Chemical compositions of the late Cretaceous granitoids across the central part of the Abukuma Highland, Japan - Revisited

Shunso Ishihara, Bruse W. Chappell
Late Cretaceous granitoids of central area in the Abukuma terrain were analyzed by polarized XRF method and compared with the Ryoke granitoids of Chubu district. The Abukuma granitoids are mostly composed of hornblende and/or biotite granodiorite to granite and less in amount of muscovite-biotite granites, and are higher in Na 2 O and Al 2 O 3 , lower in K 2 O, Rb, Pb and Ba than the Ryoke granitoids on the Harker diagrams. The Abukuma granitoids appear to be generated within the continental
more » ... st of inmatured island-arcs, having mafic magmas and heat from the upper mantle. The Abukuma granitoids are generally reduced type accepting sedimentary carbon from the continental crust, similarly to the Ryoke granitoids, but an intermediate series occurs in the eastern-end zone. Zone II granitoids, which are rich in CaO and poor in K 2 O and lithophile components such as Rb, Pb, Y, Ce and La, have weak signature of high Sr/Y ratio for adakite. An adakitic magma may have brought up from the subducting slab, but extremely modified within the continental crust.
doi:10.9795/bullgsj.59.151 fatcat:hn62yjyfzffaxbnejbbqzb7n54