Shock origin of the largest ureilitic microdiamond: structural observations and δ13C value

Constraining the internal variability of the stable isotopes of carbon and nitrogen within mantle diamonds

Planetesimal differentiation revealed by the Hf–W systematics of ureilites

Is it better to give than to receive? A stable isotope perspective on orchid–fungal carbon transport in the green orchid species <i>Goodyera repens </i>and<i> Goodyera oblongifolia</i>

Ureilites are ultramafic achondrite meteorites that likely represent a large parent body. Large olivine and pyroxene grains display a high degree of textural equilibrium, forming &amp;#8220;triple-junction&amp;#8221; contacts at their grain boundaries. However, ureilites also have primitive characteristics, for example high siderophile and carbon content, high noble gas content, and unequilibrated olivine and pyroxene compositions. So far, the origin of ureilites and their parent body are still debated as it is difficult to explain the observation of textural equilibrium juxtaposed with such primitive properties. Conventionally, ureilites are considered to be mantle residues from within an unknown, large rocky body. Because feldspar is completely depleted from most ureilite samples, it has been thought that the parent body accreted early and experienced extensive igneous differentiation processes, with primary heating attributed to short-lived 26Al decay in the early solar system. Here we report on polymict ureilite breccia Elephant Moraine 87720. We found that the sample has several unusually magnesian-rich olivine clasts with mg# (Mg/(Mg+Fe)) up to 98.7 and calcium-poor pyroxene with Wo as low as to 1.0. Moreover, we discovered two coarse-grained aluminous spinel grains with over 56.4-58.7 wt% Al2O3 and 11.3-11.8wt% Cr2O3, in contact with olivine and pyroxene grains. These aluminous spinel clasts are unique among ureilite samples. To determine the provenance of the spinel grains and other clasts (e.g., high magnesian olivine and low calcium pyroxene) in this sample, we conducted in situ oxygen 3-isotope analyses by Secondary Ion Mass Spectrometry SIMS (IMS 1280), University of Wisconsin-Madison. SIMS mineral data plot along the slope ~1 line in the oxygen 3-isotope diagram, similar to those of bulk ureilites (Greenwood et al., 2017, Chemie der Erde 77, 1-43) including ureilitic samples found in Almahata Sitta, with the same range of &amp;#8710;17O (from &amp;#8211;2.3&amp;#8240; to &amp;#8211;0.2&amp;#8240;). These grains follow the Fe-loss/addition trend defined by a molar plot of Fe/Mn versus molar Fe/Mg, showing a near constant and chondritic Mn/Mg ratio, falling in among common ureilitic compositions. We conclude that the origin of these clasts, including the aluminous spinel, is primarily ureilitic, but they extend the &amp;#948;18O measurement for ureilites up to 9.7 &amp;#8240;. We hypothesize a magmatic origin for these clasts that they were formed under low-oxygen fugacity, in a high Al/Si ratio hot melt, favouring the crystallization of Al-spinel instead of a Cr-rich endmember. The clasts in this EET 87720 specimen may possibly represent a new type of high Al, low Ca, low Cr lithic material within the ureilite parent body. Finally, we calculated a possible crystallization temperature of 1379 K using spinel-olivine equilibrium crystallization (Roeder et al 1979, Contrib. Min. Petrol. 6, 325-334). Our estimate corresponds well with the theoretical model proposed by Goodrich et al. (2004, Chemie der Erde 64, 283-327) that the UPB was hot, with a temperature above 1100 &amp;#176;C (1373 K). Our results are consistent with other petrological evidence and olivine-pigeonite-melt thermometry (Singletary and Grove, 2003, Met. Planet. Sci. 38, 95-108) which constrain smelting temperatures within the ureilite parent body.

Establishing the temporal evolution of the ureilite parent body(ies) is crucial for understanding the quantitative timescale of planetesimal formation and evolution in the protoplanetary disk. In order to establish a timeline for these early processes, age constraints on the accretion, differentiation and secondary reduction were obtained with the short-lived 53Mn-53Cr chronometer to whole-rock and sequentially digested fractions of main group ureilites. A whole-rock isochron dates the reservoir-scale Mn-Cr fractionation in the ureilite parent body(ies), associated with magmatic differentiation, to 2.89-0.51+0.56 Ma after CAI formation. This age implies that the ureilite parent body(ies) accreted no later than ∼1.5 Ma after CAI formation, at a time when the NC-CC dichotomy was already established. The 53Mn-53Cr systematics of fractions from chromite-bearing ureilites yield an age of 4.29-0.45+0.49 Ma after CAI formation for a secondary reduction event on the parent body. This event is commonly associated with the catastrophic disruption of the ureilite parent body while still hot. The chromite model ages are consistent with the isochron ages obtained from chromite-bearing ureilites. Collectively these ages indicate that chemical differentiation processes were underway on the ureilite parent body(ies) during the time interval when undifferentiated meteorite parent bodies were forming, and may have paused at the peak of planetesimal formation when planetary collisions were common.

