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The Lilesville Granite
The Lilesville Granite, also referred to as the Lilesville Igneous intrusion, pluton, is a ring-shaped body of granitic rock that spans about in Anson, Richmond, and Montgomery Counties in southern North Carolina. Composition The Lilesville Granite is composed of Megacryst, megacrysts up to 4 cm of pink potassium-rich feldspar surrounded by gray plagioclase feldspar, clear quartz, and biotite. Small amounts of muscovite and magnetite are also present. The texture of the rock ranges from medium-grained (~4-5 mm) to large, coarse grains (~4 cm). History The pluton has been determined by Rb/Sr Radiometric dating, isotope dating to be 326 +/- 27 million years old, indicating emplacement during the Pennsylvanian-Permian. A contact aureole composed mainly of mica schist and mica gneiss surrounds the body of granite, and the granite is intruded by the Pee Dee gabbro, which grades outward into diorite. During the late Precambrian-early Cambrian, there was an accumulation of felsic v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
