Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division
Scottish Univ., East Kilbride (United Kingdom). Environmental Research Centre; Univ. of Glasgow, Scotland (United Kingdom). School of Geographical and Earth Sciences
Scottish Univ., East Kilbride (United Kingdom). Environmental Research Centre; Univ. of St. Andrews, Scotland (United Kingdom). Dept. of Earth and Environmental Sciences
Univ. of Glasgow, Scotland (United Kingdom). School
of Geographical and Earth Sciences
Univ. of Glasgow, Scotland (United Kingdom). School of Geographical and Earth Sciences; Natural History Museum, London (United Kingdom). Dept. of Earth Sciences
Martian meteorite Northwest Africa (NWA) 7034 and its paired stones are the only brecciated regolith samples from Mars with compositions that are representative of the average martian crust. These samples therefore provide a unique opportunity to constrain the processes of metamorphism and alteration in the martian crust, which we have investigated via U-Pu/Xe, 40Ar/39Ar, and U-Th-Sm/He chronometry. U-Pu/Xe ages are comparable to previously reported Sm-Nd and U-Pb ages obtained from NWA 7034 and confirm an ancient (>4.3 billion years) age for the source lithology. After almost 3000 million years (Ma) of quiescence, the source terrain experienced several hundred million years of thermal metamorphism recorded by the K-Ar system that appears to have varied both spatially and temporally. Such protracted metamorphism is consistent with plume-related magmatism and suggests that the source terrain covered an areal extent comparable to plume-fed edifices (hundreds of square kilometers). The retention of such expansive, ancient volcanic terrains in the southern highlands over billions of years suggests that formation of the martian crustal dichotomy, a topographic and geophysical divide between the heavily cratered southern highlands and smoother plains of the northern lowlands, likely predates emplacement of the NWA 7034 source terrain—that is, it formed within the first ~100 Ma of planetary formation.
Cassata, William S., et al. "Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy." Science Advances, vol. 4, no. 5, May. 2018. https://doi.org/10.1126/sciadv.aap8306
Cassata, William S., Cohen, Benjamin E., Mark, Darren F., Trappitsch, Reto, Crow, Carolyn A., Wimpenny, Joshua, Lee, Martin R., & Smith, Caroline L. (2018). Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy. Science Advances, 4(5). https://doi.org/10.1126/sciadv.aap8306
Cassata, William S., Cohen, Benjamin E., Mark, Darren F., et al., "Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy," Science Advances 4, no. 5 (2018), https://doi.org/10.1126/sciadv.aap8306
@article{osti_1502038,
author = {Cassata, William S. and Cohen, Benjamin E. and Mark, Darren F. and Trappitsch, Reto and Crow, Carolyn A. and Wimpenny, Joshua and Lee, Martin R. and Smith, Caroline L.},
title = {Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy},
annote = {Martian meteorite Northwest Africa (NWA) 7034 and its paired stones are the only brecciated regolith samples from Mars with compositions that are representative of the average martian crust. These samples therefore provide a unique opportunity to constrain the processes of metamorphism and alteration in the martian crust, which we have investigated via U-Pu/Xe, 40Ar/39Ar, and U-Th-Sm/He chronometry. U-Pu/Xe ages are comparable to previously reported Sm-Nd and U-Pb ages obtained from NWA 7034 and confirm an ancient (>4.3 billion years) age for the source lithology. After almost 3000 million years (Ma) of quiescence, the source terrain experienced several hundred million years of thermal metamorphism recorded by the K-Ar system that appears to have varied both spatially and temporally. Such protracted metamorphism is consistent with plume-related magmatism and suggests that the source terrain covered an areal extent comparable to plume-fed edifices (hundreds of square kilometers). The retention of such expansive, ancient volcanic terrains in the southern highlands over billions of years suggests that formation of the martian crustal dichotomy, a topographic and geophysical divide between the heavily cratered southern highlands and smoother plains of the northern lowlands, likely predates emplacement of the NWA 7034 source terrain—that is, it formed within the first ~100 Ma of planetary formation.},
doi = {10.1126/sciadv.aap8306},
url = {https://www.osti.gov/biblio/1502038},
journal = {Science Advances},
issn = {ISSN 2375-2548},
number = {5},
volume = {4},
place = {United States},
publisher = {AAAS},
year = {2018},
month = {05}}
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 555, Issue 1-2https://doi.org/10.1016/j.nima.2005.09.014