Variety of high-magnesium basalt that is very rich in the mineral olivine
Not to be confused with Pykrete.
"Picrite" redirects here. For the component of triple-base NQ propellants, see Nitroguanidine.
Picrite basalt or oceanite from the Piton de la Fournaise
Picrite basalt or picrobasalt is a variety of high-magnesium olivine basalt that is very rich in the mineral olivine. It is dark with yellow-green olivine phenocrysts (20-50%) and black to dark brown pyroxene, mostly augite.
The olivine-rich picrite basalts that occur with the more common tholeiitic basalts of Kīlauea and other volcanoes of the Hawaiian Islands are the result of accumulation of olivine crystals either in a portion of the magma chamber or in a caldera lava lake.[1] The compositions of these rocks are well represented by mixes of olivine and more typical tholeiitic basalt.
The name "picrite" can also be applied to an olivine-rich alkali basalt: such picrite consists largely of phenocrysts of olivine and titanium-rich augite pyroxene with minor plagioclase set in a groundmass of augite and more sodic plagioclase and perhaps analcite and biotite.
More generally the classification of fine grained rocks recognises a group known as 'picritic rocks' that are characterised by high magnesium content and less than 45% SiO2. Because of the high Mg content they do not fit in the TAS diagram of classification. They include picrite, komatiite and meimechite.
Picrites and komatiites are somewhat similar chemically (defined as >18% MgO), but differ in having 1 to 2% total alkalis and <1% total alkalis respectively. Komatiite lavas are products of more magnesium-rich melts, and good examples exhibit the spinifex texture.[2] They are largely restricted to the Archean. In contrast, picrites are magnesium-rich because crystals of olivine have accumulated in more normal melts by magmatic processes.[citation needed]
Picrite basalt is found in the lavas of Mauna Kea and Mauna Loa in Hawaiʻi[3], Curaçao, in the Piton de la Fournaise[4] volcano on Réunion Island and various other oceanic island volcanoes.
Picrite basalt has erupted in historical times from Mauna Loa during the eruptions of 1852 and 1868 (from different flanks of Mauna Loa).[5]
Picrite basalt with 30% olivine commonly erupts from the Piton de la Fournaise.[6]
In addition to extrusive occurrences, it also occurs in minor intrusions.
Picritebasalt or picrobasalt is a variety of high-magnesium olivine basalt that is very rich in the mineral olivine. It is dark with yellow-green olivine...
primitive melt may have had the composition of picritebasalt, but picritebasalt is uncommon in flood basalt provinces. One possibility is that a primitive...
include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite. The variety of basalt in the series was...
high-alumina basalts, ultrapotassic igneous rocks, and ultramafic rocks. The basaltic occurrence of phlogopite is in association with picritebasalts and high-alumina...
mafic alkaline magma, either an alkalic picritebasalt or an ankaramite. This evolves to an alkali olivine basalt or basanite. Thereafter the series branches...
Reykjanes Ridge. The erupted rocks are from the tholeiitic magma series and picritebasalt. There is not a central volcano, but rather a number of flat-topped...
overall composition is mafic (rich in magnesium and iron), chiefly basalt and picritebasalt (picrobasalt). Other associated volcanic features include a chain...
the volcano are greenish in color, due to olivine sand derived from picritebasalt lavas. The Grand Brûlé is formed from solidified lava flows accumulated...
microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive...
shield covers about 50 km2 (19 sq mi). Four small lava shields are picritebasalt and one lava shield contains about 3 km3 (0.72 cu mi)of olivine tholeiite...
Helgrindur volcanic system. The rocks tend to be alkaline hyaloclastite basalt or picritebasalt, however a central rhyolite formation is known. In total length...
made up of MORB (Mid Ocean Ridge Basalt), alkali basalt, tholeiitic basalt, and picritebasalt. Basaltic volcanic rocks up to 2.5 kilometres (1.6 mi) thick...
rock with a composition between phonolite and tephrite Picrite – Variety of high-magnesium basalt that is very rich in the mineral olivinePages displaying...
Heard Island were formed in the Miocene by mildly alkalic, olivine and picritebasalt. The composition at and near Amsterdam and Saint Paul Island are distinct...
limited area. The recent lava has picrite, olivine tholeiite basalt characteristics but before the ice age there were basaltic andesite and rhyolite eruptions...
rocks, with phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite".[citation needed] The IUGS recommends...
of fine-grained basalt with most of the mass of the intrusion being made up of picrite, dolerite, and high level intrusives. The picrite is a farinaceous-grained...
(2007). "Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites". Geochemistry, Geophysics, Geosystems. 8 (2): n/a...
mantle convection, the formation of planets and the origins of granite and basalt.: 1 It is an integrated field of chemistry and geology. The term geochemistry...
tools, spear tools, stone knives, and adzes, which are mostly made of picritebasalt and thus suspected to be related to Penghu, of the Niuchoutzi Culture...
either picritebasalt, alkali basalt, trachyandesite and trachyte. Areas have been observed on Bounty showing pillow basalts and giant tubular basalt to tabular/blocky...
volcanoes or flood basalts, because the less viscous lava can flow for long distances from the vent. The thickness of a solidified basaltic lava flow, particularly...
Pillow lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite, dacite or even...
dolomite, mudstone, tholeiite, and picrite interleaved with conglomerate. Also dykes of augite syenite, picrite and 580 Ma tholeiite dolerite were intruded...
lava cone surrounded by a lava apron; the older shields are made from picrite, the younger, bigger ones from olivine-tholeiite. They were probably formed...
Prokhorov. - 3rd ed. 1969-1978. Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): polybaric fractionation of rising melts in the mantle? Chemical...
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