Source of the Lachlan fold belt flysch linked to convective removal of the lithospheric mantle and rapid exhumation of the Delamerian-Ross fold belt

Abstract

During the Cambrian-Ordovician the paleo-Pacific margin of Gondwana underwent a rapid transition from a site of convergent deformation (Delamerian-Ross orogeny) to one of sedimentation during which the thick turbiditic sequences of the adjacent basal Lachlan fold belt were deposited. Laser-probe 40Ar-39Ar data show that the synkinematic (523-486 Ma), mid-crustal I- and S-type granites and metamorphic country rocks of the Delamerian fold belt were rapidly cooled at 490-485 Ma, coincident with the intrusion of a suite of high-level, postkinematic A-type granites and gabbros (ca. 497-481 Ma). 40Ar-39Ar data on detrital muscovites from the basal sections of the Lachlan fold belt provide informat..