Page 158 - Handbook of Gold Exploration and Evaluation

136 Handbook of gold exploration and evaluation

3.2 Plate tectonic rock cycle (Derived from Fichter, 1999).

diversity of the rocks and increasing the volume of felsic igneous rocks. The
composition of the rocks thus gets progressively lower on the Bowen Reaction
Series scale with each repeated fractionating of material by the parent Earth
processes. Indeed, although no record remains of the original rocks of the
Earth's crust the parent mafic in the Archaean must have generated an oceanic
lithosphere quite different from the parent mafic magma today. Similar changes
occur in the chemistry of the sedimentary processes each time the sedimentary
rocks are metamorphosed to the metamorphic stage, the result being an igneous
rock lower on the reaction series.
Note that most of the evidence for the above interpretation is based upon the
geological history of the Cainozoic Era and more particularly upon the erosion

3.3 Multiple tectonic rock cycles.