A refractory inclusion with solar oxygen isotopes and the rarity of such objects in the meteorite record     

Levke Kp  Kazuhide Nagashima  Andrew M. Davis  Alexander N. Krot 《Meteoritics & planetary science》2020,55(3):524-534

NASA's Genesis mission revealed that the Sun is enriched in ¹⁶O compared to the Earth and Mars (the Sun's Δ¹⁷O, defined as δ¹⁷O–0.52×δ¹⁸O, is –28.4 ± 3.6‰; McKeegan et al. 2011). Materials as ¹⁶O‐rich as the Sun are extremely rare in the meteorite record. Here, we describe a Ca‐Al‐rich inclusion (CAI) from a CM chondrite that is as ¹⁶O‐enriched as the Sun (Δ¹⁷O = –29.1 ± 0.7‰). This CAI also has large nucleosynthetic anomalies in ⁴⁸Ca and ⁵⁰Ti (δ‐values are –8.1 ± 3.3 and –11.7 ± 2.4‰, respectively) and shows no clear evidence for incorporation of live ²⁶Al; (²⁶Al/²⁷Al)₀ = (0.03 ± 0.11) × 10^–5. Due to their anomalous isotopic characteristics, the rare CAIs consistent with the Genesis value could be among the first materials that formed in the solar system. In contrast to the CAI studied here, the majority of CAIs formed in or interacted with a reservoir characterized by a Δ¹⁷O value near –23.5‰. Combined with ²⁶Al‐²⁶Mg systematics, the oxygen isotopic compositions of FUN (fractionation and unidentified nuclear effects), UN, and normal CAIs suggest that nebular conditions were favorable for solids to inherit this value for an extended period of time. Many later‐formed materials, such as chondrules, planetesimals, and terrestrial planets, formed in reservoirs with Δ¹⁷O near 0‰. The distribution could be easier to explain if the common CAI value of –23.5‰, which is consistent with the Genesis value within 3σ, represented the average composition of the protoplanetary disk.  相似文献   

Hydrogen fluence in Genesis collectors: Implications for acceleration of solar wind and for solar metallicity     

Gary R. Huss  Elizabeth Koeman‐Shields  Amy J. G. Jurewicz  Donald S. Burnett  Kazuhide Nagashima  Ryan Ogliore  Chad T. Olinger 《Meteoritics & planetary science》2020,55(2):326-351

NASA's Genesis mission was flown to capture samples of the solar wind and return them to the Earth for measurement. The purpose of the mission was to determine the chemical and isotopic composition of the Sun with significantly better precision than known before. Abundance data are now available for noble gases, magnesium, sodium, calcium, potassium, aluminum, chromium, iron, and other elements. Here, we report abundance data for hydrogen in four solar wind regimes collected by the Genesis mission (bulk solar wind, interstream low‐energy wind, coronal hole high‐energy wind, and coronal mass ejections). The mission was not designed to collect hydrogen, and in order to measure it, we had to overcome a variety of technical problems, as described herein. The relative hydrogen fluences among the four regimes should be accurate to better than ±5–6%, and the absolute fluences should be accurate to ±10%. We use the data to investigate elemental fractionations due to the first ionization potential during acceleration of the solar wind. We also use our data, combined with regime data for neon and argon, to estimate the solar neon and argon abundances, elements that cannot be measured spectroscopically in the solar photosphere.  相似文献   

Oxygen and Al‐Mg isotopic compositions of grossite‐bearing refractory inclusions from CO3 chondrites     

Steven B. Simon  Alexander N. Krot  Kazuhide Nagashima 《Meteoritics & planetary science》2019,54(6):1362-1378

The distribution of the short‐lived radionuclide ²⁶Al in the early solar system remains a major topic of investigation in planetary science. Thousands of analyses are now available but grossite‐bearing Ca‐, Al‐rich inclusions (CAIs) are underrepresented in the database. Recently found grossite‐bearing inclusions in CO3 chondrites provide an opportunity to address this matter. We determined the oxygen and magnesium isotopic compositions of individual phases of 10 grossite‐bearing CAIs in the Dominion Range (DOM) 08006 (CO3.0) and DOM 08004 (CO3.1) chondrites. All minerals in DOM 08006 CAIs as well as hibonite, spinel, and pyroxene in DOM 08004 are uniformly ¹⁶O‐rich (Δ¹⁷O = ?25 to ?20‰) but grossite and melilite in DOM 08004 CAIs are not; Δ¹⁷O of grossite and melilite range from ~ ?11 to ~0‰ and from ~ ?23 up to ~0‰, respectively. Even within this small suite, in the two chondrites a bimodal distribution of the inferred initial ²⁶Al/²⁷Al ratios (²⁶Al/²⁷Al)₀ is seen, with four having (²⁶Al/²⁷Al)₀ ≤1.1 × 10^?5 and six having (²⁶Al/²⁷Al)₀ ≥3.7 × 10^?5. Five of the ²⁶Al‐rich CAIs have (²⁶Al/²⁷Al)₀ within error of 4.5 × 10^?5; these values can probably be considered indistinguishable from the “canonical” value of 5.2 × 10^?5 given the uncertainty in the relative sensitivity factor for grossite measured by secondary ion mass spectrometry. We infer that the ²⁶Al‐poor CAIs probably formed before the radionuclide was fully mixed into the solar nebula. All minerals in the DOM 08006 CAIs, as well as spinel, hibonite, and Al‐diopside in the DOM 08004 CAIs retained their initial oxygen isotopic compositions, indicating homogeneity of oxygen isotopic compositions in the nebular region where the CO grossite‐bearing CAIs originated. Oxygen isotopic heterogeneity in CAIs from DOM 08004 resulted from exchange between the initially ¹⁶O‐rich (Δ¹⁷O ~?24‰) melilite and grossite and ¹⁶O‐poor (Δ¹⁷O ~0‰) fluid during hydrothermal alteration on the CO chondrite parent body; hibonite, spinel, and Al‐diopside avoided oxygen isotopic exchange during the alteration. Grossite and melilite that underwent oxygen isotopic exchange avoided redistribution of radiogenic ²⁶Mg and preserved undisturbed internal Al‐Mg isochrons. The Δ¹⁷O of the fluid can be inferred from O‐isotopic compositions of aqueously formed fayalite and magnetite that precipitated from the fluid on the CO parent asteroid. This and previous studies suggest that O‐isotope exchange during fluid–rock interaction affected most CAIs in CO ≥3.1 chondrites.  相似文献   

The Cretaceous Ofuku Pluton and Its Relation to Mineralization in the Western Akiyoshi Plateau,Yamaguchi Prefecture,Japan          下载免费PDF全文

Yuka Sasaki  Teruyoshi Imaoka  Mariko Nagashima  Kazuo Nakashima  Takafumi Sonehara  Koshi Yagi  Tetsumaru Itaya 《Resource Geology》2016,66(2):85-113

The relationship between the magmatism of the Cretaceous Ofuku pluton and mineralization in and around the Akiyoshi Plateau, Yamaguchi Prefecture, Japan was investigated using a combination of field observation, petrographic and geochemical analyses, K–Ar geochronology, and fluid inclusion data. The Ofuku pluton has a surface area of 1.5 × 1.0 km, and was intruded into the Paleozoic accretionary complexes of the Akiyoshi Limestone, Ota Group and Tsunemori Formation in the western part of the Akiyoshi Plateau. The pluton belongs to the ilmenite‐series and is zoned, consisting mainly of early tonalite and granodiorite that share a gradational contact, and later granite and aplite that intruded the tonalite and granodiorite. Harker diagrams show that the Ofuku pluton has intermediate to silicic compositions ranging from 60.4 to 77.9 wt.% SiO₂, but a compositional gap exists between 70.5 to 73.4 wt.% SiO₂ (anhydrous basis). Modal and chemical variations indicate that the assumed parental magma is tonalitic. Quantitative models of fractional crystallization based on mass balance calculations and the Rayleigh fractionation model using major and trace element data for all crystalline phases indicate that magmatic fractionation was controlled mainly by crystal fractionation of plagioclase, hornblende, clinopyroxene and orthopyroxene at the early stage, and quartz, plagioclase, biotite, hornblende, apatite, ilmenite and zircon at the later stage. The residual melt extracted from the granodiorite mush was subsequently intruded into the northern and western parts of the Ofuku pluton as melt lens to form the granite and aplite. The age of the pluton was estimated at 99–97 Ma and 101–98 Ma based on K–Ar dating of hornblende and biotite, respectively. Both ages are consistent within analytical error, indicating that the Ofuku pluton and the associated Yamato mine belong to the Tungsten Province of the San‐yo Belt, which is genetically related to the ilmenite‐series granitoids of the Kanmon to Shunan stages. The aplite contains Cl‐rich apatite and REE‐rich monazite‐(Ce), allanite‐(Ce), xenotime and bastnäsite‐(Ce), indicating that the residual melt was rich in halogens and REEs. The tonalite–granodiorite of the Ofuku pluton contains many three‐phase fluid inclusions, along with daughter minerals such as NaCl and KCl, and vapor/liquid (V/L) volume ratios range from 0.2 to 0.9, suggesting that the fluid was boiling. In contrast, the granite and aplite contain low salinity two‐phase inclusions with low V/L ratios. The granodiorite occupies a large part of the pluton, and the inclusions with various V/L ratios with chloride daughter minerals suggest the boiling fluids might be related to the mineralization. This fluid could have carried base metals such as Cu and Zn, forming Cu ore deposits in and around the Ofuku pluton. The occurrence and composition of fluid inclusions in the igneous rocks from the Akiyoshi Plateau are directly linked to Cu mineralization in the area, demonstrating that fluid inclusions are useful indicators of mineralization.  相似文献   

AFM study on surface nanotopography of matrix olivines in Allende carbonaceous chondrite     

Jun Nozawa  Junya Yamada  Ken Nagashima  Hitoshi Miura 《Icarus》2009,204(2):681-654

By means of nanoscale surface observation, we have proposed a new approach for investigating fine crystals of cosmic materials to reveal their origin and growth conditions. Several different morphologies of polyhedral fine olivines with faceted faces have been found in Allende carbonaceous chondrite (4.5 byr in geochronological age). In the present work, molecular level topography of the faceted matrix olivine by Atomic Force Microscopy (AFM) has successfully been performed. The matrix olivine found to have preserved growth step pattern on its surface even though quite long time has passed since they formed in the early Solar System. The surface pattern suggests that the faceted matrix olivine could have been condensed from the gas phase, and possibly that these olivine crystals had continued to grow under a rapid cooling condition (0.1-1 K s⁻¹). The estimated cooling rate agrees well with predictions based on hypothetical rapid heating and cooling events such as shock wave heating.  相似文献   

Highly N-enriched chondritic clasts in the CB/CH-like meteorite Isheyevo     

L. Bonal  G.R. Huss  K. Nagashima  J.P. Bradley 《Geochimica et cosmochimica acta》2010,74(22):6590-6609

The metal-rich carbonaceous chondrites (CB and CH) have the highest whole-rock ¹⁵N-enrichments (δ¹⁵N up to 1500‰) among planetary materials. They are also characterized by the absence of interchondrule fine-grained matrix. The only fine-grained material is present as lithic clasts, which experienced extensive aqueous alteration in contrast to the surrounding high-temperature components (chondrules, refractory inclusions, metal grains). Hence, the clasts are foreign objects that were incorporated at a late stage into the final parent body of Isheyevo. Their origin is poorly constrained. Based on mineralogy, petrography, and thermal processing of the aromatic carbonaceous component, different types of clasts have been previously identified in the CB/CH-like chondrite Isheyevo. Here, we focus on the rare lithic clasts characterized by the presence of anhydrous silicates (chondrules, chondrule fragments, and CAIs). Their mineralogy and oxygen isotopic compositions reveal them to be micro-chondrules, fragments of chondrules, and refractory inclusions related to those in the Isheyevo host, suggesting accretion in the same region. In contrast to previously studied IDPs or primitive chondritic matrices, the fine-grained material in the clasts we studied is highly and rather uniformly enriched in heavy nitrogen, with bulk δ¹⁵N values ranging between 1000‰ and 1300‰. It is also characterized by the presence of numerous ¹⁵N hotspots (δ¹⁵N ranging from 1400‰ to 4000‰). No bulk (δD <-240‰) or localized deuterium enrichments were observed. These clasts have the highest bulk enrichment in heavy nitrogen measured to date in a fine-grained material. They represent a unique material, of asteroidal or cometary origin, in our collection of cosmomaterials. We show that they were ¹⁵N-enriched before their incorporation in the final parent body of Isheyevo. They experienced an extensive aqueous alteration that most likely played a role in redistributing ¹⁵N over the whole fine-grained material and may have significantly modified its initial hydrogen isotopic composition. Based on a review of isotopic fractionation models, we conclude that the nitrogen isotopic fractionation process, its timing, and its location are still poorly constrained. The ¹⁵N-rich clasts may represent the surviving original carrier of the ¹⁵N anomaly in Isheyevo whole-rock.  相似文献   

Microscopic oxygen isotopic homogeneity/heterogeneity in the matrix of the Vigarano CV3 chondrite     

Takuya Kunihiro  Kazuhide Nagashima 《Geochimica et cosmochimica acta》2005,69(3):763-773

Two-dimensional ¹⁸O/¹⁶O isotopic analysis of the Vigarano matrix was conducted by secondary ion-imaging using a novel two-dimensional ion-imager. Quantitative oxygen-isotope images (isotopographs) of the Vigarano matrix show that ¹⁶O-rich micrograins are scattered within ¹⁶O-poor matrix. This heterogeneous O-isotopic distribution indicates that matrix is composed of different O-isotopic components that formed in different locations and/or at different times. However, the O-isotopic composition of groundmass in the matrix is the same as the bulk isotopic composition of the matrix within ±5‰ uncertainty. The spatial resolution and isotopic precision of our technique should allow submicron-size objects (>0.2 μm) with extreme O-isotopic anomalous characteristics (δ¹⁸O_SMOW ∼250‰) to be detectable in isotopographs. Because the mean grain size of the matrix is ∼0.2 μm, the inability to detect such O-isotopic anomalous objects indicates that isotopically anomalous micrograins (e.g., presolar grains) are extremely rare in the Vigarano matrix and that most objects in the matrix were formed in the solar nebula or in the parent body.  相似文献   

Occurrence of 3-hydroxy acids in microalgae and cyanobacteria and their geochemical significance     

Genki I. Matsumoto  Hideyuki Nagashima 《Geochimica et cosmochimica acta》1984,48(8):1683-1687

3-Hydroxy acids were detected in pure cultured microalgae: Chlorophyta—Chlamydomonas reinhardtii and Chlorella pyrenoidosa and Rhodophyta—Cyanidium caldarium (two strains), and cyanobacteria (Cyanophyta)—Anacystis nidulans, Phormidium foveolarum, Anabaena variabilis and Oscillatoria sp. Normal and branched (iso and anteiso) 3-hydroxy acids in the ranges of C₈-C₂₆ were found in all the samples studied at concentrations ranging from 0.036 to 2.3 and 0.000 to 0.12 mg g^?1 of dry sample, respectively. The major constituents were generally even-carbon numbered normal acids with carbon chain lengths below C₂₀. Microalgae and cyanobacteria may be the important sources of 3-hydroxy acids in natural environments.  相似文献   

A deep near-infrared survey around the giant radio galaxy PKS 1343–601     

T. Nagayama  P. A. Woudt  C. Nagashima  Y. Nakajima  D. Kato  M. Kurita  T. Nagata  H. Nakaya  M. Tamura  K. Sugitani  K. Wakamatsu  S. Sato 《Monthly notices of the Royal Astronomical Society》2004,354(4):980-990

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Northwest Africa 8418: The first CV4 chondrite     

G. J. MacPherson  K. Nagashima  A. N. Krot  S. M. Kuehner  A. J. Irving  K. Ziegler  L. Mallozzi  C. Corrigan  D. Pitt 《Meteoritics & planetary science》2023,58(1):135-157

Northwest Africa (NWA) 8418 is an unusual chondrite whose properties do not exactly match those of any other known chondrite. It has similarities to the CV (Vigarano group), CK (Karoonda group), and CL (Loongana group) chondrites, but its abundance of large calcium-aluminum-rich inclusions (CAIs) and the low NiO content (<0.2 wt%) of its matrix olivine ally it most closely with the CV group. The absence of grossular, monticellite, wollastonite, and sodalite from the alteration products of the CAIs; the magnesium-rich nature of the matrix olivines (Fa₃₈) relative to that of the CV3 chondrites (~Fa₅₀); and the presence of secondary Na-bearing plagioclase and chlorapatite indicate a metamorphic temperature >600 °C. NWA 8418 contains kamacite, taenite, and troilite, and lacks magnetite and pentlandite. We propose that NWA 8418 be reclassified as a reduced CV4 chondrite, which makes it the first CV chondrite of petrologic type 4.  相似文献