Title of Oral/Poster Presentation

Hematite and zircon (U-Th)/He thermochronometry from Deadman Creek, Sangre de Cristo Mountain Range, Colorado

Presenter Information

Brianna HillFollow

Class

Article

Graduation Year

2018

College

College of Science

Department

Geology Department

Faculty Mentor

Alexis Ault

Presentation Type

Poster Presentation

Abstract

Authors: B. Hill, A. Ault, J. Caine

The Sangre de Cristo Mountains in south-central Colorado experienced multiple overprinting tectonic events in the last ~1.7 billion years. Low-temperature thermochronometry enables detailed investigation of this complex history and periods of rock exhumation related to specific tectonic events. Here, we apply zircon and hematite (U-Th)/He analyses to constrain the time-temperature history of the Mesoproterozoic (~1.4-1.7 Ga) crystalline basement rocks and faulting in the Sangre de Cristo Mountains. Two major structures cut Mesoproterozoic crystalline rocks in the Deadman Creek study area. The contractional Deadman Thrust fault likely developed during Laramide orogeny and the Sangre de Cristo normal fault likely accommodated extension as part of the Rio Grande rift. These faults both strike south-southeast, but the Deadman thrust dips shallowly to the west-southwest and is cut by the steeply dipping Sangre de Cristo.

Eight crystalline basement rock samples were collected in an elevation transect along a ridge south of Deadman Creek. Each sample yielded abundant zircons for zircon (U-Th)/He analysis. Target zircon crystals range in texture from clear and prismatic to purple-brown and rounded. Hematite occurs as fault veins and cements fault breccia. Three samples of hematite-cemented breccia were collected for hematite (U-Th)/He analyses and aliquots comprising coarse-grained specular plates were extracted. In order to reconstruct a detailed thermal history for the region, we will acquire new zircon and hematite (U-Th)/He data from these samples and integrate it with the existing published geologic and thermochronologic data from the region. We anticipate that zircon (U-Th)/He data will provide information about the timing and tempo of erosional exhumation of the basement rock during the Ancestral Rocky and/or the Laramide orogenies. Hematite (U-Th)/He data may constrain the timing of fault processes associated the Laramide orogeny and/or Rio Grande rifting responsible for exhumation of the basement rocks.

Location

North Atrium

Start Date

4-13-2017 3:00 PM

End Date

4-13-2017 4:15 PM

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Apr 13th, 3:00 PM Apr 13th, 4:15 PM

Hematite and zircon (U-Th)/He thermochronometry from Deadman Creek, Sangre de Cristo Mountain Range, Colorado

North Atrium

Authors: B. Hill, A. Ault, J. Caine

The Sangre de Cristo Mountains in south-central Colorado experienced multiple overprinting tectonic events in the last ~1.7 billion years. Low-temperature thermochronometry enables detailed investigation of this complex history and periods of rock exhumation related to specific tectonic events. Here, we apply zircon and hematite (U-Th)/He analyses to constrain the time-temperature history of the Mesoproterozoic (~1.4-1.7 Ga) crystalline basement rocks and faulting in the Sangre de Cristo Mountains. Two major structures cut Mesoproterozoic crystalline rocks in the Deadman Creek study area. The contractional Deadman Thrust fault likely developed during Laramide orogeny and the Sangre de Cristo normal fault likely accommodated extension as part of the Rio Grande rift. These faults both strike south-southeast, but the Deadman thrust dips shallowly to the west-southwest and is cut by the steeply dipping Sangre de Cristo.

Eight crystalline basement rock samples were collected in an elevation transect along a ridge south of Deadman Creek. Each sample yielded abundant zircons for zircon (U-Th)/He analysis. Target zircon crystals range in texture from clear and prismatic to purple-brown and rounded. Hematite occurs as fault veins and cements fault breccia. Three samples of hematite-cemented breccia were collected for hematite (U-Th)/He analyses and aliquots comprising coarse-grained specular plates were extracted. In order to reconstruct a detailed thermal history for the region, we will acquire new zircon and hematite (U-Th)/He data from these samples and integrate it with the existing published geologic and thermochronologic data from the region. We anticipate that zircon (U-Th)/He data will provide information about the timing and tempo of erosional exhumation of the basement rock during the Ancestral Rocky and/or the Laramide orogenies. Hematite (U-Th)/He data may constrain the timing of fault processes associated the Laramide orogeny and/or Rio Grande rifting responsible for exhumation of the basement rocks.