Phase relations of a high-Mg basalt from the Aleutian Island Arc: Implications for primary island arc basalts and high-Al basalts

Crystallization of primitive basaltic magmas at crustal pressures and genesis of the calc-alkaline igneous suite: experimental evidence from St Vincent, Lesser Antilles arc

“…7, 8) and qz (Fig. 8) components, essential features of the calc-alkaline differentiation trend (e.g., Grove and Baker 1984;Gust and Perfit 1987;Sisson and Grove 1993a). Thus, early crystallization of ferromagnesian silicates produces compositions typical of the more evolved members of the arc sequence.…”

“…Early experiments, performed under anhydrous conditions (Tatsumi et al 1983;Gust and Perfit 1987;Ulmer 1989;Bartels et al 1991;Draper and Johnston 1992), produced derivative melts resembling HAB, although significant differences with natural compositions were noted (e.g., Draper and Johnston 1992). Sisson and Grove (1993a, b) clearly showed that the derivation of HAB-like residual melts from more primitive basaltic parents requires hydrous conditions.…”

“…However, their experiments were performed at pressures of 1 and 2 kbar. Crystallization of arc basalts may not be restricted to such shallow depths: the generation of HAB has been commonly placed at moderate to high pressure, i.e., in the 8-10 kbar range (e.g., Gust and Perfit 1987). Therefore, there is a need to examine the crystallization of HMB in the presence of water at pressures above 2 kbar.…”

High-alumina basalts from the Bogda Mountains suggest an arc setting for Chinese Northern Tianshan during the Late Carboniferous

“…Numerous studies have suggested that the high-MgO anhydrous or slightly hydrous tholeiite HAB can be generated by some extents of crystal fractionation from primary magma with higher Mg# at high pressure (5-10 kbar) near the arc crust-mantle boundary (Bartels et al, 1991;Falloon and Green, 1987;Fujii and Scarfe, 1985;Green et al, 1967;Gust and Perfit, 1987). This contrasts with the low crystallization pressure (1-2 kbar) and high water content (2-4 wt%) proposed for low-MgO calc-alkaline HAB (Sisson and Grove, 1993a).…”

Arc Crust-Magma Interaction in the Andean Southern Volcanic Zone from Thermobarometry, Mineral Composition, Radiogenic Isotope and Rare Earth Element Systematics of the Azufre-Planchon-Peteroa Volcanic Complex, Chile

“…Chromian spinel was identified in many samples using the energy dispersive spectrometer on the EPMA and often occurs as inclusions in olivine (Shoji, 1992). The co-precipitation of olivine and magnetite indicate oxidizing conditions near the nickel-nickel oxide (NNO) buffer (Gust and Perfit, 1987).…”