Mesoarchean Rift and Marginal Basins of the Pilbara Craton

Abstract

The c. 3220 Ma breakup of the Paleoarchean Pilbara Craton was followed by a 60-million-year period of northwest–southeast plate separation. Three continental microplates (East Pilbara, Karratha, and Kurrana Terranes) were separated by two expanding rift basins. Between the Karratha Terrane (KT) and the East Pilbara Terrane (EPT), the Regal Basin evolved from a spreading centre to form a belt of MORB-like basaltic crust. The early Mesoarchean Mosquito Creek Basin formed with separation of the EPT and Kurrana Terrane (KUT) but is now almost entirely concealed beneath the late Mesoarchean Mosquito Creek Formation. Continental breakup of the Pilbara Craton marked the end of Paleoarchean vertical deformation and the beginning of Mesoarchean plate tectonic processes in the Pilbara. Paleoarchean melts derived from crustal recycling of much older crust were succeeded by Mesoarchean juvenile, mantle-derived melts. Passive margin successions such as the 3223–3165 Ma Soanesville Group and the 3220–3160 Ma Nickol River Formation were deposited along the margins of the continental microplates. Separation of the EPT and KT ended at c. 3160 Ma due to the collision of the KT with another plate converging from the northwest.