High-Mg andesites from the North China craton - melts of slab or delaminated lower continental crust? The eastern block of the North China craton breaks the rule that "cratons are forever". Whereas the North China craton formed in the Archean and remained an island of stability through the Paleozoic (as expected of cratons), a fundamental change in its structure occurred during the Mesozoic, when the crust was intruded by volumninous melts. The big question is - what caused the transformation of this stable craton into a tectonically and magmatically active region and exactly when did this occur? The key may lie in understanding the origin of some very interesting lavas that erupted in the Jurassic. These high Mg andesites have the chemical characteristics of melts from subducted slabs, yet it remains unknown whether subduction occurred in this region during the Mesozoic. In order to unravel the origin of these unique rocks, the project will entail detailed petrographic, electron microprobe and laser-ablation ICP-MS characterization of the lavas, their phenocrysts and melt inclusions trapped within the phenocrysts.

Supervisors: Roberta Rudnick, Bill McDonough and Philip Piccoli