Meteoritics最新文献

{"title":"Weathering in Antarctic H and CR chondrites: Quantitative analysis through Mössbauer spectroscopy","authors":"R. Burns, T. Burbine, D. S. Fisher, R. Binzel","doi":"10.1111/J.1945-5100.1995.TB01159.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01159.X","url":null,"abstract":"Abstract— Mossbauer spectroscopy is a very useful tool for identifying ferric iron weathering products in meteorites because of the capability to quantify the relative amounts of ferric iron in them. Mossbauer measurements were made of 33 Antarctic H chondrites (predominately H5) and two paired Antarctic CR chondrites. The primary goals of this study are to determine if Mossbauer spectroscopy can be used to determine which phases are weathering in Antarctic meteorites and if the relative amounts of ferric iron correlate with terrestrial age. Determining which minerals are weathering in ordinary chondrites appears very difficult due to variations in composition for different ordinary chondrites of the same meteorite class and possible problems in preparing homogeneous samples. The analysis of the two paired CR chondrites appears to indicate that metallic iron is predominately weathering to produce ferric iron for this class of meteorite. No correlation is seen between the relative amounts of ferric iron and terrestrial age for ordinary chondrites. One Antarctic H5 chondrite (ALHA77294) with a short 14C age of 135 ± 200 years from the dating of interior carbonate weathering products does have a relatively low amount of ferric iron, which is consistent with this meteorite being exposed on the surface for a relatively short time.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"625-633"},"PeriodicalIF":0.0,"publicationDate":"1995-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01159.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The origin of circumstellar silicon carbide grains found in meteorites","authors":"K. Lodders, B. Fegley","doi":"10.1111/J.1945-5100.1995.TB01164.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01164.X","url":null,"abstract":"— Condensation calculations for C-rich circumstellar envelopes are used to model the condensation sequence of C, TiC, and SiC, and trace-element patterns observed in circumstellar SiC grains. Some properties of carbon star envelopes are briefly discussed, and condensation temperatures for major and trace elements are computed for a wide array of total pressure, C/O-ratios, and s-process elemental abundances. The comparison of calculated patterns for trace-element solid solutions in SiC with the different observed patterns measured by Amari et al. (1995) yields an association of the grains to at least three different groups of carbon stars.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"661-678"},"PeriodicalIF":0.0,"publicationDate":"1995-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01164.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Planar deformation features in quartz grains from the resurge deposit of the Lockne structure, Sweden","authors":"A. Therriault, M. Lindström","doi":"10.1111/J.1945-5100.1995.TB01167.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01167.X","url":null,"abstract":"— Microscopic planar deformation features (PDFs) in quartz grains are diagnostic of shock meta-morphism during hypervelocity impact cratering. Measurements of the poles of sets of PDFs and the optic axis of 25 quartz grains were carried out for a sample of the Loftarsten deposit from the Lockne area, Sweden. The most abundant PDFs observed in the sample from the Lockne area correspond to those found at known impact craters (i.e., ω (1013} and π (1012). This study confirms the previous suggestion that the Lockne structure is an impact crater. The Loftarsten is, therefore, interpreted as the final stage of resurge deposition after a marine impact at Lockne in the Middle Ordovician.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"700-703"},"PeriodicalIF":0.0,"publicationDate":"1995-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01167.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63677045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Search for extractable fullerenes in the Allende meteorite","authors":"D. Heymann","doi":"10.1111/J.1945-5100.1995.TB01149.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01149.X","url":null,"abstract":"— In an effort to confirm earlier observations of fullerenes in the Allende meteorite by Becker et al. (1994), we have treated nine separate whole-rock chips of this meteorite with toluene to search for extractable C60 and C70 fullerenes. The analysis was done with high performance liquid chromatography. Less than 1 ppb C60 and C70 were detected in a total of 131.82 g of this meteorite. Becker et al. (1994) have estimated a content of 100 ppm in one Allende sample. Either they have grossly overestimated the C60 content of their sample, or Allende is very inhomogeneous concerning fullerenes.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"436-438"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01149.