In geology, the term foliation refers to the property, possessed by some crystalline rocks, of dividing into plates or slabs, which is due to the cleavage structure of one of the constituents, as mica or hornblende. It may sometimes include slatey structure or cleavage, though the latter is usually independent of any mineral constituent, and transverse to the bedding, it having been produced by pressure. Research Foliation
Metamorphic rock is rock that has been altered by intense heat, pressure, or both. It may originally have been sedimentary or igneous rock, or even different metamorphic rock. The changes that take place during metamorphism can affect both the structure of the rock and its composition. Very often the rock is re-crystallized. Contact metamorphism is a localized form of metamorphism that is produced by the heat of an igneous intrusion. Limestone may then be altered into marble, and clay into a hard, tough rock (a hornfels). The zone affected in this way is called a metamorphic aureole. Hydrothermal metamorphism, or metasomatism, is produced by hot aqueous fluids emanating from igneous intrusions. Chinaclay is produced in this way from granite. In dynamic metamorphism, or cataclasis, rocks are broken down mechanically by shearing and crushing; mylonite, a fine-grained banded rock, is a typical product. Regional metamorphism takes place on a large scale. The rocks are subjected to heat, deformation, and the action of hot fluids
that may affect their chemical composition. In the lowest grades of regional metamorphism, slates and phyllites (the latter with better- developed crystals than slate) are formed. More intense regional metamorphism results in the development of schists, rocks with a characteristic wavy foliation. At the highest grades, gneisses are formed: coarsely crystalline rocks with alternate light and dark bands. The normal sequence, from lower to higher metamorphic grade, is known as prograde metamorphism. The process can be reversed if, for example, rocks of a high grade are subsequently maintained for a long time at a lower temperature than was reached during the first metamorphism. Alteration from a higher to a lower grade is termed retrograde metamorphism. Research Metamorphic Rock
In architecture foliation describes the enrichment of an opening by means of foils, arranged in trefoils, quatrefoils, etc. and also, one of the ornaments. Research Foliation
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Research Foliation