The ∼3.5 Ga Dresser Formation from the North Pole Dome of the Pilbara Craton (Western Australia) contains some of the oldest evidence for life on Earth. Here, we present a detailed study of microstructure-specific carbon isotopic composition of organic matter (OM) preserved in Dresser Formation bedded cherts and hydrothermal chert vein using in situ Secondary-Ion Mass Spectrometry (SIMS). The OM in these rocks occurs mainly as clots that, together with minor fine OM layers and laminae, are considered primary textures formed prior to host rock lithification. Other than rare OM-rich stylolites, no evidence was found for later OM migration beyond the micrometer scale. Average δ13C(OM) values in specific microstructural types range between −33.6‰ and −25.7‰. No correlation is seen between measured δ13C values and H/C ratios in the studied OM microstructures. This lack of correlation and the low metamorphic grade of the rocks studied argue against significant modification of OM isotopic composition by later metamorphic alteration. It is thus concluded that the range of δ13C values found in the samples represents primary OM isotopic variability. Within some individual samples variable δ13C(OM) values are correlated with specific microstructural types. This observation is not consistent with solely abiotic OM formation via Fisher-Tropsch type reactions. When compared with associated δ13C(ankerite) values, average δ13C(OM) values indicate C isotopic fractionation [Δ13C(Ank–OM)] of 25–33‰, which translates to dissolved CO2–OM isotopic fractionation [Δ13C(CO2–OM)] of 20–30‰. This range of Δ13C(CO2–OM) is consistent with enzymatic C fixation via the Calvin cycle utilized by photoautotrophs and the reductive acetyl-CoA pathway utilized by chemolithoautotrophs. Photosynthetic OM formation is supported by the relatively shallow water depth inferred for the Dresser environment and the restricted occurrence of stromatolites to shallow water deposits in this unit, whereas chemolithosynthesis is supported by the abundance of OM in sub-seafloor hydrothermal chert veins. The range of δ13C(OM) values observed in the samples may therefore represent the remains of different organisms utilizing different C-fixation pathways. Other biologic effects, such as the growth rate and density of microbial communities, and further heterotrophic overprinting of the autotrophic biomass may have also contributed to the observed range of δ13C(OM) values.

