摘要:

Ruhobobo is a new meteorite which fell in Rwanda, Africa, in 1976. We found and analyzed olivine (Fa 23.4), opx (Fs 19.7, Wo 1.4), cpx (Fs 7.5, Wo 44.0), plagioclase (An 11.7, Or 5.6), chromite, “whitlockite”, kamacite, taenite and troilite. Based on these analyses and on microscopic observation, Ruhobobo is an unshocked L6 chondr

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00180.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Two new ordinary chondrites were found about 40 km west of Albuquerque, New Mexico. Correo is an H4 chondrite with distinct chondrules and major olivine (Fo81.4), orthopyroxene (En82.3) and plagioclase (An12). Suwanee Spring is an L5 chondrite with few distinct chondrules and a highly recrystallized matrix. Major minerals are olivine (Fo75.4), orthopyroxene (En77.7) and plagioclase (An9). The metallic Ni‐Fe phases of both meteorites are typical of slowly‐cooled ordinary chondri

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00181.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The Beaver‐Harrison, Utah chondrite (find July 24, 1979), a single, shock‐veined stone of 925 grams, consists of major olivine (Fa25.0), low‐Ca pyroxene (En77.3Fs21.1Wo1.6) and metallic nickel‐iron; minor troilite and plagioclase (Ab82.6An11.1Or6.3), accessory high‐Ca pyroxene (En47.0Fs8.5Wo44.5), chromite (Cm8.7Sp10.6Uv9.4Pc0.6Hc0.7), chlorapatite and whitlockite; and hydrous ferric oxide of terrestrial weathering origin. Mineral compositions indicate L‐group classification, and homogeneity of minerals, highly recrystallized texture and presence of clear plagioclase suggest that the meteorite belongs to petrol

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00182.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A petrographic survey of>1600 chondrules in thin‐sections of 12 different mildly to highly unequilibrated H‐, L‐, and LL‐chondrites, as well as morphological and textural study of 141 whole chondrules separated from 11 of the same chondrites, was used to determine the relative abundances of definable chondrule primary textural types. Percentage abundances of various chondrule types are remarkably similar in all chondrites studied and are ∼ 47–52 porphyritic olivine‐pyroxene (POP), 15–27 porphyritic olivine (PO), 9–11 porphyritic pyroxene (PP), 3–4 barred olivine (BO), 7–9 radial pyroxene (RP), 2–5 granular olivine‐pyroxene (GOP), 3–5 cryptocrystalline (C), and ≤ 1 metallic (M). Neither chondrule size nor shape is strongly correlated with textural type. Compound and cratered chondrules, which are interpreted as products of collisions between plastic chondrules, comprise ∼ 2–28% of nonporphyritic (RP, GOP, C) but only ∼ 2–9% of porphyritic (POP, PO, PP, BO) chondrules, leading to a model‐dependent implication that nonporphyritic chondrules evolved at number densities (chondrules per unit volume of space) which were 102to 104times greater than those which prevailed during porphyritic chondrule formation (total range of ∼ 1 to ∼ 106m−3). Distinctive “rims” of fine‐grained sulfides and/or silicates occur on both porphyritic and nonporphyritic types and appear to post‐date chondrule formation. Apparently, either the same process(es) contributed chondrules to all unequilibrated ordinary chondrites or, if genetically different, the various chondrule types were well mixed before incorporation into chondrites. Melting of pre‐existing mat

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00183.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Large vugs occur in the ordinary chondrite, Farmington. They contain the same phases present in the body of the meteorite, either as vug wall lining or as crystals attached to linings. The morphologies of these phases indicate a history of melting and vapor deposition. These vugs are compared with vugs in the ordinary chondrites, Orvinio and Tadjera, and with published reports of vugs in Rose City and Shaw. It is concluded that although shock events may not cause heating above the liquidus for the body of the meteorite, local pockets of melting and vapor formation do occur due to inhomogenieties in the shock wave pattern. Vugs represent such pockets. Vug formation, as a consequence of shock processing, is widespread among ordinary chondrites and shows no correlation with the average temperature of shock heating, subsequent average cooling rate (as indicated by metallurgical criteria), or blackening of body color.

