DOI: 10.5066/p1acwnbp
title: Thin section images, automated mineralogy scans, lithogeochemistry, and Nd-Sr-Pb isotopic analysis of samples from a mostly buried layered mafic intrusion, Wet Mountains, Colorado 2022-2024

description: This dataset includes thin section images, automated mineralogy mineral maps, whole-rock geochemical data, and whole-rock Nd-Sr-Pb isotopic analysis of samples collected from nine mafic-ultramafic outcrops in the Wet Mountains, southern Colorado, during the summer of 2022. These data will accompany an upcoming journal publication and are intended to supplement recently collected airborne magnetic and ground gravity data that indicate a mostly buried mafic-ultramafic intrusion of unknown age (Grauch et al., 2023; Magnin and Anderson, 2023; Magnin et al., 2023). Outcrop locations were identified based on previous mapping by Taylor (1974). A single thin section was made from each sample, and both plain- and cross-polarized light (PPL and XPL, respectively) images were taken of the entire section using a flatbed film scanner. Automated mineralogy (AM) scans were collected from half of each thin section using a TESCAN Integrated Mineral Analyzer (TIMA) at the Colorado School of Mines Mineral and Materials characterization facility. Whole-rock major and trace element geochemistry of samples used for thin sections and of separate compositional layers in thin section JWM-129 (i.e., JWM-129.1, -129.2) were analyzed by Activation Laboratories Ltd., Ancaster, Ontario. Platinum group element chemistry was collected and analyzed by AGAT Laboratories, Calgary, Alberta. Five whole-rock samples and two mineral separates were analyzed using Sm-Nd thermal ionization mass spectrometry (TIMS) at the University of Colorado Boulder TIMS Facility and Clean Room. The same five whole-rock samples were also analyzed for Rb-Sr and Pb-Pb isotopes using TIMS at the same lab. All analyses were performed between October 2022 and February 2024.
The images contained in the zip file are categorized by sample name and additionally labeled with PPL, XPL, and AM categories. Automated mineralogy image names end with a letter indicating whether the top (T), bottom (B), left (L), or right (R) half of the thin section was scanned. A csv file of the modal mineral percentages from automated mineralogy is also included in the zip file. Sample locations/descriptions, whole rock geochemistry, Nd-Sr-Pb isotopes, and a data dictionary are included in csv files.

References
Grauch, V.J.S., Anderson, E.D., Brown, P.J., and Allen Langhans, A.D., 2023, Airborne magnetic and radiometric survey of the Wet Mountains and surrounding region, Custer and Fremont Counties, south-central Colorado, 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9PISI0X.

Magnin, B.P. and Anderson, E.D., 2023, Gravity data in the Wet Mountains area, southcentral Colorado, 2021 to 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P9XJ7FMM.

Magnin, B.P., Kuiper, Y.D., and Anderson, E.D., 2023, Ediacaran‐Ordovician Magmatism and REE Mineralization in the Wet Mountains, Colorado, USA: Implications for Failed Continental Rifting: Tectonics, v. 42, no. 4, 28 p. https://doi.org/10.1029/2022TC007674.

Taylor, R.B., 1974, Reconnaissance geologic map of the Deer Peak quadrangle and southern part of the Hardscrabble Mountain Quadrangle, Custer and Huerfano counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map I-870, https://doi.org/10.3133/i870.