Cooling rates and crystallization dynamics of shallow level pegmatite-aplite dikes, San Diego County, California

Abstract

The George Ashley Block (GAB) is a rockslide block located in the Pala pegmatite district of Southern California. It is layered, asymmetric, pocket containing, and peraluminous. The GAB consists of quartz (42 vol%), Na-rich plagioclase (27%), potassium feldspar (24%), muscovite (7%), Mn-rich garnet (2%), biotite (1%), and a trace of tourmaline and gahnite. It contains only small amounts of the incompatible elements that characterize differentiated pegmatite bodies. P 2 O 5 , MnO, and F are present in amounts of <1 wt% each; B, Be, Ce, Li, Nb, Nd, and Th are <100 ppm each.