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Yuji Ichiyama Akira Ishiwatari Kazuto Koizumi Yoshito Ishida Sumiaki Machi 《Island Arc》2007,16(3):493-503
Abstract Permian basalt showing typical spinifex texture with >10 cm-long olivine pseudomorphs was discovered from the Jurassic Tamba accretionary complex in southwest Japan. The spinifex basalt occurs as a river boulder accompanied by many ferropicritic boulders in a Permian chert-greenstone unit. Groundmass of this rock is holocrystalline, suggesting a thick lava or sill for its provenance. Minor kaersutite in the groundmass indicates a hydrous magma. The spinifex basalt, in common with the associated ferropicritic rocks, is characterized by high high field strength element (HFSE) contents (e.g. Nb = 62 ppm and Zr = 254 ppm) and high-HFSE ratios (Al2 O3 /TiO2 = 3.9, Nb/Zr = 0.24 and Zr/Y = 6.4) unlike typical komatiites. The spinifex basalt and ferropicrite might represent the upper fractionated melt and the lower olivine-rich cumulate, respectively, of a single ultramafic sill (or lava) as reported from the early Proterozoic Pechenga Series in Kola Peninsula. Their parental magma might have been produced by hydrous melting of a mantle plume that was dosed with Fe- and HFSE-rich garnet pyroxenite. The spinifex basalt is an evidence for the Pechenga-type ferropicritic volcanism taken place in a Permian oceanic plateau, which accreted to the Asian continental margin as greenstone slices in Jurassic time. 相似文献
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A. López Garcia J. L. Valdés Navarro J. A. López Orti R. López Machi 《Astrophysics and Space Science》1990,171(1-2):289-292
The astrographic plates measuring process applied at the Astronomical Observatory of Valencia has been described.The measure of astrographic plates of our minor planets observation programme has been carried out by means of a binocular microscope with a photometer, held by a personal computer through an interface. The process of measure in each position of the plate holder is automated, once two stars are selected and the sequence of the objects to be measured is defined.The process will be improved in the next future, by the substitution of the searching device (a photometer) by a CCD camera plus a digitizer board.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
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