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Any of a group of igneous rocks characterized by a porphyritic texture in which abundant, large crystals of dark-colored minerals appear set in a not visibly crystalline matrix.



melanocratic igneous dike rock that differs from the corresponding igneous rocks to which it is genetically related by its sharply increased content of dark minerals (usually at least 30 percent of the rock). The color of lamprophyre varies from dark gray to black. Its constituents include feldspar (sometimes feldspathoid) and dark minerals (biotite, amphibole, pyroxene, and sometimes olivine). In the porphyritic varieties of lamprophyre the phenocrysts are usually represented by dark minerals—this is called lamprophyric texture. There are calcalkalic lamprophyres (spessartite, kersantite) and alkalic lamprophyres (camptonite, alnöite). Lamprophyres sometimes grade into porphyrites.

References in periodicals archive ?
A 1-2 m thick lamprophyre dyke in Beavertail State Park cross-cuts [S.
More leucocratic lamprophyres occur as veins within the thick basaltic sills and are made of abundant kaersutite and minor clinopyroxene phenocrysts in a groundmass that consists of alkaline feldspar and devitrified glass.
Moreover, it strikes parallel to numerous smaller dykes of lamprophyres and semilamprophyres.
39]Ar technique and hence to better constrain the age of pre-rifting alkaline magmatism in southeastern New England and establish if it did, indeed, progress from north to south as suggested by other lamprophyre ages from Avalonia (Fig.
Tournon (1984) reported for the same area an isolated block of picrite instead, and Calero (1987) reported in the Tortugal area a similar ultramafic rock but classified it as lamprophyre (monchiquite).
The rock in the second vent is a quartz porphyry which also contains topaz, and there is a long contact zone into which a lamprophyre was intruded.
1998; Buchan and Ernst 2004), small lamprophyre, and alkalic rock-carbonatite plugs and dykes, and are overlain by scattered outliers of Proterozoic and Phanerozoic sedimentary cover (see reports listed in Fig.
The Discover Abitibi Initiative (DAI) recently released the results of a lamprophyre study, designed to determine the diamond bearing potential of lamprophyres in Timmins, Kirkland Lake and Timiskaming areas.
West of the Otish Mountains and east of James Bay, a smaller rush for diamonds has been underway since last year when Dianor Resources announced in June the discovery of a clear yellow, octahedral to cubic microdiamond in one of the many lamprophyre dikes in the area.
Prior to the intrusion of the granodiorite stock, steeply dipping east-trending lamprophyre dykes were discordantly emplaced into the Silurian Kingsclear Group.