Petrological and mineralogical study of enstatite chondrites with reference to their thermal histories

We investigated the complicated thermal histories of 8 Antarctic enstatite chondrites. In this report we present results of our mineralogical and petrological studies. Three of them (Yamato (Y)-791790,791810 and 791811) are EH4 chondrites, but experienced higher temperature events in comparison with most of the other EH4s. Y-791790 includes a shock-induced melt vein. Y-86760 is recognized as a new EH melt rock that cooled rapidly from high temperatures. Absences of daubreelite in the EH4s and roedderite and forsterite in the melt rocks are consistent with such high temperature events. We infer that the parent body (or bodies) of EH chondrites experienced heavy impacts after or during metamorphism. Some EH4s and melt rocks cooled rapidly from high temperatures near the surface of the parent body, whereas the others cooled slowly in the depth of the parent body or were later reheated. Y-791510 contains glassy matrix unusually enriched in CaO, in the interstices among enstatite grains. The opaque mineralogy of Y-791510 is inconsistent with that of EH or EL. We propose that Y-791510 represents a new grouplet of enstatite chondrites

Titanium-rich oxide-bearing plagioclase-olivine inclusions in the unusual Ningqiang carbonaceous chondrite

Two plagioclase-olivine inclusions (POIs) from the unusual Ningqiang carbonaceous chondrite were studied to understand their mineralogy and crystallization history. In addition to the major phases plagioclase, spinel, olivine and pyroxene, Ningqiang POIs are characterized by interstitial assemblages composed of Ca-rich and Ca-poor pyroxenes, Ti-rich oxides and the other phases. The Ti-rich oxides include an unidentified titanium mineral series referred to as phase T, Ca-rich and Mg, Fe-rich armalcolites, geikielite, perovskite and rutile. This is the first reported occurrence of Ca-rich armalcolite and geikielite, and the second report of phase T in meteorites. Most of the constituent phases crystallized from the POI melts, and the Ti-rich oxides were the last phases in the crystallization sequence. Precipitation of the Ti-rich oxides may be related to the low abundance of Ca-rich pyroxene in the POIs

Sulfur isotopic compositions of submicrometer SiC grains from the Murchison meteorite

We report C, Si, N, S, Mg-Al, and Ca-Ti isotopic compositions of presolar silicon carbide (SiC) grains from the SiC-rich KJE size fraction (0.5-0.8 μm) of the Murchison meteorite. One thousand one hundred thirteen SiC grains were identified based on their C and Si isotopic ratios. Mainstream, AB, C, X, Y, and Z subtypes of SiC, and X-type silicon nitride (Si₃N₄) account for 81.4%, 5.7%, 0.1%, 1.5%, 5.8%, 4.9%, and 0.4%, respectively. Twenty-five grains with unusual Si isotopic ratios, including one C grain, 16 X grains, 1 Y grain, 5 Z grains, and 2 X-type Si₃N₄ grains were selected for N, S, Mg-Al, and Ca-Ti isotopic analysis. The C grain is highly enriched in ²⁹Si and ³⁰Si (δ²⁹Si = 1345‰ ± 19‰, δ³⁰Si = 1272‰ ± 19‰). It has a huge ³²S excess, larger than any seen before, and larger than that predicted for the Si/S supernova (SN) zone, providing evidence against the elemental fractionation model by Hoppe et al. Two SN models investigated here present a more satisfying explanation in terms of a radiogenic origin of ³²S from the decay of short-lived ³²Si (τ1/2 = 153 yr). Silicon-32 as well as ²⁹Si and ³⁰Si can be produced in SNe by short neutron bursts; evidence for initial 44Ti (τ1/2 = 60 yr) in the C grain is additional evidence for an SN origin. The X grains have marginal ³²S excesses, much smaller than expected from their large ²⁸Si excesses. Similarly, the Y and Z grains do not show the S-isotopic anomalies expected from their large Si isotopic anomalies. Low intrinsic S contents and contamination with isotopically normal S are the most likely explanations

Progress in study of Chinese Antarctic Meteorites

This paper reviews and summarizes the Chinese Antarctica meteorite search, classification and research. During the past four Antarctic explorations, a total of 9834 meteorites were collected in the Grove Mountains region. Among them, 2431 meteorites were classified by the end of 2008. So far, 684 meteorites have been officially published in the Meteoritical Bulletin, Meteoritical Society, including 2 martian meteorites, 2 eucrites, 6 ureilites, 5 mesosiderites, 1 pallasite, 1 iron and 10 carbonaceous chondrites. Comprehensive studies were carried out on a number o f these rare type meteorites. In addition, we propose to continue the meteorite searching project in Grove Mountains and other reg ions in Antarctica. We also suggest several key topics of the future researches on the Chinese Antarctic meteorites

