Replacement of olivine by serpentine in the carbonaceous chondrite Nogoya (CM2)

Isotope record of mineralogical changes in a spectrum of aqueously altered CM chondrites

“…Consequently and contrary to our observations, reactions 2 and 3 show that progressive serpentinization leads to increasingly D-poor phyllosilicates in more altered CM chondrites. Moreover, oxygen isotope signatures from calcite grains in CM chondrites predict a closed system for a more or less static fluid (Lindgren et al, 2017), in agreement with the low permeability of CM chondrites and compositional indicators of a static fluid from olivine replacement by serpentine (Velbel et al, 2012). These findings suggest that H 2 removal was not very efficient, reducing the likelyhood of significant D/H fractionation during serpentinization.…”

Comprehensive study of carbon and oxygen isotopic compositions, trace element abundances, and cathodoluminescence intensities of calcite in the Murchison CM chondrite

“…Therefore, we infer that the serpentinization process observed for our type 1 grains occurred during the early stage of alteration where only highly reactive minerals were altered and these reactive minerals controlled the composition of the local alteration fluids. Then, the fluids evolved towards more Mg-rich compositions due to the gradual alteration of anhydrous silicate (Velbel et al, 2012). This is supported by the observed zoning of CL intensity, which indicates that CL intensity became larger with the progressive growth of calcite crystals (Fig.…”

“…The authors argued that the cations required for the replacive minerals would have been sourced by dissolution of highly reactive matrix minerals (fine-grained metal, sulfide, and Fe-rich matrix silicates). This reaction corresponds to alteration stage 2 outlined by Velbel et al (2012), where rapid alteration of fine-grained Fe-host minerals controlled the local fluid composition. Therefore, we infer that the serpentinization process observed for our type 1 grains occurred during the early stage of alteration where only highly reactive minerals were altered and these reactive minerals controlled the composition of the local alteration fluids.…”

“…The matrix in Acfer 094 has D 17 O $ 0& (Sakamoto et al, 2007), whereas chondrules in Acfer 094 have negative D 17 O values of $À2& to À5& (Ushikubo et al, 2012). Velbel et al (2012) suggested that in the earliest alteration stages the compositions of local aqueous fluids were controlled by rapid alteration of chondrule glass and fine-grained ferroan olivine, and in later alteration stages coarse forsteritic olivine controlled the fluid compositions.…”

Replacement of olivine by serpentine in the Queen Alexandra Range 93005 carbonaceous chondrite (CM2): Reactant–product compositional relations, and isovolumetric constraints on reaction stoichiometry and elemental mobility during aqueous alteration

“…Research on CM matrix (and, more recently, chondrule alteration as well) has established a range of degrees of aqueous alteration within CMs of petrologic type 2 (McSween and Richardson, 1977;McSween, 1979aMcSween, ,b, 1987Zolensky et al, 1993Zolensky et al, , 1997Browning et al, 1996;Rubin et al, 2007;Chizmadia and Brearley, 2008;Howard et al, 2009Howard et al, , 2011Takir et al, 2013;Garenne et al, 2014), and from petrologic type 2 to type 1 in CM chondrites (Zolensky et al, 1997;Alexander et al, 2013). CM matrix is initially more Fe-rich than all but the most Fe-rich chondrules in the least altered meteorites and becomes progressively more Mg-rich in meteorites that show independent evidence of more extensive aqueous alteration (McSween and Richardson, 1977;McSween, 1979aMcSween, ,b, 1987Zolensky et al, 1993Zolensky et al, , 1997Browning et al, 1996;Rubin et al, 2007;Chizmadia and Brearley, 2008;Howard et al, 2009Howard et al, , 2011Velbel and Palmer, 2011;Velbel et al, 2012;Takir et al, 2013; see review by Brearley, 2006). Zolensky et al (1993) suggested that differential destruction of olivines with different compositions and therefore different mineral-water reaction kinetics were responsible for variations in the composition of fine-grained serpentine with progressive aqueous alteration of finegrained rims and matrix in CM chondrites.…”