Fluorite particles inducing butterfly aggregates of incipient microperthite in alkali feldspar from a syenite, the Patagonian Andes, southern Chile

摘要: Alkali feldspar grains found in a syenite from the Patagonian Andes, southern Chile, have bulk compositions of about Or 4 0 Ab 5 9 An . , and consist two parts when viewed under an optical microscope: clear part anda turbid part. Grain interiors are mixtures parts, whereas rims mainly turbid. The microscopically part, which is almost free micropores, cryptoperthitic, microperthitic. microperthite patch type, turbidity due to abundant micropores that polygonal generally less than 1 μm diameter. has been formed by coarsening primary cryptoperthite hydrothermal reactions. incipient stage formation recorded as segregation Or-rich with diagonal elongation Ab-rich into aggregates "butterfly" shape. Each butterfly aggregate 10 length. centers usually occupied round fluorite particles diameter, were identified EPMA TEM analyses. may at fluid stage. started along interfaces changed further coarsening. timing process important relation evolution microtextures, behavior fluorine alkaline igneous rocks.