Evolution of the Archaean continental crust: Insights from the experimental study of Archaean granitoids

Abstract

Experimental petrology is a valuable tool to test different models proposed to account for the origin of Archaean granitoids. However, a feasible petrogenetic model needs to be supported by studies from different disciplines. Therefore, the present article is a synthesis of experimental studies on the origin of Archaean granitoids (TTG and K-rich granites). Besides, a review of the published work about their origin is briefly discussed. Finally, the experimental synthesis and new results, along with the review presented allow us to propose a model for the evolution of the early continental crust. The petrogenetic evolution of the Archaean crust was catalysed by progressive decrease in geothermal gradients. The thermal structure of the early Archaean down-going plates was favourable for melting the oceanic crust at low depths (P < 10 kbar) in subducting slabs to produce TTG magmas, without interaction with the mantle during ascent. The progressive cooling of the earth produced an increase in the dip of the subducting slab, favouring partial melting of the basaltic rocks at higher depths (P < 10 kbar) and the interaction of TTG magmas with the overlying mantle wedge. Crustal evolution at the Archaean--Proterozoic boundary was dominated by the generation of different sort of voluminous K-granite batholiths, the origin of which is controversial. In this study, it is considered an origin of K-granites by interaction between hydrous sanukitoids magma and tonalitic crust.