Meteoritics最新文献_第6页

Basaltic volcanism on the Allende parent body 阿连德母体上的玄武岩火山作用

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01071.X

S. R. Taylor

引用次数: 0

A magnetic study of the Millbillillie (eucrite) achondrite: Evidence for a dynamo‐type magnetising field millbillilllie (eucrite)无球粒陨石的磁性研究:发电机型磁场的证据

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01077.X

S. Morden

{"title":"A magnetic study of the Millbillillie (eucrite) achondrite: Evidence for a dynamo‐type magnetising field","authors":"S. Morden","doi":"10.1111/J.1945-5100.1992.TB01077.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1992.TB01077.X","url":null,"abstract":"— The magnetic properties of the Millbillillie eucrite have been intensively studied using mutually oriented samples. The magnetic carrier has been identified as single domain/pseudo-single domain kamacite. It is believed that due to clast-rich/clast-poor layering, the rock has been subjected to minimum shock since formation. This is supported by the presence of a stable, unidirectional remanence. Three separate palaeointensity tests (IRM/NRM, ARM-NRM, and Thellier heating) have been used to determine the strength of the palaeofield. The criteria for the suitability of samples to be used in such tests are discussed, as are the three methods; IRM/NRM is deemed the least accurate. The results obtained (IRM/NRM: 6 μT and 25 μT; ARM-NRM: 31 μT, 28 μT, and 15 μT; Thellier: 30 μT, 37 μT, 15 μT) indicate that the rock cooled in a strong magnetic field. Modes of formation, given that Millbillillie has a layered structure, and the nature of the HED parent body, are discussed. A volcanic genesis is preferred over formation in an impact melt. An internal dynamo field is favoured for dynamical reasons, and calculations based on the assumption that 4 Vesta is a possible HED parent body indicate that an iron core may be present in such a body.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"27 1","pages":"560-567"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1992.TB01077.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63663604","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}

引用次数: 16

The meteorite collection sites of Antarctica 南极洲的陨石收集点

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01073.X

W. Cassidy, R. Harvey, J. Schutt, G. Delisle, K. Yanai

{"title":"The meteorite collection sites of Antarctica","authors":"W. Cassidy, R. Harvey, J. Schutt, G. Delisle, K. Yanai","doi":"10.1111/J.1945-5100.1992.TB01073.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1992.TB01073.X","url":null,"abstract":"— Antarctic meteorites have been and are being well studied but the potential for glaciological and climatological information in the sites where they are found is only beginning to be realized. To date, meteorite stranding surfaces have been identified only in East Antarctica: (1) The MacKay Glacier/David Glacier region contains the Allan Hills and the Reckling Moraine/Elephant Moraine stranding surfaces. Because the Allan Hills Main Icefield has a large proportion of meteorites with long terrestrial ages, these concentrations of meteorites must have had catchment areas extending well inland, in contrast to the present. Where known, bedrock topography is mesa-like in form and influences ice flow directions. Ice levels at the Allan Hills may have been higher by 50–100 m in the past. Reckling Moraine and Elephant Moraine are located on a long patch of ice running westward from Reckling Peak; the ice appears to be pouring over a bedrock escarpment. (2) In North Victoria Land, ice diverges around Frontier Mountain and flows into a site behind the barrier where ablation occurs extensively. It is proposed that meteorites and rocks were dumped by ice flow at the mouth of a valley in the lee of the mountain at the site where a meltwater pond existed, in a depression produced by ablation. Later, the pond migrated headward along the valley to a point where it is today, leaving a morainal deposit with the meteorites at a higher level. (3) Between the Beardmore and Law Glaciers, ice flows sluggishly into the southwestern margin of the Walcott Neve. Northeastern sections of the Walcott are virtually barren of meteorites. The entering Plateau ice is diverted northward to flow along the base of Lewis Cliff. This flow apparently terminates in an ice tongue protruding into a vast moraine, where a very large concentration of meteorites was found on the ice. This final segment of flowing ice is called the Lewis Cliff Ice Tongue. Meteorite Moraine, a subsidiary occurrence 2 km to the northeast, is also found against morainal deposits. The origin of the moraines and the history of meteorite concentration at this site is the subject of some debate. (4) The Transantarctic Mountains are submerged along one segment many hundreds of km in length by ice flowing off the Polar Plateau. The Thiel Mountains, Pecora Escarpment and Patuxent Range are the only surface indications of the underlying mountains along this interval, and meteorite stranding surfaces are found at each of these sites. Little is yet known about ice dynamics at these sites. (5) The immense Yamato Mountains meteorite stranding surface covers an area of about 4000 km2. So far, most meteorites have been recovered in the upper reaches of this blue ice field, where ice flow is slowed by outlying subice barriers of the Yamato Mountains. Individual massifs in this range extend northward over 50 km, and the Yamato Meteorite Icefield loses 1100 m in elevation over this distance. (6) The Sor Rondane Mountains form ","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"27 1","pages":"490-525"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1992.TB01073.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63663760","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}

