| 释义 |
rhyodacite Geol.|raɪəˈdeɪsaɪt|
[f. rhyolite + dacite.]
A type of extrusive volcanic rock having a porphyritic texture and intermediate in composition between rhyolite and dacite.
1913A. N. Winchell in Jrnl. Geol. XXI. 214 The volcanic equivalent of granodiorite, which may be appropriately called rhyodacite, forms another intermediate group between the alkalcic and the alkaline rocks. 1932A. Johannsen Descriptive Petrogr. Igneous Rocks II. 356 Rhyodacites are the extrusive equivalents of granodiorites. They are rocks of porphyritic habit, usually white, yellowish, reddish, or grayish in colour, and showing phenocrysts of quartz, plagioclase, and some ferromagnesian constituent, in a microcrystalline, cryptocrystalline, or glassy ground⁓mass. 1970Macdonald & Abbott Volcanoes in Sea vii. 143/2 The rhyodacite of Mauna Kuwale, in the Waianae Valley on Oahu, appears to be an unusual, extreme type derived by differentiation of the tholeiitic basalt magma in the same way that trachyte is derived from alkalic basalt. 1977A. Hallam Planet Earth 164/1 Most provinces of rhyolitic volcanics contain substantial amounts of rhyodacite as well as true rhyolite. |