Proterozoic geology of the central Sante Fe Range, northern New Mexico

Approximately 15 km² were mapped in the central Santa Fe Range, between the Pecos-Picuris and Borrego faults. Two major lithologic assemblages are present: (1) a south-dipping block of migmatitic supracrustal rocks which have volcanic and volcaniclastic protoliths; and (2) a suite of deformed calc-alkalic plutonic rocks ranging in composition from granite to quartz diorite. The boundaries separating these two assemblages are, at least in part, tectonic. The supracrustal rocks experienced a syn-kinematic episode of localized partial melting at metamorphic conditions of T = 650 to 730°C and 5.2 to 5.5 kbars. The calc-alkalic plutonic suite can be divided into an early felsic group and a later mafic group. Intrusion, solidification and deformation of the felsic group pre-dated the solidification of migmatite leucosomes. Intrusion of the mafic group may have been contemporaneous with the migmatization event. Whole-rock major and trace-element data for the calcalkalic suite show fractionation trends similar to those seen in Phanerozoic arc-related plutonic rock suites. A younger group of alkali granites and associated epidote veins intruded most of the above mentioned lithologies.