摘要:

Plagioclases in different types of lunar highland rocks (all highly feldspathic) are twinned according to different laws and in different styles. Carlsbad and Carlsbad‐albite twins, presumed to be growth twins, occur mainly in rocks which show igneous texture, and which have not been severely brecciated. These two twin laws appear to be absent from cataclastic rocks, including cataclastic anorthosite, possibly because the original twins were preferentially broken up in cataclasis (the composition plane being a plane of weakness). Pericline and lamellar albite twins, presumed to be deformation twins (except for some albite growth twins) occur in all types of rocks, and obvious deformation features, such as bending of lamellae, are well shown in many cataclastic rocks. Surprisingly, some Carlsbad and Carlsbad‐albite twins are found in rocks with granoblastic texture, which presumably recrystallized in the solid state. This contrasts with previous observations on terrestrial metamorphic rocks, in which such growth twins are scarce or absent. The difference may be due to a higher rate of temperature change in the shock‐heated lunar rocks. Further study of plagioclase twin laws in lunar rocks may assist in deciphering the complicated history of the high

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00074.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The chemical composition of the newly observed fallen chondrites Parambù, 1967, and Marilia, 1971, was determined. Wet chemical methods were used for major elements analyses and the abundances of heavy trace elements from tungsten to uranium were determined by spark source mass spectrometry.The chemical composition confirmed the classification of Marilia as an H‐group chondrite by Avanzo et al. (1973): Parambù was classified as an LL‐group chon

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Quantitative analytical data on 11 elements in chondrite Pampa del Infierno and achondrites Manegaon, Chassigny, Goalpara, Nakhla, Lakangaon and Shergotty are given. To our knowledge, Manegaon and Lakangaon have not been analysed before. Composition, assignment and origin of each meteorite are briefly discussed.

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00077.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Photographic methods for the location of meteorite falls are restricted to hours of darkness and limited by weather conditions, resulting in a low detection rate. The importance of rapid recovery of newly‐fallen meteorites leads to the consideration of seismic methods for the location of impact points. The purpose of this paper is to discuss the degree to which seismic networks can augment the detection of meteorites by conventional means. Factors involved in the generation of seismic waves are considered. The present sophistication of experimental and computational techniques in seismology should enable a microearthquake detection network to locate within 2 km the impacts of larger meteorites. The detection limits are determined by meteorite size and the configuration and instrumentation of the seismograph networ

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00078.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Glass particles have been separated from the Bununu howardite microbreccia and analyzed with the electron microprobe. Preliminary SEM studies of the glass reveal fragments, spherules, teardrops, and rods: particles reminiscent of glasses recovered from the lunar surface. When plotted, individual glass analyses from both the Bununu and Malvern howardites range through the howardite group and extend into the eucrite group with the average glass compositions slightly enriched in CaOand depleted inMgOwhen compared with the bulk chemical analyses. These glasses presumably represent quenched, impact‐melted rocks, or partial melts of the major rock types and/or matrix in Bununu and Malvern.Shock‐produced features which have been observed in known terrestrial and lunar impact breccias are also present in Bununu. Crystal deformation, maskeylenite and glass veining in clasts and glass spherules and shards in the matrix point to impact brecciation as the likely mechanism to form the features observed in Bununu and other howardi

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00079.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SEM photographs were taken of euhedral olivine grains from the Murchison C2 chondrite and several terrestrial and lunar occurrences. In general, the crystal faces of the meteorite grains are rough and uneven, with irregular growth patterns. They are very similar to crystal faces on terrestrial olivine grains that formed by sublimation from a vapor phase. They are very different from the relatively smooth and featureless surfaces of magmatic olivine crystals that precipitated from igneous melts. Qualitatively, the surface morphology of the crystal supports the contention that many euhedral crystals of olivine in C2 meteorites condensed from a gas phase.

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00080.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Based on the results of the study of regmaglyptic relief of individual specimens of the Sighote‐Alin iron meteorite shower, three main stages of fragmentation have been established for a meteoritic body moving through the atmosphere with cosmic velocity. During the first stage, the fragmentation took place at a relatively high cosmic velocity, the fragments being subjected to a major aerodynamic influence. In the second stage, the velocity had decreased due to atmospheric resistance and the fragments were subjected to less drastic aerodynamic action in the regmaglyptic formation. During the third stage, fragments were further fragmented when their cosmic velocities had been almost completely absorbed and the new fracture surfaces were practically untouched by atmospheric influence. As a result of such a multistage fragmentation, the main scatter‐ellipse was over‐lapped by two secondary ellipses, thereby complicating the patterns of scattering of individual specimens of the meteorite shower, which turns out to contain a number of anom

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00081.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY