Growth and differentiation of the continental crust

Declining radiogenic heat production since the Archaean has resulted in a secular evolution from a régime of numerous fast-moving small thin torsionally weak plates to the present régime of larger thicker torsionally stronger plates moving at an average rate of less than one-sixth of the Archaean rate; this has been accompanied by episodic changes in geological effects. By 2500 Ma B.P., about 85% of the present crustal mass had grown by the addition and amalgamation of mafic and calc-alkaline rocks in oceanic arcs at an average rate of 11.17 Pg/a. During the early Proterozoic, the first large cratons were stabilized and, locally, thickened and differentiated; the Proterozoic was an era of little continental growth, falling average sea level, and intracontinental deformation. By 700 Ma B.P . cratons had become much more stable, marginal accretionary terrians had begun to develop with an average Phanerozoic growth rate of 1.64 Pg/a, and blueschists and ophiolites sensu stricto witness the advent of the extant plate tectonic régime.