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Bawku LL5 Chondrite","authors":"S. Reed, G. Chinner","doi":"10.1111/J.1945-5100.1995.TB01153.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01153.X","url":null,"abstract":"— A meteorite fall was observed on 1989 December 29 in the vicinity of Bawku, North Ghana (11°05′N, 0°11′W). Two fragments (59 and 1498 g) of a stony meteorite were subsequently recovered. This is classified as an LL5 monomict breccia of shock category S2. The olivine and pyroxene compositions are Fa26.8 and Fs22.6 respectively.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"468-469"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01153.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robert Sinclair Dietz (1914–1995)","authors":"S. Koppes","doi":"10.1111/J.1945-5100.1995.TB01155.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01155.X","url":null,"abstract":"","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"474-474"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01155.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geophysical studies of the Montagnais impact crater, Canada","authors":"M. Pilkington, L. Jansa, R. Grieve","doi":"10.1111/J.1945-5100.1995.TB01151.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01151.X","url":null,"abstract":"— The 45-km diameter Montagnais impact structure, Nova Scotia, Canada, is characterized by a positive, circular 8 mGal gravity anomaly associated with its central uplift. The negative gravity anomaly, which is expected for a complex crater of this size, is not observed within the structure, and magnetic data lack any well-defined, crater-related signature. The absence of a negative gravity anomaly implies that no low-density zone generally related to fracturing and brecciation exists. Since Montagnais appears well preserved, this zone has not been removed by erosion. Its formation may have been impeded due to the lack of competency in the target rocks. The crater was formed in a shallow marine environment where the lack of strength in the unconsolidated sediments may have prevented the preservation of voids and fractures that cause a negative gravity anomaly as observed over other impact craters. Additionally, the efficient absorption of impact energy by unconsolidated target material may have inhibited fracture/void development. Although the gravity signature of impact craters formed on land is well known, structures occurring in unconsolidated target material, such as continental shelf environments, constitute another signature that should also be recognized.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"446-450"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01151.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sulfur and selenium in chondritic meteorites","authors":"G. Dreibus, H. Palme, B. Spettel, J. Zipfel, H. Wänke","doi":"10.1111/J.1945-5100.1995.TB01150.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01150.X","url":null,"abstract":"— We report here new analyses of S and Se in carbonaceous chondrites (2 CIs, 11 CMs, 6 CO3s, 7 CV3s, 2 C4s, 4 CRs, and 1 CH), 2 rumurutiites, ordinary chondrites (2 Hs, 2 Ls, and 1 LL), 3 anomalous chondrites, 3 acapulcoites, 3 lodranites, and in silicate inclusions of the Landes IAB iron meteorite. To avoid problems from inhomogeneous distribution of sulfides, the same samples that had been analysed for Se by INAA were analysed for S using a Leybold Heraeus Carbon and Sulfur Analyser (CSA 2002). \u0000 \u0000 \u0000 \u0000With the measured CI contents of 5.41% S and 21.4 ppm Se a CI S/Se ratio of 2540 is obtained. A nearly identical S/Se ratio of 2560 ± 150 is found for carbonaceous chondrites (average of falls). The average ratio of all meteorite falls analysed in this study was 2500 ± 270. These data suggest that the new S content of Orgueil with 5.41% provides a reliable estimate for the average Solar System. The new solar system abundance of S of 4.62 × 105 (atoms/106 Si) is in good agreement with the solar photospheric abundance of 7.21 (log (a(H)) = E12) (Anders and Grevesse, 1989). \u0000 \u0000 \u0000 \u0000Among the 50 analysed meteorites, 24 were finds from hot (Australia, Africa) and cold (Antarctica) deserts. Weathering effects in the carbonaceous chondrites and in one lodranite from the hot deserts resulted in losses of S, Se, Na and occasionally Ni. Sulfur is apparently more affected by weathering than Se. No losses were observed in ordinary chondrite finds and in meteorites collected in the Antarctica, except for the obvious loss of Na in the CM-chondrite Y 74662. \u0000 \u0000 \u0000 \u0000The low S-content of 0.096% in Gibson, a lodranite, is probably not representative of this group of meteorites. Gibson is a find from the Australian desert and has lost S and also Se by weathering. Two other lodranites, finds from Antarctica, have about 2% S.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"439-445"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01150.