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 ?
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:
5 kilometer-long mineralized corridor defined by a coincident gold soil anomaly and magnetic low located adjacent to a large intrusive center and associated with a series of rhyodacite porphyry sills and dikes.
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.
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.
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).
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.
prospect, hole KW06-01 was drilled vertically to 880 feet and encountered sheared and veined intermediate volcaniclastic andesite country rock and interbedded felsic rhyolite to rhyodacite units.
Geological formation around this epicenter includes continental clastic rocks, dacite, rhyolite, rhyodacite, migmatite and gneiss.