Lamprophyre

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lamprophyre

[′lam·prə‚fī·ər]
(petrology)
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.

Lamprophyre

 

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
Kaersutite separated from lamprophyres CR 574 and SE 78 yield mean ages of 165.
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.
Deformations of lamprophyre dykes 28-26 Ma in age along a NW-SE-striking transtensional zone related to this fault are visible in the Techlovice quarries (Cajz and Adamovic, 2003) and correspond to E-W extension.
Emplacement and evolution of intermediate to basic dyke rocks and lamprophyres in this part of the Bohemian Massif were characterised by Nemec (1970, 1974), Vrana et al.
A classification and nomenclature of volcanic rocks, lamprophyres and melilitic rocks: Recommendations and suggestion of the IUGS on the Systematic of igneous Rocks.
1999): Mafic precursors, peraluminous granitoids, and late lamprophyres in the Avila batholith; a model for the generation of Variscan batholiths in Iberia.
A common feature of the lamprophyres noted by Hodgson (1968) is the formation of loose spheroids on weathered surfaces caused by the presence of coarse-grained, feldspar-rich ocelli [= eyes in Latin] which are more weather-resistant than the finer-grained matrix.
It consists of alkaline lamprophyres that are considered volatile-enriched equivalents of alkali basalts (Rock, 1991, p.
The rocks are very similar in appearance, age and geological setting to the diamond bearing lamprophyres and volcanic breccias under development for diamonds 400 kiometres away, in the Wawa area on the eastern shores of Lake Superior.
1979: Classification y nomenclature of volcanic rocks, lamprophyres, carbonatites, and melilitic rocks: recommendations and suggestions of the IUGS Subcommission on the Systematics of Igneous Rocks.
3], and (4) olivine with Fo contents of ~88-92 (some of the lamprophyres have two populations of olivine with clusters of similar high Fo values).