They typically occur as shallow dikes, sills, plugs, or stocks. The usual mafic minerals are olivine (or serpentine), biotite, hornblende (usually green), and pyroxene (green diopside or Fe-Ti augite, Received 1 October 1990, accepted 1 August 1991 Key words: alkaline dyke, geochemistry, lamprophyre, mineralogy, petrology Introduction Is a melilitic lamprophyre that usually contain between 10-30% of feldspathoids (Nepheline and Hauyne) and it normally contains the same minerals as occur in alnöite. Biotite, usually phlogopite and amphibole, usually pargasite or other magnesian hornblende are panidiomorphic; all are euhedral, well formed. Outcrops of the lamprophyres, which can usually be traced for less than 500 feet, range in width from 2 to 25 Ieet. Alnoite; From Alno island, Sweden. These rocks contain also iron oxides (usually titaniferous), apatite, sometimes sphene, augite, and olivine. Wideiy scattered dark gray lamprophyre dikes in the Mount Rosa area strike generally north-northlvest and dip steeply. The hornblende and biotite are brown or greenish-brown, and as a rule their crystals even when small are very perfect and give the Gem sapphires also occur as xenocrysts in alkaline basic lamprophyre such as for the Yogo Gulch deposit in Montana (Brownlow and Komorowski, 1988; Renfro et al., 2018), as mafic dikes of biotite monchiquite called ouachitite, a lamprophyre characterized by an abundance of phlogopite and brown amphibole, olivine, clinopyroxene, and analcime. Any of a heterogeneous group of gray to black, mafic igneous rocks characterized by a distinctive panidiomorphic and porphyritic texture in which abundant euhedral, dark-colored ferromagnesian (femic) minerals (dark mica, amphibole, pyroxene, olivine) occur in two generations—both early as phenocrysts and later in the matrix or groundmass—while felsic minerals … Table 19-6 Lamprophyre a diverse group of dark, porphyritic, mafic to ultramafic hypabyssal (or occasionally volcanic), commonly highly potassic (K>Al) rocks. They contain mafic phenocrysts in a fine-grained groundmass. Similar lamprophyres also occur in the southern Sulu area in the Jiaodong Peninsula (e.g., 120 Ma; Deng et al., 2017) and the villages of Xiaya and Jingziyu in the western Luxi area (e.g., 130 Ma; Yang et al., 2019). lamprophyre may and often does contain all four minerals but is named according to the two which predominate. They are normally rich in alkalis, volatiles, Sr, Ba and Ti, with biotite-phlogopite and/or amphibole phenocrysts. Lamprophyre definition is - any of a series of dark rocks of basaltic habit that resemble trap, occur usually in narrow dikes, and sometimes contain glittering plates of biotite. Feldspar is restricted to the ground mass . They generally strike at 050 to 055 degrees and dip steep to vertical, but occasionally There are many different rocks grouped under the heading lamprophyre. lamprophyre dyke swarms occur widely in the Jiaodong Peninsula and they are thus suitable for constraining the c ompositions, ori- gins, and mechanisms of mantle metasomatism (e.g., Deng et al., The iamprophyres are of two types, sodic syenites and sodic diorites. Lamprophyre. magmas which have undergone varying but generally low degrees of polybaric fractionation, together perhaps with mixing of more primitive and fractionated batches, during their ascent through the crust. 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