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00184.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The Loop meteorite was found in 1962 in Gaines County, Texas, at a location very close to that where the Ashmore chondrite was found in 1969. The two specimens were assumed to be fragments of the same meteorite.The Loop meteorite is a type L6 chondrite composed of olivine (Fo75.4Fa24.6), orthopyroxene (En77.6Wo1.5Fs20.9), clinopyroxene (En47.5Wo45.1Fs7.4), plagioclase (Ab84.3Or5.5An10.2), Fe‐Ni metal, troilite, and chromite. Fe‐Ni metal is represented by kamacite (5.8‐6.4 wt % Ni, 0.88‐1.00 wt % Co), taenite (30.0–52.9 wt % Ni, 0.16‐0.34 wt % Co), and plessite (16.8–28.5 wt % Ni, 0.38‐0.54 wt % Co). Native copper occurs as rare inclusions in Fe‐Ni metal. Both chondrules and matrix have similar mineral compositions.The mineral chemistry of the Loop meteorite is quite different from that of the Ashmore, which was classified as an H5 chondrite by Bryan and Kullerud (1975). Therefore, the Ashmore and Loop meteorites are two different chondrites, even though they were recovered from the same ge

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Cilimus is a new Indonesian chondrite. Its mineralogy and chemistry categorize it as a veined, intermediate‐to‐white hypersthene or L‐5 chondrite. Black veins and impact‐produced glasses including maskelynite show evidence that Cilimus has been severely

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

According to its petrography, uniform olivine, Fa23.8, and pyroxene, Fs20.4, a total iron content of 22.9 wt % Fe, 16.4 wt % FeO and an FeO/FeO + MgO ratio of 24.7 mol %, the Tambakwatu is a veined, intermediate hypersthene (Cia) or L6 chondrite.

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00187.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

New chemical analyses of the Krymka and Manych chondrites and a review of data for other low‐iron type 3 chondrites show that the ratio of metallic to total iron varies widely in LL3 chondrites and is an imperfect basis for distinguishing between these meteorites and L3 chondrites. More reliable chemical criteria — total Fe/Mg and Ni/Mg ratios, and Fe‐S relationships — indicate that Krymka, Manych, Carraweena and Bishunpur are LL3 chondrites rather than samples of an iron‐poor subgroup of th

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00188.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Bulk chemical and mineral analyses of five L6 chondrites of shock facies d to f bring the number of L6 falls analyzed by Jarosewich to 20 and enable us: 1) to examine the chemical effects of shock melting in chondrites of the same petrologic type that presumably sample a limited stratigraphic range in their parent body; and 2) to seek depth‐related chemical variations by comparing the compositions of L3 and melt‐free L6 chondrites.The mean Fe/Mg, Si/Mg, S/Mg and Ni/Mg ratios of melt‐free L6 chondrites (shock facies a to c) are virtually identical to those of L3 chondrites, suggesting that L‐group material had the same bulk composition early (L6) and late (L3) in the accretion of the parent body. Wider variations of S/Mg and Ni/Mg in L6 chondrites may signify that L6 material was less well mixed than L3, or that some mobilization of metal and troilite occurred at shock intensities (facies c) too low to melt silicates.L6 chondrites that experienced shock melting of silicates (facies d to f) show wide variations of Fe/Mg, Si/Mg, S/Mg and Ni/Mg. It appears that most of the major element variation in the L‐group is tertiary (shock‐related) rather than primary (nebular, accretionary) or secondary (metamorphic).There is some evidence that L‐group chondrites comprise two subgroups with different Fe/S ratios, but these subgroups are now poorly defined and their significan

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00189.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY