The internal structure and geodynamics of Mars inferred from a 4.2-Gyr zircon record

Costa, Maria M.; Jensen, Ninna K.; Bouvier, Laura C.; Connelly, James N.; Mikouchi, Takashi; Horstwood, Matthew S.A.; Suuronen, Jussi-Petteri; Moynier, Frédéric; Deng, Zhengbin; Agranier, Arnaud; Martin, Laure A. J.; Johnson, Tim E.; Nemchin, Alexander A.; Bizzarro, Martin. 2020 The internal structure and geodynamics of Mars inferred from a 4.2-Gyr zircon record. Proceedings of the National Academy of Sciences, 117 (49). 30973-30979. https://doi.org/10.1073/pnas.2016326117

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Official URL: http://dx.doi.org/10.1073/pnas.2016326117

Abstract/Summary

Combining U–Pb ages with Lu–Hf data in zircon provides insights into the magmatic history of rocky planets. The Northwest Africa (NWA) 7034/7533 meteorites are samples of the southern highlands of Mars containing zircon with ages as old as 4476.3 ± 0.9 Ma, interpreted to reflect reworking of the primordial Martian crust by impacts. We extracted a statistically significant zircon population (n = 57) from NWA 7533 that defines a temporal record spanning 4.2 Gyr. Ancient zircons record ages from 4485.5 ± 2.2 Ma to 4331.0 ± 1.4 Ma, defining a bimodal distribution with groupings at 4474 ± 10 Ma and 4442 ± 17 Ma. We interpret these to represent intense bombardment episodes at the planet’s surface, possibly triggered by the early migration of gas giant planets. The unradiogenic initial Hf-isotope composition of these zircons establishes that Mars’s igneous activity prior to ∼4.3 Ga was limited to impact-related reworking of a chemically enriched, primordial crust. A group of younger detrital zircons record ages from 1548.0 ± 8.8 Ma to 299.5 ± 0.6 Ma. The only plausible sources for these grains are the temporally associated Elysium and Tharsis volcanic provinces that are the expressions of deep-seated mantle plumes. The chondritic-like Hf-isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir, indicating that Mars has been in a stagnant-lid tectonic regime for most of its history. Our results imply that zircon is ubiquitous on the Martian surface, providing a faithful record of the planet’s magmatic history.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1073/pnas.2016326117
ISSN:	0027-8424
Date made live:	20 Jan 2021 13:43 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/529434

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1073/pnas.2016326117

ISSN:

0027-8424

Date made live:

20 Jan 2021 13:43 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/529434