^1,2Swarna Prava Das,³Alessandro Maturilli,³Aurélie Van den Neucker,⁴Markus Patzek,⁵Dipak Kumar Panda,⁶Gopal K. Pradhan,^1,2Guneshwar Thangjam,^1,2,7Surya Snata Rout
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70183]
¹School of Earth and Planetary Sciences, National Institute of Science Education and Research (NISER), Khordha, Odisha,752050, India
²Homi Bhabha National Institute, Training School Complex, Mumbai, 400094, India
³Institute of Space Research, German Aerospace Centre (DLR), Berlin, 12489, Germany
⁴Institut für Planetologie (IfP), Universität Münster, Münster, 48149, Germany
⁵Planetary Science Division, Physical Research Laboratory, Ahmedabad, Gujarat, 380009, India
⁶Department of Physics, School of Applied Sciences, KIIT Deemed to be University, Bhubaneswar, 751024, India
⁷Center for Interdisciplinary Sciences (CIS), NISER Bhubaneswar, Khordha, Odisha, 752050, India
Published by arrangement with John Wiley & Sons

Volatile-rich xenolithic clasts in different types of brecciated meteorites represent unique pristine solar system material. This study investigates the maturity and thermal history of organic matter using Raman spectroscopy and aqueous alteration effects using infrared spectroscopy in the matrix of 15 volatile-rich clasts (C1 and CM-like) present in a polymict eucrite (NWA 7542) and a howardite (Sarıçiçek). Most of the studied C1 and CM-like clasts show similar maturity of organic matter as CI chondrites and CM chondrites, respectively. One CM-like clast from the polymict eucrite NWA 7542 shows Raman spectral signatures of heating after aqueous alteration, and another C1 and a CM-like clast from the howardite Sarıçiçek exhibit unique Raman spectral properties probably related to differences in accreted precursor organics compared to CI and CM-chondrites. One olivine-rich, unclassified clast has a high concentration of fayalitic olivine in its matrix, similar to oxidized CV chondrites and other features similar to CM- or C2 chondrites. Various evidence shows that this clast was heated up to 700–800 °C post aqueous alteration followed by the formation of fayalitic olivine during a metasomatic alteration process. Peak metamorphic temperature (PMT) estimated using different thermometric approaches does not provide reliable data for clasts altered at low temperatures (<200 °C).