14 – 16 July 2020 | Perth, Western Australia

Preliminary descriptions

Pre-conference field trips

Pilbara Craton: evolving Archean tectonic styles

(5 – 12 July 2020)

(Guides: Martin Van Kranendonk, Hugh Smithies) A week-long trip across the beautifully-exposed Pilbara Craton, investigating two contrasting litho-stratigraphic terranes. This trip will commence with an exploration of the 3.5–3.2 Ga East Pilbara Terrane, with its classic granite dome-and-greenstone keel geometry indicative of “vertical tectonics”, and sites with traces of early life. It will then move to the western part of the craton, where we will investigate successions and structures that document a drastically different tectonic style, including an arc complex, and crustal-scale shear zones indicative of terrane accretion.

Paleoproterozoic reworking of an Archean craton, a transect through the southern Gawler Craton

(5 – 12 July 2020)

(Guides: Rian Dutch, Stacey Curtis) The Gawler Craton, in southern Australia, consists of an Archean granite-greenstone core surrounded by, and built upon, a series of late Archean to Paleoproterozoic volcano-sedimentary basins and intrusive suites. The region has undergone at least two major phases of deformation during the latest Archean to earliest Paleoproterozoic and now records a complex polymetamorphic history of crustal reworking. This history of pervasive Proterozoic reworking makes the Gawler Craton unique among the Archean Cratons of Australia. This field trip will begin in the relatively undeformed Archean core of the craton and will traverse towards the southern coastline of the Eyre Peninsula, where there are fantastic exposures of polydeformed granulite facies sediments of the Sleaford Complex and exposures of the crustal scale Kalinjala Shear Zone. This trip will focus on aspects of the growth of the Australian continent during the late Archean to Paleoproterozoic and the challenges of unravelling tectonic histories in multiply deformed terranes.

Post-conference field trips

The Archean-Proterozoic boundary — out with the old, in with the new; a traverse through the Mount Bruce Supergroup

(18 – 25 July 2020)

(Guides: David Martin, Heather Howard, Simon Johnson) The Archean-Proterozoic boundary has always been regarded as reflecting a fundamental change in Earth surface processes and environments. However, the currently accepted chronometric definition is now being questioned. This trip will explore these processes and products as documented in the exceptional Neoarchean to earliest Paleoproterozoic exposures of the Fortescue, Hamersley and Turee Creek Groups in Western Australia, and also evaluate candidates for a chronostratigraphic GSSP related to the Great Oxidation Event.

A traverse across the Yilgarn Craton in Western Australia – from the Jack Hills to the Yamarna Terrane

(18 – 25 July 2020)

(Guides: Tony Kemp, Ivan Zibra) The one-week excursion will feature an east-west traverse across the northern Yilgarn Craton, combining geophysical, structural, geochemical, geochronological and isotopic data to outline the tectono-magmatic and metamorphic evolution of this large remnant of Eo- to Neoarchean continental crust. The excursion will start in the western corner of the craton, in the Narryer Terrane. Rocks of the Mt Narryer and Jack Hills metasedimentary belts, which both contain Hadean (> 4000 Ma) detrital zircon crystals, will be examined, along with flanking ancient quartzofeldspathic gneisses that have protolith ages from 3730 Ma to 2750 Ma. In the Youanmi and Eastern Goldfields Terranes, the excursion will mainly focus on the structures developed during the c. 2730–2660 Ma Yilgarn Orogeny, with the aim of discussing the relationship between shearing, magmatism and crustal evolution from the crustal scale down to the thin section scale. Main highlights include the Moyagee Fault near Mount Magnet, which represent the oldest-known seismogenic fault on Earth, and the high-pressure granulite-facies greenstones exposed along a major terrane boundary (the Ida Fault).

Mineral Deposits in the Yilgarn Craton

(18 – 25 July 2020)

(Guides: Steffen Hagemann, Nico Thébaud) The Yilgarn Craton has long been recognised as having world-class Au endowment. Yet the endowment varies dramatically between terranes within the craton and between constituent geological domains, showing a tendency to cluster in districts or ‘camps’. This one-week excursion will visit classic geological localities and gold deposits from the Yilgarn Craton showcasing the deposit style diversity and focusing on Au mineral system formation from regional-scale down to deposit-scale formation.