¹Tianqi Xie,¹Gordon R. Osinski,^1,2Sean R. Shieh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13728]
¹Department of Earth Sciences/Institute for Earth and Space Exploration, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 5B7 Canada
²Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

Earth’s moon is a primary exploration target for space agencies around the world. The Moon records and preserves key information about fundamental processes that shape planetary crusts such as impact cratering. Understanding shock effects in lunar anorthite (Ca-rich endmember of plagioclase feldspar), the principal component of anorthosite and the most common crustal mineral on the Moon, is key to the early evolution of the Moon and terrestrial planets in the solar system. However, there has not been a systematic study of shock effects in lunar anorthite using modern analytical techniques that could be used in future lunar surface exploration, such as Raman spectroscopy. This study examined 23 polished thin sections from all six Apollo missions using optical and Raman spectroscopy. We documented a variety of shock features recording low to moderate shock levels, including fractures, deformed twins, undulatory extinction, planar features, and partially isotropic plagioclase. A notable nonobservation was the absence of planar deformation features (PDFs) or completely isotropic (i.e., diaplectic glass) in this suite of samples. Raman spectroscopy results of the observed shock features show similar progressive changes in terrestrial samples: As shock level increases, band broadening, reduction of intensities, and peak loss were observed. Our Raman data are efficient in identifying shock levels and distinguishing planar features from PDFs and deformed twins, and differentiating amorphous areas from crystalline plagioclase, suggesting Raman spectroscopy as a useful tool for purposely selecting moderately to strongly shocked samples to return in future lunar missions. Our study can also help the interpretation of Raman data of impact materials from the past and future exploration missions and demonstrate the utility of Raman spectroscopy for documenting and selecting samples for future lunar missions.

^1,2,3Alan E. Rubin,^1,3Bastian Baecker
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13725]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095–1567 USA
²Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, Maine, 04217 USA
³Baker Hughes, Baker-Hughes-Str. 1, Celle, 29229 Germany
Published by arrangement with John Wiley & Sons

Phosphorus X-ray maps of olivine phenocrysts in many type II (FeO-rich) porphyritic chondrules in LL3.00 Semarkona and CO3.05 Y 81020 reveal multiple sets of thin dark/bright (P-poor/P-rich) layers that resemble oscillatory zoning. Such discrete layers are generally not evident in BSE images or in Fe, Cr, Ca, Al, Mg, or Mn X-ray maps because rapid diffusion of these cations in olivine at high temperatures smoothed out their initial distributions, thereby mimicking normal igneous zoning. In contrast, the relatively slow diffusion of P in olivine preserves original dendritic or hopper morphologies of olivine crystals; these skeletal structures formed during quenching after initial chondrule melting. The skeletal olivine crystals were filled in with low-P olivine during cooling after one or more subsequent heating events, mainly involving the melting of mesostasis. Crystallization of mafic silicates depleted the mesostasis in FeO and MgO and enriched it in silico-feldspathic components. Sectioning of the olivine grains at particular orientations can produce apparent oscillatory zoning in P. Strong evidence of a secondary melting event is evident in Semarkona chondrule H5k. Phenocryst H5k-2 in this chondrule has a relict core (with rhythmic P zoning layers) that was fractured and severed; it is overlain by a set of differently oriented subparallel P-poor olivine layers. Chondrule C6f from Y 81020 contains a large multi-lobed olivine phenocryst that still preserves hopper cavities, partially outlined by P-poor/P-rich olivine layers. The thin P-rich rims surrounding many olivine phenocrysts could reflect a short period of rapid grain growth after a late-stage chondrule reheating event.

¹H. Palme,¹J. Zipfel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13720]
¹Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, Senckenberganlage 25, Frankfurt, 60325 Germany
Published by arrangement with John Wiley & Sons

Between 1973 and 1994, 15 samples of CI chondrites were analyzed by neutron activation analysis at the Max-Planck-Institute for Chemistry, Department of Cosmochemistry in Mainz, Germany. The analyses comprise nine Orgueil samples and three samples of Ivuna, two of Alais and one of Tonk. Samples came from various sources and had masses between 5 and 600 mg. Most data are published here for the first time. The results for the nine Orgueil samples demonstrate the essentially homogeneous chemical composition of Orgueil at a level of a few milligrams. The analytical results of Ivuna, Alais, and Tonk agree, with only few exceptions, with the results of Orgueil analyses. All samples agree within ±3% in their contents of Sc, Ir, Cr, Fe, Co, Zn, and Se. The elements Sc and Ir represent the refractory component; Cr, Fe, and Co the main component; and Zn and Se the volatile component. Thus, in all CI chondrites there are essentially the same fractions of the fundamental cosmochemical components. The essentially identical chemical composition of all samples shows that their water contents are constant at about 20 ± 5 wt%. There is excellent agreement between the data listed here with data reported in the relevant literature. There is no doubt that the CI composition is a well-defined entity, which is thought to represent the non-gaseous compositions of the solar nebula and the photosphere of the Sun. In addition, we conclude that the recently proposed new CI chondritic chlorine and Br values are too low, when compared to earlier measurements.

¹Jean-Guillaume Feignon,^2,3Sietze J. de Graaff,⁴Ludovic Ferrière,^2,3Pim Kaskes,^2,3Thomas Déhais,²Steven Goderis,²Philippe Claeys,¹Christian Koeberl
Meteoritcs & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13705]
¹Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
²Research Unit: Analytical, Environmental & Geo-Chemistry, Department of Chemistry, Vrije Universiteit Brussel, AMGC-WE-VUB, Pleinlaan 2, Brussels, 1050 Belgium
³Laboratoire G-Time, Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, 1050 Belgium
⁴Natural History Museum, Burgring 7, Vienna, A-1010 Austria
Published by arrangement with John Wiley & Sons

The IODP-ICDP Expedition 364 drilling recovered a 829 m core from Hole M0077A, sampling ˜600 m of near continuous crystalline basement within the peak ring of the Chicxulub impact structure. The bulk of the basement consists of pervasively deformed, fractured, and shocked granite. Detailed geochemical investigations of 41 granitoid samples, that is, major and trace element contents, and Sr–Nd isotopic ratios are presented here, providing a broad overview of the composition of the granitic crystalline basement. Mainly granite but also granite clasts (in impact melt rock), granite breccias, and aplite were analyzed, yielding relatively homogeneous compositions between all samples. The granite is part of the high-K, calc-alkaline metaluminous series. Additionally, they are characterized by high Sr/Y and (La/Yb)N ratios, and low Y and Yb contents, which are typical for adakitic rocks. However, other criteria (such as Al2O3 and MgO contents, Mg#, K2O/Na2O ratio, Ni concentrations, etc.) do not match the adakite definition. Rubidium–Sr errorchron and initial 87Sr/86Srt=326Ma suggest that a hydrothermal fluid metasomatic event occurred shortly after the granite formation, in addition to the postimpact alteration, which mainly affected samples crosscut by shear fractures or in contact with aplite, where the fluid circulation was enhanced, and would have preferentially affected fluid-mobile element concentrations. The initial (ɛNd)t=326Ma values range from −4.0 to 3.2 and indicate that a minor Grenville basement component may have been involved in the granite genesis. Our results are consistent with previous studies, further supporting that the cored granite unit intruded the Maya block during the Carboniferous, in an arc setting with crustal melting related to the closure of the Rheic Ocean associated with the assembly of Pangea. The granite was likely affected by two distinct hydrothermal alteration events, both influencing the granite chemistry: (1) a hydrothermal metasomatic event, possibly related to the first stages of Pangea breakup, which occurred approximately 50 Myr after the granite crystallization, and (2) the postimpact hydrothermal alteration linked to a long-lived hydrothermal system within the Chicxulub structure. Importantly, the granites sampled in Hole M0077A are unique in composition when compared to granite or gneiss clasts from other drill cores recovered from the Chicxulub impact structure. This marks them as valuable lithologies that provide new insights into the Yucatán basement.

