Moe Matsuoka et al. (>10)*
Earth, Planets and Space 69, 120 Link to Article [https://doi.org/10.1186/s40623-017-0705-4]
¹Tohoku University, Sendai, Japan

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Pedro Corona-Chávez, ²María del Sol Hernández-Bernal, ³Pietro Vignola, ⁴Rufino Lozano-Santacruz, ⁵Juan Julio Morales-Contreras, ⁴Margarita Reyes-Salas, ⁵ Jesús Solé-Viñas, ⁶José F.Molina
Chemie der Erde (in Press) Link to Article [https://doi.org/10.1016/j.chemer.2017.12.003]
¹Universidad Michoacana de San Nicolás de Hidalgo, Instituto de Investigaciones en Ciencias de la Tierra, Edificio U, Ciudad Universitaria, Morelia, 58020, Mexico
²Universidad Nacional Autónoma de México, Escuela Nacional de Estudios Superiores, Unidad Morelia, 58190, Mexico
³Consiglio Nazionale delle Ricerche (CNR) – Istituto per la dinamica dei processi ambientali, via Botticelli 23, 20133 Milan, Italy
⁴Universidad Nacional Autónoma de México, Instituto de Geología, Circuito interior Ciudad Universitaria, 04510, Mexico
⁵Universidad Nacional Autónoma de México, Instituto de Geofísica, Unidad Morelia, 58190, Mexico
⁶Departamento de Mineralogía y Petrología, Universidad de Granada, Spain
Copyright Elsevier

We present the results of physical properties, petrography, bulk chemistry, mineral compositions, phase relations modelling and Noble gases study of the meteorite El Pozo. The petrography and mineral compositions indicate that the meteorite is an L5 chondrite with a low shock stage of S2-S3. Heterogenous weathering was preferentially along shock structures. Thermobarometric calculations indicate thermal equilibrium conditions between 768 °C and 925 °C at ∼4 to 6 kb, which are substantially consistent with the petrological metamorphism type 5. A pseudosection phase diagram is relatively consistent with the mineral assemblage observed and PT conditions calculated. Temperature vs. fO2 diagram shows that plagioclase compositional stability is very sensitive to Tschermack substitution in orthopyroxene, clinopyroxene and XAn plagioclase during the high temperature metamorphic process. Based on noble gases He, Ne, Ar and K contents a cosmogenic exposure age CRE of 1.9 Myr was calculated. The 21Ne would be totally cosmogenic, with no primordial Ne. The 21Ne/22Ne value (0.97) is higher than solar value. According to the cosmogenic Ne content, we argue that El Pozo chondrite originally had a pre-atmospheric mass of 9–10 kg, which would have been produced by a later collision after the recognized collision of the L-chondrite parent body ∼470 Ma ago.

^1,2Julien Siebert, ¹Paolo A. Sossi, ¹Ingrid Blanchard, ¹Brandon Mahan, ^1,3James Badro, ^1,2Frédéric Moynier
Earth and Planetary Science Letters 485, 130-139 Link to Article [https://doi.org/10.1016/j.epsl.2017.12.042]
¹Institut de Physique du Globe de Paris, Université Sorbonne Paris Cité, 75005, Paris, France
²Institut Universitaire de France, France
³Earth and Planetary Science Laboratory, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
Copyright Elsevier

The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth’s core. Here we quantify the metal–silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P–T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth’s Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post nebular volatilization.