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Full-Text Articles in Tectonics and Structure
Genesis Of Trondhjemite By Low-Pressure Fraction Anatexis Of Hornblende-Gabbro At Alvand Plutonic Complex (Hamedan, Nw Iran): Insights From Geochemical Modelling., Federico Lucci, Adel Saki, Mirmohammad Miri, Ahmad Rabiee, John C. White
Genesis Of Trondhjemite By Low-Pressure Fraction Anatexis Of Hornblende-Gabbro At Alvand Plutonic Complex (Hamedan, Nw Iran): Insights From Geochemical Modelling., Federico Lucci, Adel Saki, Mirmohammad Miri, Ahmad Rabiee, John C. White
EKU Faculty and Staff Scholarship
Amphibole-dominated dehydration melting of gabbro is the primary process responsible for the genesis of adakites, low-K tonalites, modern trondhjemites, and plagiogranites aswell as Archean tonalite-trondhjemite-granodiorite suites that represent the earliest examples of continental crust. Previous literature has mostly focused on the role of Al-rich amphibole during anatexis of a mafic source and many of these studies have investigated this process through experimental melting runs. However, due to experimental boundary conditions, little is known about partial melting of amphibole-bearing mafic rock at temperatures < 800°C for upper crustal conditions (pressure < 500 MPa). Classic and forward thermobarometric modelling suggests that in situ trondhjemite leucosomes, hosted by Cheshmeh-Ghasaban mafic metatexites (Alvand Plutonic Complex, Hamedan, NW Iran), represent a rare natural case study of a low-temperature incipient amphibole-dominated anatectic event of a mafic source with a primary assemblage (Pl+Hbl+Cpx+Bt+Opx) typical of a hornblende-bearing gabbroic rock.
Peralkaline Silicic Extrusive Rocks: Magma Genesis, Evolution, Plumbing Systems, And Eruption., Ray Macdonald, John C. White, Harvey E. Belkin
Peralkaline Silicic Extrusive Rocks: Magma Genesis, Evolution, Plumbing Systems, And Eruption., Ray Macdonald, John C. White, Harvey E. Belkin
EKU Faculty and Staff Scholarship
Peralkaline silicic extrusive rocks are an important component of the volcanological record. Here we review several aspects of their formation and evolution, including the tectonic settings in which they occur, their main petrological and geochemical features, the magmatic lineages along which they evolve, and the parameters (T, P, fO2, melt water contents) that control the lineages. Particular attention is paid to the composition of the extraordinary melts formed at the lowest temperatures. Various lines of evidence are presented to explain the silica-gaps in some lineages. The partial melting of continental crust and the role of crustal contamination …