引用次数: 126

Search for microaustralites in deep‐sea sediments less than 20,000 years old 在不到2万年的深海沉积物中寻找微澳大利亚岩

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01083.X

B. Glass, Jiquan Wu

引用次数: 6

Rhenium and osmium systematics on iron and stony iron meteorites 铁和石铁陨石上的铼和锇分类学

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01078.X

T. Hirata, A. Masuda

{"title":"Rhenium and osmium systematics on iron and stony iron meteorites","authors":"T. Hirata, A. Masuda","doi":"10.1111/J.1945-5100.1992.TB01078.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1992.TB01078.X","url":null,"abstract":"Abstract— Re and Os abundances and 187Os/186Os isotopic ratios in 12 iron meteorites of various groups and five stony iron meteorites have been determined by an inductively coupled plasma mass spectrometry (ICP-MS). The series of iron meteorites studied have Re and Os concentrations ranging from 0.004 to 3.3 ppm and 0.03 to 41 ppm, respectively. The 187Re/186Os ratios in these meteorites fall between 3.0 and 6.1 and the 187Os/186Os between 1.0 and 1.2, giving an initial 187Os/186Os isotopic ratio of 0.790 and a Re-Os age of iron meteorites of 4.30 ± 0.28 Ga when employing the decay constant of 1.64 × 10−11 yr−1. The observed Re-Os age for iron meteorites appears somewhat younger than that for chondrites. The resultant younger age might be due either to a very slow cooling of the parental planetesimals or due to a secondary “shock” event. However, for definite conclusions about the Re-Os age, higher precisions of the Re and Os isotopic measurements and of the decay constant of 187Re are required. Furthermore, the clear elucidation of the mechanisms for the fractionation of the Re/Os abundance ratios are related to the understanding of the meaning of the Re-Os age. \u0000 \u0000The Re and Os abundances in pallasite stony iron meteorites are extremely low compared with those for most iron meteorites. On the other hand, the Re and Os abundances in mesosiderite stony iron meteorites show values comparable with those observed in most iron meteorites. The difference in Re and Os abundances in pallasite and mesosiderite stony iron meteorites strongly suggests that these stony iron meteorites are different in origin or history of chemical evolution. \u0000 \u0000Re and Os abundances in the series of iron and stony iron meteorites were found to have a wide variation covering nearly four orders of magnitude, with a very high correlation coefficient (0.996), and a slope very slightly less than unity. The regression line observed here covers various groups of iron meteorites, stony iron meteorites and also chondrites. Masuda and Hirata (1991) suggested the possible direct mixing process of particles of most refractory metallic elements with gaseous clouds of less refractory matrix elements, since the Re and Os were predicted theoretically to be the first elements to condense as a solid phase from the high temperature solar nebula. The aims of this paper are to present a reliable technique for the Re-Os chronology and to study the cosmochemical sequences of the meteoritic metals.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"27 1","pages":"568-575"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1992.TB01078.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63663815","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}

引用次数: 19

Trapping of noble gases in proton‐irradiated silicate smokes 质子辐照硅酸盐烟雾中惰性气体的捕获

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01076.X

R. Nichols, J. Nuth, C. Hohenberg, C. Olinger, M. Moore

{"title":"Trapping of noble gases in proton‐irradiated silicate smokes","authors":"R. Nichols, J. Nuth, C. Hohenberg, C. Olinger, M. Moore","doi":"10.1111/J.1945-5100.1992.TB01076.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1992.TB01076.X","url":null,"abstract":"— We have measured Ne, Ar, Kr and Xe in Si2O3 “smokes” that were condensed on Al substrates, vapor-deposited with various mixtures of CH4, NH3, H2O and noble gases at 10 K and subsequently irradiated with 1 MeV protons to simulate conditions during grain mantle formation in interstellar clouds. The noble gases were analyzed using conventional stepwise heating and static noble gas mass spectrometry. Neither Ne nor Ar is retained by the samples upon warming to room temperature, but Xe is very efficiently trapped and retained. Kr is somewhat less effectively retained, typically depleted by factors of about 10–20 relative to Xe. Isotopic fractionation favoring the heavy isotopes of Xe and Kr of about 5–10‰/amu is observed. Correlations between the specific chemistry of the vapor deposition and heavy noble gas retention are most likely the result of competition by the various species for irradiation-produced trapping sites. The concentration of Xe retained by some of these smokes exceeds that observed in phase Q of meteorites and, like phase Q, they do not seem to be carriers of the light noble gases. Such artificially prepared material may, therefore, offer clues concerning the incorporation of the heavy planetary noble gases in meteoritic material and the nature of phase Q.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"27 1","pages":"555-559"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1992.TB01076.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63664007","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}

