Tephrite


Also found in: Dictionary, Wikipedia.
Related to Tephrite: phonolite, trachyte

tephrite

[′te‚frīt]
(petrology)
A group of basaltic extrusive rocks composed chiefly of calcic plagioclase, augite, and nepheline or leucite, with some sodic sanidine.

Tephrite

 

a porphyritic volcanic rock of ashgray, dark gray, or, rarely, black color.

The principal mass in tephrite is fine-grained, semivitreous, and dense and contains inclusions of pyroxene (titanaugite, acmite-augite, and sometimes aegirihe) and plagioclase. It sometimes contains anorthoclase, sanidine, and leucite and, less frequently, haiiyne, nepheline, hornblende, biotite, and titanite. Leucite, nepheline, sodalite, or other tephrites are distinguished according to the predominant feldspathoids. Like other effusive rocks, tephrite is accompanied by ashes, lapilli, and tuffs.

Tephrites are the effusive analogues of plutonic alkaline tetralite gabbroids. They are part of magma formations, which counts for the concentration of titanium, tantalum, zirconium, nepheline, and rare and trace elements. Leucite tephrites are found among the lavas of Vesuvius and Monte Somma in Italy; nepheline tephrites are found in the Eifel region of the Federal Republic of Germany and in the Azores and Canary Islands; sodalite, haiiyne, and analcime tephrites are found in Czechoslovakia and central France.

Mentioned in ?
References in periodicals archive ?
The rock association of the lower set (i) also includes the tephrite sill from the Bechlejovice borehole, dated by Bellon et al.
96 * DO-1-1: fresh trachyandesite, DO-1-2: zeolitized trachyandesite, DO-2: trachyandesite ("hauyne tephrite") and DO-3 nepheline tephrite (Hibsch 1915), all from the Dobranka locality, DO-4: zeolitized tephrite, Ovesna.
Phenocryst-poor latite and trachyte are interpreted as the result of mineral separation, and phenocryst-rich tephrite porphyry and olivine diabase porphyry are the result of phenocryst accumulations in the magma chamber.
Rock types present in the dikes range from tephrite to rhyolite.
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.
On a total alkali-silica plot (LeMaitre, 1984) compositions span a broad range from tephrite to trachyte (Fig.
Compositions of clinopyroxene phenocrysts plot on the diopside-augite boundary (Subcommittee on Pyroxenes, 1988) for pyroxenes from the tephrite porphyry dikes.
Lanthanum to lutetium ratios range from 144, olivine diabase porphyry, to 379, tephrite porphyry.