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The tholeiitic magma series (/ ˌ θ oʊ l eɪ ˈ ɪ t ɪ k /) 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 ...
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 ...
Tholeiitic magma series rocks are found, for example, at mid-ocean ridges, back-arc basins, oceanic islands formed by hotspots, island arcs and continental large igneous provinces. [ 24 ] All three series are found in relatively close proximity to each other at subduction zones where their distribution is related to depth and the age of the ...
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
1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms. Fractional crystallization , or crystal fractionation , is one of the most important geochemical and physical processes operating within crust and mantle ...
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 ...
[3] Peralkaline rocks are indicative of continental rift-related volcanicity (e.g. the peralkaline rhyolites of the East African Rift in central Kenya) as well as continental and oceanic hotspot volcanicity (e.g. the peralkaline rhyolites of the Glass House Mountains in eastern Australia and the Canary Islands in the Atlantic Ocean).
Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism.