WebDacite (/ ˈ d eɪ s aɪ t /) is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides.It has a fine-grained to porphyritic texture and is intermediate in composition between … http://earthsci.org/mineral/mindep/phor_dep/por_dep.html
Mixing of magmas from multiple sources in the petrogenesis of …
WebFigure 20.6 A model for the formation of a porphyry deposit around an upper-crustal porphyritic stock and associated vein deposits. [SE] Banded Iron Formation . Most of the world’s major iron deposits are of the banded … Webbasalt, extrusive igneous (volcanic) rock that is low in silica content, dark in colour, and comparatively rich in iron and magnesium. Some basalts are quite glassy (tachylytes), and many are very fine-grained and compact. It is more usual, however, for them to exhibit porphyritic structure, with larger crystals (phenocrysts) of olivine, augite, or feldspar in a … open ended maths questions time
Phenocryst - Wikipedia
WebAndesite is volcanic rock named after the Andes Mountains. Intermediate in silica content, it is usually gray in color and may be fine-grained or porphyritic. Andesite is the volcanic equivalent of diorite.It consists of the plagioclase feldspar minerals andesine and oligoclase, together with one or more dark, ferromagnesian minerals such as pyroxene and biotite. WebBasalt is the most common rock on Earth’s surface. Specimens are black in color and weather to dark green or brown. Basalt is rich in iron and magnesium and is mainly composed of olivine, pyroxene, and plagioclase. Most specimens are compact, fine-grained, and glassy. They can also be porphyritic, with phenocrysts of olivine, augite, or ... WebPorphyry ( / ˈpɔːrfəri / POR-fə-ree) is the name given to decorative granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate … iowa second district