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Planetary cratering 1. The question of multiple impactor populations: Lunar evidence","authors":"W. Hartmann","doi":"10.1111/J.1945-5100.1995.TB01152.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1995.TB01152.X","url":null,"abstract":"— This paper addresses several current issues related to use of craters in interpreting planetary surface histories. The primary goal is to test the widely adopted hypothesis of multiple populations of impactors at different times or places in the Solar System. \u0000 \u0000 \u0000 \u0000New data presented here revise a “lunar highland” crater diameter distribution that has been widely used as evidence of an early distinct population of impactors. This curve, which has a depression of the size distribution at mid-sizes, does not, in fact, represent the lunar highlands generally. I show that it is associated with regions of intercrater plains. The more extensive the obliteration by intercrater plains, the deeper the depression. Modeling indicates that the depression of the curve is caused by the obliteration process itself. The oldest, most cratered regions of lunar highlands do not show the depression. \u0000 \u0000 \u0000 \u0000These findings call into question earlier interpretations of multiple populations of impactors in the Solar System and of a distinctive primordial population. \u0000 \u0000 \u0000 \u0000The present work is consistent, instead, with (1) a relatively uniform size distribution of interplanetary impactors, of mixed origins, back to 4 Ga ago and throughout the sampled Solar System; (2) fragmentation as the process that produced that size distribution; (3) saturation equilibrium on the most heavily cratered surfaces; and (4) differences in structure in the size distribution caused not by distinct impactor populations but by episodes of endogenic obliteration. \u0000 \u0000 \u0000 \u0000If accepted, these results would modify some studies of solar system evolution, including assertions of two to five distinct populations of impactors, assumptions of lack of saturation equilibrium, and identifications of specific heliocentric or planetocentric sources for impactors within outer planet satellite systems.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"30 1","pages":"451-467"},"PeriodicalIF":0.0,"publicationDate":"1995-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1995.TB01152.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63676593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body","authors":"L. Nyquist, B. Bansal, H. Wiesmann, C. Shih","doi":"10.1111/J.1945-5100.1994.TB01102.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1994.TB01102.X","url":null,"abstract":"Neodymium, stontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age and the formation interval between its crystallization and condensation of Allende CAIs from the solar nebula. Pyroxene and phosphate were found to contain approximately 8% of its Sm and Nd inventory. A conventional Sm-147-Nd-143 isochron yielded an age of 4.53 +/- 0.04 Ga (2 sigma and Epsilon(sub Nd sup 143)) = 0.45 +/- 1.1. An Sm-146-Nd-142 isochron gives initial Sm-146/Sm-144 = 0.0076 +/- 0.0009 and Epsilon (sub Nd sup 142) = -2.5 +/- 0.4. The Rb-Sr analyses give initial Sr-87/Sr-86 Iota(sub Sr sup 87) = 0.698972 +/- 8 and 0.698970 +/- 18 for LEW and ADOR, respectively, relative to Sr-87/Sr-86 = 0.71025 for NBS987. The difference, Delta Iota(sub Sr Sup 87), between Iota (sub sr sup 87) for the angrites and literature values for Allende CAIs, corresponds to approximately Ma of growth in a solar nebula with a CI chondrite value of Rb-87/Sr-86 = 0.91, or approximately 5 Ma in a nebula with solar photospheric Rb-87/Sr-86 = 1.51. Excess Cr-53 from extinct Mn-53(t(sub 1/2) = 3.7 Ma)in LEW86010 corresponds to initial Mn-53/Mn-55 = 4.4 +/- 1.0 x 10(exp -5) for the inclusions as previously reported by the Paris group (Birck and Allegre, 1988). The Sm-146/Sm-144 value found for LEW86010 corresponds to solar system initial (Sm-146/Sm-144) = 0.0080 +/- 0.0009 for crystallization 8 Ma after Allende, the difference between Pb-Pb ages of angrites and Allende, or 0.0086 +/- 0.0009 for crystallation 18 Ma after Allende, using the Mn-Cr formation interval. The isotopic data are discussed in the context of a model in which an undifferentiated 'chondritic' parent body formed from the solar nebula approximately Ma after Allende CAIs and subsequently underwent differentiation accompanied by loss of volatiles. Parent bodies with Rb/Sr similar to that of CI, CM, or CO chondrites could satisfy the Cr and Sr isotopic systematics. If the angrite parent body had Rb/Sr similar to that of CV meteorites, it would have to form slightly later, approximately 2.6 Ma after the CAIs, to satisfy the Sr and CR isotopic systematics.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"29 1","pages":"872-885"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1994.TB01102.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63673248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}