Trachyte


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Related to Trachyte: phonolite

trachyte

[′tra‚kīt]
(petrology)
The light-colored, aphanitic rock (the volcanic equivalent of syenite), composed largely of alkali feldspar with minor amounts of mafic minerals.

Trachyte

 

a cenotypal extrusive, usually porphyritic rock. Porphyritic phenocrysts and microlites embedded in volcanic glass are represented by sanidine; neutral and acid plagioclase, biotite, pyroxene, or amphibole are encountered in lesser amounts. Trachyte is the extrusive equivalent of syenite. It consists of up to 60 percent silica and up to 10 percent alkalies. The rock is rough to the touch. There are glassy trachytes, such as obsidians and pumices, and trachytic tuffs. Trachytes grade into liparites, andesites, and basalts. They are found in the Caucasus and, outside the USSR, in Italy and France. Trachyte is a relatively rare rock. (See also.)

References in periodicals archive ?
From oldest to youngest (Elston and Snider, 1964), they are diabase porphyry, olivine diabase porphyry, fine-grained diabase, latite or trachyte, tephrite porphyry, and rhyolite.
Plagioclase dramatically removes Sr at intermediate stages and alkali feldspars sequester Ba and Rb as late-stage trachytes and phonolites form in alkaline magmas.
2] contents, the syenitic suite has higher Nb/Y than the granitic suite, and the samples plot in the alkalic fields as the intrusive equivalents of volcanic rocks such as trachyte and alkali rhyolite.
The geology of the Texas Davis Mountains AVA is dominated by a large area of older volcanic rocks (rhyolite, trachyte, lava flows) at lower elevations in the north and east, and younger volcanic rocks (trachyte, rhyolite, tuff, latite) at the higher elevations in the central and southwest areas, including Mount Livermore, Black Mountain and surrounding peaks (Fig.
The DC claims cover 798 acres immediately adjacent to claims held by Evolving Gold to the west and south encompassing part or all of five phonolite stocks, one trachyte stocks and several phonolite dikes intruded into Archean-age basement rocks.
Geologically, the Law is a volcanic plug, formed around 335 million years ago and composed of phonolitic trachyte.
While this service offers the most direct route through Venice and wonderful views of the city, you have to accept the boat's lurching motion and industrial-level shudders as part of the fun Joining the crowds at the city's main harbour, we bounced our wheelie suitcases over the trachyte and sandstone pavements, passing naff restaurants and tacky carnival masks as we passed through the world's most famous piazza - St Mark's Square.
While this service offers the most direct route through Venice and wonderful views of the city, you have to accept the boat's lurching motion and industrial-level shudders as part of the fun Joining the crowds at the city's main harbour, we bounced our suitcases over the trachyte and sandstone pavements, passing naff restaurants, lanky teenagers and tacky carnival masks as we walked through the world's most famous piazza - St Mark's Square.
However, a small number of basalt, scoria and trachyte statues were also fashioned outside of the Rano Raraku quarry.
Most of the tools were made from trachyte, a rock with a much smoother surface than that of other rock types available at Gona.
ground Oberon NSW (4) trachyte hammer-dressed Kimberley WA (5, 8) basalt flaked, hammer-dressed?
The vein follows a North 60 West trending structure that is up to 50 meters wide and together with a dark gray, aphanitic trachyte porphyry dike cuts fractured, sheared, and hornfelthized andesite and diorite wall rocks.