Julia Roszjar

Knut Metzler

Addi Bischoff

Jean-Alix J-A Barrat

Thorsten Geisler

Richard C Greenwood

Ian A Franchi

Stephan Klemme

Thermal history of Northwest Africa 5073-A coarse-grained Stannern-trend eucrite containing cm-sized pyroxenes and large zircon grains

Keywords: eucrite, bulk chemistry, petrology, trace elements, oxygen isotopes, µ-Raman spectroscopy, zircon annealing

published or not. The documents may come

Introduction

The so-called HED suite of achondrites (Howardites, Eucrites, and Diogenites) makes up the largest suite of igneous rocks available from any Solar System body besides the Earth and the Moon [START_REF] Mittlefehldt | Non-chondritic meteorites from asteroidal bodies[END_REF]. Eucrites represent basaltic rocks and gabbroic cumulates, whereas diogenites are ultramafic rocks (orthopyroxenites, olivine-bearing orthopyroxenites, harzburgites, and dunites), mainly composed of orthopyroxene and olivine (e.g., [START_REF] Mittlefehldt | Non-chondritic meteorites from asteroidal bodies[END_REF][START_REF] Beck | Diogenites as polymict breccias composed of orthopyroxenite and harzburgite[END_REF]. Howardites are polymict breccias, consisting of various amounts of eucritic and diogenitic lithologies. The close relationship between HEDs is convincingly supported by petrographic, mineralogical, chemical, and isotopic evidences (see [START_REF] Mcsween | HED Meteorites and their relationship to the geology of Vesta and Dawn mission[END_REF] for a review), and suggest that they derived from the same parent body, possibly the asteroid 4 Vesta (e.g., [START_REF] Mccord | Asteroid Vesta: Spectral reflectivity and compositional implications[END_REF][START_REF] Consolmagno | Composition and evolution of the eucrite parent body: Evidence from rare earth elements[END_REF][START_REF] Binzel | Chips off of Asteroid 4 Vesta: Evidence for the parent body of basaltic achondrite meteorites[END_REF][START_REF] Drake | The eucrite/Vesta story[END_REF]. However, a few eucrites display unusual petrographic features and distinct oxygen isotopic compositions and could, therefore, have originated from distinct parent bodies (e.g., [START_REF] Yamaguchi | A new source of basaltic meteorites inferred from Northwest Africa 011[END_REF][START_REF] Scott | Oxygen isotopic constraints on the origin 489 and parent bodies of eucrites, diogenites, and howardites[END_REF][START_REF] Gounelle | A unique basaltic micrometeorite expands the inventory of solar system planetary crusts[END_REF][START_REF] Bland | An anomalous basaltic meteorite from the innermost main belt[END_REF]. Eucrites are widely thought to represent either surface or near-surface basaltic liquids (lava flows or shallow intrusions) or crystal accumulations from basaltic liquids. Most eucrites experienced a complex post-crystallization history, including prolonged thermal metamorphism that produced recrystallization textures and caused exsolution and inversion of pyroxenes (e.g., [START_REF] Takeda | Degree of equilibrium of eucritic pyroxenes and thermal metamorphism of the earliest planetary crust[END_REF][START_REF] Metzler | Thermal and impact metamorphism on the HED parent asteroid[END_REF][START_REF] Yamaguchi | Global metamorphism on the eucrite parent body[END_REF], 2009;[START_REF] Mayne | Petrology of the unbrecciated eucrites[END_REF], and multiple impact events. Thus, many eucrites are brecciated, and were formed in the regolith and mega-regolith of their parent body (e.g., [START_REF] Stöffler | Shock effects in meteorites[END_REF]. They consist of mineral and/or lithic fragments embedded in a fine-grained, generally fragmented matrix (e.g., [START_REF] Takeda | Degree of equilibrium of eucritic pyroxenes and thermal metamorphism of the earliest planetary crust[END_REF][START_REF] Metzler | Thermal and impact metamorphism on the HED parent asteroid[END_REF][START_REF] Bischoff | Nature and origins of meteoritic breccias. Meteorites and the early solar system II[END_REF][START_REF] Llorca | The Puerte Lápice eucrite[END_REF]. From a chemical point of view, eucrites can be subdivided into basaltic (noncumulate), and cumulate eucrites, both of which occur also as clasts in polymict eucrites and howardites (e.g., [START_REF] Takeda | Comparison of Antarctic and non-Antarctic achondrites and possible origin of the differences[END_REF]. Cumulate eucrites are coarse-grained rocks with high Mg-numbers [Mg# = molar Mg/(Mg + Fe)], low incompatible trace element abundances compared to other eucrites, and pronounced positive Eu anomalies -a feature consistent with plagioclase accumulation. Basaltic eucrites can be subdivided into three compositional distinct groups on the basis of their Mg# or FeO total /MgO wt.% ratio, TiO 2 contents, and incompatible trace element abundances (e.g., [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF][START_REF] Warren | Composition and origin of Nuevo Laredo trend eucrites[END_REF][START_REF] Mittlefehldt | Non-chondritic meteorites from asteroidal bodies[END_REF][START_REF] Yamaguchi | Crustal partial melting on Vesta: Evidence from highly metamorphosed eucrites[END_REF]: Main Group Nuevo Laredo-trend eucrites, Stannern-trend eucrites and the residual eucrites. Main Group Nuevo Laredo-trend eucrites are the most common ones. They display wide variations in Mg# with only moderate variations in incompatible element abundances. They are believed to represent a fractional crystallization trend (e.g., [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF][START_REF] Warren | Composition and origin of Nuevo Laredo trend eucrites[END_REF].

Stannern-trend eucrites are rare. They include three falls (Stannern, Bouvante, and Pomozdino), and about a dozen finds from Antarctica (e.g., Y-75011) and from the Sahara (e.g., NWA 4523 and NWA 1000). They display the same major element abundances as the less evolved rocks of the Nuevo Laredo group, but exhibit high Ti and incompatible trace element abundances, and significant negative Eu, Sr, and Be anomalies. The origin of these eucrites is controversial. It has been proposed that the Stannern-trend eucrites could have been generated from the same mantle source as Main Group eucrites but at smaller degrees of partial melting, and possibly at slightly different oxygen fugacities [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF][START_REF] Mittlefehldt | Geochemistry of eucrites: genesis of basaltic eucrites, and Hf and Ta as petrogenetic indicators for altered Antarctic eucrites[END_REF]. Alternatively, it has been proposed that the high incompatible trace element abundances could be explained by an intricate in-situ crystallization process [START_REF] Barrat | The differentiation of eucrites: the role of in-situ crystallization[END_REF], or by the involvement of highly evolved KREEP-like melts [START_REF] Warren | Eucrite Bluewing 001: a Stannern-like bulk composition and its linkage with other unequilibrated HED basalts (abstract)[END_REF]. The contamination of Main Group eucritic magmas might be also explained by melts derived from partial melting of the asteroid's crust, which would can successfully explain both the high incompatible trace elements concentrations and the distinctive Eu, Sr, and Be anomalies shown by the Stannern-trend eucrites [START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF]. Finally, the residual eucrites display major element abundances consistent with Main Group eucrites, but light REE depletions and positive Eu anomalies. Partial melting followed by extraction of a few percent of partial melts can satisfactorily explain these features [START_REF] Yamaguchi | Crustal partial melting on Vesta: Evidence from highly metamorphosed eucrites[END_REF]. At present, it is generally thought that the differentiation history of the eucrite parent body has been triggered by the formation of a global magma ocean (e.g., [START_REF] Takeda | A layered-crust model of a howardite parent body[END_REF][START_REF] Righter | A magma ocean on Vesta: core formation and petrogenesis of eucrites and 471 diogenites[END_REF][START_REF] Ruzicka | Vesta as the howardite, eucrite and diogenite parent body: 477 implications for the size of a core and for large-scale differentiation[END_REF][START_REF] Warren | Magnesium oxide-iron oxide mass balance constraints and a more detailed model for the 502 relationship between eucrites and diogenites[END_REF][START_REF] Greenwood | Widespread magma oceans on asteroidal bodies in the early Solar System[END_REF]. This hypothesis is at first glance consistent with the petrology of the eucrites, but cannot easily account for the geochemistry of the diogenites (e.g., [START_REF] Mittlefehldt | Petrology and geochemistry of the Elephant Moraine A79002 diogenite: A genomict breccia containing a magnesian harzburgite component[END_REF][START_REF] Barrat | Geochemistry of diogenites: Still more 392 diversity in their parental melts[END_REF][START_REF] Barrat | Relative chronology of crust formation on asteroid 4-Vesta: Insights from the geochemistry of diogenites[END_REF]. Thus, the magmatic and thermal histories of the parent body were certainly much more complicated than generally believed and more detailed studies of HED meteorites are necessary to further our understanding of the process leading to the formation of HED meteorite genesis. Recently, we have identified NWA 5073, a eucrite which displays some unique features. This single, unbrecciated stone is characterized by an unusual texture with cm-sized unequilibrated pyroxenes crosscut by numerous secondary olivine-rich veins, and mesostasis areas containing large zircon grains. Here, we report on the bulk chemistry, petrology, and isotopic characteristics of this exceptional meteorite and discuss its genesis and complex post-crystallization history. Preliminary data on NWA 5073 have been previously presented by Roszjar et al. (2009a-c) and [START_REF] Roszjar | Lu-Hf systematics of the NWA 5073 eucrite reflect a complex thermal history (abstract)[END_REF].

