Characteristics of a New Carbonaceous Chondrite, Metal-Rich-Lithology Found in the Carbonaceous Chondrite Breccia Aguas Zarcas

The Aguas Zarcas meteorite fell in Costa Rica on 23 April 2019 at 21:07 local time, with a total mass of about 27 kg. Hundreds of fusion-crusted stones ranging from 0.1 to 1868 g were recovered (The Meteoritical Bulletin). The meteorite was classified as a CM chondrite, but some lithlogies show a different texture to that of CM. In this study, we investigated the petrography, mineral-ogy, chemistry, and isotopic composition of an unusual Metal-rich-lithology from this fresh fall

Mineralogical Study of a White Clast from Murchison (CM2): Comparison with R-Chondrites

R-chondrites share some properties with ordinary chondrites (OC) and carbonaceous chondrites (CC). The proportions of the textural types of chondrule from R chondrites and their FeO/(FeO+MgO) ratios are similar to those of OC, but the high matrix abundance in R chondrites more closely resembles that of CC (matrix abundances: OC ~12 vol% vs. CC 34->60 vol%;). In this study, we characteristize the mineralogy of a white clast from Murchison (CM2), which was earlier considered to be a R-chondrite. First, all the petrographic and mineralogical characteristics will be described and compared with those of R-chondrites. Finally, all data will be considered in order to test, whether this clast is a real R-chondrite or a unique recrystallized chondrite

A Re-Investigation of a Chondritic Xenolith in the Murchsion (CM2) Chondrite: Formation by Fluid-Assisted Percolation During Metamorphism

The CM chondrites are generally complex impact breccias, in which lithic clasts and mineral fragments showing various degrees of aqueous alteration and possibly originating from different parent bodies are mixed together. The occurrence of CM-like clasts in other chondritic and achondritic meteorite breccias is also well-documented, however, reports on the occurrence of foreign clasts in CM chondrites are rare. In this study, we reinvestigated the white clast in the Murchison CM chondrite and demonstrate that the clast is not related to R chondrites as earlier suggested. In addition to the classification we discuss the origin and the history of its formation by studying several aspects like mineralogy, bulk chemistry, Rare Earth Elements (REE), oxygen isotopes, and the soluble organic compounds

A light, chondritic xenolith in the Murchison (CM) chondrite - Formation by fluid-assisted percolation during metasomatism?

The main mineralogical characteristics of a large light-colored clast within the Murchison CM breccia are discussed in detail including data on the mineralogy, bulk chemistry, organics, and oxygen isotopes. Petrographic study shows that the white clast consists of two areas with different granoblastic textures: (1) a coarse-grained (average grain size: similar to 200 mu m) and (2) a fine-grained lithology (average grain-size: similar to 20 mu m). The Fa-content of olivine in the clast is the same as Fa within olivine from Rumuruti (R) chondrites (Fa: similar to 38 mol%); however, the concentrations of the elements Ni and Ca in olivine are significantly different. The fragment also contains Ca-rich pyroxene, similar to An(30-38)-plagioclase/maskelynite, Cr-rich spinel, several sulfide phases, a nepheline-normative glass, and traces of merrillite and metal. The occurrence of maskelynite and nepheline-normative amorphous phase in restricted areas of the well-recrystallized rock may indicate remarkable P-T-excursions during shock metamorphism. The O-isotope composition of the clast falls below the terrestrial fractionation line (TFL), lying in the field of CM chondrites and is significantly different from data for bulk R chondrites. The study of the soluble organic matter revealed a highly-oxidized carbon chemistry and organomagnesium compounds reflecting high temperature and pressure processes

Heterogeneous nature of the carbonaceous chondrite breccia Aguas Zarcas – Cosmochemical characterization and origin of new carbonaceous chondrite lithologies.

