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The tholeiitic magma series (/ ˌθoʊliˈaɪtɪk /) is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic ...
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
All alkaline series magmas are thought to have evolved from a primitive mafic alkaline magma, either an alkalic picrite basalt or an ankaramite. This evolves to an alkali olivine basalt or basanite. Thereafter the series branches to the sodic series, the potassic series, or the nephelinic, leucitic, and analcitic series. [1] [2]: Ch6
Variolite. Beach pebble of variolitic pillow lava (varolite) from the Olympic Peninsula, Washington state. Variolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimeter-scale spherical or globular structures, called varioles, in a fine-grained matrix.
Basalt (UK: / ˈbæsɔːlt, - əlt /; [1] US: / bəˈsɔːlt, ˈbeɪsɔːlt /) [2] is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low- viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt.
The ratio of magnesium to silica in the lava is a sign of what stage the volcano is in, as over time the volcano's lavas shift from alkalic to tholeiitic lava, and then back to alkalic. [3] Although volcanism and erosion are the chief factors in the growth and denudation of a volcano, other factors are also involved. Subsidence is known to occur.
Basanite is an aphanitic (fine-grained) igneous rock that is low in silica and enriched in alkali metals. Of its total content of quartz, feldspar, and feldspathoid (QAPF), between 10% and 60% by volume is feldspathoid and over 90% of the feldspar is plagioclase. Quartz is never present. This places basanite in the basanite/ tephrite field of ...
Central Atlantic magmatic province. The Central Atlantic magmatic province (CAMP) is the Earth's largest continental large igneous province, covering an area of roughly 11 million km 2. It is composed mainly of basalt that formed before Pangaea broke up in the Mesozoic Era, near the end of the Triassic and the beginning of the Jurassic periods.