Analytical Methods

The textural and mineralogical investigations of the sample were performed by optical and electron microscopy on a thin section (PL07217). Modal abundance of major phases and mesostasis were determined based on multiple point-counting applied on a backscattered electron (BSE) photomicrograph using an Olympus Analysis software. A JEOL A840 scanning electron microscope (SEM) equipped with energy dispersive spectrometers (EDS; INCA; Oxford Instrument) at the Interdisciplinary Center for Electron Microscopy and Microanalysis (ICEM) at the Westfälische Wilhelms-Universität Münster was used for detailed petrographic investigations. Qualitative analyses have been carried out using an acceleration voltage of 20 kV, and a beam current of 15 nA. High contrast, low brightness BSE imaging has been used for systematic identification and localization of Zr-bearing phases. Quantitative analyses of mineral compositions were obtained using a JEOL JXA 8900 Superprobe electron probe micro analyzer (EPMA) operated at an acceleration voltage and beam current of 15 kV and 15 nA, respectively. Natural and synthetic standards of well-known compositions were used as standards. Matrix corrections were made according to the Фρ(z) procedure of [START_REF] Armstrong | Quantitative elemental analysis of individual microparticles with electron beam instruments[END_REF].

Prior to micro-Raman spectroscopy, investigations of zircon grains were performed on the JEOL A840 SEM at conditions described above. BSE imaging allowed selection of 10 appropriate grains with sufficient diameter ranging from 10-25 µm that were free of cracks and inclusions, and were representative of the whole zircon population in NWA 5073 in terms of mineral shape and mineral paragenesis with surrounding phases. The same spots on individual zircon grains investigated by Raman spectroscopy were subsequently analyzed for major, minor, and trace element concentrations by wavelength-dispersive analysis using a Cameca SX 100 EPMA at the Institut für Mineralogie, Universität Hamburg. Major (Si, Zr, Hf) and minor (Al, Fe, P, Ca, Mn, Y) elements were analyzed in a first sequence using a beam current of 20 nA, an acceleration voltage of 15 keV, total counting times of 30 s, and a beam diameter of 1-2 µm. Th and U concentrations were subsequently determined in a separate cycle with total counting times of 600 s (10 × 60 s) for the U-M β and Th-M α line, and a beam current and acceleration voltage of 200 nA and 15 kV, respectively, to achieve a better precision. A small overlap of the Th-M α on the U-M  line was corrected using the method proposed by [START_REF] Åmli | Microprobe analysis of REE minerals using empirical correction factors[END_REF]. For these conditions the detection limit of U and Th is about 20-30 ppm.

Micro-Raman spectroscopic measurements were performed subsequently, but prior to compositional analysis by EPMA to preclude any possible irreversible modifications of the radiationdamaged structure as a result of the electron beam impact. Micro-Raman spectroscopic analyses were carried out on a polished, cleaned thin section of NWA 5073 using a Jobin Yvon HR800 dispersive Raman spectrometer at the Institut für Anorganische und Analytische Chemie at the Westfälische Wilhelms-Universität Münster. The 632.187 nm line of a Nd-YAG laser was used as excitation source with a beam power of ~10 mW at the exit of the laser. The scattered Raman light was collected with a 100 times objective (N.A. =0.9) with charge-coupled device detector (CCD) after being dispersed by a grating of 1800 grooves mm -1 . The spectrometer slit width was set to 150 µm, yielding a spectral resolution of 1.9 cm -1 near 1000 cm -1 as determined from Ne light bands. The lateral resolution was about 1-2 µm. A possible spectrometer drift was monitored by measuring the 520.7 cm -1 band of silicon and the spectral lines of the Ne-lamp immediately before and after the sample analyses.

Information about the structural state of individual zircon grains was obtained by examining the total spectrum and by monitoring the intensity, full width at half maximum (FWHM), and the frequency of the internal antisymmetric ν 3 (SiO 4 ) stretching mode located near 1008 cm -1 in a non-metamict zircon.

This band was monitored because (i) it has been shown that it is most suitable for quantifying radiation damage [START_REF] Wopenka | Trace element zoning and incipient metamictization in a lunar zircon: Application of three microprobe techniques[END_REF][START_REF] Nasdala | Heterogeneous metamictization of zircon on a microscale[END_REF][START_REF] Nasdala | Constraining a SHRIMP U-Pb age: microscale characterization of zircons from Saxionian Rotliegende rhyolites[END_REF][START_REF] Palenik | Radiation damage in zircon[END_REF], since it is the strongest Raman band of zircon and thus easy to measure precisely [START_REF] Dawson | The vibrational spectrum of zircon (ZrSiO 4 )[END_REF][START_REF] Nasdala | Heterogeneous metamictization of zircon on a microscale[END_REF]Zhang et al., 2000a), and (ii) it is not significantly red-shifted by impurity-related structural disorder such as caused by variations in the Hf concentration [START_REF] Hoskin | Raman spectral shift in the isomorphous series (Zr 1x Hf x )SiO 4[END_REF]. The broad band profile in the frequency region between 900 and 1100 cm -1 results from an overlap of the  3 (SiO 4 ) with the adjacent, internal  1 (SiO 4 ) stretching mode (A 1g symmetry; [START_REF] Dawson | The vibrational spectrum of zircon (ZrSiO 4 )[END_REF] at about 975 cm -1 and, in radiation-damaged zircon, from the contribution of a broad background feature at a lower frequency, which has been assigned to the amorphous component in metamict zircon (Zhang et al., 2000a). Quantitative band parameters were obtained by deconvoluting the overall band profile in the frequency region between 800 and 1100 cm -1 with three Voigt functions and a linear background as shown by [START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF]. The reproducibility of the fitted frequency is better than 0.2 cm -1 and that of the linewidth is in the order of ±0.5 cm -1 at a linewidth smaller than 20 cm -1 and ±1.0 cm -1 for larger linewidths. The effect of the finite slit width on the measured linewidth, given as the full width at half maximum (FWHM), was then corrected by the method of [START_REF] Tanabe | Correction of finite slit width effects on Raman line widths[END_REF].

From radioactive decay of the 238 U, 235 U, and 232 Th isotopes, the number of α-decay events for different U and Th concentrations were calculated according to the following equation:

D α = 8 N 1 [exp(λ 1 t -1)] + 7 N 2 [exp(λ 2 t -1)] + 6 N 3 [exp(λ 3 t -1)] (1)
where N 1 , N 2 , and N 3 are the present concentrations of 238 U, 235 U, and 232 Th in the zircon grains, respectively, λ 1 , λ 2 , and λ 3 are the decay constants for 238 U, 235 U, and 232 Th in years -1 , respectively, and t is the age of the zircon. For our calculations we assumed an age of 4.55 Ga.

The bulk chemical composition of NWA 5073 has been determined at the Institut Universitaire Européen de la Mer (IUEM), Plouzané, using ~100 mg of powdered sample material.

The powdered whole rock fraction, derived from initially ~12 g sample material and devoid of fusion crust, was precleaned with ethanol and ultra pure MilliQ® water in an ultrasonic bath, before it was carefully crushed into small pieces in an agate mortar. Subsequently, a representative fraction of 0.48 g was powdered. About 100 mg of the latter were used for bulk rock analyses. Major elements (Ti, Al, Cr, Fe, Mn, Mg, Ca, Na, K, and P) were determined by ICP-AES (inductively coupled plasma-atomic emission spectrometry) using the procedure described by [START_REF] Cotten | Origin of anomalous Rare-Earth Element and Yttrium enrichments in subaerially exposed basalts -Evidence from French-Polynesia[END_REF]. The accuracy of this system is better than 5%, and the reproducibility better than 3%. Trace element concentrations were measured by ICP-MS (inductively coupled plasma-mass spectrometry) using a Thermo Element 2 spectrometer following the procedure described by [START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF]. Based on standard measurements and sample duplicates, trace element concentration reproducibility is generally better than 5%, except for W, which is generally better than 10%.

Trace element abundances of pyroxenes and plagioclases in NWA 5073 were determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at the Institut Universitaire Européen de la Mer, Plouzané. The analyses were performed under a He atmosphere using an ArF-Excimer (193 nm wavelength) laser ablation system (Geolas Pro102), connected to a Finnigan Thermo Element 2 spectrometer. Concentrations were determined on individual spots using a 60 µm-diameter laser beam and a laser repetition rate of 10 Hz. Background and peak were measured for 40 s and 210 s, respectively. For all data, NIST 612 and BCR-2G glass standards were both used for external calibration of relative element sensitivities, using values given by [START_REF] Jochum | Chemical characterisation of the USGS reference glasses GSA-1G, GSC-1G, GSD-1G, GSE-1G, BCR2-G, BHVO2-G, and BIR1-G using EPMA, ID-TIMS, ID-ICP-MS and LA-ICP-MS[END_REF].

Replicate analyses of the USGS basaltic-glass standard BIR-1G run at intervals during the analytical session, yielded an external reproducibility generally better than 5% (1σ relative standard deviation).

Analytical and data reduction procedures followed those described by [START_REF] Barrat | Trace element geochemistry of K-rich impact spherules from howardites[END_REF]. Results

were normalized to CaO abundances measured by electron microprobe as an internal standard to account for variable ablation yield.

Oxygen isotope analysis was carried out at the Open University using an infrared laser fluorination system [START_REF] Miller | High precision δ 17 O isotope measurements of oxygen from silicates and other oxides: Method and Applications[END_REF]. A 2 mg aliquot of NWA 5073, taken from a larger batch of homogenized powdered sample material (~100 mg), was loaded in the sample chamber, together with various international and internal oxygen isotope standards. To maximize yields and decrease the risk of cross contamination, the powdered sample and standards were fused in vacuum to form a glass bead prior to fluorination. O 2 was liberated by heating the glass beads using an infrared CO 2 laser (10.6 μm)

in the presence of 210 torr of BrF 5 . After fluorination, the O 2 released was purified by passing it through two cryogenic nitrogen traps and over a bed of heated KBr. O 2 was analyzed using a Micromass Prism III dual inlet mass spectrometer. Published system precision (1σ) [START_REF] Miller | High precision δ 17 O isotope measurements of oxygen from silicates and other oxides: Method and Applications[END_REF], based on replicate analyses of international (NBS-28 quartz, UWG-2 garnet) and internal

with λ = 0.5247.

