The importance of early crustal architecture for subsequent basin-forming, magmatic and fluid flow events. The Granites-Tanami Orogen example

Abstract

The Paleoproterozoic Granites-Tanami Orogen (GTO) consists of tightly folded, predominantly greenschist facies rocks. The orogen, a component of the North Australian Craton includes a ca. 1864 Ma succession of turbiditic and pelagic sedimentary rocks interbedded with volcanic rocks and abundant dolerite sills in a back-arc basin setting, which is intruded by collision-related ca. 1800 Ma granitic rocks. Integrated 4D interpretation of deep seismic profiles, gravity and magnetic field observations associated with available surface geology and igneous isotope geochemistry suggest that the GTO forms an imbricated crust developed on a partially inverted S-dipping, rifted Archean basement. The rifting took place in the Paleoproterozoic around 1864 Ma, and was followed by E–W orientated compressional deformation ca. 1850 Ma with the development of northerly trending isoclinal folds and associated faults. Orthogonal collisional tectonics followed at ca. 1800 Ma, which is associated with S-verging kilometre-scale, folds, faults, and orogenic lode-gold deposits in the region. Recognition of the preserved early rift architecture in the GTO has major implications for the subsequent evolution of the orogen. The early architecture has influenced all subsequent deposition, deformation, magmatic and fluid events, including spatial control of the ca. 1864 Ma rock succession to the location of intrusive bodies and fluid transfer during formation of ca. 1800 Ma orogenic gold mineralization.