rhyodacite


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rhyodacite

[rī′äd·ə‚sīt]
(petrology)
A group of extrusive porphyritic igneous rocks containing quartz, plagioclase, and biotite phenocrysts in a fine-grained to glassy groundmass composed of alkali feldspar and silica minerals. Also known as dellenite; quartz lattice.
References in periodicals archive ?
Past exploration at Maripa includes 134 core holes, for a total of 9,000 metres, which partially defined five (5) broad gold zones, namely Changement, Filon Dron, Maripa Sud-Est, Rhyodacite and Filon Scieur.
The material studied is an extrusive porphyritic igneous rock called rhyodacite tuff.
The lithology around CP is composed of gneiss (quartz-feldspars), shale (quartz-mica), marble, amphibolite, and quartzite from Permic to Jurassic [24] and metamorphic, granitic, and granodiorite rocks which are intruded by batholitic rocks [16], together with dacite and andesite from Miocene and rhyodacite from Quaternary [25].
Rainbow Falls, one of California's most photographed waterfalls, plunges 101 feet over a rhyodacite lip.
The geochemical studies show that the Deosai volcanics are dacite to rhyodacite in composition while the meta-volcanics of Burji-La Formation show basalt to basaltic-andesite in composition.
The volcanic rocks in the Tarom area vary from rhyodacite and dacite to basalt.
The enargite-bearing rhyodacite porphyry hosting the mineralisation, shown in figures 1 and 2, has yielded the following results:
Melanic soils develop from a variety of parent materials (Van der Merwe 2000), including arkosic sandstone, siltstone, mudstone, shale, diamictite, dolerite, basalt, notite, amphibolite, granite, gneiss, rhyodacite, and carbonates.
It is characterized as a Plinian eruption, of explosive power and with a widely dispersed rhyodacite ash (Hanson, 1965) composed of glass, plagioclase, hornblende, hypersthene, and magnetite (Lerbekmo and Campbell, 1969).
Field examination in January by Leadville's team of geologists indicates there is significant widespread gold mineralization occurring together with silica flooding and silica veinlet stockworks hosted by a flow-banded rhyodacite unit.
The mine unit traditionally called "trachyte" is rhyodacite, and that called "andesite" is, in part, basaltic andesite, both of which are of calc-alkaline affinity.
It consists of a potassic rhyodacite intruded into Triassic sediments.