Results

Mineralogy

Northwest Africa 5073 is a desert find with a total mass of 185 g, representing an unequilibrated, mesostasis-rich basaltic eucrite with the coarsest subophitic to slightly variolitic (fanspherulitic) texture among the known eucrites. It is an unbrecciated rock that preserved its crystallization texture. It is mainly composed of elongated, unequilibrated pyroxene crystals up to 1.2 cm and plagioclase laths up to 0.3 cm in length (Fig. 1). Large phenocrysts of pyroxene make up approximately 25 vol.% of the whole rock (Table 1). In variolitic areas, the plagioclase tends to be skeletal, i.e., it occurs as partly hollow crystals, which is indicative of rapid cooling. Euhedral chromite grains, occasionally dendritic, frequently occur with grain sizes up to 0.8 mm. Their chemical composition (Table 2) is in the range of those for the unequilibrated eucrite Pasamonte [START_REF] Mittlefehldt | Non-chondritic meteorites from asteroidal bodies[END_REF]. Fine-grained areas (mesostasis) that make up about 8.5 vol.% of the rock, occur interstitially to the large crystals (Figs. 1 and3). Terrestrial weathering of the sample is indicated by the breakdown of about half of the metals and the occurrence of calcite, and Ba-sulfates in some cracks all over the thin section. According to the scheme proposed for chondrites by [START_REF] Wlotzka | A weathering scale for the ordinary chondrites (abstract)[END_REF], NWA 5073 is moderately weathered (W2-3).

Large pyroxene crystals are chemically unequilibrated with cores of En 51-60 Fs 34-5 Wo 2-8 and rims of En 20-34 Fs 42-63 Wo 8-34 (Figs. 2 and3; Table 2). The pyroxene composition depicted in Fig. 2, reflects magmatic zoning from Mg-rich cores to Fe-rich rims of large pigeonite laths adjacent to surrounding plagioclase crystals, which is typical of more rapidly cooled basalts containing pyroxene that has not exsolved on a µm scale, e.g., Y-75011 [START_REF] Takeda | Mineralogy and 39 Ar-40 Ar age of an old pristine basalt: Thermal history of the HED parent body[END_REF]. As emphasized by e.g., Takeda et al. (1982), chemical zoning in pyroxene primarily depends on the bulk chemistry of the basaltic melt and on crystal-growth conditions such as the degree of supercooling and nucleation. Re-equilibration of chemical zoning in pyroxene crystals did not occur in our sample. Thus, NWA 5073 was not formed in a slow cooling environment, as indicated by the skeletal nature of plagioclases, (see Fig. 3a), and

was not affected by a long-term, high-temperature event, which would have resulted in reequilibration of pyroxene crystals. The large pyroxene crystals are frequently twinned and fractured mainly perpendicular to the c-axis. This is in strong contrast to the adjacent plagioclase crystals which do not show this fracturing. The small pyroxenes interstitial to the large crystals show similar Ca contents as the rims of large crystals, but contain somewhat more Fe (Fig. 2, open squares, Table 2).

Occasionally, very thin (<1µm) exsolution lamellae of augite in the host pyroxenes can be observed (e.g., Fig. 3). Pyroxenes in contact with the mesostasis frequently have a corroded appearance. Large pyroxene grains are crosscut by fractures that are mainly filled by Fe-rich olivine. Originating from these veins, a distinct Fe-enrichment of the adjacent host pigeonite can be observed, which clearly parallels the veins (Fig. 3). Pyroxene areas distant to these veins appear as Mg-rich "cores", surrounded by Fe-enriched areas. These "cores" seem to have preserved their original composition from primary crystallization (Fs ~34 ). Additionally, Fe has effectively diffused from the olivine veins and larger fractures devoid of olivine veins into the host pyroxene crystals along certain crystallographic orientations, which probably represent cleavage plans (see Figs. 3d and4a-b). Veins of Fe-rich olivine (Fa 65-71 ) are clearly restricted to the large pyroxene crystals and always end abruptly at their boundaries. These veins are very irregular with distinct thickness variations (Fig. 3a-c). The olivine appears to have grown along preexisting fractures of its host pyroxene, while adjacent large plagioclase crystals are devoid of it (Fig. 3a-c). Euhedral chromite, and troilite crystals, and sporadic subrounded apatite grains occur within these veins (Fig. 3d). Similar olivine veins have been described from a few other eucrites and howardites, namely Macibini, Y-7308, Y-790260, Y-75011, Y-82202, NWA 049, NWA 1000, and NWA 2061 (Takeda and Yanai, 1982;[START_REF] Takeda | Mineralogical comparison of antarctic and non-antarctic HED (howardites-eucrites-diogenites) achondrites[END_REF][START_REF] Metzler | Gefüge und Zusammensetzung von Gesteinsfragmenten in polymikten achondritischen Breccien[END_REF][START_REF] Warren | Northwest Africa 1000: A new eucrite with maskelynite, unequilibrated pyroxene crisscrossed by fayalite-rich veins, and Stannern-like geochemistry[END_REF][START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF].

Two primary feldspar generations occur, namely large plagioclase laths (up to 3 mm in length) and small plagioclase grains located in the mesostasis, both of which are compositionally in the typical eucrite range (e.g., [START_REF] Mittlefehldt | Non-chondritic meteorites from asteroidal bodies[END_REF] of An 76-92 Ab 8-22 Or 0-3 (Fig. 5; Table 2). The plagioclases found in mesostasis areas tend to be more Ab-rich compared to large plagioclase laths (Fig. 5). Many large plagioclase crystals are clouded by myriads of exsolved tiny pyroxene and SiO 2 grains, as commonly observed in eucrites (e.g., [START_REF] Harlow | Clouding of pyroxene and plagioclase in eucrites: implications for post-crystallization processing[END_REF][START_REF] Metzler | Thermal and impact metamorphism on the HED parent asteroid[END_REF]. Additional to the primary plagioclases, we identified another, probably second generation of feldspars that are typically An 97-100 in composition (Fig. 5) and were usually found in association with Fe-rich olivine veins within large pyroxene laths (Fig. 4).

The mesostasis consists of tridymite laths up to 0.8 mm, Ni-poor metallic Fe (<300 µm), ilmenite (<60 µm), chromite, plagioclase, augite, apatite, merrillite, troilite, zircon, baddeleyite, and very small amounts of Fe-rich olivine. In addition, sporadic anorthite (An 95 ) was found. In some cases the mesostasis areas are not well-defined and appear blurred. More than 30 grains of Zr-bearing phases, such as zircon, baddeleyite, and zirconolite grains, with diameters ranging from 1 to 30 µm were found in the mesostasis (Fig. 6; Roszjar et al., 2009b). They are typically located interstitial to ilmenite, pyroxene, plagioclase, and iron metal, and/or occur as inclusions in ilmenite and are subhedral to anhedral, and rounded in shape. The major element composition is consistent for all analyzed zircon grains (see Table 2), and within the range of prior published data on eucrite zircon grains [START_REF] Saiki | Zircon in magnesian, basaltic eucrite Yamato 791438 and its Possible Origin (abstract)[END_REF][START_REF] Bukovanská | Zircons in the Padvarnikai brecciated eucrite (abstract)[END_REF]Ireland and Bukovanská, 1992;Yamaguchi et al., 2001;[START_REF] Yamaguchi | Occurrence and possible origin of zircon in basaltic eucrites (abstract)[END_REF][START_REF] Misawa | U-Pb and 207 Pb-206 Pb ages of zircons from basaltic eucrites: Implications for early basaltic volcanism on the eucrite parent body[END_REF][START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF]Roszjar et al., 2009c). In addition to BSE images that were taken for all selected zircon grains, cathodoluminescence images were exemplarily taken for some of them. Here it was found that the luminescence behavior is distinct from grain to grain. Nevertheless, some zircon grains are characterized by partial luminescence with a preferred direction, increasing towards the edges of the grains, also giving evidence for a thermal reaction front caused by a metamorphic event (Fig. 6).

Shock features

Northwest Africa 5073 as a whole is very weakly shocked, possibly equivalent to a S2 stage as defined for chondrites [START_REF] Stöffler | Shock metamorphism of ordinary chondrites[END_REF][START_REF] Bischoff | Shock metamorphism as a fundamental process in the evolution of planetary bodies: Information from meteorites[END_REF]. Evidence for shock is given by the undulatory extinction of about half of the plagioclases and the occurrence of dislocation lines in large pyroxene laths.

There is also evidence for an earlier shock event which affected this meteorite prior to annealing during thermal metamorphism. Minor tiny, euhedral to subhedral troilite (FeS) grains and blebs of metallic Fe-Ni that are usually <3 µm, occur within the plagioclase crystals and are arranged in curvilinear trails, frequently aligned in a pearl chain manner, which do not follow the cleavage planes and are restricted to the interiors of individual silicate crystals. It is known that metal and sulfide are readily mobilized and re-precipitated in the shape of trails during shock metamorphism [START_REF] Rubin | A shock-metamorphic model for silicate darkening and compositionally variable plaglioclase in CK and ordinary chondrites[END_REF].

These inclusions are in principle the cause of the silicate darkening which can be described as impactgenerated "shock darkening" [START_REF] Rubin | A shock-metamorphic model for silicate darkening and compositionally variable plaglioclase in CK and ordinary chondrites[END_REF][START_REF] Dodd | Meteorites-A Petrologic-Chemical Synthesis[END_REF]. After annealing the metal and sulfide veins are probably transformed to the tiny blebs described above.

Bulk chemical composition

The major and trace element abundances of NWA 5073 share similarities with other Stannerntrend eucrites, such as Bouvante and Stannern (Table 3). Northwest Africa 5073 has respectively FeO total /MgO ratio (2.31) and Sc concentration (25.8 µg/g) slightly lower, and MgO (8.70 wt%), Cr 2 O 3 (0.59 wt%) concentrations higher to that of typical Main Group eucrites (e.g., [START_REF] Warren | Siderophile and other geochemical constraints on mixing relationships among HED-meteorite breccias[END_REF].

