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Picrite |
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picrite [′pi‚krīt]
(petrology) A medium- to fine-grained igneous rock composed chiefly of olivine, with smaller amounts of pyroxene, hornblende, and plagioclase felspar. Picrite an effusive rock composed of augite and olivine. Pi-crite also contains admixtures of hornblende, biotite, and or-thopyroxene and of various secondary minerals, including ilmenite, magnetite, and apatite. The olivine is often altered and replaced by serpentine, as well as by iddingsite, chlorite, and sometimes actinolite. Picrites are holocrystalline. However, they sometimes contain a certain amount of glass inset with augite and olivine (picrite porphyry). The chemical composition of picrites is 38–41 percent SiO2, 5-10 percent Al2O3, and 20-29 percent MgO. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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No references found | 2001, A note on the IUGS reclassification of the high-Mg and picritic volcanic rocks: Journal of Petrology, v. During the 2001-2002 field season Nevada Star and the Geological Survey of Canada geologists discovered previously unrecognized picritic (ferro-picrite) volcanic and pyroclastic flows up to 600 m thick proximal to the ultramafic intrusions which host many of the nickel-copper-platinum group element mineral occurrences. Melt, fluid and crystal inclusions in olivine phenocrysts from Kerguelen plume-derived picritic basalts; evidence for interaction with the Kerguelen Plateau lithosphere: Chemical Geology, v. |
picritic |
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