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

Type Article
Date 2020-12
Language English
Author(s) Costa Maria M.1, Jensen Ninna K.1, Bouvier Laura C.1, Connelly James N.1, Mikouchi TakashiORCID2, Horstwood Matthew S. A.3, Suuronen Jussi-PetteriORCID4, Moynier Frederic5, Deng ZhengbinORCID5, Agranier Arnaud6, 7, Martin Laure A. J.8, Johnson Tim E.9, Nemchin Alexander A.9, Bizzarro Martin1, 5
Affiliation(s) 1 : Univ Copenhagen, Globe Inst, Ctr Star & Planet Format, DK-1350 Copenhagen, Denmark.
2 : Univ Tokyo, Univ Museum, Tokyo 1180033, Japan.
3 : British Geol Survey, Geochronol & Tracers Facil, Nicker Hill, Nottingham NG12 5GG, England.
4 : European Synchrotron Radiat Facil, F-38000 Grenoble, France.
5 : Univ Paris, Inst Phys Globe Paris, F-75005 Paris, France.
6 : Univ Bretagne Occidentale, Lab Geosci Ocean UMR CNRS 6538, Pl Nicolas Copernic, F-29280 Plouzane, France.
7 : Univ Bretagne Occidentale, Inst Univ Europeen Mer, Pl Nicolas Copernic, F-29280 Plouzane, France.
8 : Univ Western Australia, Ctr Microscopy Characterizat & Anal, Perth, WA 6009, Australia.
9 : Curtin Univ, Sch Earth & Planetary Sci, Perth, WA 6845, Australia.
Source Proceedings Of The National Academy Of Sciences Of The United States Of America (0027-8424) (Natl Acad Sciences), 2020-12 , Vol. 117 , N. 49 , P. 30973-30979
DOI 10.1073/pnas.2016326117
WOS© Times Cited 2
Keyword(s) Mars, meteorites, zircon, geodynamics
Abstract

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 similar 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.

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Costa Maria M., Jensen Ninna K., Bouvier Laura C., Connelly James N., Mikouchi Takashi, Horstwood Matthew S. A., Suuronen Jussi-Petteri, Moynier Frederic, 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 Of The United States Of America, 117(49), 30973-30979. Publisher's official version : https://doi.org/10.1073/pnas.2016326117 , Open Access version : https://archimer.ifremer.fr/doc/00686/79847/