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GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 253-15
Presentation Time: 9:00 AM-6:30 PM

DETRITAL SHOCKED ZIRCON PROVIDES FIRST MAXIMUM AGE CONSTRAINT OF 1472 MA FOR THE SANTA FE IMPACT STRUCTURE, NEW MEXICO (USA)


MONTALVO, Pedro1, CAVOSIE, Aaron J.2, ERICKSON, Timmons M.3, KIRKLAND, Christopher L.3, EVANS, Noreen J.3, MCDONALD, Bradley J.3, TALAVERA, Cristina4 and LUGO-CENTENO, Cristina5, (1)Department of Geology, University of Puerto Rico - Mayaguez, P.O. Box 9000, Mayaguez, PR 00681, (2)TIGeR (The Institute for Geoscience Research), John de Laeter Centre, Department of Applied Geology, Curtin University, Perth, 6102, Australia; Department of Geosciece, University of Wisconsin-Madison, Madison, WI 53706; Department of Geology, University of Puerto Rico - Mayaguez, P.O. Box 9000, Mayaguez, PR 00681, (3)TIGeR (The Institute for Geoscience Research), John de Laeter Centre, Department of Applied Geology, Curtin University, Perth, 6102, Australia, (4)Department of Imaging and Applied Physics, Curtin University, Kent Street, Bentley, 6102, Australia, (5)Department of Earth Sciences, Syracuse, New York, NY 13244, pedro.montalvo1@upr.edu

Shocked minerals provide diagnostic evidence of impact structures, which are prone to erosion, burial and tectonic deformation. Zircon {112} twins are considered diagnostic evidence of shock deformation, and have been identified at several impact structures such as Vredefort [1,2,3,4], Sudbury [5], Ries [6], Rock Elm [7], and in lunar impact breccia [8]. The Santa Fe impact structure contains shatter cones and shocked quartz, but is highly tectonized and eroded; previous reports of impact age (1200–300 Ma) and size (6–13 km) are poorly constrained [9]. Here, we report the first occurrence of shock-twinned zircon in both sediments and bedrock at the Santa Fe impact structure.

A total of 6619 grains from fifteen sediment samples and two rock samples were surveyed; seven shocked grains were identified (7/6619 = 0.1%). One shocked zircon was identified in a biotite schist shatter cone. Five of the seven shocked zircon grains were EBSD mapped; three were analyzed with multiple SIMS spots. EBSD mapping revealed {112} deformation twin lamellae in each of the five zircon grains. U-Pb geochronology for three grains yield crystallization ages from 1715±22 to 1472±35 Ma.

This study revealed the first confirmed shocked zircon at Santa Fe. Zircon, in addition to xenotime and quartz [9,10], is the third confirmed shocked mineral at Santa Fe; its occurrence indicates that exposed bedrock experienced shock pressures of ~ 20 GPa. The crystallization age for a shocked zircon of 1472±35 Ma offers the first and only reliable maximum impact age constraint. The new detrital shocked zircon sites indicate that shocked rocks and minerals may be distributed over an area up to 9 km2, from which scaling laws indicate a crater diameter of 9-14 km.

References: [1] Moser et al. (2011) Can. Jour. Earth Sci., 48, 117-139, [2] Erickson et al. (2013a) Am. Min., 98, 59-65, [3] Montalvo et al. (2017) Am. Min. 102, 813-823, [4] Cavosie et al. (2017) AGU Mon., in press, [5] Thomson et al. (2014) GSA Bull., 126, 720-730, [6] Erickson et al. (2017) Cont. Min. Pet., 172, 6 , [7] Cavosie et al. (2015) Geo., 43, 315-318, [8] Timms et al. (2012) Met. Plan. Sci., 47, 120-141, [9] Fackelman et al. (2008) EPSL, 270, 290-299, [10] Cavosie et al. (2016) Geo., 44, 803-806.

Session No. 253--Booth# 36

T149. Celebrating Dr. John W. Valley's Contributions to Isotope Geochemistry and Beyond, from the Hadean to the Holocene (Posters)
Tuesday, 24 October 2017: 9:00 AM-6:30 PM
Halls 4EF (Washington State Convention Center)
Geological Society of America Abstracts with Programs. Vol. 49, No. 6
doi: 10.1130/abs/2017AM-301967
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