Similar "high" MgO abundances were previously measured on Pomozdino by [START_REF] Warren | Pomozdino: An anomalous, high-MgO/FeO, yet REE-rich eucrite[END_REF], and led these authors to propose that this meteorite could be a partial cumulate. Moreover, an increase of MgO can be produced by a slight oversampling of pyroxene in the powdered sample. Because NWA 5073 is unequilibrated, these two possibilities can be easily discussed. We have calculated the apparent distribution coefficient between the pigeonite cores (with n = 27) and the whole rock composition (K D Fe/Mg = (Fe/Mg) pigeonite core /(Fe/Mg) whole rock ). The result, K D Fe/Mg =0.32± 0.01 (2σ), is in very good agreement with experimental distribution coefficients obtained for eucritic systems (K D Fe/Mg =0.30; [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF]. A lower value would have been obtained if the powder contained a pyroxene excess. Thus, the pigeonite cores formed from a parental melt displaying the same Fe/Mg as the analyzed powder. We conclude that the whole rock composition is probably close to its parental melt.

However, we suspect that the rather high Cr 2 O 3 abundance is an artifact produced by a very small excess of chromite in the powder.

Weathered meteorite finds from the Sahara generally exhibit marked Ba and Sr enrichments that are sensitive indicators for the development of secondary phases (e.g., [START_REF] Stelzner | In interdisciplinary study of weathering effects in ordinary chondrites from the Acfer region Algeria[END_REF][START_REF] Barrat | Petrology and geochemistry of the unbrecciatted achondrite North West Africa 1240 (NWA 1240): an HED parent body impact melt[END_REF][START_REF] Crozaz | Chemical alteration and REE mobilization in meteorites from hot and cold deserts[END_REF]. NWA 5073 is no exception, and displays high Ba and Sr concentrations (177 µg/g and 2131 µg/g, respectively). It should be noted that its Th/U ratio (=3.38) and Pb abundances (= 0.24 µg/g), which are other possible indicators of weathering, do not show perturbed values.

Although NWA 5073 is characterized by a low FeO/MgO ratio (Fig. 7, Table 3), it displays high levels of concentrations for incompatible elements, as exemplified by the REEs (Fig. 8). This suggests that NWA 5073 is a new member of the Stannern-trend eucrites, transitional between the Main Group and the REE-rich eucrites such as Stannern or Bouvante. Indeed, NWA 5073 exhibits a much more pronounced negative Eu anomaly (Eu/Eu*=0.68) and a higher Gd/Lu ratio than a regular Main Group or Nuevo Laredo eucrite, and its REE-pattern is parallel to those of the Stannern-trend eucrites (e.g., Bouvante and Stannern). These similarities extend to other incompatible trace element abundances, and, interestingly, NWA 5073 displays a marked negative Be anomaly (Fig. 9) which is a distinctive feature of the Stannern-trend eucrites [START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF]. Thus, we can deduce that NWA 5073 is clearly a new member of this rare group of eucrites.

Mineral chemical composition

In addition to bulk rock trace elements, REE concentrations of pyroxenes and plagioclases have been determined with LA-ICP-MS. Results are shown in Table 4. CI normalized REE patterns for pyroxenes and plagioclases are presented in Fig. 10. In eucrites, pyroxene is one of the dominant phases next to plagioclase, and a sensitive indicator of intrinsic variables such as oxygen fugacity and temperature that may affect their crystallization sequence. Therefore, major, minor, and trace elements have been investigated in order to decipher the evolution of the NWA 5073 meteorite. Rare earth element abundances of selected pyroxene cores in NWA 5073 are in the range of 0.02× (La) to 2.2×

(Lu) CI chondritic abundances, relative to the values given in [START_REF] Evensen | Rare Earth abundances in chondritic meteorites[END_REF], which is within the range presented by [START_REF] Pun | Unequilibrated eucrites and the equilibrated Juvinas eucrite: Pyroxene REE systematics and major, minor, and trace element zoning[END_REF] [START_REF] Hsu | Mineral chemistry and the petrogenesis of eucrites: I. Noncumulate eucrites[END_REF][START_REF] Floss | Trace element constraints on the origins of highly metamorphosed Antarctic eucrites[END_REF]. The REE patterns of single plagioclases are slightly fractionated with LREE being enriched. The total abundance of REE ranges from 2× (La) to 0.1 (Er) × CI [START_REF] Evensen | Rare Earth abundances in chondritic meteorites[END_REF], except for Eu (Table 4).

Oxygen isotope composition

The oxygen isotope composition of NWA 5073 obtained in this study (δ 17 O = 1.89 ‰, δ 18 O = 4.05 ‰, Δ 17 O = -0.24 ‰) is plotted in Fig. 11 along with the data for other HED samples obtained by [START_REF] Greenwood | Widespread magma oceans on asteroidal bodies in the early Solar System[END_REF]. The Δ 17 O value for NWA 5073 is close to the average HED value of -0.239 ± 0.007 (1σ) obtained by [START_REF] Greenwood | Widespread magma oceans on asteroidal bodies in the early Solar System[END_REF] and indicates that the meteorite is a normal member of the HED suite (Roszjar et al., 2009a). NWA 5073 was not acid leached prior to oxygen isotope analysis and has a slightly elevated δ 18 O value compared to the eucrites analyzed by [START_REF] Greenwood | Widespread magma oceans on asteroidal bodies in the early Solar System[END_REF], which may reflect a small degree of terrestrial weathering. However, the δ 18 O composition of NWA 5073 is within the range obtained by [START_REF] Wiechert | Oxygen isotope evidence for rapid mixing of the HED parent body[END_REF], which extends to δ 18 O values of 4.5‰.

Structural state of zircon grains as obtained by Raman spectroscopy

It has been demonstrated that micro-Raman spectroscopy is a powerful tool to quantify the degree of self-irradiation damage in single zircon grains caused by the radioactive decay of incorporated U and Th (metamictization) as well as the structural recovery by thermal annealing [START_REF] Nasdala | The degree of metamictization in zircon: a Raman spectroscopic study[END_REF][START_REF] Nasdala | Constraining a SHRIMP U-Pb age: microscale characterization of zircons from Saxionian Rotliegende rhyolites[END_REF][START_REF] Nasdala | Metamictisation of natural zircon: accumulation versus thermal annealing of radioactivity-induced damage[END_REF][START_REF] Wopenka | Trace element zoning and incipient metamictization in a lunar zircon: Application of three microprobe techniques[END_REF]Zhang et al., 2000a-c;[START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF][START_REF] Geisler | Isothermal annealing of partially metamict zircon: evidence for a three-stage recovery process[END_REF][START_REF] Palenik | Radiation damage in zircon[END_REF]. As already mentioned, the  3 (SiO 4 ) band, reflecting antisymmetric Si-O stretching motions of the SiO 4 tetrahedra, is particularly sensitive to structural changes associated with self-irradiation. Raman measurements of zircon grains in sample NWA 5073 reveal a decreased frequency and an increased broadening of the  3 (SiO 4 ) band with increasing radiation dose (D; Fig.

12) as calculated from the U and Th concentration measured by EPMA and an inferred age of 4.55 Ga (Table 5). The frequency shift is attributed to an increase in interatomic distances, i.e., to a slight expansion of the lattice of the crystalline domains, whereas the increase in linewidths is attributed to the fact that the distribution of bond lengths and bond angles within and between SiO 4 tetrahedra becomes increasingly irregular [START_REF] Wopenka | Trace element zoning and incipient metamictization in a lunar zircon: Application of three microprobe techniques[END_REF].

In the diagram linewidth (given as FWHM) vs. frequency of the  3 (SiO 4 ) band all measurements plot along the radiation damage trend (RDT; Fig. 13a) that is mainly defined by measurements from variably self-irradiation-damaged, alluvial zircons from Sri Lanka [START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF]. Dry annealing experiments with self-irradiation-damaged zircon revealed that episodically annealed samples plot above the RDT (arrows in Fig. 13a). A comparison of Raman data from natural zircons with experimental annealing trends thus allows recognizing episodically annealed zircons, provided that post-annealing radiation damage did not completely obscure the annealing effect, i.e., did not push the data points back to the RDT in the frequency versus linewidth diagram shown in Fig. 13a. This means that most likely only relatively recent episodic annealing events are recognizable in this diagram.

However, the observed congruency with the RDT does not imply that the NWA 5073 zircons were not annealed during their history. In fact, from the diagram linewidth of the  3 (SiO 4 ) band vs. α-decay dose (D; Fig. 13b) it can be observed that all analyzed zircon grains from the NWA 5073 eucrite plot consistently below the so-called damage accumulation curve, defined by [START_REF] Palenik | Radiation damage in zircon[END_REF].

Samples that have been neither episodically nor continuously annealed during their geological history (i.e., that have accumulated the entire damage over their geologic history) should plot, within errors, onto this accumulation trend. The observation that most of the measurements from zircon grains of sample NWA 5073 plot significantly below this curve is unambiguous evidence that they were thermally annealed [START_REF] Palenik | Radiation damage in zircon[END_REF], either continuously for a prolonged period of time or episodically as a result of a short time heating event. In the latter case, however, the heating event must have occurred very early in their history.

Discussion

Most HED meteorites show textural and chemical evidence for extensive thermal annealing after crystallization such as: Fe-Mg equilibration in pyroxenes, exsolution of Ca-pyroxenes within host pigeonites, plagioclase and pyroxene clouding, and recrystallization of lithic clasts and clastic matrices (e.g., [START_REF] Duke | Petrology of eucrites, howardites and mesosiderites[END_REF][START_REF] Mason | The pyroxene-plagioclase achondrites[END_REF][START_REF] Takeda | Degree of equilibrium of eucritic pyroxenes and thermal metamorphism of the earliest planetary crust[END_REF][START_REF] Metzler | Thermal and impact metamorphism on the HED parent asteroid[END_REF][START_REF] Yamaguchi | Global metamorphism on the eucrite parent body[END_REF][START_REF] Bogard | 39 Ar-40 Ar ages of eucrites and thermal history of asteroid 4 Vesta[END_REF][START_REF] Llorca | The Puerte Lápice eucrite[END_REF]. Moreover, many eucrites were brecciated and reheated by impacts (e.g., [START_REF] Metzler | Thermal and impact metamorphism on the HED parent asteroid[END_REF][START_REF] Bogard | 39 Ar-40 Ar ages of eucrites and thermal history of asteroid 4 Vesta[END_REF]. In the case of NWA 5073, the thermal history seems to be very complex. In the following, we discuss possible scenarios to explain both chemical and textural characteristics of this sample.