On April 23rd, 2019, the Aguas Zarcas meteorite fall occurred in Costa Rica. Because the meteorite was quickly recovered, it contains valuable extraterrestrial materials that have not been contaminated by terrestrial processes. Our X-ray computed tomography (XCT) and scanning electron microscopy (SEM) results on various pre-rain fragments from earlier work (Kerraouch et al., 2020; 2021) revealed several distinct lithologies: Two distinct metal-rich lithologies (Met-1 and Met-2), a CM1/2 lithology, a C1 lithology, and a brecciated CM2 lithology consisting of different petrologic types. Here, we further examined these lithologies in the brecciated Aguas Zarcas meteorite and report new detailed mineralogical, chemical, isotopic, and organic matter characteristics. In addition to petrographic differences, the lithologies also display different chemical and isotopic compositions. The variations in their bulk oxygen isotopic compositions indicate that the various lithologies formed in different environments and/or under diverse conditions (e.g., water/rock ratios). Each lithology experienced a different hydration period during its evolution. Together, this suggests that multiple precursor parent bodies may have been involved in these processes of impact brecciation, mixing, and re-assembly. The Cr and Ti isotopic data for both the CM1/2 and Met-1 lithology are consistent with those of other CM chondrites, even though Met-1 displays a significantly lower ε50Ti isotopic composition that may be attributable to sample heterogeneities on the bulk meteorite scale and may reflect variable abundances of refractory phases in the different lithologies of Aguas Zarcas. Finally, examination of the organic matter of the various lithologies also suggests no strong evidence of thermal events, but a short-term heating cannot completely be excluded. Raman parameters indicate that the peak temperature has been lower than that for Yamato-793321 (CM2, ∼400 °C). Considering the new information presented in this study, we now better understand the origin and formation history of the Aguas Zarcas daughter body

The old, unique C1 chondrite Flensburg – Insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies

On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Germany, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. An exceptionally short exposure time of ∼5000 years was determined. The 24.5 g stone has a fresh black fusion crust, a low density of −9 m3/kg). The rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained matrix. The most abundant phases are phyllosilicates. Carbonates (∼3.9 vol.%) occur as calcites, dolomites, and a Na-rich phase. The relict chondrules (often surrounded by sulfide laths) are free of anhydrous silicates and contain abundant serpentine. Lithic clasts are also surrounded by similar sulfide laths partly intergrown with carbonates. 53Mn-53Cr ages of carbonates in Flensburg indicate that brecciation and contemporaneous formation of the pyrrhotite-carbonate intergrowths by hydrothermal activities occurred no later than 4564.6 ± 1.0 Ma (using the angrite D'Orbigny as the Mn-Cr age anchor). This corresponds to 2.6 ± 1.0 or 3.4 ± 1.0 Ma after formation of CAIs, depending on the exact absolute age of CAIs. This is the oldest dated evidence for brecciation and carbonate formation, which likely occurred during parent body growth and incipient heating due to decay of 26Al. In the three oxygen isotope diagram, Flensburg plots at the 16O-rich end of the CM chondrite field and in the transition field to CV-CK-CR chondrites. The mass-dependent Te isotopic composition of Flensburg is slightly different from mean CM chondrites and is most similar to those of the ungrouped C2 chondrite Tagish Lake. On the other hand, 50Ti and 54Cr isotope anomalies indicate that Flensburg is similar to CM chondrites, as do the ∼10 wt.% H2O of the bulk material. Yet, the bulk Zn, Cu, and Pb concentrations are about 30% lower than those of mean CM chondrites. The He, Ne, and Ar isotopes of Flensburg show no solar wind contribution; its trapped noble gas signature is similar to that of CMs with a slightly lower concentration of 20Netr. Based on the bulk H, C, and N elemental abundances and isotopic compositions, Flensburg is unique among chondrites, because it has the lightest bulk H and N isotopic compositions of any type 1 or 2 chondrite investigated so far. Moreover, the number of soluble organic compounds in Flensburg is even lower than that of the brecciated CI chondrite Orgueil. The extraordinary significance of Flensburg is evident from the observation that it represents the oldest chondrite sample in which the contemporaneous episodes of aqueous alteration and brecciation have been preserved. The characterization of a large variety of carbonaceous chondrites with different alteration histories is important for interpreting returned samples from the OSIRIS-REx and Hayabusa 2 missions