<p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" class="first" dir="auto" id="d13504e114">Ureilites are primitive achondrite meteorites resulting from fractional melt extraction deep within their parent body [ <a class="xref-link" href="#r1">1</a>]. Rich in carbon (up to 7%), they exhibit various carbon phases, including amorphous carbon, graphite, diamond, and diamond-like structures [ <a class="xref-link" href="#r2">2</a>- <a class="xref-link" href="#r4">4</a>]. While the existence of lonsdaleite—the hexagonal form of diamond—has been debated due to challenges in detection and synthesis [ <a class="xref-link" href="#r5">5</a>], this study provides new insights into its formation mechanism. Using optical petrography, electron probe microanalysis (EPMA), and transmission electron microscopy (TEM), we investigated the carbon phases in several ureilite meteorites. EPMA mapping with energy dispersive x-ray (EDX) and cathodoluminescence (CL) spectroscopies allowed us to distinguish between different carbon phases (Figure <a class="xref-link" href="#fg001">1</a>a). Site-specific specimens were prepared via focused ion beam (FIB) for detailed TEM analysis. Electron diffraction patterns revealed that lonsdaleite forms through a martensitic-like pseudomorph transformation from pre-existing graphite, preserving its original morphology (Figure <a class="xref-link" href="#fg001">1</a>b). This transformation mechanism confirms that lonsdaleite can exist as a distinct phase under ambient conditions. <p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" dir="auto" id="d13504e135">The diamonds identified within these ureilites exhibit low defect densities, which is inconsistent with a shock-origin formation that typically introduces significant defects. We propose that metal catalysts, potentially troilite (FeS) or pentlandite [(Fe,Ni) ₉S ₈], present in the meteorites play a crucial role in diamond formation through processes analogous to high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods. These catalysts likely lower the pressures and temperatures required for diamond synthesis, facilitating their formation under conditions present within the ureilite parent body. Our findings not only elucidate the distinct formation pathways of lonsdaleite and diamond in ureilites but also suggest potential methods for manufacturing ultrahard materials. The martensitic transformation pathway for lonsdaleite offers a blueprint for creating shaped ultrahard tools, given its predicted superior mechanical properties over diamond. Additionally, understanding the catalytic role of metals in diamond formation could lead to more efficient synthetic processes. This study enhances our comprehension of the dynamic processes shaping ureilite parent bodies and opens new avenues in material science. <div class="fig panel" id="fg001"> <a class="named-anchor" id="fg001"> <!-- named anchor --> </a> <div class="figure-container so-text-align-c"> <img alt="" class="figure" src="/document_file/5a856858-f997-4c9d-9327-dbf10a413eb2/ScienceOpen/image/207_6724042b6737b-AlanSalekAPMC2025_fig1.jpg"/> </div> <div class="panel-content"> <div class="label">Figure 1</div> <div class="caption" id="d13504e146"> <p class="first" dir="auto" id="d13504e147">a) Cathodoluminescence map of polished cross-section from ureilite NWA 7983 showing olivine and pyroxene as green, other iron silicates as blue, diamond as red and lonsdaleite as yellow. b) TEM image from a lonsdaleite region indicated by the red circle in a) with an inset of the diffraction pattern (white circle) which was indexed to the &lt;001&gt; zone of lonsdaleite. </div> </div> </div>

Based on AMS 14C dating data, carbon and nitrogen isotope analyses were conducted on mammal bone collagen of deer, cattle and pigs from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River. These analyses were conducted to reconstruct palaeodiets of mammals, palaeoecology, palaeoenviroment and previous human activities in the study area. Results show that the collagen loss of bone did not change the in vivo isotopic composition of carbon and nitrogen stable isotopes, and most of the bone fossils were well preserved. The bone collagen of samples from deer had a mean δ13C of −23.1‰ and a mean δ15N of 4.7‰, suggesting that deer subsisted in a closed habitat and fed on branches and leaves. The bone collagen of cattle had a mean δ13C of −19.6‰ and a mean δ15N of 5.2‰, which indicates that cattle subsisted in an open habitat and fed on grasses and stems. The δ13C values show that both deer and cattle fed on C3 plants and lived in the same ecosystem, but the t-test results show that deer δ13C and δ15N values were both more negative than those of cattle, indicating that they inhabited different niches. The δ13C and δ15N values of cattle partially overlapped those of deer, suggesting some competition in diets between them. The t-tests show that the δ13C and δ15N values of pigs were more positive than those of cattle and deer, which signifies that pigs occupied a higher trophic level compared to cattle and deer. The wide range of pig δ13C values demonstrates that pig trading had been taking place from early Neolithic Age to late Bronze Age. There were no significant differences in deer δ13C and δ15N values among different archaeological periods, making it clear that climatic, ecological and environmental conditions were kept relatively stable from 2200 to 4200 a BP. This stability may have been responsible for the extensive and complete cultural layers at the Zhongba site. The minimum number of samples required to estimate the mean δ13C values of deer, pigs and cattle are 8, 73 and 16, respectively, and for mean δ15N values of deer, pigs and cattle, the minimum numbers are 4, 5 and 6, respectively.

