摘要:

Hydrothermal annealing experiments have been performed on samples of the Sharps meteorite in order to investigate the mechanism responsible for the metamorphism‐related, 105‐fold range in the thermoluminescence (TL) sensitivity in ordinary chondrites. Duplicate 50 mg samples of meteorite were annealed under the following conditions: (a) 168 h at 785°C and 1 kbar; (b) the same time, temperature and pressure, but with 2 wt% water; (c) 174 h at 855°C and 0.77 kbar with 2 wt% water and 2 molal sodium disilicate (NadiSi); (d) the same time, temperature and pressure as the preceding samples, but with 10 wt% H2O and 2 molal NadiSi. Samples annealed under the first three sets of conditions showed little or no change in their TL sensitivities, however the samples annealed with 10 wt% water and 2 molal NadiSi showed a 3 to 10‐fold increase in TL sensitivity, and the temperature of the TL peak was suggestive of feldspar in the high‐temperature form. We suggest that these data are consistent with the TL sensitivity‐metamorphism relationship in ordinary chondrites being due to the formation of the TL phosphor, feldspar, by the crystallization of chon

ISSN:0094-8276    

DOI:10.1029/GL013i009p00969

年代:1986

数据来源: WILEY

摘要:

We explain two common40Ar/39Ar age spectra shapes in biotite. One features a dip in ages at mid‐temperature regions of the spectrum. The other has exactly the opposite characteristic, i.e. a bump upwards in age at the same position. The explanation assumes that the vast majority of biotites consist of two almost completely independent K‐Ar phases. During laboratory step‐heating of irradiated biotite, the argon from these two phases is separated via release over two different temperature ranges. Biotite is therefore a clock with two

ISSN:0094-8276    

DOI:10.1029/GL013i009p00973

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i009p00976

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i009p00979

年代:1986

数据来源: WILEY

摘要:

A search of ion concentration data from the AE‐E, AE‐C, and DE‐2 spacecraft was made to look for evidence of the small‐comet influx into the upper atmosphere that has been suggested by Frank, Sigwarth and Craven (1986a). No simple signature of these events was discovered, though many events should have been encountered in the data examined. Either the cometary flux is more than an order of magnitude less than proposed, or else the ionospheric signature is more subtle than assum

ISSN:0094-8276    

DOI:10.1029/GL013i009p00981

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i009p00985

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i009p00989

年代:1986

数据来源: WILEY