Magma genesis of adakites
Examining the genesis of adaktic magmas to examine whether slab crust melting can occur beneath the forearc of warm subduction zones.
Magma genesis of adakites. a) (1) Downgoing oceanic crust melts beneath the forearc and (2) slab melts stall into a upper crustal magma reservoir. b) (1) Mantle melts stall into (2) lower (~30 km depth) and (3) upper crustal magma storage regions where they fractionate. c) Zoom of the lower crustal magma reservoir. After Ribeiro et al. (in review).
At subduction zones, the shallow part of the downgoing plate is believed to be too cold to melt before reaching the arc front (i.e., in the forearc). Yet, occurrence of adakites in the forearc challenges this paradigm. Adakites are subduction zone rocks with distinctive geochemical features, which are commonly considered as the melting product of young (< 25 Ma), downgoing oceanic crust. However, adakite petrogenesis has remained controversial over the past decades, and several studies have proposed alternative models, such as high-pressure fractionation of mantle melts or basalt under-platting.
Here, I seek to place new constraints on adakite petrogenesis in warm subduction zones (i.e., Philippines) and above an asthenospheric window (i.e., Baja California, Mexico) by using amphibole compositions to estimate the magma storage depth and the composition of the parental melt.
Here, I seek to place new constraints on adakite petrogenesis in warm subduction zones (i.e., Philippines) and above an asthenospheric window (i.e., Baja California, Mexico) by using amphibole compositions to estimate the magma storage depth and the composition of the parental melt.
Further readings
Ribeiro J.M., Maury R.C., M. Grégoire (2016) Are adakites slab melts or high-pressure fractionated mantle melts? Journal of Petrology, doi: 10.1093/petrology/egw023.
Ribeiro J.M., Benoit M., Maury R.C. (2008) Adakite genesis: amphibole composition and geobarometric constraints, GSA meeting in Houston, Vol. 40, No. 6, p. 249, Paper no 193-1.
Macpherson C., Dreher S., Thirlwall M. (2006) Adakites without slab melting: High pressure differentiation of island arc magma, Mindanao, the Philippines. Earth and Planetary Science Letters, doi:10.1016/j.epsl.2005.12.034.
Schiano P., Clocchiatti R., Shimizu N., Maury R., Jochum K., Hofmann A. (1995) Hydrous, silica-rich melts in the sub-arc mantle and their relationship with erupted arc lavas, Nature, 377(6550), 595-600, doi:10.1038/377595a0.
Ribeiro J.M., Benoit M., Maury R.C. (2008) Adakite genesis: amphibole composition and geobarometric constraints, GSA meeting in Houston, Vol. 40, No. 6, p. 249, Paper no 193-1.
Macpherson C., Dreher S., Thirlwall M. (2006) Adakites without slab melting: High pressure differentiation of island arc magma, Mindanao, the Philippines. Earth and Planetary Science Letters, doi:10.1016/j.epsl.2005.12.034.
Schiano P., Clocchiatti R., Shimizu N., Maury R., Jochum K., Hofmann A. (1995) Hydrous, silica-rich melts in the sub-arc mantle and their relationship with erupted arc lavas, Nature, 377(6550), 595-600, doi:10.1038/377595a0.
