lamprophyre


lamprophyre
lamprophyric /lam'preuh fir"ik/, adj.
/lam"preuh fuyeur'/, n. Petrol.
any dark intrusive rock in which dark minerals occur both as phenocrysts and as groundmass.
[1885-90; lampro- ( < Gk lamprós clear) + -PHYRE]

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rock
      any of a group of dark gray to black intrusive igneous rocks that generally occur as dikes (tabular bodies inserted in fissures). Such rocks are characterized by a porphyritic texture in which large crystals (phenocrysts) of dark, iron-magnesium (mafic) minerals are enclosed in a fine-grained to dense matrix (groundmass). The abundance, large size, well-formed crystal outline, and brilliantly reflecting cleavage faces of the mafic phenocrysts give the rock a striking appearance. Mafic minerals, including biotite, hornblende, augite, or olivine, not only constitute virtually all of the phenocrysts but occur in the groundmass as well, together with much potash feldspar, plagioclase, or feldspathoid.

      Petrographically, lamprophyres are set apart from most other igneous rocks by the presence of mafics, by the lack of feldspar phenocrysts, and by the abundance of mafics combined with alkali-rich feldspar. Chemically, the lamprophyres are unique because of their low silica content and a high iron, magnesium, and alkali content. The commonest lamprophyres are associated with large masses of granite and diorite. Classic examples occur in the Highlands and southern uplands of Scotland, the Lake District of Ireland, the Vosges, the Black Forest, and the Harz Mountains.

      Lamprophyres show a strong tendency to weather and decompose. Many have been altered, undoubtedly while the rocks lay some distance beneath the surface. The common alteration products include carbonate, chlorite, serpentine, and limonite.

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Universalium. 2010.

Look at other dictionaries:

  • lamprophyre — ● lamprophyre nom masculin Roche magmatique, filonienne, très riche en minéraux ferromagnésiens noirs, hydratés (micas, amphiboles) ou anhydres (pyroxènes) …   Encyclopédie Universelle

  • Lamprophyre —   [zu griechisch lamprós »leuchtend« und phýrein »vermischen«], Singular Lamprophyr der, s, Petrologie: Gruppe dunkler, feinkörniger Ganggesteine, vorwiegend aus Plagioklas und Alkalifeldspat als hellen sowie Biotit, diopsidischer Augit und… …   Universal-Lexikon

  • Lamprophyre — Lamprophyres (Greek λαµπρός (lamprós) = bright and φύρω (phýro) = to mix) are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions. They are alkaline silica… …   Wikipedia

  • Lamprophyre — Un lamprophyre est une roche magmatique filonienne à texture microgrenue. Cette roche est caractérisée par les présence de beaucoup de mica noir et/ou d amphibole brune avec de l olivine, des feldspaths, des clinopyroxènes. Il en existe trois… …   Wikipédia en Français

  • lamprophyre — noun An uncommon, small volume ultrapotassic igneous rock primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions …   Wiktionary

  • lamprophyre — lam·pro·phyre …   English syllables

  • lamprophyre — /ˈlæmprəfaɪə/ (say lampruhfuyuh) noun a group of dark dyke rocks in which dark minerals occur both as phenocrysts and in the groundmass, and light coloured minerals occur in the groundmass; the essential constituents are biotite, hornblende,… …   Australian English dictionary

  • lamprophyre — …   Useful english dictionary

  • Lamprophyr — Lamprophyre – vom griechischen λαµπρός (lamprós) = hell, glänzend (in Bezug auf die Kristallflächen von Amphibol und Biotit, die im frisch aufgeschlagenen Zustand hell aufleuchten) und φύρω (phýro) = vermengen, eingeführt durch Carl Wilhelm von… …   Deutsch Wikipedia

  • phyre — lamprophyre porphyre …   Dictionnaire des rimes


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