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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 ...
Rocks in the alkaline magma series are distinguished from rocks in the subalkaline tholeiitic and calc-alkaline magma series by their high content of alkali metal oxides (K 2 O plus Na 2 O) relative to silica (SiO 2). They are distinct from the rare peralkaline magmas, which have excess alkali oxides relative to alumina (Na 2 O + K 2 O > Al 2 O 3).
Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which include tholeiitic basalts and calc-alkaline basalts. [6]
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 ...
These represent the low-silica end of the calc-alkaline magma series and are characteristic of volcanic arcs above subduction zones. [ 43 ] Boninite is a high- magnesium form of basalt that is erupted generally in back-arc basins ; it is distinguished by its low titanium content and trace-element composition.
Volcanic arcs are characterized by explosive eruption of calc-alkaline magma, though young arcs sometimes erupt tholeiitic magma [7] and a few arcs erupt alkaline magma. [8] Calc-alkaline magma can be distinguished from tholeiitic magma, typical of mid-ocean ridges, by its higher aluminium and lower iron content [9]: 143–146 and by its high ...
Mazama is surrounded by monogenetic cinder cones, lava fields, and shield volcanoes made up of calc-alkaline basalt and andesite, tholeiite, and shoshonitic andesite. Varying in age from 600,000 to 40,000 years old, these edifices closely resemble other monogenetic volcanoes in the High Cascades.
The petrogenesis of continental arcs is generally different from that of oceanic arcs, so more calc-alkaline and alkaline rocks can be found at a continental arc, with fewer tholeiites and low-K rocks. [4] Calc-alkaline phenocryst-rich dacite, andesite and rhyolite rocks are abundant in continental arc.