The Chlorine Isotopic Composition Of Lunar UrKREEP

Since the long standing paradigm of an anhydrous Moon was challenged there has been a renewed focus on investigating volatiles in a variety of lunar samples. However, the current models for the Moons formation have yet to fully account for its thermal evolution in the presence of H2O and other volatiles. When compared to chondritic meteorites and terrestrial rocks, lunar samples have exotic chlorine isotope compositions, which are difficult to explain in light of the abundance and isotopic composition of other volatile species, especially H, and the current estimates for chlorine and H2O in the bulk silicate Moon. In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed a comprehensive in situ high precision study of chlorine isotopes, using NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) of lunar apatite from a suite of Apollo samples covering a range of geochemical characteristics and petrologic types

Insights into the Martian Regolith from Martian Meteorite Northwest Africa 7034

Everything we know about sedimentary processes on Mars is gleaned from remote sensing observations. Here we report insights from meteorite Northwest Africa (NWA) 7034, which is a water-rich martian regolith breccia that hosts both igneous and sedimentary clasts. The sedimentary clasts in NWA 7034 are poorly-sorted clastic siltstones that we refer to as protobreccia clasts. These protobreccia clasts record aqueous alteration process that occurred prior to breccia formation. The aqueous alteration appears to have occurred at relatively low Eh, high pH conditions based on the co-precipitation of pyrite and magnetite, and the concomitant loss of SiO2 from the system. To determine the origin of the NWA 7034 breccia, we examined the textures and grain-shape characteristics of NWA 7034 clasts. The shapes of the clasts are consistent with rock fragmentation in the absence of transport. Coupled with the clast size distribution, we interpret the protolith of NWA 7034 to have been deposited by atmospheric rainout resulting from pyroclastic eruptions and/or asteroid impacts. Cross-cutting and inclusion relationships and U-Pb data from zircon, baddelleyite, and apatite indicate NWA 7034 lithification occurred at 1.4-1.5 Ga, during a short-lived hydrothermal event at 600-700 C that was texturally imprinted upon the submicron groundmass. The hydrothermal event caused Pb-loss from apatite and U-rich metamict zircons, and it caused partial transformation of pyrite to submicron mixtures of magnetite and maghemite, indicating the fluid had higher Eh than the fluid that caused pyrite-magnetite precipitation in the protobreccia clasts. NWA 7034 also hosts ancient 4.4 Ga crustal materials in the form of baddelleyites and zircons, providing up to a 2.9 Ga record of martian geologic history. This work demonstrates the incredible value of sedimentary basins as scientific targets for Mars sample return missions, but it also highlights the importance of targeting samples that have not been overprinted by metamorphic processes, which is the case for NWA 7034

Alteration of Sedimentary Clasts in Martian Meteorite Northwest Africa 7034

The martian meteorite Northwest Africa (NWA) 7034 and pairings represent the first brecciated hand sample available for study from the martian surface [1]. Detailed investigations of NWA 7034 have revealed substantial lithologic diversity among the clasts [2-3], making NWA 7034 a polymict breccia. NWA 7034 consists of igneous clasts, impact-melt clasts, and "sedimentary" clasts represented by prior generations of brecciated material. In the present study we conduct a detailed textural and geochemical analysis of the sedimentary clasts

Differentiation of peraluminous granite 'en route' to the surface

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GRA 06128 - H & Cl isotopes

Raw H and Cl isotope data obtained by NanoSIMS on phosphates in meteorite GRA 0612

Carbonaceous chondrite organics triple oxygen isotope composition

Raw oxygen isotope data obtained by secondary ion mass spectrometry (both CAMECA IMS 1270/80 and NanoSIMS 50L ion probes) on organics from CI and CM chondrites

NanoSIMS Pb/Pb dating of tranquillityite in high-Ti lunar basalts: Implications for the chronology of high-Ti volcanism on the Moon

In this study, we carried out Pb/Pb dating of tranquillityite in high-Ti mare basalts 10044, 75055, and 74255, using a Cameca NanoSIMS 50 at a spatial resolution of ∼3 μm. The analyses yielded 207Pb/ 206Pb dates of 3722 ± 11 Ma for sample 10044, 3772 ± 9 Ma for sample 75055, and 3739 ± 10 Ma for sample 74255, at 95% confidence level. These dates are consistent with previously determined crystallization and emplacement ages of these samples using different radiogenic systems. These high-precision ages allow refinement of the timing of some of the high-Ti basaltic volcanism on the Moon. Crystallization ages of three different high-Ti basalt units, integrating these new Pb/Pb ages with previous Rb-Sr and Sm-Nd age determinations, are consistent with previous estimates but associated with uncertainties 3 to 5 times lower. In addition, the data obtained in this study confirm that tranquillityite contains very low amounts of initial common Pb and has a high-Pb ionization efficiency, making it an excellent candidate for Pb/Pb dating by ion microprobe. The higher spatial resolution afforded by NanoSIMS 50 and the recent discovery of tranquillityite in several terrestrial mafic rocks opens up a new area of research allowing an independent and rapid age dating of basaltic rocks in polished sections.</p