Denton S. EBEL^1,2,3, Marina E. GEMMA^1,4, Samuel P. ALPERT^1,3, Jasmine BAYRON⁵, Ana H. LOBO⁶, and Michael K. WEISBERG^1,3,7
Meteoritics & Planetary Science (in Press)
Link to Article [https://doi.org/10.1111/maps.14191]
¹Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
²Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
³Department of Earth and Environmental Sciences, Graduate Center of the City University of New York, New York,
New York, USA
⁴Department of Geosciences, Stony Brook University, Stony Brook, New York, USA
⁵Department of Geography, Hunter College, City University of New York, New York, New York, USA
⁶Department Physics & Astronomy, University of California Irvine, Irvine, California, USA
⁷Department of Physical Sciences, Kingsborough College, City University of New York, Brooklyn, New York, USA
Published by arrangement with John Wiley & Sons

Abundances, apparent sizes, and individual chemical compositions of chondrules, refractory inclusions, other objects, and surrounding matrix have been determined for Semarkona (LL3.00) and Renazzo (CR2) using consistent methods and criteria on X-ray element intensity maps. These represent the non-carbonaceous (NC, Semarkona) and carbonaceous chondrite (CC, Renazzo) superclans of chondrite types. We compare object and matrix abundances with similar data for CM, CO, K, and CV chondrites. We assess, pixel-by-pixel, the major element abundance in each object and in the entire matrix. We determine the abundance of “metallic chondrules” in LL chondrites. Chondrules with high Mg/Si and low Fe/Si and matrix carrying opposing ratios complement each other to make whole rocks with near-solar major element ratios in Renazzo. Similar Mg/Si and Fe/Si chondrule–matrix relationships are seen in Semarkona, which is within 11% of solar Mg/Si but significantly Fe-depleted. These results provide a robust constraint in support of single-reservoir models for chondrule formation and accretion, ruling out whole classes of astrophysical models and constraining processes of chondrite component formation and accretion into chondrite parent bodies.

Vincent GUIGOZ ¹, Anthony SERET² , Marc PORTAIL¹ , Ludovic FERRIERE³,
Guy LIBOUREL^2,4, Harold C. CONNOLLY Jr^5,6,7 , and Dante S. LAURETTA⁶
Meteoritics & Planetary Science (in Press) Open Access
Link to Article [https://doi.org/10.1111/maps.14225]
¹DCNRS, CRHEA, Universite C^ote d’Azur, Valbonne, France
²Observatoire de la C^ote d’Azur, CNRS, Laboratoire Lagrange, Universite Cote d’Azur, Nice, France
³Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
⁴Hawai‘i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawai‘i at
Manoa, Honolulu, Hawai‘i, USA
⁵Department of Geology, Rowan University, Glassboro, New Jersey, USA
⁶Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
⁷Department of Earth and Planetary Science, American Museum of Natural History, New York, New York, USA
Published by arrangement with John Wiley & Sons

Carbonates, as secondary minerals found in CM chondrites, have been widely employed for reconstructing the composition of the fluids from which they precipitated. They also offer valuable insights into the hydrothermal evolution of their parent bodies. In this study, we demonstrate that high-resolution cathodoluminescence (HR-CL) analyses of calcites derived from the brecciated Cold Bokkeveld CM2 chondrite can effectively reveal subtle compositional features and intricate zoning patterns. We have identified two distinct types of cathodoluminescence (CL) centers: a blue emission band (approximately 375–425 nm), associated with intrinsic structural defects, and a lower energy orange extrinsic emission (around 620 ± 10 nm), indicating the presence of Mn cations. These compositional variations enable discrimination between the calcite grain types previously designated as T1 and T2 in studies of CM chondrites. T1 calcites exhibit variable CL and peripheral Mn enrichments, consistently surrounded by a rim composed of Fe-S-rich serpentine–tochilinite assemblage. Conversely, T2 calcites display homogeneous CL and more abundant lattice defects. These polycrystalline aggregates of calcite grains, devoid of serpentine, contain Fe-Ni sulfide inclusions and directly interface with the matrix. We propose that changes in the Mn content of calcite (indicated by the intensity of orange CL emission) are influenced by variations in redox potential (Eh) and pH of the fluid phase. This proposed hydrothermal evolution establishes a parallel between terrestrial serpentinization followed by carbonation processes and the aqueous alteration of CM chondrites, warranting further exploration and investigation of this intriguing similarity.