Martian mantle mineralogy investigated by the 176Lu–176Hf and 147Sm–143Nd systematics of shergottites

Debaille, Vinciane; Yin, Qing‐Zhu; Brandon, A. D.; Jacobsen, Ben

doi:10.1016/j.epsl.2008.02.008

Cited by 100 publications

(143 citation statements)

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“…The primary evidence for this conclusion comes from the decay of 146 Sm to 142 Nd, which occurs with a half-life of 103 Ma (Lugmair & Marti 1977). In the case of Mars and the Moon, the early planetary-scale differentiation events are clearly shown in most radiometric systems (Tera & Wasserburg 1974;Carlson & Lugmair 1988;Jagoutz 1991;Harper et al 1995;Nyquist et al 1995;Borg & Draper 2003;Foley et al 2005;Rankenburg et al 2006;Caro et al 2008;Debaille et al 2008). On the Earth, with the exception of U-Pb (Patterson 1956) and Hf-W (Kleine et al 2002;Yin et al 2002a), which are affected by core formation, the effect of early differentiation of the silicate earth on conventional radiometric systems (Rb-Sr, Sm-Nd, Lu-Hf and U-Th-Pb) is sufficiently subtle that it has been masked by the continuing differentiation of the Earth's interior caused by the growth of the CC.…”

Section: Introductionmentioning

confidence: 99%

“…Tera & Wasserburg 1974;Carlson & Lugmair 1988;Nyquist et al 1995). Following recognition that the Shergottite, Nakhlite and Chassignite (SNC) meteorites probably derive from Mars, chemical and isotopic study of these planetary fragments showed that Mars too is a highly differentiated object, with the separation of mantle from crust occurring within tens of millions of years of Solar System formation Borg & Draper 2003;Foley et al 2005;Caro et al 2008;Debaille et al 2008). A demonstration of even quicker igneous processing of smaller planetary objects is provided by the ca 4563 Ma ages obtained for parent body differentiation of the angrite and eucrite meteorites (Lugmair & Shukolyukov 1998;Amelin 2008;Markowski et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Composition of the Earth's interior: the importance of early events

Carlson

Boyet

2008

Phil. Trans. R. Soc. A.

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The detection of excess 142 Nd caused by the decay of 103 Ma half-life 146 Sm in all terrestrial rocks compared with chondrites shows that the chondrite analogue compositional model cannot be strictly correct, at least for the accessible portion of the Earth. Both the continental crust (CC) and the mantle source of mid-ocean ridge basalts (MORB) originate from the material characterized by superchondritic 142 Nd/ 144 Nd. Thus, the mass balance of CC plus mantle depleted by crust extraction (the MORB-source mantle) does not sum back to chondritic compositions, but instead to a composition with Sm/Nd ratio sufficiently high to explain the superchondritic 142 Nd/ 144 Nd. This requires that the mass of mantle depleted by CC extraction expand to 75–100 per cent of the mantle depending on the composition assumed for average CC. If the bulk silicate Earth has chondritic relative abundances of the refractory lithophile elements, then there must exist within the Earth's interior an incompatible-element-enriched reservoir that contains roughly 40 per cent of the Earth's 40 Ar and heat-producing radioactive elements. The existence of this enriched reservoir is demonstrated by time-varying 142 Nd/ 144 Nd in Archaean crustal rocks. Calculations of the mass of the enriched reservoir along with seismically determined properties of the D″ layer at the base of the mantle allow the speculation that this enriched reservoir formed by the sinking of dense melts deep in a terrestrial magma ocean. The enriched reservoir may now be confined to the base of the mantle owing to a combination of compositionally induced high density and low viscosity, both of which allow only minimal entrainment into the overlying convecting mantle.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Composition of the Earth's interior: the importance of early events

Carlson

Boyet

2008

Phil. Trans. R. Soc. A.

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“…Among the more than 45 known unpaired Martian meteorites are seven nakhlite specimens (Nakhla, Lafayette, Governador Valadares, Northwest Africa (NWA) 817, NWA 998, Yamato (Y-) 000593, Miller Range (MIL) 03346), all of which have crystallization ages of 1.3-1.4 Ga and cosmic-ray exposure ages of 11 ± 1.5 Ma (see Nyquist et al 2001;Treiman 2005). The nakhlites are distinctive among Martian meteorites because they have experienced less shock than other types, and they have textural and mineralogical features suggesting that they represent a series of cumulate igneous rocks within one or more closely related hypabyssal magma bodies or thick lava flows (e.g., Treiman 1987;Friedmann-Lentz et al 1999;Treiman 2005;Debaille et al 2007). All nakhlites are remarkable for the presence around or cross-cutting primary igneous grains of secondary minerals (especially material commonly termed iddingsite), proposed to have been produced by deuteric, hydrothermal, or weathering processes involving fluid-mediated reactions on Mars.…”

