FURTHER STUDIES OF THE IGNEOUS ROCKS OF THE NORTHERN AND CENTRAL PHILMONT SCOUT RANCH IN CIMARRON, NM

Recently, Ferguson and Skotnicki (2006) mapped the Baldy Mountain Quadrangle in Colfax County, New Mexico. They reported on three sets of igneous rocks and noted that the igneous suite is predominantly intermediate composition monzonite. In our geochemical and petrologic study samples of “granitoid” igneous rocks collected from 4 localities in the northern and central region of the Philmont Scout Ranch in Cimarron NM were analyzed for major, minor and REE. The average wt. % is: SiO₂ 68.86; Al₂O₃, 16.14; FeO, 1.64; Fe₂O₃, 0.64; MgO, 0.84; CaO, 2.88; K₂O, 3.1; Na₂O, 4.43; TiO₂, 0.29; MnO, 0.04; P₂O₅, 0.15; and Cr₂O₃, 0.03. Average CIPW norms are: Q, 23.2; or, 18.6; ab, 38.05; an 12.9; C, 0.88; di 0.54; hy 3.99; mt 0.95; il, 0.57; and ap 0.34. ⁸⁷Sr/⁸⁶Sr values range from 0.705267 to 0.707161 with a 2 σ of 0.000007 to 0.000008. Chondrite-normalized REE plots show HREE enrichment. Mantle normalized spider diagrams(Sun and McDonough, 1989) show negative Nb and P anomalies. Plots of Nb vs. Y after Pearce et al. 1984 indicate Volcanic Arc Granites(VAG)+ syn-Collisional Granites(syn-COLG). Plots of Ta vs. Yb (after Pearce et al. 1984) indicate Volcanic Arc Granites(VAG) and plots of Rb vs. Y+Nb(after Pearce et al. 1984) indicate Volcanic Arc Granites(VAG).