Abstract
Imperfect flow separation and remixing of crystals and melt produced chemical, mineral and textural variability on the scale of several cm to m in coarse-grained granitic rocks of this pluton. This is believed to have developed during emplacement because the resultant layering conforms to the geometry of the pluton and is better developed towards the margins. Crystallization regimes superimposed on flow separation and remixing produced more complex variations than expected from granitic cumulate processes alone. The process is chemically comparable to restite mixing, but it is difficult to show that many minerals involved in the flow are restites. Local compositional inhomogeneities also formed by deformation and disaggregation of enclaves. Marginal granites, distinguished from the central granites by pink feldspar + biotite +- muscovite rather than white feldspar + amphibole + biotite, are more evolved but overlap the compositional range of the central granites. Mineralogical and textural similarity and a gradational contact between the two granites indicate that they are related and that the pluton's subtle reverse zoning was produced by a continuous in situ process. Flow separation and remixing, operating more efficiently and on a large scale, may have produced the more evolved composition of the marginal granites, but proximity to the contact is more important than composition in determining mineralogy. There is slight evidence for contamination of the marginal granites by the wall rocks; compared to central granites they have small LREE depletions and HREE enrichments, which more closely reflect the LREE depletion and HREE enrichment of the wall rocks. A later and distinct evolution is indicated for the fine- grained biotite granites.