Formation of primary phases in a magma chamber and excavation

Since NWA 5073 is a coarse-grained basaltic sample containing large, elongated pyroxene crystals that preserved their igneous Mg-Fe zoning, we can infer that this sample derived from a relatively fast cooling magma source. However, due to the texture and the composition of the crystals (e.g., Al content), the cooling rate must have been slower than 1 °C/hour [START_REF] Walker | Dynamic crystallization of a eucritic basalt[END_REF][START_REF] Powell | Experimental solidification of a eucrite basalt: Microprobe studies (abstract)[END_REF]. Large pyroxene laths might represent an early crystallized phase from a magma that experienced fast excavation during volcanic eruption. The process of fast excavation is affiliated to thermal and pressure relief that caused mechanical stress in preexisting pyroxene crystals, probably leading to fracturing and bending of the crystals. A fast excavation of the magma onto the surface of the parent body results in quenching of the melt. Thus, this explains the observed skeletal, and seemingly cotectic crystallisation of silicates (pyroxenes and plagioclases) and other minor phases, while leaving the large previously crystallized pyroxene crystals relatively unaffected.

Episode of secondary annealing and rapid cooling

Several mineralogical and chemical observations clearly indicate an episode of thermal annealing that caused disturbance of the NWA 5073 sample: (1) disturbance of the Lu-Hf system, as demonstrated by [START_REF] Roszjar | Lu-Hf systematics of the NWA 5073 eucrite reflect a complex thermal history (abstract)[END_REF], (2) Fe-diffusion along cracks and cleavage planes within the zoned pyroxene crystals (Fig. 3b-d), and (3) recovery of the crystal structure of zircon grains (Fig. 13b). Based on these observations, it is possible to constrain the time-temperature conditions of the reheating event which is discussed in the following.

The observation of [START_REF] Roszjar | Lu-Hf systematics of the NWA 5073 eucrite reflect a complex thermal history (abstract)[END_REF] that about half of the mineral fractions, mainly pyroxene-rich fractions and the whole rock, form an isochron of 4.68 ± 0.14 (2σ) Ga, whereas the other half, e.g., chromite, metal, plagioclase-rich fractions, define a secondary isochron of 4.31 ± 0.14 (2σ) Ga, is clear evidence that the Lu-Hf system in some minerals was disturbed. Since the time gap between the primary crystallisation of the eucrite and the event that disturbed the Lu-Hf system is at least ~370 Ma, thermal metamorphism, driven by internal heat on the parent body, can be ruled out as the cause for the isotope resetting. On the contrary, it is rather likely that the thermal event was short and intensive. This is supported be the observations that (i) the primary pyroxenes preserved their initial magmatic Mg-Fe-Ca zoning, (ii) the exsolution lamellae of augite in the host pyroxene grains are very thin (<1µm), (iii) and the mesostasis shows a fine-grained subophitic texture. A short, but intense heating event more than 300 Ma after the primary crystallization of the eucrite is only conceivable by a shock-triggered process, e.g., by a superheated impact melt produced by a large impact. The impact melt could have been injected into neighbouring target rock lithologies, causing a short thermal pulse followed by fast cooling. Fast cooling is indicated by the absence of recrystallization textures, which have neither been observed in the coarse mineral grains nor in the fine-grained mesostasis. As discussed by [START_REF] Yamaguchi | Heating experiments of the HaH 262 eucrite and implication for the metamorphic history of highly metamorphosed eucrites (abstract)[END_REF] small fractions of melt can be formed when a eucrite is heated to a temperature slightly above its solidus of about 1100°C [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF] for a short period of time. However, a temperature above the solidus would have caused re-melting of mesostasis components, and a depletion of light rare earth elements (LREE) of the whole rock, which has not been observed (Fig. 8). This suggests that the NWA 5073 sample was in fact reheated to a certain degree for a short period of time, but most likely not re-melted. The absence of any evidence for partial re-melting constrains the maximum annealing temperature to about 1100°C.

Assuming a maximum reheating temperature of 1100°C and that the reheating process possibly also triggered Fe-diffusion along cracks and cleavage planes in large pyroxenes (Fig. 3d), the duration of the heating event can now be estimated from the relation 2

D L Dt 
, where L D is the diffusion length, D the diffusion coefficient for Fe-diffusion in pyroxene, and t the diffusion time. From BSE images (e.g., Fig. 3d), we measured an average diffusion path length, L D , of about 25 µm for Fe-diffusion between the Fe-rich olivine veins into the pyroxene. Using published diffusion coefficients for Fe-Mg diffusion in pyroxene [START_REF] Freer | Diffusion in Silicate Minerals and Glasses: A Data Digest and Guide to the Literature[END_REF][START_REF] Cherniak | Diffusion in pyroxene, mica and amphibole[END_REF][START_REF] Ganguly | Fe 2+ -Mg interdiffusion in orthopyroxene: Retrival from the data on intracrystalline exchange reaction[END_REF], we estimated that the heating to a temperature of about ~1100°C could have only lasted for some hours (5 hours at most). This order of magnitude for the duration of the reheating event obtained from this back-of-the-envelope calculation is also consistent with the observation that the pigeonite pyroxenes still show chemical zoning, i.e., were not re-equilibrated. It is noted that the order of magnitude of hours would also hold for slightly longer diffusion lengths and slightly lower temperatures.

Probably the most convincing evidence for a secondary heating event is given by the Raman measurements of ten zircon grains. In the plot of the linewidth of the ν 3 (SiO 4 ) stretching band near 1008 cm -1 , expressed as the full width at half maximum (FWHM), versus the calculated radiation dose of a single zircon grain (D), most analyzed points plot below the radiation damage accumulation curve (Fig. 13b). We recall that samples that have neither been episodically nor continuously annealed during their geological history and accumulated the entire structural damage should plot on this curve.

Laboratory dry annealing experiments with radiation-damaged zircon revealed that the temperature and duration of a thermal event determines the degree of structural recovery that occurs after a certain degree of structural damage has been accumulated, i.e., during an episodic annealing event [START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF][START_REF] Geisler | Isothermal annealing of partially metamict zircon: evidence for a three-stage recovery process[END_REF]. Considering the low U and Th concentrations measured today, the zircons accumulated only a limited amount of radiation damage during the first 370 Ma after their crystallisation in the eucrite melt. Experimental work has shown that significant structural recovery of less self-irradiation-damaged samples within time scales of a few hours only occurs at temperature in excess of about 900°C [START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF]Zhang et al., 2000b;[START_REF] Geisler | Isothermal annealing of partially metamict zircon: evidence for a three-stage recovery process[END_REF]. It is thus likely that the actual temperature of the event affecting the NWA 5073 eucrite was between 900 and 1100°C.

Formation of olivine-rich veins

The occurrence of veins composed of Fe-rich olivine, secondary plagioclase, and small troilite and chromite grains inside these veins within large pyroxene phenocrysts (Fig. 3) requires careful consideration, especially as recent papers have suggested that minerals in these veins might have crystallized from fluids or gases during a metasomatic reaction [START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF]. At this point we would like to make very clear that the authors have rather different views concerning the formation of the olivine-rich veins within the cores of pyroxene. Thus, we try to unravel the origin of the olivinerich veins in NWA 5073, suggesting two valid possible mechanisms of formation that will be discussed separately in the following paragraphs:

(a) Formation of the olivine-rich veins in NWA 5073 by metasomatism

Based on distinct mineralogical features in eucrites, [START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF] defined a three-type classification scheme for secondary alteration. The first type is characterized by Fe-enrichment along cracks that cross cut large pyroxene crystals, and by occasional occurrence of Fe-rich olivine in some fractures (e.g., Pasamonte). The second type reveals involves deposits of Fe-rich olivine (Fa 64-86 ) and minor amounts of troilite inside the cracks as well as the sporadic occurrence of secondary Ca-rich plagioclase (An 97-98 ) associated with Fe-rich olivine (NWA 2061, Y-75011, and Y-82202). The third type is identifiable by a more frequent occurrence of Ca-rich secondary plagioclase, partial fillings of cracks or rims of primary plagioclases with small crystals of secondary plagioclase, and Fe-enrichment of pyroxenes accompanied by significantly decreased Al contents (NWA 049; [START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF].

According to this scheme, NWA 5073 belongs to the second type, as it contains secondary plagioclase (An 97-100 ) associated with Fe-rich olivine veins, typically located at the grain boundaries between larger primary plagioclase and large pyroxene laths. Based on these observations, [START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF] proposed that Fe-rich olivine veins may be secondary precipitation products formed by the interaction between pyroxene crystals and Fe-rich gas or fluid phases that invaded the pyroxene crystals along fractures and offset planes. The chemical composition of the metasomatic agent is at present not well constrained but could have been aqueous [START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF].

