Paper No. 38-16
Presentation Time: 1:30 PM-5:30 PM
RAMAN SPECTROMETRY OF QUARTZ INCLUSIONS IN GARNET (QUIG) FROM THE RINCON RANGE, NORTH-CENTRAL NEW MEXICO: PROGRADE PRESSURE AND TEMPERATURE ESTIMATES FOR THE PICURIS OROGENY
Proterozoic metapelites that outcrop in the Rincon Range in north-central New Mexico are part of a fold and thrust belt that was subject to a regional tectonothermal event (Picuris Orogeny ~1400 Ma). These metapelites record upper amphibolite facies conditions during this event. These rocks preserve schistose textures and contain the minerals quartz + muscovite + garnet +sillimanite + staurolite + ilmenite + accessory minerals [± chlorite ± chloritoid] with prominent quartz inclusions in garnet and staurolite porphyroblasts. The garnet porphyroblasts are euhedral to elongate and range in size from 4 mm to 2 cm. They contain inclusions of predominantly quartz and muscovite with minor zircon, monazite, ilmenite, magnetite, and rutile. Preliminary Confocal Laser Raman spectrometry for QuiG barometry was conducted on quartz inclusions in garnets from two samples and using the main ~464 cm-1 band for quartz. Raman spectra from inclusions were recorded and compared to those from matrix quartz at ambient pressure conditions. Offset data for peak shifts range from 0 to -1.31 cm-1, equivalent to internal pressures for the quartz inclusions ranging from 0 to -1424 bars (n=12). Temperature estimates for initial garnet growth are 530 ± 25ºC based on phase equilibria and preliminary thermodynamic modeling. These conditions are consistent with a prograde P-T path that passed just above the aluminosilicate triple-point during the ~1400 Ma Picuris Orogeny. These results suggest a mid-crustal burial depth for the Rincon Range. Burial likely occurred prior to significant heating that reached conditions for partial melting in the sillimanite field, which is recorded in nearby samples.