Microgranitoid enclaves in some I- and S-type granites from southern China

Abstract

The three I-type plutons of Guantian (GT), Guidong (GD), Shangbao (SB) and the two S-type plutons of Xucun (XC) and Xiuning (XN) as well as their microgranitoid enclaves in southern China have been studied. Restite in the Motianling (MT) metasomatic granite in this area is described in this paper as well. Microgranitoid enclaves in the I-type granitoids may be divided into autoliths and schlierens which have marked differences both in petrography and geochemistry. In the S-type granitoids, schlierens are the major microgranitoid enclaves, but autoliths are rare. The metasomatic granite contains only restite without other enclaves. The microgranitoid enclaves and their host rocks have close eNd (T) values and the same minerals within them are similar in composition. The microgranitoid enclaves, in general, don’t represent the products of mixing of the syn-plutonic foreign mafic magma and the host acidic magma. They are the records of the evolution of intermediate-acidic magma itself. The formation of autoliths is related to the interdiffusion of different constituents in magma. Schlierens are the products of immiscible fractionation of the magma.