Constrained 3D modeling of the Mesoproterozoic Benagerie Volcanics, Australia

Abstract

The Benagerie Volcanics form part of a hotspot track that affected large sections of eastern Australia during the Mesoproterozoic. Understanding the location and controls on eruption centres of the Benagerie Volcanics and coeval plutons is difficult because they do not outcrop and are known only from limited drillhole data. We have applied various combinations of forward and inversion modeling of magnetic and gravity to well-constrained (petrophysics and drillholes) areas to characterize the 3D geometry and extent of the volcanic province and its crustal architecture, thereby adding to a better understanding of the emplacement mechanisms involved. We interpret the SW limit of the Benagerie Shear Zone corridor to be a major terrane boundary separating relatively magnetic crust to the SW from crust with low magnetic susceptibility to the NE. 2D and 3D models show a pronounced thickening of felsic material coincident with the shear zone that may be interpreted as a plutonic root, thereby corroborating interpretations that this shear zone acted as a structural conduit for the ascent and emplacement of magma.