Lamprophyre
Chemical Process (Liquid-phase Growth) - Closed system under ground (Melt precipitation)
Mineral composition
Mafic minerals > 60 vol% (Mafic). Felsic minerals are Plagioclase, Orthoclase, or Felspathoid. Quartz is not included.
Chemical composition
SiO2 < 45 wt% (Basic).
Texture
Equigranular texture composed of grains more than a few mm, associated with larger euhedral phenocrysts.
Required Geological Setting
Occurrence
Rock forming minerals in lamprophyre, mafic (basic) volcanic rock formed from magma under groud. Lamprophyres are observed as dykes associated with granitoids. Phenocrysts of lamprophyre, mafic dykes, are composed of biotite, amphiboles and/or pyroxenes, whereas those of granite porphyry, felsic dykes, are quartz and/or feldspar.
Distribution of lamprophyre described in this site. Red is ilmenite-series granite, and blue is magnetite-series granite.
Mineral Assemblages
Kersantite: Biotite (Phenocryst), Plagioclase
Minette: Biotite (Phenocryst), Orthoclase
Ouachitite: Biotite (Phenocryst), Felspathoid
Spessartite: Hornblende (Phenocryst), Augite (Phenocryst), Plagioclase
Vogesite: Hornblende (Phenocryst), Augite (Phenocryst), Orthoclase
Camptonite: Alkaline amphibole (Phenocryst), Alkaline pyroxene (Phenocryst), Olivine (Phenocryst), Plagioclase, (Phlogopite)
Soda-minette: Alkaline amphibole (Phenocryst), Alkaline pyroxene (Phenocryst), Olivine (Phenocryst), Orthoclase, (Phlogopite)
Monchiquite: Alkaline amphibole (Phenocryst), Phlogopite (Phenocryst), Olivine (Phenocryst), Calcite, Analcime
Alnöite, Alnoite: Biotite (Phenocryst), Alkaline pyroxene (Phenocryst), Olivine (Phenocryst), Calcite, Melilite
Localities
- Taira-machi (Spessartite)