Work Description

Title: Apatite and Zircon (U-Th)/He Thermochronometry Data from the Colorado Front Range, Boulder County, Colorado, USA Open Access Deposited

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Methodology
  • Methodology for determining apatite and zircon (U-Th)/He ages for rock samples from the Front Range, Boulder, Colorado, USA. Rock samples were collected from the Southern Rocky Mountains west of Boulder, Colorado, in 2016. The samples were primarily collected from Proterozoic igneous and metamorphic rocks. Individual apatite and zircon grains were extracted from the rock samples using standard crushing, magnetic, and density techniques. Individual apatite and zircon mineral grains were hand-selected under a microscope and encapsulated in Nb foil tubes. Naturally occurring <sup>4</sup>He in each grain was extracted via laser heating on an ASI Alphachron Helium Instrument at the University of Michigan and measured by isotope dilution mass spectrometry on a quadrupole mass spectrometer. See Niemi and Clark, 2018, for detailed analytical procedures at the University of Michigan.

  • Individual grain packets were subsequently dissolved in HNO<sub>3</sub> and the quantity of U, Th, and Sm in each grain were measured by inductively-coupled plasma mass spectrometry at the University of Arizona. See Reiners and Nicolescu, 2006. The (U-Th-Sm)/He thermochronologic ages derived from individual mineral grains were determined using the standard radiogenic age equations, solved using a Matlab script. Age errors are propagated from analytical uncertainties. Age corrections due to alpha-ejection follow standard protocols. In table 1 we report standard deviations on sample mean ages where this value is ≤15 % and the range of ages for samples with >15 % s.d. on the sample mean age.

  • Niemi, N.A. and Clark, M.K., 2018. Long-term exhumation rates exceed paleoseismic slip rates in the central Santa Monica Mountains, Los Angeles County, California. Geology, 46(1), pp.63-66.

  • Reiners, P.W. and Nicolescu, S., 2006. Measurement of parent nuclides for (U–Th)/He chronometry by solution sector ICP-MS. ARHDL Report, 1, pp.1-33.
Description
  • These data were produced in the scope of research into understanding the application of zircon (U-Th)/He thermochronometric data derived from rocks with complex radiation damage distributions to the extraction of long-term (>1 Gyr) thermal histories of the Earth's upper crust. The samples used in this study were collected from the Front Range in Colorado, USA. The low-temperature (apatite and zircon (U-Th)/He) thermochronometric ages presented in this data set are sensitive to near-surface temperatures (~80C and 180C, respectively) and record the progressive exhumation of the rock mass from which the samples were collected towards the Earth's surface. These thermochronometric ages, and the differences between them, provide insight into the deep-time (~1000 Ma - 100 Ma) thermal history of the Colorado Front Range.
Creator
Depositor
  • naniemi@umich.edu
Contact information
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Funding agency
  • Other Funding Agency
Other Funding agency
  • University of Michigan
Keyword
Resource type
Last modified
  • 11/29/2022
Published
  • 05/25/2022
Language
DOI
  • https://doi.org/10.7302/g4eg-vr84
License
To Cite this Work:
Murray, K. E., Niemi, N. A., Clark, M. C. (2022). Apatite and Zircon (U-Th)/He Thermochronometry Data from the Colorado Front Range, Boulder County, Colorado, USA [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/g4eg-vr84

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Files (Count: 5; Size: 70.7 KB)

Thumbnailthumbnail-column Title Original Upload Last Modified File Size Access Actions
FrontRange_tables_DeepBlue.xlsx 2022-04-08 2022-04-08 55.3 KB Open Access
Table2_3_Units.txt 2022-05-25 2022-05-25 799 Bytes Open Access
Table1_U-Th_He_Results_Summary_v2.csv 2022-05-25 2022-07-09 1.3 KB Open Access
Table2_Zircon_U-Th_He_Results.csv 2022-05-25 2022-05-25 7.21 KB Open Access
Table3_Apatite_U-Th_He_Results.csv 2022-05-25 2022-05-25 6.05 KB Open Access

Table 2
- Grain ID
- [U] ppm (unit: ppm)
- [U] SD (unit: ppm)
- [Th] (unit: ppm)
- [Th] SD (unit: ppm)
- [eU] (unit: ppm)
- 4He (unit: ncc)
- 4He error (unit: ncc)
- [4He] (unit: ncc/g)
- Mass (unit: mg)
- FT
- Half-width (unit: µm)
- Shape*
- Length (unit: µm)
- Uncorr. Age (unit: Ma)
- Age (unit: Ma)
- Age Error (unit: Ma)

Table 3
- Grain ID
- [U] ppm (unit: ppm)
- [U] SD (unit: ppm)
- [Th] (unit: ppm)
- [Th] SD (unit: ppm)
- [Sm] (unit: ppm)
- [Sm] SD (unit: ppm)
- [eU] (unit: ppm)
- 4He (unit: ncc)
- 4He error (unit: ncc)
- [4He] (unit: ncc/g)
- Mass (unit: mg)
- FT
- Half-width (unit: µm)
- Shape*
- Length (unit: µm)
- Uncorr. Age (unit: Ma)
- Age (unit: Ma)
- Age Error (unit: Ma)

* shapes: nn = complete grain, np = missing one termination, pp = missing both terminations

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