(b) Formation of the olivine-rich veins in NWA 5073 by incongruent melting

The large pyroxene crystals contain olivine-rich veins that abruptly end at their margins (Fig. 3a-c). The Fe-rich olivine within these veins is accompanied by An-rich plagioclase, and small Cr-rich oxides (chromites) and troilites. As shown in Fig. 3, all other adjacent silicate phases (small pyroxenes and large plagioclases) are devoid of these veins. We believe that the chromites may be of genetic significance, as it is known that the solubility of Cr 3+ in silicate melts is rather high and Cr 3+ is immobile in hydrous fluids (e.g., [START_REF] Roeder | Crystallization of chromite and chromium solubility in basaltic melts[END_REF]. Thus, mobilization and precipitation of small chromite grains in the olivine-rich veins found in NWA 5073 seems to indicate a magmatic albeit secondary origin. As an alternative to the arguments presented in the previous paragraph, it may have been that veins of olivine, anorthite, and Cr-rich oxides were formed by incongruent in-situ melting of pyroxene (Fs 34 Wo 2 ) at a temperature slightly above the temperature of formation of primary, Mg-rich pigeonites, i.e. at about 1150°C [START_REF] Stolper | Experimental petrology of eucritic meteorites[END_REF]. This is suggested to have taken place during a short period of a small temperature excursion in the magma chamber. The process of incongruent melting must have taken place after formation of primary pyroxenes in the magma chamber, but prior to excavation of the sample. During this peritectic reaction, olivine forms and the remaining melt crystallizes minor, extremely Ca-rich plagioclase. A similar process of incongruent melting of pigeonites producing olivine (Fo 35-55 ) plus silica was experimentally shown by e.g., [START_REF] Huebner | Partial melting of pyroxenes and the origin of mare basalts (abstract)[END_REF] and [START_REF] Huebner | The melting relations at 1bar of pyroxenes composed largely of Ca-, Mg-, and Fe-bearing components[END_REF]. It should be noted that the experimental data confirm that the olivines in the veins (Fa 65-71 ) are in equilibrium with the outer rims of large pyroxene grains and the small pyroxenes (~Fs 62-68 ; Table 2). Since the pyroxene, which melts incongruently, does not contain significant Na, the crystallizing plagioclase has to be low in Na and, consequently, extremely rich in Ca (An 97-100 ). Cr-and S-rich oxides that are found within the olivine-rich veins are sometimes also located within the primary pyroxenes. The incongruent melting of pigeonite requires only a few tens of degrees above the peritectic temperature, so that if we employ the aforementioned experimental data we estimate some 1150°C for the formation of the olivine veins in this scenario.

In summary, it seems that both interpretations for the formation of olivine-rich veins in large pyroxenes, as discussed above, have some inconsistencies which cannot be resolved at this point. The metasomatism model cannot fully explain the occurrence of Fe-rich olivine veins in large pyroxene phenocrysts, while the adjacent silicate phases (small pyroxenes and large plagioclases) are devoid of them. Furthermore, the occurrence of chromite within these veins is hardly explained by metasomatic fluids. On the other hand, the model which involves incongruent melting cannot readily explain certain textural observations, such as the only minor occurrence of olivine-rich veins in contact with plagioclase. To unravel the process which leads to the formation of such Fe-rich olivine veins in large pyroxenes, one would need further oxygen isotope data of these veins. Furthermore, more realistic melting experiments on bulk eucrite samples and pyroxenes would be helpful.

Pairing or launch-pairing of some Stannern-trend eucrites?

According to sample textures, grain sizes, including the occurrence of Fe-rich olivine veins in large pyroxenes and secondary plagioclases, NWA 5073 resembles some other Stannern-trend eucrite finds from the Sahara, namely NWA 1000 and NWA 2061. Since the occurrence of Fe-rich olivine veins in large pyroxene crystals is not restricted to the NWA 5073 sample, but was also found to occur in other eucrites and howardites, namely Y-7308, Y-790260, Y-75011, and NWA 1000, Macibini, and NWA 2061 (Takeda and Yanai, 1982;[START_REF] Takeda | Mineralogical comparison of antarctic and non-antarctic HED (howardites-eucrites-diogenites) achondrites[END_REF][START_REF] Metzler | Gefüge und Zusammensetzung von Gesteinsfragmenten in polymikten achondritischen Breccien[END_REF][START_REF] Warren | Northwest Africa 1000: A new eucrite with maskelynite, unequilibrated pyroxene crisscrossed by fayalite-rich veins, and Stannern-like geochemistry[END_REF][START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF]and Barrat, unpublished data), one can argue that these findings give some evidence for a largescale but certainly not global parent body process. However, NWA 1000 is severely shocked (S4), as documented by the transformation of half of the plagioclase into maskelynite [START_REF] Warren | Northwest Africa 1000: A new eucrite with maskelynite, unequilibrated pyroxene crisscrossed by fayalite-rich veins, and Stannern-like geochemistry[END_REF]. Thus, NWA 5073 and NWA 1000 are certainly not fall-paired. Since NWA 2061 is as REE-rich as Stannern and thus distinct to NWA 5073, a pairing between those eucrites and NWA 5073 seems unlikely.

However a certain pairing, especially for the Stannern-trend eucrite finds with the NWA 5073 sample, can only be unequivocally proven by obtaining noble gas exposure ages. However, some of these samples may be launch-paired.

Summary and Conclusions

In summary, our results are: (i) Northwest Africa 5073 is a coarse-grained basaltic, unequilibrated, and non-brecciated eucrite with a subophitic to slightly variolitic (fan-spherulitic) texture, mainly composed of small equilibrated pyroxenes (~40 vol.%), elongated, unequilibrated pyroxene phenocrysts up to 1.2 cm (~ 25 vol.%), plagioclase laths up to 0.3 cm in apparent length (~26 vol. %), and about 8. The field of the basaltic eucrites has been drawn from a compilation of more than 170 analyses mainly from [START_REF] Warren | Siderophile and other geochemical constraints on mixing relationships among HED-meteorite breccias[END_REF], references listed in [START_REF] Barrat | The Stannern trend eucrites: contamination of main group eucritic magmas by crustal partial melts[END_REF], and the residual eucrites from [START_REF] Yamaguchi | Crustal partial melting on Vesta: Evidence from highly metamorphosed eucrites[END_REF]. Residual eucrites cannot be distinguished from the basaltic eucrites in this diagram.

Fig. 8: Rare Earth Element (REE) abundances relative to CI chondritic abundance [START_REF] Evensen | Rare Earth abundances in chondritic meteorites[END_REF], given for NWA 5073 bulk rock in comparison to Stannern, NWA4523, Juvinas, and Nuevo Laredo. plagioclase grains are reported within the data range highlighted in light gray. The average of pigeonite cores (n=8) is given by white triangles. Data range for all analyzed pigeonite cores is highlighted in dark gray. One single small, Fe-rich pyroxene (light gray circles), closely associated with a mesostasis area, is extremely enriched in REE (Lu 10×CI). This analysis has not been used for average pyroxene core calculation. [START_REF] Miller | Isotopic fractionation and the quantification of 17 O anomalies in the oxygen threeisotope system: an appraisal and geochemical significance[END_REF]. In FWHM). The radiation damage trend (RDT, gray field) is defined by variably, self-irradiationdamaged, terrestrial zircons (Saxonian rhyolites and Sri Lanka zircons data from [START_REF] Nasdala | Constraining a SHRIMP U-Pb age: microscale characterization of zircons from Saxionian Rotliegende rhyolites[END_REF]2004;Zhang et al., 2001a, b;own unpubl. data). A synthetic, non-metamict zircon is also plotted .

Recent episodic annealing of heavily metamict zircon would shift the data points to the upper right in this diagram (highlighted by arrows), as indicated by dry heating experiments [START_REF] Geisler | Kinetics of thermal recovery and recrystallization of partially metamict zircon: a Raman spectroscopic study[END_REF][START_REF] Geisler | Isothermal annealing of partially metamict zircon: evidence for a three-stage recovery process[END_REF]. (b) Plot of the linewidth (FWHM) of the  3 (SiO 4 ) band vs. the α-decay dose (calculated accumulated radiation dose) for all analyzed zircon grains in NWA 5073. Uncertainties are in the range of 2σ. All data points plot below the radiation damage accumulation curve defined by [START_REF] Palenik | Radiation damage in zircon[END_REF], unambiguously indicating post-crystallization thermal annealing. Note that annealing of the NWA 5073 zircons is also obvious when compared with the Saxonian rhyolite zircons, which have neither episodically nor continuously been annealed [START_REF] Nasdala | Constraining a SHRIMP U-Pb age: microscale characterization of zircons from Saxionian Rotliegende rhyolites[END_REF] and were used to determine the damage accumulation curve. For more details of how the damage accumulation curve was defined see [START_REF] Palenik | Radiation damage in zircon[END_REF].

  5 vol.% mesostasis. (ii) This sample is very weakly shocked and moderately weathered (W2-3). (iii) Based on its oxygen isotope composition (δ 17 O = 1.88 ‰, δ 18 O = 4.05 ‰, Δ 17 O = -0.239 ‰), we can deduce that NWA 5073 is a normal member of the HED suite of achondrites. (iv) The large unequilibrated pyroxenes preserved their initial magmatic Mg-Fe-Ca zoning and are crosscut by olivine-rich veins (Fa 65-71 ) which are restricted to them. These veins also contain minor chromite, troilite, and very Ca-rich plagioclase. (v) Three different plagioclase generations occur: (a) large primary plagioclases crystals (An 76-92 Ab 8-22 Or 0-3 ), (b) small primary plagioclase grains of similar composition as the large ones that are concentrated in mesostasis areas and, (c) a secondary generation of small plagioclases (An 97-100 ), typically 5-20 µm in diameter, always found in association with Fe-rich olivine veins. (vi) Due to the occurrence of these olivine-rich veins in large pyroxene crystals and the sporadic occurrence of secondary plagioclase associated with the former, NWA 5073 belongs to stage 2-type eucrites, according to the classification scheme for secondary alteration as proposed by Barrat et al. (2011). Other members of this group include NWA 2061, Y-75001, Y-82202, and probably NWA 1000 (Barrat et al., 2011). (vii) Based on its bulk chemical composition (e.g., high Ti with TiO 2 = 0.77 wt.%, La = 4.18 µg/g, negative Be anomaly), NWA 5073 displays a distinctive Stannern-trend signature. (viii) The REE pattern of NWA 5073 bulk rock, which is characterized by flat LREE and a slight HREE-depletion (La n /Yb n =1.38) with a pronounced negative Eu anomaly (Eu/Eu*=0.68), resembles those of other Stannern-trend eucrites.(ix) Northwest Africa 5073 contains zircon grains up to 30 µm in size that were invariably found in the mesostasis. These zircon grains are metamict and were annealed, indicating a short hightemperature event (probably induced by shock) occurring after primary crystallization of main sample constituents. (x) A short but intense heating event that caused disturbance of the sample is also indicated by the disturbance of the Lu-Hf system, and Fe-diffusion along cracks and cleavage planes within unequilibrated pyroxene crystals. (xi) According to sample textures, grain sizes, and the degree of alteration, including the occurrence of olivine-rich veins in large pyroxenes, as well as secondary plagioclases, NWA 5073 resembles some other Stannern-trend eucrite finds from the Sahara, namely NWA 1000, NWA 2061 and NWA 4523. However, these four samples are unlikely fall-paired as discussed above.