The study of Mg isotope compositions of terrestrial rocks and meteorites

The study of Mg isotopes has been carried out for about 40 years since 1970s. With analytical progress, the study is not only limited to the excess of 26Mg due to decay of short-lived 26Al in primitive meteorites, also extended to mass-dependent fractionation of Mg isotopes in meteorites and terrestrial rocks. This paper reviews recent development in Mg isotope researches

Shock metamorphism of ordinary chondrites from Grove Mountains, Antarctica

Shock effects of 93 Grove Mountains (GRV) ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various micro textures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV chondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction (23 out of 93) of heavily shocked samples (S4-S5). Most o f the heavily shocked meteorites are L group (22 out of 23), except for one H chondrite. The distinct shock metamorphism between H and L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites (especially Type 5 and 6)

GRV 051523: A new eucrite

Grove Mountains (GRV) 051523 is a newly identified eucrite, consisting mainly of coarse-grained pyroxene (62.9 vol %) and plagioclase (34.2 vol %), with less abundant opaque minerals (2.7 vol %), minor silica and tiny FeO-rich olivine (Fa75). Coarse-grained pyroxenes show exsolution of augite lamellae in pigeonite or vice versa. Width of most exsolution lamellae in pyroxenes is 1-3 μm. Opaque minerals are mainly chromite, ilmenite and sulfides. The meteorite was heavily shocked, as indica ted by breccias and melt veins. Coarse-grained pyroxenes commonly contain abundant tiny or needle-like chromite inclusions with orientation, probably due to heavy shock events. Pyroxenes in various petrographic occurrences exhibit highly homogeneous compositions, indicating that GRV 051523 experienced intense thermal metamorphism in the parent asteroid 4 Vesta. GRV 051523 is classified as Type 5-6. This new eucrite will have additional constraints on chemical composition, magmatic differentiation, multi-stage shock and thermal history of Vesta

Spatio-temporal analysis of driving factors of water resources consumption in China

Abstract(#br)China is the largest consumer of water resources in the world, the total consumption of water resources is still increasing year by year. What are the main reasons for rising water resource consumption? This paper constructs China’s spatio-temporal LMDI (the Logarithmic Mean Divisia Index) model to decompose water resources consumption into twelve driving factors with panel data from 2000 to 2015 and explores the main factors driving the rising water resource consumption. The results are summarized as following: (1) The intensity effect is the most important driving factor decreasing water resources consumption; (2) The loss of farmers reduces the water resources consumption in the agricultural sector, and the increase of urban population drives the rising water resource consumption in the residential sector; (3) The effect of industrial structure is different depending on regions; (4) In the agricultural sector, the driving factors have their own characteristics in each region

ASIME 2018 White Paper. In-Space Utilisation of Asteroids: Asteroid Composition -- Answers to Questions from the Asteroid Miners

In keeping with the Luxembourg government's initiative to support the future use of space resources, ASIME 2018 was held in Belval, Luxembourg on April 16-17, 2018. The goal of ASIME 2018: Asteroid Intersections with Mine Engineering, was to focus on asteroid composition for advancing the asteroid in-space resource utilisation domain. What do we know about asteroid composition from remote-sensing observations? What are the potential caveats in the interpretation of Earth-based spectral observations? What are the next steps to improve our knowledge on asteroid composition by means of ground-based and space-based observations and asteroid rendez-vous and sample return missions? How can asteroid mining companies use this knowledge? ASIME 2018 was a two-day workshop of almost 70 scientists and engineers in the context of the engineering needs of space missions with in-space asteroid utilisation. The 21 Questions from the asteroid mining companies were sorted into the four asteroid science themes: 1) Potential Targets, 2) Asteroid-Meteorite Links, 3) In-Situ Measurements and 4) Laboratory Measurements. The Answers to those Questions were provided by the scientists with their conference presentations and collected by A. Graps or edited directly into an open-access collaborative Google document or inserted by A. Graps using additional reference materials. During the ASIME 2018, first day and second day Wrap-Ups, the answers to the questions were discussed further. New readers to the asteroid mining topic may find the Conversation boxes and the Mission Design discussions especially interesting.Comment: Outcome from the ASIME 2018: Asteroid Intersections with Mine Engineering, Luxembourg. April 16-17, 2018. 65 Pages. arXiv admin note: substantial text overlap with arXiv:1612.0070