Isotopic analysis of tochilinite (carbonate and magnetite) in Winchcombe: Temperature constraints on early-stage aqueous alteration in the CM parent bodyOPEN ACCESS 

· by · in , , , , , ,

M. D. Suttle, R. Findlay, I. A. Franchi, C. Biagioni, X. Zhao, F. A. J. Abernethy, L. Riches, L. Folco

MAPS, Version of Record online: 03 September 2025

LINK (OPEN ACCESS)
PDF (OPEN ACCESS)

“We report the first oxygen isotope measurements of tochilinite (δ17O: 11.0 ± 2.1‰, δ18O: 23.5 ± 4.0‰ and Δ17O: −1.1 ± 1.2‰) in a CM chondrite (Winchcombe, lithology C [CM2.2/2.3]). We analyzed type-I tochilinite-cronstedtite intergrowths (TCIs)—formed by pseudomorphic replacement of kamacite. Alongside T1 and T2 calcite and magnetite, these secondary phases define a linear trendline in δ17O-δ18O isotope space with a slope of 0.50, slightly shallower than the mass-dependent slope (0.52). This demonstrates that, in addition to dominant mass-dependent fractionation (controlled by mineral-specific and temperature-dependent equilibrium processes), mass-independent mixing between 16O-rich anhydrous silicates, and 16O-poor water influenced the evolving Δ17O composition of alteration fluids. Petrographic evidence shows tochilinite and T1 calcite formed early and are closely associated in the alteration sequence. Assuming isotopic equilibrium between these phases, we estimate formation temperatures of approximately 135°C and a δ18Owater value of 28‰. These findings align with previous hydrothermal synthesis experiments and underscore the value of multi-phase isotopic measurements for reconstructing the fluid history of chondritic parent bodies.”

Related posts (automatically generated):

  1. The Aguas Zarcas carbonaceous chondrite meteorite: Brecciation and aqueous alteration on the parent body
  2. The formation and aqueous alteration of CM2 chondrites and their relationship to CO3 chondrites: A fresh isotopic (O, Cd, Cr, Si, Te, Ti, and Zn) perspective from the Winchcombe CM2 fallOPEN ACCESS 
  3. CM carbonaceous chondrite petrofabrics and their implications for understanding the relative chronologies of parent body deformation and aqueous alterationOPEN ACCESS 
  4. A Coordinated Approach to Investigate the Heterogeneity of Aqueous Alteration at the Micro-Scale in the Winchcombe Meteorite, a CM Fall
  5. Phyllosilicate Rich Rims in Mukundpura Meteorite: Implications for Parent Body Aqueous Alteration
  6. The Sequence of Carbonate Mineralization in the CM Carbonaceous Chondrites Revealed by the Winchcombe Meteorite
  7. LOW-TEMPERATURE AQUEOUS ALTERATION ON THE CR CHONDRITE PARENT BODY: IMPLICATIONS FROM IN SITU OXYGEN-ISOTOPE ANALYSES
  8. PAH Content of CM Chondrites: Influence of Aqueous Alteration on the Parent Body?
  9. Petrographic and Isotopic C and O Survey of the Earliest Stages of Aqueous Alteration of CM Chondrites
  10. Magnetite in Comet Wild 2: Evidence for parent body aqueous alterationOPEN ACCESS 
Tags: , , , , , , ,