229 Crustal Petrology (Posters)

This session explores various igneous and metamorphic processes that have shaped Earth’s crust. We welcome contributions from the micro- to macroscale, from the deep to shallow crust, and from field- to laboratory- to modeling-based.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Isotopic Insights into Progressive Rodingitization in the Dun Mountain Ophiolite, Aotearoa New Zealand

Paper number: 229-11
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

  • Charlie Hite Presenting Author
    Colorado College Geology Department, Colorado Springs, CO
  • Jesus Lara Rivas
    Colorado College Geology Department, Colorado Springs, CO
  • Nandana Goswami (she/her)
    School of the Earth, Ocean & Environment, University of South Carolina, Columbia, SC
  • Aaron Satkoski
    Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX
  • David Mims
    Colorado College Geology Department, Colorado Springs, CO
  • Jake Hams
    Colorado College Geology Department, Colorado Springs, CO
  • Michelle Gevedon
    Colorado College Geology Department, Colorado Springs, CO
  • Claudiu Nistor
    Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX
  • Jaime Barnes
    Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX
  • Lisa Stockli
    Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX
  • Daniel Stockli
    Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX
  • Besim Dragovic
    School of the Earth, Ocean & Environment, University of South Carolina, Columbia, SC

Abstract

Rodingites are Ca-rich metasomatic rocks commonly found as veins, pods, or dikes in serpentinized ultramafic terranes, formed via interaction of mafic protoliths with high-pH, Ca-rich fluids during serpentinization. Despite localized occurrence, rodingites provide critical records of fluid–rock interaction within the mafic crust and associated mantle and mantle wedge; they also contain underutilized petrogenetic indicator minerals that may constrain the timing and conditions of metasomatism. Rodingite samples were collected from the Dun Mountain Ophiolite Belt and associated mélanges, and display mineralogical evidence of variable degrees of rodingitization, with the progression of plagioclase, to hydrogrossular and andradite ± clinopyroxene, to vesuvianite (e.g., Li et al., 2004). We pair Raman spectra analysis, with oxygen, strontium, and calcium isotope ratios in garnet, pyroxene, vesuvianite and host serpentine to: (1) test whether rodingitization and serpentinization are truly concomitant processes by identifying serpentine polymorphs and testing for equilibrium among ẟ18O values of rodingite garnet and serpentinite phases; (2) determine whether progressive rodingitization may result in the wide range of isotopic compositions exhibited by rodingites; and (3) develop an understanding of the timing and tectonic position of the ophiolite and associated mélanges during rodingitization. ẟ18O ratios are consistent with those of altered ocean crust (2.3 to 7.3‰; n=31), and inter-mineral variability exceeds what can be accounted for by equilibrium fractionation or temperature effects alone; heterogeneity in ẟ44/40Ca values of garnet and pyroxene approach that observed in crustal and mafic rocks globally (−1.38 to 2.88‰; n=15); 87Sr/86Sr ratios are dominated by mafic protolith compositions and indicate an influx of seawater (0.70340 to 0.7050; n=16).

Li, X.-P., Rahn, M., and Bucher, K., 2004, Metamorphic Processes in Rodingites of the Zermatt-Saas Ophiolites: International Geology Review, v. 46, p. 28–51, doi:10.2747/0020-6814.46.1.28.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414593

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