Petrochemistry of the Palisades sheet, Cimarron Pluton, northern New Mexico
Stephen A. Kish, Paul C. Ragland, and Robert P. Cannon
The middle Tertiary Cimarron pluton is exposed in northern New Mexico at the transition between the Southern Rocky Mountain and Great Plains physiographic provinces. This epizonal pluton is a >180 km2, stacked laccolithic body, over 1 km thick in the vicinity of Baldy and Touch-Me-Not Mountains. The base of the pluton is in contact with either Precambrian crystalline rocks or sandstones of the late Paleozoic Sangre de Cristo Formation. Overlying intrusive sheets were emplaced into Mesozoic and early Tertiary sedimentary rocks.
A detailed petrographic and geochemical study of the 400-m-thick lowermost intrusive sheet of the pluton exposed in Cimarron Creek Canyon (informally known as the Palisades sill) reveals a uniform composition transitional between trachydacite and rhyolite. The rocks consist of about 40% phenocrysts of partially resorbed quartz, plagioclase, biotite and hornblende in a very fine-grained groundmass of quartz, K-feldspar and plagioclase. The unaltered rock is characterized by high Na2O content and a distinctive REE pattern—low total REE and a significant depletion in heavy REE; (Ce/Yb)n = 16 and Yb = 0.6 ppm. The initial 87Sr/86Sr of the pluton (~0.7052) is similar to the values of plutons associated with the Questa caldera.
- Kish, Stephen A.; Ragland, Paul C.; Cannon, Robert P., 1990, Petrochemistry of the Palisades sheet, Cimarron Pluton, northern New Mexico, in: Tectonic development of the southern Sangre de Cristo Mountains, New Mexico, Bauer, Paul W.; Lucas, Spencer G.; Mawer, Christopher K.; McIntosh, William C., New Mexico Geological Society, Guidebook, 41st Field Conference, pp. 341-347.