Fore-arc evolution in the Tasman Geosyncline: The origin of the southeast Australian continental crust
Titel:
Fore-arc evolution in the Tasman Geosyncline: The origin of the southeast Australian continental crust
Auteur:
Crook, Keith A. W.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 27 (1980) nr. 1-2 pagina's 215-232
Jaar:
1980-09
Inhoud:
A new general model describing the extended evolution of fore-arc terrains is used to analyse the evolution of the southern Tasman Geosyncline and the concomitant growth and kratonisation of the continental crust of southeast Australia during the Palaeozoic. The southern Tasman Geosyncline comprises ten arc terrains (here defined), most of which are east-facing, and several features formed by crustal extension. Each arc terrain consists of several strato-tectonic units: a volcanic arc, subduction complex and fore-arc sequence formed during subduction; and an overlying post-arc sequence which post-dates subduction and is composed of flysch, neritic sediments or subaerial volcanics. When these materials attained a thickness of c. 20 km their internal heat-balance caused partial melting of the subduction complex and the hydrated oceanic lithosphere trapped beneath it, to yield S- and I-type granitic magma. The magma rose, inducing pervasive deformation of each arc terrain and emplacement of granitoid plutons at high levels in the evolving crust. Transitional basins then developed in many terrains on top of their volcanic arcs or the thinner parts of the buried accretionary prisms. After deformation of the transitional sequences, platform cover accumulated, marking the completion of kratonisation. Analysis of each arc terrain in terms of the above units leads to a predicted 'stratigraphy' for the continental crust of southeast Australia. The crust is complexly layered, with lateral discontinuities reflecting the boundaries of arc terrains which were successively accreted, principally back-arc to fore-arc, during crustal development.
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