We have generated thermometry data for numerous ureilite meteorites and developed a thermal model for the ureilite parent body (UPB), which we use to examine the effects of size, composition, and formation time on the thermal evolution of the UPB.We find that MgO-rich ureilites sampled mantle at 1200-1250 o C, whereas FeO-rich ureilites were subject to a far broader range of temperatures ranging between 1050 and 1280 o C. When combined with the thermal models, our results imply that, (1) the UPB formed within 1 m.y. of initial condensation of the Solar System, (2) ureilites are metamorphic residues of core and crust extraction, with pyroxene chemistries and textures reflecting moderate to extensive melt loss, and in some samples, melt readdition, and (3) ureilites sample a broad range of depths in the UPB mantle with sparse MgO-rich samples possibly coming from a deeper mantle and numerous FeO-rich samples coming from shallower levels.The broad temperature range for the FeOrich ureilites might be explained by variation over a small depth range in proximity to a hotter shallow magma ocean that was heated by concentrated 26 Al, the Al having been preferentially extracted from the mantle during partial melting.Only rare samples might come from an igneous crust that formed from the shallow magma ocean.Pyroxene chemistry suggests that the UPB may have been large enough to achieve pressures >2 kbar in the lower mantle, and coupled with the thermal models, this implies that the parent body had a diameter on the order of 1000 km.Acknowledging the strong evidence of a catastrophic impact in ureilite meteorites, we propose that the UPB was not totally destroyed as commonly supposed, but rather, a giant impact entirely removed the crust and the majority of the mantle.This would leave a dense M-type asteroid equivalent in size to some present in the solar system today; Psyche is possibly the remnant of the UPB, but may be slightly too low in FeO.There are several other good candidates amongst the M-type asteroids, such as 22 Kalliope at 150 km diameter and density of 4.8-5.9g cm -3 .

Differences in the stable carbon isotope ratios of plants utilizing the C3 vs. C4 photosynthetic pathway have been used to broadly identify the natal host origins of herbivorous insects. This study explored whether adequate variation exists between the carbon isotope ratios of different C3 plants in the host range of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) to enable accurate identification of natal host‐plant species. Isotope ratio mass spectrometry (IRMS) analysis of 13C/12C ratios of moths reared on four crop plant species [Gossypium hirsutum (L.), Nicotiana tabacum L., Glycine max (L.) Merrill, and Arachis hypogaea L.] and two common weed species [Geranium carolinianum L. and Linaria canadensis (L.) Chaz.] revealed a range of δ13C values within that expected for plants utilizing the C3 photosynthetic pathway. Analysis of vegetative and reproductive tissues from the plants utilized in the study resulted in statistically different δ13C values for some plant species; nevertheless, the range of δ13C values observed for many plant species overlapped. Significant differences in mean δ13C values were detected between groups of moths reared on different host‐plant species, but there was no significant correlation between the δ13C values of moths vs. the δ13C value of plant tissue on which they were reared. Feral tobacco budworm moths collected over 3 years were found to have carbon isotope ratios consistent with those having fed on C3 plants, confirming little utilization of C4 plant species by the insect. Results demonstrate that within the range of C3 host plants tested, carbon isotope signatures are not sufficiently unique to enable a reliable determination of natal origin of feral tobacco budworm with current IRMS technology.

Planetary formation models show that terrestrial planets are formed by the accretion of tens of Moon- to Mars-sized planetary embryos through energetic giant impacts. However, relics of these large proto-planets are yet to be found. Ureilites are one of the main families of achondritic meteorites and their parent body is believed to have been catastrophically disrupted by an impact during the first 10 million years of the solar system. Here we studied a section of the Almahata Sitta ureilite using transmission electron microscopy, where large diamonds were formed at high pressure inside the parent body. We discovered chromite, phosphate, and (Fe,Ni)-sulfide inclusions embedded in diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 GPa. Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo.

Carbon isotope fractionation during diamond growth in depleted peridotite: Counterintuitive insights from modelling water-maximum CHO fluids as multi-component systems

Carbon isotope and abundance systematics of Icelandic geothermal gases, fluids and subglacial basalts with implications for mantle plume-related CO2 fluxes

Do stable isotopes in carbonate cement of Mio-Pleistocene Himalayan sediments record paleoecological and paleoclimatic changes?

We analyzed the C isotopic compositions of 32 unbrecciated ureilites, which represent mantle debris from a now disrupted, C-rich, differentiated body. The δ13C values of their C fractions range from −8.48 to +0.11‰. The correlations obtained between δ13C, δ18O and Δ17O values and the compositions of the olivine cores, indicate that the ureilite parent body (UPB) accreted from two reservoirs displaying distinct O and C isotopic compositions. The range of Fe/Mg ratios shown by its mantle was not the result of melting processes involving reduction with C (“smelting”), but was chiefly inherited from the mixing of these two components. Because smelting reactions are pressure-dependent, this result has strong implications for the size of the UPB, and points to a large parent body, at least 690 km in diameter. It demonstrates that C-rich primitive matter distinct from that represented by carbonaceous chondrites was present in some areas of the early inner Solar System, and could have contributed to the growth of the terrestrial planets. We speculate that differentiated, C-rich bodies, or debris produced by their disruption, were an additional source of volatiles during the later accretion stages of the rocky planets, including Earth.