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Volcanic ultramafic rocks are rare outside of the Archaean and are essentially restricted to the Neoproterozoic or earlier. Subvolcanic ultramafic rocks and dykes persist longer, but are also rare. There is evidence of ultramafic rocks elsewhere in the solar system. Examples include komatiite [2] and picritic basalt.
Komatiite / k oʊ ˈ m ɑː t i ˌ aɪ t / is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% magnesium oxide (MgO). [1] It is classified as a 'picritic rock'. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content.
Lherzolite – an ultramafic and ultrabasic rock that is composed of olivine and pyroxene – An ultramafic rock, essentially a peridotite Monzodiorite – igneous rock Pages displaying wikidata descriptions as a fallback An intrusive igneous rock intermediate in composition between diorite and monzonite
Small volcanic bomb of (black) basanite with (green) dunite. Dunite (/ ˈ d uː n aɪ t, ˈ d ʌ n aɪ t /), also known as olivinite (not to be confused with the mineral olivenite), is an intrusive igneous rock of ultramafic composition and with phaneritic (coarse-grained) texture.
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase ...
Greenstone belts are primarily formed of volcanic rocks, dominated by basalt, with minor sedimentary rocks inter-leaving the volcanic formations. Through time, the degree of sediment contained within greenstone belts has risen, and the amount of ultramafic rock (either as layered intrusions or as volcanic komatiite) has decreased.
The volcanic rock resulting from subsequent cooling is often also called lava. A lava flow is an outpouring of lava during an effusive eruption. ... Ultramafic lavas, ...
Greenstone is metamorphosed mafic to ultramafic volcanic rock that formed in volcanic eruptions in the early stage of Earth formation. [2] The volcanic-sedimentary greenstone sequence occupies the majority of the Archean crustal record, which is about 30%. [2]