trachybasalt

trachybasalt

[¦tra·kē·bə′sȯlt]
(petrology)
An extrusive rock characterized by calcic plagioclase and sanidine, with augite, olivine, and possibly minor analcime or leucite.
References in periodicals archive ?
By volcanic rock TAS classification, D1 and D2 belong to trachybasalt and D3 and D4 belong to trachyte.
The volcanic strata mainly consist of basalt, trachybasalt, andesite, and basaltic andesite that are intruded by monzonite, monzodiorite, granodiorite, and syenite.
Volcanic rocks include basalt, trachybasalt, basaltic andesite and andesite and plutonic rocks consist of monzonite, granodiorite, monzodiorite, and quartz monzonite.
Suite B-P Alkaline basalt Trachybasalt K-alkaline No.
Alkali basalts, trachybasalts, and trachyandesites are porphyritic rocks exhibiting phenocrysts and/or microphenocrysts of clinopyroxene ([Wo.sub.44-49][Fs.sub.7-15]), olivine ([Fo.sub.65-83]), plagioclase ([An.sub.28-76]), magnetite, and biotite set in a glassy groundmasses consisting of microlites of clinopyroxene ([Wo.sub.46-49][Fs.sub.13-18]), magnetite, ilmenite, biotite, plagioclase ([An.sub.20-45]), alkali feldspar ([Or.sub.52-65]), nephelineanalcime ([Ne.sub.37-73][Ks.sub.22-38]), amphibole, and apatite [+ or -] titanite [+ or -] zircon.
In tephrite and trachybasalt the phenocryst of plagioclase, augite, olivine, pargasite and phlogopite are embedded in the groundmass of plagioclase, Ti-augite, pargasite, phlogopite, apatite, opaque minerals (ilmenite) and devitrified glass (Sawada et al., 1992).
The ultramafic unit is intruded by thin (a few meters to less than 2 cm wide) trachybasalts and surrounded and overlain by massive basalts, trachybasalts and basaltic trachy-andesite flows and breccias.
Basaltoid rocks are represented here by predominant tephrites and basanites, rare foidites, and singular basalts and trachybasalts (Bolewski and Parachoniak, 1982; Kozlowska-Koch, 1987; Wierzcholowski, 1993; Lorenc et al., 2004).
The Eocene lavas are mostly andesites, trachyandesites, trachybasalts and analcime-bearing tephrites with shoshonitic to alkaline geochemical signatures.