Abstracts for Virtual Thermo2020
February 16, 2020, Session 5
Evidence for a Late Cretaceous impact structure in Black Mesa, Arizona
Daan Beelen1*, Ray Donelick2
1 SAnD Consortium, Colorado School of Mines, 1500 Illinois St, Golden, Colorado, USA
2 Apatite.com Partners LLC, 1075 Matson Road, Viola, Idaho, USA
This study presents evidence for a hitherto undiscovered impact structure in Black Mesa, NE Arizona. The structure’s macrostructure is mapped on satellite data as a series of concentric catchments and landscape geometries approximately 7 kilometers in diameter, with upward tilting strata dipping from the center of the structure. Subsequent field research has yielded observations of meso-scale impact structures in the form of melt breccia’s and titled blocks with abundant pseudotachylite melt. Partially molten and shocked zircon grains inside the molten breccias were identified using a SEM, and X-ray diffraction indicates elevated amounts of ultra-refractory elements within the same samples. The structure lies within strata belonging to the Upper Cretaceous Toreva Member and Wepo Members, Mesa Verde Group, Upper Cretaceous.
Apatite fission track (AFT) data were measured for two samples showing evidence of partial melting. Apatite grains – and their associated fission track data – were sorted into sub-groups using rare earth element concentrations and uranium-lead ages. The pooled AFT ages for all sub-groups studied are shown in the figure below.
Seven apatite grain sub-groups are common to both samples studied. For sample P10014_004, apatite grain sub-groups 2A and 4A yield pooled AFT ages of 70.6 -12.4/+15.1 Ma (95% CI; 14 grains) and 63.2 -8.6/+9.9 (95% CI; 30 grains), respectively, and a weighted mean age of 65.5 ± 7.7 Ma (2σ). The evidence presented here insinuates to the presence of the largest impact structure in the state of Arizona and may have implications to the Cretaceous–Paleogene mass extinction, although more work is necessary to prove these theories.
Field work on the Navajo Nation was conducted under a permit from the Navajo Nation Minerals Department. Any person(s) wishing to conduct geologic investigations on the Navajo Nation must first apply for and receive a permit from the Navajo Nation Minerals Department, P.O. Box 1910, Window Rock, Arizona 86515 and Telephone No. +1 (928) 871-6587
High-resolution fission track analysis of detrital apatite grains grouped using UPb ages and REE concentrations
Ray Donelick1, Cleber Soares2, Liu Zhaoqian3, Rachel Hoar4,*, Daan Beelen5, Andrew Donelick6, and Richard Carlton7
1 Apatite.com Partners LLC, 1075 Matson Road, Viola, Idaho, USA
2 Chronuscamp Research, Rua João Rodrigues dos Santos 60, Itapira, São Paulo, Brazil
3 Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, China
4 Geology & Geophysics, Texas A&M University, College Station, Texas, USA
5 SAnD Consortium, Colorado School of Mines, 1500 Illinois St, Golden, Colorado, USA
6 Gone Fission Mining LLC, 238 E 5th Street, Walsenburg, Colorado, USA
7 Navajo Nation Minerals Department, PO Box 1910, Window Rock, Arizona, USA
O’Sullivan et al. (2018, G3, v. 19, no. 9; 2020, Earth-Science Reviews, v. 201, no. 103044) demonstrate how UPb age and rare earth element (REE) concentrations can provide useful genetic and provenance information for detrital apatite grains. Here, we use UPb age, REE concentrations, and parameter Rmr0 to bin apatite grains – and their associated fission track data – into kinetic populations for thermal history modeling. Each UPb age is based on a single LA-QICP-MS spot analysis with an assumed common-Pb component (after Chew and Donelick, 2012, MAC Short Course, v. 42). The REEs are C1-chondrite normalized using – as a matrix-matched standard – the same Durango crystal studied by Chew et al. (2016, Chemical Geology, v. 435). Kinetic parameter Rmr0 is determined using LA-QICP-MS data (Na, Mg, Al, Si, P, S, Cl, Ca, Mn, Fe, As, Br Y, 14 REEs, Hg, Pb, Th, U), assuming only chlorine (measured after Chew et al. 2014, Geostandards and Geoanalytical Research, v. 38; US Patent 8,901,485) and fluorine (calculated from chlorine) in the halogen site.
Conventional AFT analysis uses measured values such as Dpar (US Patent 5,267,274) or elemental compositions (e.g., chlorine concentration from EPMA) to distribute apatite fission track data into kinetic populations. The protocol used here offers a higher degree of resolution of the annealing kinetics, because the apatite fission track data are first distributed into provenance groups defined by UPb age and REE concentrations. Within these provenance groups, apatite fission track data can be further distributed into kinetic populations using Rmr0, much like the conventional analysis.
This work was funded in part by The National Science and Technology Major Project of China (No.2016ZX05035-001-003 and No.2016ZX05002-006-007) and National Natural Science Foundation of China (No.41302112).
A mobile fission track microscope system for STEM education in remote communities
Ray Donelick1, Andrew Donelick2,*, Cleber Soares3, Tais Fontes Pinto4, Zachary Dodds5, Daan Beelen6, Murat Tamer7
1 Apatite.com Partners LLC, 1075 Matson Road, Viola, Idaho, USA
2 Gone Fission Mining LLC, 238 E 5th Street, Walsenburg, Colorado, USA
3 Chronuscamp Research, Rua João Rodrigues dos Santos 60, Itapira, São Paulo, Brazil
4 Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
5 Computer Science Department, Harvey Mudd College, Claremont, California, USA
6 SAnD Consortium, Colorado School of Mines, 1500 Illinois St, Golden, Colorado, USA
7 Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA
We tested and demonstrated components of a mobile fission track microscope system, at American Associate of Petroleum Geologists, Annual Conference and Exhibition, in San Antonio, Texas during May 2019. The microscope system and the technology behind it can be hauled anywhere – such as from Idaho to our AAPG exhibitor’s booth in Texas – using a personal vehicle and requires simple climate-controlled space with electricity.
Fission track thermochronology – its calibration and its application – will benefit from datasets comprised of 1000s of datum points per sample. We envision employing young students (in USA, Grades 6-12 for example) to collect the bulk of these data for select interesting samples using our mobile fission track microscope system. We believe this system can be used to excite and educate young students in a range of science, technology, engineering, and mathematics (STEM) disciplines. The young students can do the heavy lifting of finding and initially characterizing mineral grains for fission track analysis using various AI tools. Results from the young students can be vetted by digitally connected and collaborating professional scientists. This mobile fission track laboratory enables distance learning with a personal touch while applying state-of-the-art science in collaboration with an international network of passionate and skilled scientists.
We envision the following value propositions:
- For young students
- introduction to STEM using state-of-the-art science over a range of subjects: natural sciences from isotope geology to tectonics to meteorites, chemistry and physics, computer science
- hands-on experience in a true ‘peer laboratory’ on par with any advanced laboratory anywhere