Section: Introductionmentioning

confidence: 99%

Petrology of Martian meteorite Northwest Africa 998

Treiman

Irving

2008

Meteorit & Planetary Scien

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Petrology of Martian meteorite Northwest Africa 998replacing or forming overgrowths on olivine and augite, ∼1% titanomagnetite, and other phases including potassium feldspar, apatite, pyrrhotite, chalcopyrite, ilmenite, and fine-grained mesostasis material. Minor secondary alteration materials include "iddingsite" associated with olivine (probably Martian), calcite crack fillings, and iron oxide/hydroxide staining (both probably terrestrial). Shock effects are limited to minor cataclasis and twinning in augite. In comparison to other nakhlites, NWA 998 contains more low-calcium pyroxenes and its plagioclase crystals are blockier. The large size of the intercumulus feldspars and the chemical homogeneity of the olivine imply relatively slow cooling and chemical equilibration in the late-and post-igneous history of this specimen, and mineral thermometers give subsolidus temperatures near 730 °C. Oxidation state was near that of the QFM buffer, from about QFM−2 in earliest crystallization to near QFM in late crystallization, and to about QFM + 1.5 in some magmatic inclusions. The replacement or overgrowth of olivine by pigeonite and orthopyroxene (with or without titanomagnetite), and the marginal replacement of augite by pigeonite, are interpreted to result from late-stage reactions with residual melts (consistent with experimental phase equilibrium relationships). Apatite is concentrated in planar zones separating apatite-free domains, which suggests that residual magma (rich in P and REE) was concentrated in planar (fracture?) zones and possibly migrated through them. Loss of late magma through these zones is consistent with the low bulk REE content of NWA 998 compared with the calculated REE content of its parent magma.

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“…Based on their crystal size and modal mineralogy they are subdivided into basaltic, olivinephyric, and lherzolitic shergottites and one wehrlite. This mineralogical subdivision more or less reflects another subdivision based on their geochemical composition (depleted, intermediate and enriched in light rare earth elements) (e.g., McSween 1994; Debaille et al 2007;Debaille et al 2008). The remarkable characteristic of the shergottites is their "young" crystallization ages, ranging from 165 to 475 Ma (Nyquist et al 2001), even though Pb-Pb isotope systematics were used to argue for "old" crystallization ages of around 4.1 Ga (Bouvier et al 2005;Bouvier et al 2008).…”

Section: Martian Materials and The Composition Of Marsmentioning

confidence: 99%

“…More specifically, the trace element and isotopic variations observed among shergottites is successfully modeled as a mixture between a depleted mantle component, represented by mafic cumulates of the magma ocean, and a strongly enriched component, most likely represented by the late-stage residual liquid of the magma ocean Borg and Draper 2003;Elkins-Tanton et al 2003, 2005bDebaille et al 2008). Debaille et al (2008) observed that equilibrium crystallization is more appropriate to generate the observed chemical compositions of the shergottites, while they acknowledged that the crystallization of a magma ocean is certainly a hybrid process, where some crystals have time to equilibrate with the magma while others sink directly to the bottom of the magma ocean without equilibration. This observation is consistent with the expected dynamics of a turbulent magma ocean, because turbulence can keep the minerals suspended long enough for equilibration to occur.…”

Section: Magma Ocean Crystallization and Cumulate Overturnmentioning

confidence: 99%

Core Formation and Mantle Differentiation on Mars

Mezger¹,

Debaille²,

Kleine³

2012

Quantifying the Martian Geochemical Reservoirs

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Geochemical investigation of Martian meteorites (SNC meteorites) yields important constraints on the chemical and geodynamical evolution of Mars. These samples may not be representative of the whole of Mars; however, they provide constraints on the early differentiation processes on Mars. The bulk composition of Martian samples implies the presence of a metallic core that formed concurrently as the planet accreted. The strong depletion of highly siderophile elements in the Martian mantle is only possible if Mars had a large scale magma ocean early in its history allowing efficient separation of a metallic melt from molten silicate. The solidification of the magma ocean created chemical heterogeneities whose ancient origin is manifested in the heterogeneous 142 Nd and 182 W abundances observed in different meteorite groups derived from Mars. The isotope anomalies measured in SNC meteorites imply major chemical fractionation within the Martian mantle during the life time of the short-lived isotopes 146 Sm and 182 Hf. The Hf-W data are consistent with very rapid accretion of Mars within a few million years or, alternatively, a more protracted accretion history involving several large impacts and incomplete metal-silicate equilibration during core formation. In contrast to Earth early-formed chemical heterogeneities are still preserved on Mars, albeit slightly modified by mixing processes. The preservation of such ancient chemical differences is only possible if Mars did not undergo efficient whole mantle convection or vigorous plate tectonic style processes after the first few tens of millions of years of its history. K. Mezger ( )

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Martian mantle mineralogy investigated by the 176Lu–176Hf and 147Sm–143Nd systematics of shergottites

Cited by 100 publications

References 56 publications

Composition of the Earth's interior: the importance of early events

Composition of the Earth's interior: the importance of early events

Petrology of Martian meteorite Northwest Africa 998

Core Formation and Mantle Differentiation on Mars

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