bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yamato 86029: Aqueously altered and thermally metamorphosed CI‐like chondrite with unusual textures
Authors: TONUI Eric K. , ZOLENSKY Michael E. , LIPSCHUTZ Michael E. , WANG Ming‐Sheng , NAKAMURA Tomoki 
Published: January 2010

Abstract— We describe the petrologic and trace element characteristics of the Yamato 86029 (Y‐86029) meteorite. Y‐86029 is a breccia consisting of a variety of clasts, and abundant secondary minerals including coarse‐ and fine‐grained phyllosilicates, Fe‐Ni sulfides, carbonates, and magnetite. There are no chondrules, but a few anhydrous olivine‐rich grains are present within a very fine‐grained phyllosilicate‐rich matrix.Analyses of 14 thermally mobile trace elements suggest that Y‐86029 experienced moderate, open‐system thermal metamorphism. Comparison with data for other heated carbonaceous chondrites suggests metamorphic temperatures of 500–600°C for Y‐86029. This is apparent petrographically, in partial dehydration of phyllosilicates to incompletely re‐crystallized olivine. This transformation appears to proceed through ‘intermediate’ highly‐disordered ‘poorly crystalline’ phases consisting of newly formed olivine and residual desiccated phyllosilicate and their mixtures. Periclase is also present as a possible heating product of Mg‐rich carbonate precursors.Y‐86029 shows unusual textures rarely encountered in carbonaceous chondrites. The periclase occurs as unusually large Fe‐rich clasts (300–500 μm). Fine‐grained carbonates with uniform texture are also present as small (10–15 μm in diameter), rounded to sub‐rounded ‘shells’ of ankerite/siderite enclosing magnetite. These carbonates appear to have formed by low temperature aqueous alteration at specific thermal decomposition temperatures consistent with thermodynamic models of carbonate formation. The fine and uniform texture suggests crystallization from a fluid circulating in interconnected spaces throughout entire growth. One isolated aggregate in Y‐86029 also consists of a mosaic of polycrystalline olivine aggregates and sulfide blebs typical of shock‐induced melt re‐crystallization.Except for these unusual textures, the isotopic, petrologic and chemical characteristics of Y‐86029 are quite similar to those of Y‐82162, the only other heated CI‐like chondrite known. They were probably derived from similar asteroids rather than one asteroid, and hence may not necessarily be paired.
Differentiation of metal‐rich meteoritic parent bodies: I. Measurements of PGEs, Re, Mo, W, and Au in meteoritic Fe‐Ni metal
Authors: PETAEV M. I. , JACOBSEN S. B. 
Published: January 2010

Abstract— We describe an analytical technique for measurements of Fe, Ni, Co, Mo, Ru, Rh, W, Re, Os, Ir, Pt, and Au in bulk samples of iron meteorites. The technique involves EPMA (Fe, Ni, Co) and LA‐ICP‐MS analyses of individual phases of iron meteorites, followed by calculation of bulk compositions based on the abundances of these phases. We report, for the first time, a consistent set of concentrations of Mo, Ru, Rh, Pd, W, Re, Os, Ir, Pt, and Au in the iron meteorites Arispe, Bennett County, Grant, Cape of Good Hope, Cape York, Carbo, Chinga, Coahuila, Duchesne, Gibeon, Henbury, Mundrabilla, Negrillos, Odessa, Sikhote‐Alin, and Toluca and the Divnoe primitive achondrite. The comparison of our LA‐ICP‐MS data for a number of iron meteorites with high‐precision isotope dilution and INAA data demonstrates the good precision and accuracy of our technique.The narrow ranges of variations of Mo and Pd concentrations within individual groups of iron meteorites suggest that these elements can provide important insights into the evolution of parent bodies of iron meteorites. Under certain assumptions, the Mo concentrations can be used to estimate mass fractions of the metal‐sulfide cores in the parent bodies of iron meteorites. It appears that a range of Pd variations within a group of iron meteorites can serve as a useful indicator of S content in the core of its parent body.
The lherzolitic shergottite Grove Mountains 99027: Rare earth element geochemistry
Authors: Hsu Weibiao , Guan Yunbin , Wang Henian , Leshin Laurie A. , Wang Rucheng , Zhang Wenlan , Chen Xiaoming , Zhang Fusheng , Lin Chengyi 
Published: January 2010

Abstract— We report here on an ion probe study of rare earth element (REE) geochemistry in the lherzolitic shergottite Grove Mountains (GRV) 99027. This meteorite shows almost identical mineralogy, petrology, and REE geochemistry to those of the lherzolitic shergottites Allan Hills (ALH) A77005, Lewis Cliff (LEW) 88516, and Yamato (Y‐) 793605. REE concentrations in olivine, pyroxenes, maskelynite, merrillite, and melt glass are basically comparable to previous data obtained from ALH A77005, LEW 88516, and Y‐793605. Olivine is the dominant phase in this meteorite. It is commonly enclosed by large (up to several mm) pigeonite oikocrysts. Non‐poikilitic areas consist of larger olivine grains (˜mm), pigeonite, augite, and maskelynite. Minor merrillite (up to 150 μm in size) is widespread in non‐poikilitic regions, occurring interstitially between olivine and pyroxene grains. It is the main REE carrier in GRV 99027 and has relatively higher REEs (200–1000 × CI) than that of other lherzolitic shergottites. A REE budget calculation for GRV 99027 yields a whole rock REE pattern very similar to that of other lherzolites. It is characterized by the distinctive light REE depletion and a smooth increase from light REEs to heavy REEs. REE microdistributions in GRV 99027 strongly support the idea that all lherzolitic shergottites formed by identical igneous processes, probably from the same magma chamber on Mars.Despite many similarities in mineralogy, petrography, and trace element geochemistry, subtle differences exist between GRV 99027 and other lherzolitic shergottites. GRV 99027 has relatively uniform mineral compositions (both major elements and REEs), implying that it suffered a higher degree of sub‐solidus equilibration than the other three lherzolites. It is notable that GRV 99027 has experienced terrestrial weathering in the Antarctic environment, as its olivine and pyroxenes commonly display a light REE enrichment and a negative Ce anomaly. Caution needs to be taken in future chronological studies.
Tectonic influences on the morphometry of the Sudbury impact structure: Implications for terrestrial cratering and modeling
Authors: Spray John G. , Butler Hadyn R. , Thompson Lucy M. 
Published: January 2010

Abstract— Impact structures developed on active terrestrial planets (Earth and Venus) are susceptible to pre‐impact tectonic influences on their formation. This means that we cannot expect them to conform to ideal cratering models, which are commonly based on the response of a homogeneous target devoid of pre‐existing flaws. In the case of the 1.85 Ga Sudbury impact structure of Ontario, Canada, considerable influence has been exerted on modification stage processes by late Archean to early Proterozoic basement faults. Two trends are dominant: 1) the NNW‐striking Onaping Fault System, which is parallel to the 2.47 Ga Matachewan dyke swarm, and 2) the ENE‐striking Murray Fault System, which acted as a major Paleoproterozoic suture zone that contributed to the development of the Huronian sedimentary basin between 2.45–2.2 Ga. Sudbury has also been affected by syn‐ to post‐impact regional deformation and metamorphism: the 1.9–1.8 Ga Penokean orogeny, which involved NNW‐directed reverse faulting, uplift, and transpression at mainly greenschist facies grade, and the 1.16–0.99 Ga Grenville orogeny, which overprinted the SE sector of the impact structure to yield a polydeformed upper amphibolite facies terrain. The pre‐, syn‐, and post‐impact tectonics of the region have rendered the Sudbury structure a complicated feature. Careful reconstruction is required before its original morphometry can be established. This is likely to be true for many impact structures developed on active terrestrial planets.Based on extensive field work, combined with remote sensing and geophysical data, four ring systems have been identified at Sudbury. The inner three rings broadly correlate with pseudotachylyte (friction melt) ‐rich fault systems. The first ring has a diameter of ˜90 km and defines what is interpreted to be the remains of the central uplift. The second ring delimits the collapsed transient cavity diameter at ˜130 km and broadly corresponds to the original melt sheet diameter. The third ring has a diameter of ˜180 km. The fourth ring defines the suggested apparent crater diameter at ˜260 km. This approximates the final rim diameter, given that erosion in the North Range is <6 km and the ring faults are steeply dipping. Impact damage beyond Ring 4 may occur, but has not yet been identified in the field. One or more rings within the central uplift (Ring 1) may also exist. This form and concentric structure indicates that Sudbury is a peak ring or, more probably, a multi‐ring basin. These parameters provide the foundation for modeling the formation of this relatively large terrestrial impact structure.
Chicxulub: Testing for post‐impact hydrothermal input into the Tertiary ocean
Authors: ROWE A. J. , WILKINSON J. J. , COLES B. J. , MORGAN J. V. 
Published: January 2010

Abstract Studies of large terrestrial impact craters indicate that post‐impact hydrothermal activity is a likely consequence of the crustal deformation and heating induced by such events. In the case of the Chicxulub basin, where marine conditions were re‐established soon after the impact, significant fluxing of seawater through the crust and hydrothermal venting into the water column might be anticipated. We have carried out geochemical analyses of Tertiary carbonate sediments within the Yaxcopoil‐1 (Yax‐1) drill hole to test for evidence of such post‐impact hydrothermal circulation. Hydrothermal activity is most likely to be found close to thick layers of melt rock inside the collapsed transient cavity, and it is estimated that Yax‐1 is located ˜20 km outside this cavity. Consequently, the most likely signature of hydrothermal venting into the water column would be geochemical anomalies attributable to fallout of suspended particulate matter from a submarine hydrothermal plume.Samples of Tertiary biomicrites from depths of 794.01 to 777.02 m have high concentrations of manganese, iron, phosphorous, titanium, and aluminium and low iron/manganese ratios relative to samples from higher in the stratigraphic succession. This geochemical anomaly decreases fairly systematically between 793.13 m and 777.02 m, above which an abrupt change in geochemistry is observed. A mass balance calculation suggests that the anomaly is unlikely to be the result of a decreasing detrital input to the carbonate sediments and the nature of the element enrichments is consistent with expectations for fallout from a distal hydrothermal plume. We conclude that a post‐impact hydrothermal system did develop at Chicxulub, which led to the expulsion of hydrothermal fluids into the Tertiary water column. Preliminary biostratigraphic and magnetostratigraphic dating on Yax‐1 core suggest that this hydrothermal activity lasted for at least 300 ka.
Stratigraphy and composition of lava flows in Mare Nubium and Mare Cognitum
Authors: Bugiolacchi Roberto , Spudis Paul D. , Guest John E. 
Published: January 2010

Abstract— Three major periods of basaltic activity characterize the infill of the basins. Each of these periods was itself punctuated by discrete phases of widespread magma eruptions: three during both the Late Imbrian Epoch and the early Eratosthenian Period and then two in the late Eratosthenian Period. We found the youngest lavas off the eastern border of the Fra Mauro peninsula and, mantling a much larger area, over most of the central western Nubium basin.Our results place the Nubium/Cognitum basalts in the low‐Ti category (1–5 wt% TiO2).The data indicate that the majority (˜90%) of the mare terrain has iron content between 18 and 22 wt%. In particular, FeO contents tend to concentrate toward two compositional poles, each of ˜20 wt%, and a much smaller one of ˜15 wt%. These values are typical of nearside lunar maria.To complement our compositional data, we present a census of craters larger than 500 m using Orbiter IV images. The result was a crater count average with frequency 5.6 × 10−2 km−2, translating into an inferred mean age of 3300 Ma for the exposed lava flows.By combining lava chemistry with age, we find a possible correlation between the ages of the most prominent flow units and their estimated titanium content, with younger basalts becoming progressively Ti‐richer with time (from 2–3 to 4–5 wt% TiO2).
Chesapeake Bay impact structure: Morphology, crater fill, and relevance for impact structures on Mars
Authors: Horton J. Wright , Ormö Jens , Powars David S. , Gohn Gregory S. 
Published: January 2010

Abstract— The late Eocene Chesapeake Bay impact structure (CBIS) on the Atlantic margin of Virginia is one of the largest and best‐preserved “wet‐target” craters on Earth. It provides an accessible analog for studying impact processes in layered and wet targets on volatile‐rich planets. The CBIS formed in a layered target of water, weak clastic sediments, and hard crystalline rock. The buried structure consists of a deep, filled central crater, 38 km in width, surrounded by a shallower brim known as the annular trough. The annular trough formed partly by collapse of weak sediments, which expanded the structure to ˜85 km in diameter. Such extensive collapse, in addition to excavation processes, can explain the “inverted sombrero” morphology observed at some craters in layered targets.The distribution of crater‐fill materials in the CBIS is related to the morphology. Suevitic breccia, including pre‐resurge fallback deposits, is found in the central crater. Impact‐modified sediments, formed by fluidization and collapse of water‐saturated sand and silt‐clay, occur in the annular trough. Allogenic sediment‐clast breccia, interpreted as ocean‐resurge deposits, overlies the other impactites and covers the entire crater beneath a blanket of postimpact sediments.The formation of chaotic terrains on Mars is attributed to collapse due to the release of volatiles from thick layered deposits. Some flat‐floored rimless depressions with chaotic infill in these terrains are impact craters that expanded by collapse farther than expected for similar‐sized complex craters in solid targets. Studies of crater materials in the CBIS provide insights into processes of crater expansion on Mars and their links to volatiles.
Shişr 043 (IIIAB medium octahedrite): The first iron meteorite from the Oman desert
Authors: AL‐KATHIRI A. , HOFMANN B. A. , GNOS E. , EUGSTER O. , WELTEN K. C. , KRÄHENBÜHL U. 
Published: January 2010

Abstract— The iron meteorite Shişr 043 is a single mass of 8267 g found in the south Oman desert 42 km NE of the Shişr village. It is the first iron identified among the >1400 individual meteorites reported from Oman. The meteorite is a slightly elongated mass showing only minor rusting, a partially smooth and partially rough surface with octahedral cleavage, and a partially preserved metallic fusion crust typically 0.75 mm thick.The undeformed Widmanstätten pattern with a mean kamacite bandwidth of 1.0 ± 0.1 mm (n = 97) indicates structural classification as a medium octahedrite. From the bulk composition, Ni = 8.06 wt%, Ga = 18.8 ppm, Ge = 37.25 ppm, and Ir = 3.92 ppm, the meteorite is classified as IIIAB, the most common group of iron meteorites. The cosmic‐ray exposure (CRE) age based on 3He, 21Ne, 38Ar concentrations and 10Be‐21Ne, 26Al‐21Ne, and 36Cl‐36Ar ratios is 290 ± 20 Ma. This age falls within the range observed for type IIIAB iron meteorites, but does not coincide with the main cluster. The cosmogenic noble gas and radionuclide data indicate that Shişr 043 had a relatively small preatmospheric mass. The low degree of weathering is consistent with a young terrestrial age of <10,000 years based on the saturated 41Ca concentration. Shişr 043 is not paired with any of the other eight known iron meteorites from the Arabian Peninsula.
Nitrogen components in IAB/IIICD iron meteorites
Authors: PONGANIS K. V. , MARTI K. 
Published: January 2010

Abstract— Isotopic variations have been reported for many elements in iron meteorites, with distinct N signatures found in the metal and graphite of IAB irons. In this study, a dozen IAB/IIICD iron meteorites (see Table 1 for new classifications) were analyzed by stepwise pyrolysis to resolve nitrogen components. Although isotopic heterogeneity has been presumed to be lost in thermally processed parent objects, the high‐resolution nitrogen isotopic data indicate otherwise. At least one reservoir has a light nitrogen signature, δ15N = −(74 ± 2)‰, at 900 °C to 1000 °C, with a possible second, even lighter, reservoir in Copiapo (δ15N ≤ −82‰). These releases are consistent with metal nitride decomposition or low‐temperature metal phase changes. Heavier nitrogen reservoirs are observed in steps ≤700 °C and at 1200 °C to 1400 °C. The latter release has a δ15N signature with a limit of ≥−16‰. Xenon isotopic signatures are sensitive indicators for the presence of inclusions because of the very low abundances of Xe in metal. The combined high‐temperature release shows 131Xe and 129Xe excesses to be consistent with shifts expected for Te(n,γ) reaction in troilite by epithermal neutrons, but there are also possible alterations in the isotopic ratios likely due to extinct 129I and cosmic‐ray spallation.The IAB/IIICD iron data imply that at least one light N component survived the formation processes of iron parent objects which only partially exchanged nitrogen between phases. Preservation of separate N reservoirs conflicts with neither the model of impact‐heating effects for these meteorites nor reported age differences between metal and silicates.
Al‐Mg isotopic evidence for episodic alteration of Ca‐Al‐rich inclusions from Allende
Authors: Fagan T. J. , Guan Y. , MacPherson G. J. 
Published: January 2010

Abstract— Textures, mineral assemblages, and Al‐Mg isotope systematics indicate a protracted, episodic secondary mineralization history for Allende Ca‐Al‐rich inclusions (CAIs). Detailed observations from one type B1 CAI, one B2, one compact type A (CTA), and one fluffy type A (FTA) indicate that these diverse types of CAIs are characterized by two distinct textural and mineralogic types of secondary mineralization: (1) grossular‐rich domains, concentrated along melilite grain boundaries in CAI interiors, and (2) feldspathoid‐bearing domains, confined mostly to CAI margins just interior to the Wark‐Lovering rim sequence.The Al‐Mg isotopic compositions of most secondary minerals in the type B1 CAI, and some secondary minerals in the other CAIs, show no resolvable excesses of 26Mg, whereas the primary CAI phases mostly yield correlated excesses of 26Mg with increasing Al/Mg corresponding to “canonical” initial 26Al/27Al ∼ 4.5–5 × 10−5. These secondary minerals formed at least 3 Ma after the primary CAI minerals. All but two analyses of secondary minerals from the fluffy type‐A CAI define a correlated increase in 26Mg/24Mg with increasing Al/Mg, yielding (26Al/27Al)0 = (4.9 ± 2.8) × 10−6. The secondary minerals in this CAI formed 1.8–3.2 Ma after the primary CAI minerals. In both cases, the timing of secondary alteration is consistent with, but does not necessarily require, alteration in an asteroidal setting. One grossular from the type B2 CAI, and several grossular and secondary feldspar analyses from the compact type A CAI, have excesses of 26Mg consistent with initial 26Al/27Al ∼ 4.5 × 10−5. Especially in the compact type A CAI, where 26Mg/24Mg in grossular correlates with increasing Al/Mg, these 26Mg excesses are almost certainly due to in situ decay of 26Al. They indicate a nebular setting for formation of the grossular.The preservation of these diverse isotopic patterns indicates that heating on the Allende parent body was not pervasive enough to reset isotopic systematics of fine‐grained secondary minerals. Secondary mineralization clearly was not restricted to a short time interval, and at least some alteration occurred coincident with CAI formation and melting events (chondrule formation) in the nebula. This observation supports the possibility that alteration followed by melting affected the compositional evolution of CAIs.
Characterization of the log lithology of cores LB‐07A and LB‐08A of the Bosumtwi impact structure by using the anisotropy of magnetic susceptibility
Authors: SCHELL Christina , SCHLEIFER Norbert , ELBRA Tiiu 
Published: January 2010

Abstract— Petrophysical data are commonly used for the discrimination of different lithologies, as the variation in mineralogy, texture, and porosity is accompanied by varying physical properties. A special field of investigation is the analysis of the directional dependence (anisotropy) of the petrophysical properties, which can provide further information on the characteristics of the lithologies, due to the fact that this parameter is different in the various rock‐forming and rock‐changing processes, e.g., deformation or sedimentation.To characterize the rocks in drill cores LB‐07A and LB‐08A, which were drilled into the deep crater moat and central uplift of the Bosumtwi impact structure, Ghana, samples were taken for the study of petrophysical properties. In the present work the magnetic properties of these samples were determined in the laboratory. The results are discussed in relation to the various lithologies represented by this sample suite.The shape and degree of magnetic anisotropy, in combination with the magnetic susceptibility, proved useful in distinguishing between the different lithologies present in the drill cores (polymict lithic breccia, suevite, shale component, and meta‐graywacke). It was possible to correlate layers of high (shale component), intermediate (graywacke, polymict lithic breccia), and low (suevite) anisotropy degree with the lithostratigraphic sequences determined for cores LB‐07A and LB‐08A. The shape of the anisotropy showed that foliation is most dominant within the shale component, whereas lineation is more pronounced in the meta‐graywacke and polymict lithic breccia. An overall increase of the anisotropy degree was observed from core LB‐07A towards core LB‐08A. Thus magnetic anisotropy data provide a useful contribution towards an improved petrophysical characterization of the lithostratigraphic sequences in drillcores from the Bosumtwi impact structure.
Gain and loss of uranium by meteorites and rocks, and implications for the redistribution of uranium on Mars
Authors: DREIBUS Gerlind , HAUBOLD Reinhard , HUISL Wolfgang , SPETTEL Bernhard 
Published: January 2010

Abstract Terrestrial alteration of meteorites results in the redistribution, gain, or loss of uranium and other elements. We have measured the maximum U adsorption capacity of a meteorite and two geochemical reference materials under conditions resembling terrestrial ones (pH 5.8). The basaltic eucrite Sioux County adsorbs 7 ppm of U. The result for the terrestrial granite AC‐E is similar (5 ppm), while the basalt BE‐N adsorbs 34 ppm of U.We have also investigated U adsorption in the presence of phosphate (0.01 M or less) in imitation of conditions that probably occurred in the earlier history of Mars. Such a process would have alterated Martian surface material and would be noticeable in Martian meteorites from the affected surface. The experiments demonstrated the counteracting effects of phosphate, which increases U adsorption, but decreases the quantity of dissolved U that is available for adsorption. U adsorption by AC‐E increases to 7 ppm. The lowered value for BE‐N of 8 ppm results from the low quantity of dissolved U in the volume of solution used.The results from the adsorption experiments and from leaching the Martian meteorite Zagami and a terrestrial basalt imply that the aqueous redistribution of U on Mars was moderate. Acidic liquids mobilized uranium and other metals, but present phosphate impeded the dissolution of U compounds. Some mobilized U may have reached the global sinks, while most of it probably was transported in the form of suspended particles over a limited distance and then settled.