Aplite

Aplite

APLITE (from the Greek word "haploos" (simple) * EN: aplite, haplite; DE: Aplit; FR: aplite; ES: aplita; RU: аплит) is the leucocratic veinous magmatic rock, which is deficient in mica and other coloured minerals.

They distinguish granitic, dioritic, syenitic, and other aplites. The most common granitic aplites are formed with quartz, alkaline feldspars, and acidic plagioclase. There may be found in non-significant quantities the biotite, muscovite, sometimes alkaline pyroxenes. Accessory minerals of the granitic aplites are the garnet, tourmaline, magnetite, allanite, apatite, zircon, and others. The structure of the aplites is fine-grained. Mineral grains within the aplite do not have the regular outlines. The colour is light gray, light pink, yellowish. The granitic aplites, which are containing alkaline feldspar and plagioclase, belong to the calcareous-alkaline ones. The plagioaplites contain exclusively acidic plagioclase and quartz. They refer to the alkaline ones the aplites, which are consisting of quartz, alkaline feldspar, and alkaline amphiboles and pyroxenes. The average chemical composition (% of mass) of the granitic aplites is: SiO2 is 75.00, TiO2 is 0.30, Al2O3 is 13.14, Fe2O3 is 0.58, FeO is 0.40, MnO is 0.07, MgO is 0.30, CaO is 1.13, Na2O is 3.54, K2O is 4.80, H2O is 0.71, P2O5 is 0.03. Aplite forms veinous bodies within the massifs of granites, syenites, diorites, with which it is genetically associated.

Aplites are one of the most common veinous magmatic rocks.

Sometimes granitic aplites form the outer zones of bodies of the granitic pegmatites. It is believed, that granitic aplites have formed themselves during the crystallization of the residual granitic magmas. Unlike pegmatites, which also are forming themselves from the residual, rich in volatiles granitic magma, aplites were forming themselves from the magma, which has lost a part of the volatile components.

It is possible, that granitic aplites are the meta-magmatic rocks, which have emerged during the interaction of the granitic magma with the fluids with increased acidity.

The density of aplites is 2500-2700 grams per cubic metre, water absorption is 0.1-1.5%, compressive strength is 100-350 megapascals. Aplites are used within the glass industry, and also as the raw material for the crushed gravel; granitic aplites are the source for the obtainment of feldspar. The largest deposit of aplites is within the USA (Piney River, Virginia state). The production of aplites during the 70s was: within Japan 0.3 million tonnes per year, within the USA (Kentucky and Virginia) 0.2 million tonnes.