Abstract
Abstract— Four different types of calcium‐ and aluminium‐rich inclusions (CAIs) have been identified in the CM2 chondrite Murray, three of which contain alteration products. Two types of altered CAIs, spinel inclusions and spinel‐pyroxene inclusions, contain primary spinel (± perovskite ± hibonite ± diopside) and secondary Fe‐rich serpentine phyllosilicates (± tochilinite ± calcite). Original melilite in these CAIs is inferred to have been altered during aqueous activity in the parent body and Fe‐rich serpentines, tochilinite and calcite were formed in its place.The other type of altered CAI is represented by one inclusion, here called MCA‐1. This CAI contains primary spinel, perovskite, fassaite and diopside with secondary calcite, paragonite, Mg‐Al‐Fe phyllosilicates and a Mg‐Al‐Fe sulphate. Importantly, MCA‐1 is similar in both primary and secondary mineralogy to a small number of altered CAIs described from other CM2 meteorites including Essebi, Murchison and a CM2 clast from Plainview. Features that these CAIs have in common include an unusually large size, a CV3‐like primary mineralogy and the presence of secondary aluminosilicates and calcite. The Al‐rich alteration products in MCA‐1 are also reminiscent of secondary minerals in refractory inclusions from CV3 meteorites, which have previously been interpreted to form by interaction of the inclusions with solar nebula gases. In common with the other types of altered CAIs in Murray, MCA‐1 is inferred to have experienced its main phase of alteration in a parent body environment. The Mg‐Al‐Fe phyllosilicates, calcite and the Mg‐Al‐Fe sulphate formed following aqueous alteration of an Al‐rich precursor, possibly Ca dialuminate. This episode of parent body alteration may have overprinted an earlier phase of alteration in a solar nebula environment from which only paragonite remains.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.