GSA Connects 2022 meeting in Denver, Colorado

Paper No. 31-3
Presentation Time: 9:00 AM-1:00 PM


MORSE, Sarah and DUMOND, Gregory, Department of Geosciences, University of Arkansas, 340 North Campus Drive, Fayetteville, AR 72701

The Wet Mountains, Colorado are underlain by exhumed Proterozoic metamorphic rock that records the deformative conditions of the mid- to lower continental crust during the accretion of provinces to Laurentia. The study area is exposed >270 km north of the recently identified 1.46-1.40 Ga Picuris orogen in northern New Mexico. The Picuris orogen is inferred to have formed in response to a regional Mesoproterozoic (ca. 1490-1400 Ma) contractional to transpressional event the impacted areas across the southwestern US. Our study is focused on the record of high temperature deformation, metamorphism, and plutonism in the central and southern Wet Mountains interpreted as the consequence of Mesoproterozoic tectonism that may be related to the Picuris orogeny. Host rocks experienced upper-amphibolite to granulite facies metamorphism and multiple episodes of penetrative, coaxial deformation attributed to NW-SE sub-horizontal contraction. This area includes the syn-deformational Oak Creek pluton (1.44 Ga) and the post-deformational San Isabel pluton (1.36 Ga) that may be used to constrain the impact of the Picuris orogen. Previous workers identified an oblique crustal section between the two plutons from 0.3-0.4 GPa in the north to 0.5-0.7 GPa in the south. The region between the plutons includes the NW-striking Newlin Creek shear zone, an area where the timing and structural relationships are poorly constrained. Previous workers determined the shear zone to be contemporaneous with the Five Points Gulch shear zone in the northern Wet Mountains, however the Newlin Creek shear zone displays flattening deformation and Northwest striking foliation. This assessment conflicts with the regional framework for NE-SW contractional shear zone motion during 1.4 Ga, which includes the Five Points Gulch shear zone. This study will utilize orthogonal transects that cross the Oak Creek and San Isabel plutons and surrounding country rocks to map the distribution of finite strain from the center of the plutons across the pluton boundaries to determine the deformation at 1.4 and 1.37 Ga. These results will be combined with mapping along and across the Newlin Creek shear zone to constrain a P-T-t-D path for the region that can be compared with the timing of orogenic events in northern New Mexico using LA-ICP-MS geochronology.