引用次数: 9

Halogens in tektites and impact glasses 陨石和撞击玻璃中的卤素

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01079.X

T. Meisel, M. Langenauer, U. Krähenbühl

引用次数: 5

Chemical and isotopic constraints on the formation and crystallization of SA-1, a basaltic Allende plagioclase-olivine inclusion 玄武岩阿连德斜长石-橄榄石包裹体SA-1的形成和结晶的化学和同位素限制

Meteoritics Pub Date : 1992-12-01 DOI: 10.1111/J.1945-5100.1992.TB01075.X

A. Kennedy, I. Hutcheon

{"title":"Chemical and isotopic constraints on the formation and crystallization of SA-1, a basaltic Allende plagioclase-olivine inclusion","authors":"A. Kennedy, I. Hutcheon","doi":"10.1111/J.1945-5100.1992.TB01075.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1992.TB01075.X","url":null,"abstract":"— SA-1, an unusual basaltic plagioclase-olivine inclusion (POI) in Allende, has concentric textural and mineralogic zones, a fine-grained, 100μm outer border and a coarse-grained interior with subophitic texture. Fassaite, diopside and olivine from the exterior border and interior of SA-1 have uniform intrinsic mass fractionation with isotopically heavy Mg (FMg = 3.6 ± 1.8‰/amu). In contrast, spinels from the spinel-rich regions adjacent to the fine-grained border have normal Mg isotopic composition (FMg = 0.1 ± 1.5‰/amu). The cores of large calcic (An90,99) plagioclase have no excess 26Mg, corresponding to 26Mg*/ 27Al < 3.7 × 10−6. The Mg isotopic heterogeneity in SA-1 requires initial cooling rates of spinel-rich regions adjacent to the fine-grained border to be greater than ∼75 °C/hr. In contrast, the subophitic texture of the interior suggests cooling rates of 5–20 °C/ hr. The minerals in SA-1 exhibit a wide range of REE abundances. Lanthanum concentrations vary from 1 × chondritic (ch) in early crystallizing diopside to 100 × ch in late crystallizing fassaite. Nepheline has 18–20 × ch LREE and 11–25 × ch HREE and iron-rich mesostasis is highly enriched in the REE with 270–400 × ch LREE and 230–280 × ch HREE. The complementary REE patterns of clinopyroxene and plagioclase and the enrichment of incompatible trace elements in the mesostasis and late crystallizing phases is consistent with closed system crystallization. The REE data for nepheline and the iron-rich mesostasis indicate these phases are in equilibrium and that nepheline crystallized from a melt. Influx of alkalies, minor Fe and halogens must have occurred during the last stages of crystallization or the inclusion must have been partially molten during Na influx as both anorthite (An99) and nepheline are present in this inclusion. The preservation of isotopic heterogeneity in an inclusion that crystallized from a melt implies that melting was incomplete, allowing for survival of the relict spinels. The major and trace element abundances in SA-1 are inconsistent with formation as a mixture of nebular materials and suggest that SA-1 contains a chemically fractionated component produced by igneous differentiation.","PeriodicalId":81993,"journal":{"name":"Meteoritics","volume":"27 1","pages":"539-554"},"PeriodicalIF":0.0,"publicationDate":"1992-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/J.1945-5100.1992.TB01075.X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63663856","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}

引用次数: 24

Projectile identification in impact melts 碰撞熔体弹丸识别

Meteoritics Pub Date : 1992-09-01 DOI: 10.1111/J.1945-5100.1992.TB00212.X

R. Grieve

引用次数: 1

Cosmic ray interactions in meteorites 宇宙射线在陨石中的相互作用

Meteoritics Pub Date : 1992-09-01 DOI: 10.1111/J.1945-5100.1992.TB00213.X

L. Schultz

引用次数: 1