^1,2Ming Chen,³Christian Koeberl,^2,4Dayong Tan,^1,2Ping Ding,^2,4Wansheng Xiao,^1,2Ning Wang,^1,2Yiwei Chen,^2,4Xiande Xie
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13711]
¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640 China
²CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640 China
³Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, A-1090 Austria
⁴Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640 China
Published by arrangement with John Wiley & Sons

The Yilan crater is 1.85 km in diameter and is located in the northeast of China’s Heilongjiang Province. The crater is exposed in the Early Jurassic granite of the regional Paleozoic–Mesozoic granite complexes. The southern third of the crater rim is missing, but other rim sections are well preserved, with a maximum elevation above the present crater floor of 150 m. A drillcore from the center of the structure shows that the crater fill consists of 110 m thick lacustrine sediments underlain by a 319 m thick brecciated granite unit mainly composed of unconsolidated granite clasts and fragments. Melt products derived from the target granite, which include melted (and recrystallized) granite clasts, vesicular glass, and teardrop-shaped glass, were found in the brecciated granite unit at 218–237 m depth. Petrographic investigations of unmelted granite clasts in the brecciated granite unit from this depth interval show the presence of multiple sets of planar deformation features (PDFs) in quartz. Orientation measurements for 79 PDF sets in 38 quartz grains with a U-stage indicate the dominance of the ω{103} and π{102} orientations with a relative frequency of 39% and 18%, respectively. Only 7.6% of the observed PDFs remain unindexed. The observations of PDFs with the appropriate orientations are clear evidence of shock metamorphism and thus of an impact origin of the Yilan structure. Crystallite aggregates of coesite embedded in silica glass were found in the impact-melted granite clasts. The carbon-14 dates of possibly impact-produced charcoal and lacustrine sediments from the crater fill suggest a young age for the impact event of 0.0493 ± 0.0032 Ma.

¹M. D. Suttle,²T. Hasse,^2,3L. Hecht
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13712]
¹Planetary Materials Group, Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD UK
²Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstr. 43, Berlin, 10115 Germany
³Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74-100, Berlin, 12249 Germany
Published by Arrangement with John Wiley & Sons

We report the recovery and characterization of a new urban micrometeorite collection derived from the rooftop of an industrial building in Germany. We identified 315 micrometeorites (diameter: 55–515 µm, size peak: ˜150 µm, size distribution slope exponent: −2.62). They are predominantly S-type cosmic spherules (97.2%) but also two G-type spherules (0.6%), an unmelted coarse-grained single-mineral micrometeorite, and eight scoriaceous particles (2.5%) or particles transitional between scoriaceous micrometeorites and porphyritic spherules. Their analysis details how the magnetite rim on partially melted micrometeorites is progressively diluted as the melt fraction increases during heating. At least 10 micrometeorites contain platinum group nuggets (PGNs). They have chondritic compositions but are depleted in volatile Pd. However, a single nugget preserves chondritic Pd concentrations. We suggest that an Fe-Ni-S bead originally containing the PGN escaped its host cavity and wet the particle exterior, creating an Fe-rich melt that protected the nugget from evaporation. This melt layer oxidized forming magnetite—indicating that wetting events can affect the texture and composition of micrometeorites. Utilizing the well-constrained surface area (8400 m²) and rooftop age (21 yr), we attempted the first global mass flux estimate based on urban micrometeorite data. This produced anomalously low values (13.4 t yr^–1), even when correcting for losses due to sample processing (<89.7 t yr^–1). Our value is approximately two orders of magnitude lower than previous estimates, indicating that >99% of particles are missing, having been lost via drainage and cleaning. Rooftop collection sites have limited potential for mass flux calculations unless problems of loss can be resolved. However, urban micrometeorite collections have other advantages, notably exceptionally well-preserved particles with extremely young terrestrial ages and the ability to extract many micrometeorites from accessible sites. Urban micrometeorites should be considered complementary to Antarctic and deep-sea collections with potential for citizen science and educational exploitation.

