Picrite


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Related to Picrite: Oceanite, ankaramite

picrite

[′pi‚krīt]
(petrology)
A medium- to fine-grained igneous rock composed chiefly of olivine, with smaller amounts of pyroxene, hornblende, and plagioclase felspar.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
'To our knowledge, the Luenha picrites are the first lava samples that could originate from the plume source that has been previously inferred from various geological and geophysical data on the Karoo province.
However, the present exposures of picrites in the Deccan province are limited and their PGE contributions seem quite insufficient to approach the magnitude of the K-T Ir anolmaly (Sutherland, 1994).
Extraction is continuing on unmineralized gabbroic dolerite and picrite.
These rocks contain more than 18 wt% MgO (Le Bas 2000) and are distinguished from other magnesium-rich rocks, such as picrites and meimechites, by having spinifex texture (characterized by spectacular arrays of subparallel or randomly-oriented skeletal, platy and bladed olivine crystals set in a glassy groundmass; Fig.
Edwards Basalt Formation--which is in turn disconformably overlain by the Widgiemooltha Komatiite Formation (olivine peridotites to picrites).