Magma series Flashcards
Consists of genetically-related magmas with a composition that evolved from a common, original, parental magma.
Magma series
Record a iron and in magnesium with increasing SiO2 and alkali concentrations due to the early crystallization of ferromagnesian minerals, hence, an enrichment in alkaline minerals. Produce largely andesites, dacites, rhyolites, and high-alumina basalts (BADR). Dominantly occurs along convergent margin environments with volcanic arcs and subduction zones.
calc-alkaline magmas
Experience enrichment in iron at low to moderate SiO2 concentrations with increasing fractionation due to depleted MgO and CaO from early crystallization of forsterite olivine and Ca- plagioclase. Produce large volumes of basalt with variations in composition. Dominantly occurs extensional environments such as ocean ridges and continental rifts, and some hotspots in intraplate settings and immature arcs in thin volcanic arc crusts.
tholeiitic magmas
Magmas that are less common than calc-alkaline or tholeiitic magmas, highly enriched in Na₂O and/or K₂O and contains an extremely diverse compositions that have SiO2 contents ranging from 0-65%. Occurs in a wide variety of environments that include stable cratons, continental rifts and subduction zones.
alkaline magmas
Characterized by high concentrations of silicic and basic rocks, with little intermediate rocks, and associated with continental rifts. Its basic component is derived from partial melting of the mantle, while its silicic component is derived from the partial melting of the continental crust from the heating of the rising basic magmas.
bimodal magma suites
A GRAPHICAL METHOD used to discriminate samples through their chemical content into correctly identifying an igneous rock.
-Ex. AFM diagram
Variation Diagrams
Bivariate diagrams showing the relative content relationship of oxide compounds FeO, MgO, CaO, Na2O, K2O and TiO2 with SiO2 as the magma evolves, creating a trend in the diagram.
Harker Diagrams
