Chromium isotopic systematics of the Sutter's Mill carbonaceous chondrite: Implications for isotopic heterogeneities of the early solar system

Abstract

Recent studies have shown that major meteorite groups possess their own characteristic 54 Cr values, demonstrating the utility of Cr isotopes for identifying genetic relationships between the planetary materials in conjunction with other classical tools, such as oxygen isotopes. In this study, we performed Cr isotope analyses for whole rocks and chemically separated phases of the new CM2 chondrite, Sutter's Mill (SM 43 and 51). The two whole rocks of Sutter's Mill show essentially identical e 54 Cr excesses (SM 43 = +0.95 AE 0.09e, SM 51 = +0.88 AE 0.07e), relative to the Earth. These values are the same within error with that of the CM2-type Murchison (+0.89 AE 0.08e), suggesting that parent bodies of Sutter's Mill and Murchison were formed from the same precursor materials in the solar nebula. Large e 54 Cr excess of up to 29.40e is observed in the silicate phase of Sutter's Mill, while that of Murchison shows 15.74e. Importantly, the leachate fractions of both Sutter's Mill and Murchison form a steep linear anticorrelation between e 54 Cr and e 53 Cr, cross-cutting the positive correlation previously observed in carbonaceous chondrites. The fact that L4 acid leachate fraction contains higher 54 Cr excesses than that of L5 step designed to dissolve refractory minerals suggests that spinel is not a major 54 Cr carrier. We also note that L5 contains 53 Cr anomalies lower than the solar initial value, suggesting it carries a component of nucleosynthetic anomaly unrelated to the 53 Mn decay. We have identified five endmember components of nucleosynthetic origin among the early solar system materials.

53Mn‐53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite

“…Regardless of the interpretation of the bulk isochron, Sutter's Mill dolomites record a younger age than the bulk trend, consistent with a later stage Mn redistribution occurring on the CM parent body. Mn‐Cr isotopes have also been measured in mineral leachates from SM51 (Yamakawa and Yin ). The leaching was performed to identify the mineral phases containing distinct manganese and Cr isotopic signatures (Yamakawa and Yin ).…”

“…Mn‐Cr isotopes have also been measured in mineral leachates from SM51 (Yamakawa and Yin ). The leaching was performed to identify the mineral phases containing distinct manganese and Cr isotopic signatures (Yamakawa and Yin ). Leachate L1 in their study is comprised of easily soluble minerals that are dissolved by weak acids, including carbonates and sulfides.…”

Cr isotopes in physically separated components of the Allende CV3 and Murchison CM2 chondrites: Implications for isotopic heterogeneity in the solar nebula and parent body processes

“…; Petitat et al. ; Yamakawa and Yin ) shows that large variations and differences exist in Cr‐isotopic compositions of leachates and residues compared to the bulk rocks. The relative roles of mixing and grain‐scale variations, parent body alteration, and incongruent leaching on chromium isotopic ratios in leaching experiments are sometimes unclear.…”

Chromium Isotopic Constraints on the Origin of the Ureilite Parent Body

“…The ε 54 Cr value, which is the mass fractionation corrected deviation of the 54 Cr/ 52 Cr ratio from the terrestrial value in parts per 10,000, varies between bulk meteorite groups and reflects heterogeneous distribution of 54 Cr-rich supernova grains in the proto-solar molecular cloud material (Dauphas et al 2010;Qin et al 2011;Nittler et al 2018). This is expressed by higher ε 54 Cr values of carbonaceous chondrites (CC;Trinquier et al 2007;Qin et al 2010a;Yamashita et al 2010;Petitat et al 2011;Yamakawa & Yin 2014;Göpel et al 2015), compared to ordinary chondrites (OC) and some differentiated meteorites (e.g., Martian meteorites, angrites, howardite-eucrite-diogenite clan, mesosiderites, acapulcoitelodranite clan, winonaites, pallasites, and iron meteorites; Trinquier et al 2007;Qin et al 2010a;Li et al 2018;Pedersen et al 2019;Zhu et al 2019b), whereas the enstatite chondrites (EC), the Earth, the Moon, and the aubrites have intermediate values (Trinquier et al 2007;Qin et al 2010a;Mougel et al 2018).…”