host the vast majority of these deposits. A consequence of this is that the early tectonic evolution of Paleoproterozoic host rocks potentially predates the formation of gold deposits by 10s of million years and does not

necessarily relate to the events leading to mineralization. An inadequate understanding of the

tectonic evolution of Paleoproterozoic terranes has thus significant implications on developing conceptual models for ore systems and restricts the efficiency of exploration for mineral deposits. The study reports the results of remapping the Granites-Tanami Orogen in Western Australia and structural, geochemical, and isotopic studies of its constituent supracrustal and intrusive rocks. Structural, geochemical, and isotopic studies on gold deposits in the region form the basis for an interpretation of the genesis of the gold deposits within the overall evolution of the terrane. The Granites-Tanami Orogen includes Mesoarchean to Paleoproterozoic rocks older than late Paleoproterozoic cover sequences. The orogen comprises isolated inliers of Archean leucocratic orthogneiss and schistose metasedimentary rocks. Paleoproterozoic tightly folded greenschist-facies sedimentary, volcanic and subvolcanic rocks included in the Tanami Group of the Tanami Basin, and ca. 1795 Ma granitic rocks. The Tanami Group in Western Australia consists of the ca. 1864 Ma Stubbins Formation and the conformably overlying Killi Killi Formation. Deposition in the basin ceased during compressional deformation around 1850 Ma.

Thesis (Ph.D.)--University of Western Australia, 2010

http://repository.uwa.edu.au:80/R/-?func=dbin-jump-full&object_id=13093&silo_library=GEN01