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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 ?
It is also older than ages reported for lamprophyre dykes elsewhere in central and southeastern New England, and if correct, indicates that alkaline magmatism in
The size of the samples and the lateral distribution of the locations indicate that diamonds in lamprophyres are widespread in the region and that further exploration may yield some positive finds, Calhoun said in a press release.
With a zone occurrence about three kilometres long and a kilometre wide; the rocks being targeted are considered to be a very rare find of xenolith-bearing lamprophyre occurring in a volcanic breccia.
A NATMAP project in 1995 located at least eight so-called ultramafic lamprophyre dykes in the Cape Chidley area of northernmost Labrador and Nunavut.
This area lies on the northern extension of the Trans-Superior Tectonic Zone (TSTZ), which encloses kimberlites and kimberlite-like ultramafic lamprophyre dykes in Michigan.
The diamond was recovered by caustic dissolution of a biotite-rich lamprophyre dyke collected by Ontario Ministry of Northern Development and Mines District Geologist Mr.
These black garnets are commonly found in the magmatic phase of ultramafic lamprophyres and were found in a Le Tac field kimberlitoid rock and also in the Selco field in Northern Ontario.
The presence of gabbro and sheared lamprophyres was also observed in the blasted trench.
The lamprophyres are xenolith bearing, similar to diamondiferous dykes currently being explored in the Wawa area of Ontario.
Locally ore controls may vary but the shearing control, with widening in flexure features is obiquitous, host rocks, predominantly metasediments, may vary to lamprophyres, porphyry or ultra-basics.
These northeast faults are thought to be deep-seated mineralizing features because of the presence of lamprophyre style intrusions and altered and mineralized fragments of lamprophyres and limestone in the explosive hydrothermal breccias located along them.
The drilling will test two separate targets - diamond bearing lamprophyre dykes and high grade silver/cobalt veins.