  Figure Captions: Fig. 1: (a) Sawn surface of a section from the 185 g main mass of NWA 5073. (b) Thin section of NWA 5073; transmitted light, crossed polarizers.

Fig. 2 :

 2 Fig. 2: Ternary phase diagram for pyroxenes (Px) analyzed in NWA 5073. Large pyroxenes preserved their initial magmatic signature, as seen by Mg-enriched pigeonite cores. The chemical composition of small pyroxenes is in the range of the rims of large pyroxene phenocrysts or even more Fe-enriched.Pyroxenes found in the mesostasis are clearly distinct as they are significantly enriched in Ca. For comparison, composition of pristine and metasomatized pyroxenes from NWA 2061 (dark gray, solidlined areas) and Y-75011 (light gray, dashed-lined areas) are shown, as these two eucrites also contain secondary Ca-rich plagioclase. The latter data are taken from[START_REF] Barrat | Possible fluid-rock interactions on differentiated asteroids recorded in eucrite eucritic meteorites[END_REF].

Fig. 3 :

 3 Fig. 3: BSE images of the bulk texture of NWA 5073 (a) and textural details of its Fe-rich olivine veins (b-d). (a) Mosaic of BSE images from a NWA 5073. (b-d) Detailed images illustrating prominent Fe-rich olivine veins that crosscut large pyroxene laths, while adjacent silikate grains are devoid of them. (b) Typical zoned pyroxene lath with En 57 Wo 5 in the crystals core and En 28 Wo 17 at the rim is crosscut by Fe-rich olivine veins that end abruptly towards adjacent plagioclases (Plg) and smaller pyroxenes (Px). (c) Pyroxene-plagioclase border that shows a clear restriction of Fe-rich olivine veins to large pyroxene crystals. (d) Enlarged Mg-rich core region of a large pyroxene lath that is crosscut by Fe-rich olivine veins (Fa 67 ) and Fe-diffusion pathways along cleavage planes. Olivine veins are often occupied by small chromite, and troilite (FeS) grains, and Sr-sulfate inclusions, with the latter being a weathering product. Fe-rich areas that are aligned parallel to the olivine veinlets are probably formed by solid-state Fe-diffusion.

Fig. 4 :

 4 Fig. 4: BSE images of secondary phases in NWA 5073. (a) and (b): Fe-rich olivine veins (Ol) in large pyroxene (Px) and Fe-diffusion paths into their pyroxene host along cleavage planes: Cc = calcite (terrestrial weathering). (c) and (d): Secondary, Ca-rich plagioclase typically 5-20 µm in diameter that were usually found in close association with Fe-rich olivine veins (Ol), are highlighted in ellipses.They are chemically distinct to adjacent large plagioclase (Plg).

Fig. 5 :Fig. 6 :

 56 Fig. 5: Ternary feldspar diagram illustrating three distinct plagioclase (Plg) types. Small plagioclase grains, located in the mesostasis, are slightly more Ab-rich (An 72-77 ) compared to larger plagioclase laths, which scatter to slightly higher An values (An 72-89 ). Secondary plagioclase is extremely enriched in Ca with An 97-100 . Fig. 6: BSE images (a) and (c) of representative zircon grains (Zr), selected for µ-Raman spectroscopy and EPMA analyses. Zircon grains typically occur in association with ilmenite (Ilm), plagioclase (Plg), Ca-pyroxene (Ca-Px), and silica (SiO 2 ). Corresponding cathodoluminescence images are given in (b) and (d). Zircon positions are highlighted as dashed areas.

Fig. 7 :

 7 Fig. 7: Diagram for bulk rock TiO 2 vs. FeO total /MgO of basaltic, including residual, eucrite samples.

Fig. 9 :

 9 Fig. 9: Trace element pattern for NWA 5073 bulk rock compared to the Stannern-trend eucrites, including Stannern and NWA 4523, and Nuevo Laredo and Juvinas eucrites. All data are given relative to the Juvinas eucrite. Sr and Ba values of NWA 5073 whole rock are high (2131 and 176ppm, respectively), probably due to terrestrial weathering[START_REF] Stelzner | In interdisciplinary study of weathering effects in ordinary chondrites from the Acfer region Algeria[END_REF] and thus are excluded from this diagram.

Fig. 10 :

 10 Fig. 10: REE pattern for plagioclase and pyroxene grains analyzed in NWA 5073. Average plagioclase (n=7) is shown by black squares, minimum and maximum values of all analyzed

Fig. 11 :

 11 Fig. 11: Oxygen isotope data for NWA 5073 compared to other eucrites (monomict, polymict, and cumulate eucrites), howardites, diogenites, and angrites. Δ 17 O values are linearized[START_REF] Miller | Isotopic fractionation and the quantification of 17 O anomalies in the oxygen threeisotope system: an appraisal and geochemical significance[END_REF]. In

  this Δ 17 O versus δ 18 O diagram, samples formed from a homogeneous reservoir that subsequently fractionated by mass-dependent processes, plot along horizontal lines. Silicate minerals on Earth have isotopic compositions consistent with mass-dependent fractionation from a single reservoir, and define the terrestrial fractionation line (TFL). Angrites define a second horizontal line, the angrite fractionation line (AFL), with a mean Δ 17 O value of -0.072 ± 0.007 (1σ). If polymict breccias are excluded, remaining HED samples also show limited Δ 17 O variation and define a single eucrite fractionation line (EFL) with a mean Δ 17 O value of -0.239 ± 0.007 (1σ). Diagram modified after[START_REF] Greenwood | Widespread magma oceans on asteroidal bodies in the early Solar System[END_REF].

Fig. 12 :

 12 Fig. 12:Representative Raman spectra of five single zircon grains in sample NWA 5073 reveal a decreased frequency and an increased broadening of the ν 3 (SiO 4 ) stretching band near ~1008 cm -1 (dashed line) with increasing radiation dose (D). The calculated α-dose, given within 2σ uncertainties, and expressed per 10 16 × α-decay events/mg sample, is shown close to the spectra for each zircon crystal Single zircon analyses are presented relative to a pure, synthetic, crystalline zircon (gray), taken from the RRUFF Raman data base.

Fig. 13 :

 13 Fig. 13: (a) Diagram of the frequency of the  3 (SiO 4 ) band analyzed in ten zircon crystals in NWA 5073 plotted against the measured linewidth of this band (given as full width at half maximum,

  . All analyzed pigeonite cores in NWA 5073 exhibit variable REE abundances that correlate with Ca concentrations, and are generally HREE-enriched with a pronounced negative Eu anomaly (Eu/Eu*=0.68). A total of 7 plagioclase grains have been analyzed for their REE abundances. The latter exhibit a pronounced positive Eu anomaly with Eu/Eu* = 61, thus are in agreement with the data range for eucrites previously reported in literature (e.g., Hsu

Table 1 .

 1 Modal abundance of major phases and mesostasis in NWA 5073 (vol.%).

	Pyroxene phenocrysts	24.8
	Primary feldspars (plagioclases)	26.4
	Small pyroxenes	39.9
	Mesostasis	8.5
	Metal	0.4

Table 2 .

 2 Chemical composition of mineral phases in NWA 5073. Results in wt.%. Al was always below detection limit, high Fe content probably caused by contamination from surrounding phases such as ilmenite and Fe-metal; apatites: Cl and F average values are 0.3 and 4.0 wt.%, respectively; § Data obtained by SEM; chromite: V 2 O 3 = 0.61 wt.%, ilmenite: V 2 O 3 = 0.3 wt.%; for ilmenite and chromite: Ni was always below detection limit.

