Formation of the Continental Crust Through Earth History

The continental crust is generally assumed to be created in island arcs, which mature towards a composition more akin to bulk continental crust. A major difference between the “juvenile” and “mature” arc stages concerns the voluminous amount of granitoid formed in mature arcs. An unsolved paradox in the idea that continental crust forms in subduction zones is that bulk estimates of island-arc crust compositions are basaltic while the bulk continental crust is andesitic. The voluminous occurrence of evolved rocks drives the average crustal arc composition towards andesitic. Accordingly,understanding the formation of evolved plutonic rocks should lead to further understanding of the continental crust formation. Similar the “low-Mg#” number of the continental crust conflicts with the high-Mg# of mantle derived melts.

The so-called Mg#-gap and the silica-enrichment of the continental crust are first order unsolved problems in earth science. Work is on the evolution and formation of the Kohistan-Ladakh arc, (NE Pakistan, NW India).