^1,2Takafumi Niihara,^3,4Tatsunori Yokoyama,⁵Tomoko Arai,^3,6Keiji Misawa
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13719]
¹Department of Systems Innovation, School of Engineering, University of Tokyo, Hongo 7-3-1, Tokyo, 113-8656 Japan
²University Museum, University of Tokyo, Hongo 7-3-1, Tokyo, 113-0033 Japan
³Department of Polar Science, The Graduate University for Advanced Studies (SOKENDAI), 10-3 Midoricho, Tachikawa, Tokyo, 190-8518 Japan
⁴Tono Geoscience Center, Japan Atomic Energy Agency, 959-31 Izumicho Jorinji, Toki, Gifu, 509-5102 Japan
⁵Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016 Japan
⁶National Institute of Polar Research, 10-3 Midoricho, Tachikawa, Tokyo, 190-8518 Japan
Published by arrangement with John Wiley & Sons

We have conducted petrological and mineralogical studies on an igneous clast in the Northwest Africa (NWA) 1685 (LL4) chondrite. This meteorite was described in the Meteoritical Bulletin as containing clasts similar to alkali-rich clasts in LL chondritic breccias Yamato (Y)-74442 (LL4), Bhola (LL3-6), and Krähenberg (LL5). We carefully compared the textures, as well as mineral and matrix compositions, of the NWA 1685 clast with those of the previously described alkali-rich clasts in the LL chondritic breccias. Olivine grains are embedded in glassy matrix and have no chemical zoning. Shock melt veins and fractures were observed only in olivine grains and did not continue into matrix. Potassium abundance of matrix glasses of the NWA 1685 clast is lower than those of alkali-rich igneous clasts in Y-74442, Bhola, and Krähenberg, indicating that the igneous clasts in NWA 1685 are different from the alkali-rich clasts previously reported in the LL chondritic breccias. The NWA 1685 clast might have formed during an impact melting and quenching event on the LL-chondrite parent body, and then been incorporated into a breccia.

¹Masaaki Miyahara,^2,3Akira Yamaguchi,⁴Eiji Ohtani,⁵Naotaka Tomioka,⁶Yu Kodama
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13724]
¹Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, 739-8526 Japan
²National Institute of Polar Research, Tokyo, 190-8518 Japan
³Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo, 190-8518 Japan
⁴Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, 980-8578 Japan
⁵Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi, 783-8502 Japan
⁶Marine Works Japan, Nankoku, Kochi, 783-8502 Japan
Published by arrangement with John Wiley & Sons

High-pressure minerals in the eucrite Padvarninkai were investigated. Parts of anorthitic plagioclase and tridymite in the host rock of Padvarninkai vitrified, indicating that the shock pressure was 22–27 GPa. Tissintite, coesite, and a majorite-bearing garnet occurred in the shock-melt veins of Padvarninkai as high-pressure minerals. Tissintite, kyanite, corundum, and dense plagioclase have occurred in the anorthitic plagioclase grains. The anorthitic plagioclase was melted and tissintite crystallized from the melt after the crystallization of kyanite and corundum. The residual melt became dense plagioclase by quenching. Tridymite has also melted and coesite crystallized from the melt. The formation of tissintite and coesite indicates that the shock pressure recorded in the veins was 2–13 GPa. The temperature increased drastically in the veins (>˜3000 K) compared with the host rock (<˜800 K). Parts of the tissintite and coesite became, respectively, amorphous (or anorthite) and quartz. Two different impact events may be recorded in Padvarninkai: The first impact event brecciated a part of the host rock, and the second impact event induced the melting of the brecciated portion, resulting in the formation of shock-melt veins where the conditions are a high temperature and a relatively low pressure. In the veins, tissintite and coesite formed first, and parts of them underwent a back-transformation due to a long cooling time.

¹Tomáš Magna,^2,3Yun Jiang,⁴Roman Skála,²Kun Wang,⁵Paolo A.Sossi,⁴Karel Žák
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.07.022]
¹Czech Geological Survey, Klárov 3, CZ-118 21 Prague 1, Czech Republic
²Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
³CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing CN-210033, China
⁴Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, CZ-16500 Prague 6, Czech Republic
⁵Institut für Geochemie und Petrologie, ETH Zürich, Clausiusstrasse 25, CH-8092 Zürich, Switzerland
Copyright Elsevier

Potassium elemental and isotope systematics were investigated for a suite of central European tektites from three strewn sub-fields in Czech Republic and possible parent sedimentary materials from the vicinity of the Ries impact structure in SE Germany, supplemented by data for several other impact-related materials (bediasites, Ivory Coast tektites, Libyan Desert Glass). This is paralleled by computation of potential K loss and attendant isotope fractionation for physico–chemical conditions typical for formation of tektite precursor melts. These theoretical calculations indicate a <0.1% loss of K from tektite precursor melts up to 2,500K and <0.002‰ change in the ⁴¹K/³⁹K ratio even for a small sphere of 0.002 m at 2,500K, precluding any significant K loss and isotope fractionation. Numerical modelling also indicates that differential velocities between surrounding gas and liquid are not sufficient to remove the gaseous boundary layer, such that the partial pressure of potassium developed around the molten moldavite beads impedes further evaporation and also contributes to back-condensation of the already evaporated potassium.

Central European tektites (moldavites) are enriched in K compared to the assumed sedimentary sources from the wider Ries area whereby the latter materials do not exceed 2.9 wt.% K₂O compared to 2.5–4.1 wt.% K₂O in moldavites. The apparent K enrichment in moldavites may be explained by a yet unaccounted process during formation of tektite precursor melts and/or unidentified source, such as volcanoclastic deposits that were produced by large Mid-Miocene volcanic centers in the Pannonian Basin. The K isotope compositions of tektites are more variable than those of sediments from the wider Ries area but they largely overlap (δ⁴¹K from −0.78 ± 0.03‰ to −0.13 ± 0.03‰ versus −0.72 ± 0.03‰ to −0.28 ± 0.02‰, respectively). These ranges mimic ⁴¹K/³⁹K variations reported for igneous and sedimentary portions of the upper continental crust (δ⁴¹K roughly between −0.7 and −0.1‰). They show a slight difference among the three investigated strewn sub-fields, depending on their respective distance from the impact. In detail, moldavites from the closest strewn sub-field in the Cheb Basin show predominantly heavy K isotope compositions and those from the farthest strewn sub-field in Western Moravia are uniformly isotopically light. The origin of this difference may reflect lithological heterogeneity of the target area.

Potassium contents in bediasites and Ivory Coast tektites range between 1.3 and 1.8 wt.% K₂O and their corresponding δ⁴¹K values vary from −0.57 ± 0.02‰ to −0.41 ± 0.03‰. Both ranges are significantly narrower than those observed for moldavites. When compared to data for possible sedimentary precursors in the Chesapeake Bay and Bosumtwi impact structure, respectively, it is apparent that these tektites were neither depleted nor enriched in potassium. The extent of their K isotope fractionation relative to plausible sources remains unconstrained. The Libyan Desert Glass displays invariant δ⁴¹K of ∼ −0.57 ± 0.06‰ at ≤0.01 wt.% K₂O. Given the silica-rich nature of LDG and the lack of possible parent materials, no further constraints can be placed at present to further resolve the source material or reveal details of LDG formation process.

¹Kevin Righter,²John Schutt,¹Nicole Lunning,²Ralph Harvey,³James Karner
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13707]
¹ARES, Mailcode XI2, NASA-JSC, Houston, Texas, 77058 USA
²Department of Earth, Environmental, and Planetary Science, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio, 44106 USA
³Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, 84113 USA
Published by arrangement with John Wiley & Sons

New analyses of Cr2O3 contents of olivines from type II chondrules in unequilibrated chondrites (UOC) from four dense collections are reported here. This survey of petrologic type 3 UOCs was undertaken to identify primitive chondrites that may have been overlooked, and to address possible pairing errors. We have identified 23 primitive UOCs (≤3.10) (only five identified previously, for a total of 28 overall), and also recommend other revisions to prior classifications and pairings.