Mesoarchean Basin Evolution Inland of Magmatic Arcs

Abstract

Tectonic, magmatic, and depositional processes from the c. 3070 Ma Prinsep Orogeny to the end of the North Pilbara Orogeny at c. 2919 Ma were directly related to ongoing northwest–southeast compression of the Pilbara Craton. This compression is interpreted to have resulted from c. 3160 Ma collision and subsequent interaction with an exotic plate northwest of the craton. Following closure of the Regal Basin at c. 3070 Ma (Chap. 7 ), geochronological evidence indicates the development of a subduction zone on the northwest margin of the Pilbara Craton resulting in a series of southeast-migrating continental magmatic arcs (Chap. 8 ). Deposition to the southeast of these arcs led to the evolution of the De Grey Supergroup, comprising the 3066–3015 Ma sedimentary Gorge Creek Group in a retro-arc basin related to the Orpheus arc; the 3015–2931 Ma, mainly sedimentary Croydon Group, overlying the Gorge Creek Group and related to the Orpheus, Maitland River, and Sisters arcs; the 3000–2990 Ma volcano-sedimentary Whim Creek Group on the southeast margin of the Maitland River arc; and the 2955–2945 Ma Bookingarra Group related partly to the Sisters arc and associated rifting. The Gorge Creek and Croydon Groups were deposited in large retro-arc basins that extended across most of the presently exposed Northern Pilbara Craton. Prior to Neoarchean breakup of the Pilbara Craton at c. 2710 Ma (Chap. 12 ), the northeast–southwest extents of these basins were probably between 500 and 1000 km. Current exposures, and allowances for deformation, indicate northwest–southeast basin widths of at least 200 km.