		SiO 2	TiO 2 Al 2 O 3 Cr 2 O 3 FeO* MnO MgO CaO Na 2 O K 2 O P 2 O 5	HfO 2	ZrO 2 Y 2 O 3 Total	Endmembers average	Endmembers min. -max.
	Major phases
	Pyroxene
	cores (n=27)	52.4	0.11	1.11 1.01 18.0 0.62 24.3 1.85 0.02 <0.01 n.d.	n.d.	n.d.	n.d. 99.41 En 55.1 Wo 4.2 Fs 40.7 En 51.0-60.0 Wo 1.7-7.6 Fs 34.0-45.0
	Pyroxene
	rims (n=27)	49.6	0.34	1.11 0.57 25.9 1.04 12.9 8.2 0.03 <0.01 n.d.	n.d.	n.d.	n.d. 99.68 En 27.5 Wo 17.4 Fs 55.1 En 19.8-34.1 Wo 8.2-33.8 Fs 42.2-62.4
	Small pyroxenes (n=11)	49.5	0.24	1.07 0.63 29.4 1.17 12.5 5.5 0.02 <0.01 n.d.	n.d.	n.d.	n.d. 100.01 En 26.4 Wo 11.6 Fs 62.0 En 22.8-35.8 Wo 5.9-18.8 Fs 58.3-68.8
	Pyroxenes
	mesostasis (n=5)	49.8	0.42	0.73 0.23 19.2 0.68	9.3 19.7 0.04 0.02 n.d.	n.d.	n.d.	n.d. 100.15 En 27.1 Wo 41.4 Fs 31.5 En 25.7-27.9 Wo 33.7-44.8 Fs 27.7-40.7
	Large Plagioclases (n=47)	47.4	0.02	32.3 <0.01 0.39 <0.01 0.10 16.9 1.65 0.16 n.d.	n.d.	n.d.	n.d. 99.00 An 84.2 Ab 14.9 Or 0.9 An 77.0-88.9 Ab 11.0-20.1 Or 0.1-2.9
	Plagioclases
	mesostasis (n=5)	51.0	0.03	30.1 0.02 0.65 <0.01 0.04 14.6 2.49 0.44 n.d.	n.d.	n.d.	n.d. 99.42 An 74.4 Ab 23.0 Or 2.6 An 77.7-76.8 Ab 20.4-24.9 Or 2.0-3.5
	Secondary
	Plagioclase (n=17)	43.0	n.d.	35.7	n.d. 1.38 n.d. 0.12 19.7 0.12 <0.01 n.d.	n.d.	n.d.	n.d. 100.00 An 98.6 Ab 1.3 Or 0.1 An 97.2-100 Ab 0-2.8 Or 0-0.3
	Minor phases
	Chromite (n=5) §	<0.1	3.2	12.6 47.9 33.9 0.76 0.84 <0.1 n.d.	n.d.	n.d.	n.d.	n.d.	n.d. 99.78
	Ilmenite (n=13) §	<0.1	53.7	n.d.	<0.1 44.1 1.17 0.53 n.d. n.d.	n.d.	n.d.	n.d.	n.d.	n.d. 99.81
	Apatite (n=19)	<0.01	n.d.	n.d.	n.d. 0.72 n.d. <0.01 54.1 <0.01 n.d. 41.8	n.d.	n.d.	0.11 99.23
	Zircon (n=10)	32.4	n.d.	n.d.	n.d. 1.58 0.02 n.d. 0.06 n.d.	n.d. 0.14	1.31	66.2 0.16 101.83
	Tridymite (n=7)	98.9	0.07	0.23 0.03 0.36 <0.01 <0.01 0.13 <0.01 0.02 n.d.	n.d.	n.d.	n.d. 99.20
	Fe-rich olivine
	veins (n=16)	31.9 <0.01 0.06 0.19 53.1 1.46 14.4 0.05 <0.01 <0.01 n.d.	n.d.	n.d.	n.d. 101.13 Fo 32.5 Fa 67.5	Fo 29-35 Fa 65-71
		Fe	Ni	Co	Cu	Cr	Zn	Ca	Si	Mg	Mn	Na	K	S
	Metal cores (n=13) 99.08 <0.01 0.16 <0.02 <0.02 <0.01 0.05 0.03 <0.01 <0.01 <0.01 <0.02 <0.02	99.33
	Data were obtained by EPMA; n.d. = not detected; *all Fe as FeO; zircon:

Table 3 .

 3 Major and trace element composition of NWA 5073, compared to Stannern, Bouvante, and Nuevo Laredo. Oxides in wt.%, trace elements in µg/g. Eu/Eu* and La n/ Yb n * are calculated relative to CI average given by[START_REF] Evensen | Rare Earth abundances in chondritic meteorites[END_REF].

		NWA 5073	Stannern	Bouvante	Nuevo Laredo
	Mass (g)	0.098	1.0	1.47	1.0 g
	TiO 2 Al 2 O 3 Cr 2 O 3 FeO	0.77 10.38 0.587 20.13	1.08 12.26 0.33 18.58	1.06 11.60 0.33 20.07	0.94 12.36 0.30 20.91
	MnO	0.58	0.55	0.50	0.63
	MgO	8.70	6.98	6.26	5.70
	CaO	9.46	10.99	10.40	10.90
	Na 2 O K 2 O P 2 O 5	0.52 0.09 0.097	0.56 0.09 0.10	0.56 0.10 0.14	0.48 0.06 0.09
	Li	11.06	12.39	13.51	11.68
	Be	0.32	0.44	0.42	0.37
	Sc	25.8	30.2	30.8	35.8
	V	78.51	56.90	55.20	60.10
	Co	8.04	3.83	7.00	2.87
	Ni	1.32	1.1	0.33	3.70
	Cu	2.43	5.07	0.88	0.25
	Zn	0.98	2.80	1.42	1.17
	Ga	1.14	1.51	1.6	1.69
	Rb	0.34	0.58	0.61	0.37
	Sr	2131	92.7	93.7	84.4
	Y	22.17	32.13	33.00	26.22
	Zr	70.1	101	99.6	70.0
	Nb	6.85	8.20	7.74	5.38
	Cs	0.008	0.016	0.023	0.017
	Ba	176	52.65	56.17	39.03
	La	4.18	5.58	5.65	3.85
	Ce	10.59	14.4	14.37	10.10
	Pr	1.57	2.15	2.18	1.52
	Nd	7.79	10.76	10.79	7.64
	Sm	2.42	3.48	3.46	2.57
	Eu	0.617	0.840	0.786	0.768
	Gd	3.18	4.44	4.47	3.44
	Tb	0.561	0.787	0.793	0.614
	Dy	3.62	5.24	5.37	4.13
	Ho	0.78	1.15	1.15	0.920
	Er	2.22	3.26	3.26	2.67
	Yb	2.04	3.06	2.87	2.56
	Lu	0.291	0.434	0.421	0.366
	Hf	1.77	2.51	2.52	1.83
	Ta	0.365	0.441	0.413	0.292
	W	0.193	0.174	0.165	0.105
	Pb	0.24	(1.59)	0.32	0.26
	Th	0.548	0.700	0.699	0.488
	U	0.162	0.177	0.182	0.116
	Eu/Eu*	0.68	0.65	0.61	0.79
	La n/ Yb n *	1.38	1.23	1.33	1.02

Table 4 .

 4 LA-ICP-MS data of silicates in NWA 5073. Results in µg/g. Fe-rich pyroxene, found in close association to a mesostasis area; not used for average pyroxene calculation.

	Pyroxene cores	1	2	3	4	5	6	7	8	single Px* average (n=8)
	La	0.010	0.025	0.005	0.005	0.013	0.007	0.021	0.008	0.366	0.012
	Ce	0.032	0.058	0.027	0.016	0.047	0.024	0.050	0.028	1.302	0.035
	Pr	0.009	0.013	0.004	0.004	0.010	0.004	0.010	0.008	0.276	0.008
	Nd	0.066	0.081	0.027	0.029	0.068	0.032	0.063	0.064	1.726	0.054
	Sm	0.068	0.054	0.020	0.037	0.059	0.020	0.048	0.050	0.883	0.044
	Eu	0.011	0.008	0.004	0.007	0.008	0.005	0.009	0.008	0.054	0.007
	Gd	0.127	0.143	0.038	0.062	0.098	0.055	0.095	0.117	1.486	0.092
	Dy	0.244	0.240	0.067	0.131	0.169	0.096	0.171	0.228	2.297	0.168
	Er	0.235	0.219	0.060	0.118	0.148	0.099	0.154	0.208	1.597	0.155
	Yb	0.295	0.290	0.072	0.151	0.184	0.149	0.221	0.270	1.865	0.204
	Lu	0.055	0.051	0.013	0.025	0.031	0.023	0.038	0.045	0.281	0.035
	Plagioclase	1	2	3	4	5	6	7	average (n=7)
	La	0.243	0.350	0.522	0.308	0.328	0.286	0.194	0.319
	Ce	0.523	0.834	1.029	0.602	0.692	0.702	0.397	0.683
	Pr	0.064	0.101	0.124	0.076	0.087	0.088	0.053	0.085
	Nd	0.295	0.463	0.584	0.323	0.388	0.400	0.254	0.387
	Sm	0.099	0.133	0.164	0.095	0.089	0.126	0.081	0.112
	Eu	2.006	2.100	2.528	1.950	1.980	2.074	1.930	2.081
	Gd	0.067	0.124	0.154	0.082	0.083	0.101	0.064	0.096
	Dy	0.052	0.120	0.157	0.078	0.069	0.123	0.047	0.092
	Er	0.022	0.054	0.071	0.046	0.040	0.062	0.028	0.046
	* single small,

Table 5 .

 5 U and Th concentrations, calculated α-decay dose, and frequencies and linewidths (FWHM) of the  3 (SiO 4 ). Raman band of analyzed zircon grains from the NWA 5073 eucrite. The dose was calculated for an inferred age of 4555 Ma; *1 Errors do not include the error of the inferred age;

	Zircon no.	U (ppm) ± 2σ	Th (ppm) ± 2σ	Dose (10 16 α-events/mg) *	± 2σ *1	Frequency (cm -1 ) *2	FWHM (cm -1 ) *2
	Z1	<23	-	<20	-	<0.067		1000.5	9.9
	Z3	<30	-	<20	-	<0.086		1001.2	8.5
	Z4	<29	-	24	21	<0.093		1003.2	7.6
	Z5	71	29	42	21	0.243	0.091	996.8	17.2
	Z6	123	29	71	21	0.421	0.092	996.6	21.6
	Z8	78	30	<21	-	0.255	0.096	999.3	12.1
	Z9	105	29	86	21	0.372	0.092	998.2	18.8
	Z10	75	30	<21	-	0.246	0.096	997.9	17.9
	Z11	104	29	<21	-	0.334	0.092	997.2	25.8
	Z13	160	29	120	21	0.559	0.092	991.7	25.3

*

Fig.13

Acknowledgements

The authors are grateful to A. Yamaguchi and an anonymous reviewer for their helpful reviews, which helped improving the paper and A. Ruzicka for thoughtful comments and for handling this article. We also thank U. Heitmann for sample preparation, C. Bollinger for assistance at the LA-ICP-MS, J.

Berndt for guidance with the electron microprobe, and M. Menneken for help with Raman measurements. This study was partially supported by the German Research Foundation (DFG; grant Bi 344/9-1) and T. Geisler acknowledges a Heisenberg scholarship from the DFG.