ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The Grier(b), New Mexico meteorite, a single mass of 929.4 grams, was found in 1969. This brecciated chondrite can be classified as an L‐group from the bulk chemical analysis, ∼ 8 wt % metal with an estimated total iron content of 25 wt %, and the constant olivine (Fa25.5) and orthopyroxene (Fs23) compositions. The main portion of the meteorite fits the criteria for an L5 (grey to intermediate hypersthene) chondrite. A conspicuous, large (several cm3) dense fragment, texturally an L6–7 chondrite, contains practically no metal or chondrules. However, there is little variation in the bulk silicate and individual phase compositions between the fragment and the matrix. In spite of this, it seems unlikely that the fragment was created in situ because metal and sulfide are not found in the fragment‐matrix contact zone; thus the formation of olivines and pyroxenes in both parts, as well as the “draining” of metal from the fragment, occurred prior to accretion with little, if any, subsequent thermal m

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Specimens from the center and the outer surface of Abee exhibit identical microstructures within their metal phase—platelets of an iron carbide. Thus the entire body must have cooled at a nearly uniform rate. The density, heat capacity, and thermal conductivity have been measured and used in a theoretical heat flow analysis. From these calculations and observations it is concluded that Abee cooled from 700 °C to 200 °C in about two ho

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

White, pale‐yellow and brown deposits occur on surfaces of fragments of the Norton County enstatite achondrite. X‐ray powder analysis of these materials indicates that they consist of several calcium‐bearing minerals: portlandite [Ca(OH)2], vaterite (CaCO3, hexagonal), calcite (CaCO3, trigonal) and bassanite (CaSO4‐1/2 H2O). We suggest that these minerals formed by weathering of oldhamite (CaS), which we found to occur in Norton County. The occurrence of portlandite suggests that at low temperatures and in the terrestrial environment, hydrolysis of oldhamite is the most important first step in the weathering sequence. Subsequent carbonation of portlandite is thought to produce vaterite, and vaterite in turn might transform into calcite. Thus, we suggest a weathering sequence in the terrestrial environment of oldhamiteportlanditevateritecalcite. The mineral bassanite is clearly also a terrestrial weathering product but its precise mode of origïn is somewhat uncertain: in the system CaSO4‐H2O, bassanite forms from gypsum at about 100 °C (an unlikely high T for the weathering environment of Nor

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00539.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The Innisfree meteorite was the third fall for which accurate orbital data were secured from a camera network. Nine fragments were found within three months of the fall with a total mass of 4.58 kg. The ellipse of fall is unusually small because of the steep path in the atmosphere. The photograph from the Vegreville station reveals six trails below 26 km and these are correlated with the six main fragments, all with masses in excess of 300 g. A photometric study indicates that Innisfree had a peak absolute magnitude Mpan= −12.1 at a height of 36 km. The recovered meteorites provide known masses for the late stages of the photographic trails which, combined with dynamical data, allow luminous efficiencies to be derived with unusual confidence. Late in the flight where shock wave effects dominate ablation, luminous efficiencies vary from 3 × 10−5to 5 × 10−2for velocities between 3 and 10 km s−1and masses from 0.3 to 2.0 kg. The mean luminous efficiency for the entire flight is estimated between 4 × 10−2

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00540.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Two irghizites, three zhamanshinites and one sample each of lechatelierite, vein‐quartz, Palaeogene silty clay and Palaeogene quartzite were analyzed using neutron activation analysis. A silicate analysis of the Palaeogene silty clay has also been performed, as well as an incomplete analysis of the Palaeogene quartzite from the Zhamanshin impact crater. The REE abundances of irghizites resemble those of sedimentary rocks. On the Köhler and Raaz diagram all projection points of irghizites lie inside the field of tektites, and indicate that they were derived from terrestrial sedimentary rocks. The Zhamanshin impact glasses may be divided into three types: (a) silica‐rich zhamanshinites (x̄SiO2= 73.89%), (b) zhamanshinites (x̄SiO2= 54.34%), and (c) silica‐poor zhamanshinites (x̄SiO2= 39.64%). These are also characterized by varying proportions of alkalis and Al. Mn and Ca contents. Irghizites and silica‐rich zhamanshinites display a depletion of Eu. Zhamanshinites do not show this Eu depletion. Partial melting is assumed to be an important process in the origin of zha

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00541.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A meteorite which fell at Lahrauli, district Basti, U.P. (India) in 1955 has been examined for mineralogical, chemical and cosmogenic characteristics. It contains pigeonite Wo7.7Fs18(with Cr2O3= 1.2% and Al2O3= 0.4%), olivine Fo79(with CaO = 0.3% and Cr2O3= 0.7%) and diamond. The basic similarities of this meteorite to Goalpara, Dyalpur, Havero and Novo Urei indicate that it is a ureilite. Cosmic ray tracks have been measured in the olivine and pyroxene grains. Track density of 2.3 × 106per cm2in olivines and VVH/VH ratio of 10−3is similar to that observed in other meteorit

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00542.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00543.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00545.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1981.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY