TY - JOUR
T1 - Grove Mountains (GRV) 020043
T2 - Insights into acapulcoite-lodranite genesis from the most primitive member
AU - McCoy, Timothy J.
AU - Corrigan, Catherine M.
AU - Dickinson, Tamara L.
AU - Benedix, Gretchen K.
AU - Schrader, Devin L.
AU - Davidson, Jemma
N1 - Funding Information:
This paper is dedicated to Klaus Keil on the occasion of his 85th birthday. Three of us (TJM, TLD, GKB) earned our PhDs under Klaus. We thank him for years of patience, mentorship, and friendship, typically in that order. He taught us many things, some of which can be repeated in this distinguished forum. Among the most important of these are quality data never diminish in value, optical microscopy is not a lost art form, pursuit of paradigm-changing theories does not replace the thrill of your first look at a new kind of meteorite, and always imagine what should be formed by the processes you are studying because some day you just might find it. All of these lessons were a key part of this study. This study was only made possible by the generous loan of GRV 020043 by the Polar Research Institute of China and the unwavering efforts of Xiufei Yu, Lizong Wu and Prof. Bingkui Miao. We thank them for all they have done on our behalf. Technical support by Tim Gooding and Tim Rose were invaluable as we worked on a very short timeline. We thank Jessica Sunshine for her interest, discussions, and challenging our ideas, all of which made this paper better. The comments and helpful suggestions of the reviewers significantly improved the manuscript.
Publisher Copyright:
© 2019
PY - 2019/12
Y1 - 2019/12
N2 - Although acapulcoites and lodranites played a key role in understanding partial differentiation of asteroids, the lack of samples of the chondritic precursor limits our understanding of the processes that formed these meteorites. Grove Mountains (GRV) 020043 is a type 4 chondrite, with abundant, well-delineated, pyroxene-rich chondrules with an average diameter of 690 μm, microcrystalline mesostasis, polysynthetically striated low-Ca pyroxene, and slightly heterogeneous plagioclase compositions. Similarities in mineralogy, mineral composition, and oxygen isotopic composition link GRV 020043 to the acapulcoite-lodranite clan. These features include a high low-Ca pyroxene to olivine ratio, high kamacite to taenite ratio, and relatively FeO-poor mafic silicates (Fa10.3, Fs10.4) relative to ordinary chondrites, as well as the presence of ubiquitous metal and sulfide inclusions in low-Ca pyroxene and ƒO2 typical of acapulcoites. GRV 020043 shows that evidence of partial melting is not an essential feature for classification within the acapulcoite-lodranite clan. GRV 020043 experienced modest thermal metamorphism similar to type 4 ordinary chondrites. GRV 020043 suggests a range of peak temperatures on the acapulcoite-lodranite parent body similar to that of ordinary chondrites, but shifted to higher temperatures, perhaps consistent with earlier accretion. The mineralogy and mineral compositions of GRV 020043, despite modest thermal metamorphism, suggests that most features of acapulcoites previously attributed to reduction were, instead, inherited from the precursor chondrite. Although partial melting was widespread on the acapulcoite-lodranite parent body, ubiquitous Fe,Ni-FeS blebs in the cores of silicates were not implanted by shock or trapped during silicate melting, but were inherited from the precursor chondrite with subsequent overgrowths during metamorphism.
AB - Although acapulcoites and lodranites played a key role in understanding partial differentiation of asteroids, the lack of samples of the chondritic precursor limits our understanding of the processes that formed these meteorites. Grove Mountains (GRV) 020043 is a type 4 chondrite, with abundant, well-delineated, pyroxene-rich chondrules with an average diameter of 690 μm, microcrystalline mesostasis, polysynthetically striated low-Ca pyroxene, and slightly heterogeneous plagioclase compositions. Similarities in mineralogy, mineral composition, and oxygen isotopic composition link GRV 020043 to the acapulcoite-lodranite clan. These features include a high low-Ca pyroxene to olivine ratio, high kamacite to taenite ratio, and relatively FeO-poor mafic silicates (Fa10.3, Fs10.4) relative to ordinary chondrites, as well as the presence of ubiquitous metal and sulfide inclusions in low-Ca pyroxene and ƒO2 typical of acapulcoites. GRV 020043 shows that evidence of partial melting is not an essential feature for classification within the acapulcoite-lodranite clan. GRV 020043 experienced modest thermal metamorphism similar to type 4 ordinary chondrites. GRV 020043 suggests a range of peak temperatures on the acapulcoite-lodranite parent body similar to that of ordinary chondrites, but shifted to higher temperatures, perhaps consistent with earlier accretion. The mineralogy and mineral compositions of GRV 020043, despite modest thermal metamorphism, suggests that most features of acapulcoites previously attributed to reduction were, instead, inherited from the precursor chondrite. Although partial melting was widespread on the acapulcoite-lodranite parent body, ubiquitous Fe,Ni-FeS blebs in the cores of silicates were not implanted by shock or trapped during silicate melting, but were inherited from the precursor chondrite with subsequent overgrowths during metamorphism.
KW - Acapulcoite
KW - Asteroid
KW - Chondrite
KW - Melting
KW - Meteorite
KW - Mineralogy
KW - Petrology
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U2 - 10.1016/j.chemer.2019.125536
DO - 10.1016/j.chemer.2019.125536
M3 - Article
AN - SCOPUS:85072264128
SN - 0009-2819
VL - 79
JO - Chemie der Erde
JF - Chemie der Erde
IS - 4
M1 - 125536
ER -