Abstract by Javier Matos
Deciphering the petrogenesis of two A-type granites: the Mount Osceola and the Conway granites, White Mountain Batholith, New Hampshire
The A-type granites are alkaline, anhydrous, and occur in anorogenic settings. These granites have high concentrations of REE, K2O, Na2O, SiO2, FeOtotal, Y, Nb, Ta, Hf, Zr, Th and U, but are low in Al2O3, MgO, and CaO, and can be divided into two groups. The A1 group represents differentiation of mantle-derived magmas, and are emplaced during intraplate rifting or associated with hotspots. The second A2 group are post-collisional, having been derived from continental crust. Both groups plot as within plate granites in tectonic discrimination diagrams.
The White Mountain Batholith is a member of the White Mountain Plutonic-Volcanic Suite of New Hampshire. Two of the units present are the Mount Osceola and the Conway Granites. The Fe-rich biotites and the whole-rock major and trace elements concentrations of both granites show they are A1 group granites.