TY - JOUR
T1 - High-pressure phases in shock-induced melt of the unique highly shocked LL6 chondrite Northwest Africa 757
AU - Hu, Jinping
AU - Sharp, Thomas
N1 - Funding Information:
We thank Dr. Oliver Tschauner, Dr. Adrian Brearley, and the anonymous reviewer for the constructive comments to this paper. NASA Cosmochemistry Grants NNG06GF09G and NN09AG41G supported this research. We thank B.S. students Riley Trickey and Brandon Kent for their contributions to this work and the NASA Arizona Space Grant Consortium for supporting them. We thank A. Bischoff and the Institut für Planetologie/ICEM for supplying the NWA 757 sample. We thank Dr. Kurt Leinenweber for the help with refining the X-ray diffraction patterns. We gratefully acknowledge the use of facilities within the LeRoy Eyring Center for Solid State Science at Arizona State University. Synchrotron X-ray diffraction was performed at GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS), Argonne National Laboratory. GeoSoilEnviroCARS is supported by the National Science Foundation–Earth Sciences (EAR-1128799) and Department of Energy–GeoSciences (DE-FG02-94ER14466). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Publisher Copyright:
© The Meteoritical Society, 2016.
PY - 2016/7/1
Y1 - 2016/7/1
N2 - Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20–25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.
AB - Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20–25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.
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U2 - 10.1111/maps.12672
DO - 10.1111/maps.12672
M3 - Article
AN - SCOPUS:84971596971
SN - 1086-9379
VL - 51
SP - 1353
EP - 1369
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 7
ER -