| 二叠纪末期生物绝灭的地内原因 |
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| THE TERRESTRIAL CAUSE OF ORGANIC EXTINCTION BY THE END OF PERMIAN |
| The evidences from northwestern Hunan Province have verified that the violent voleanie eruptions took places at the time of Permo-Triasic boundary.The iron mierospherules contain 70%-73% of ,Fe, which is nearly sa.me with tlie theoretical value (72.1%) of magnetite. The contents of their Ni, Cr, Co and Ti are much less than that of the meteorites. On the morphology, they can he divided into two sorts, globular and bomb-like ones. It has been inferred that the globulars were formed from melt iron magma in the sea and the bomb-like ones by condensing in the air.Besides a large amount of SO(?) (30%-50%), the volcanic ashes mainly consist of rock-making elements including A12O3 (about 15%), SiO2(about 15%), CaO( about 5% ). K2O(about 2%) and MgO (about 3%). β-quartzes are mostly found in the circumstances of high temperature. The rhombus crackles that the quartzes have show that there was a strong-stress field at that time, which may be brought by the crust-moving and volcanic eruption. The clay rocks around the boundary bed are basically composed of illite-montmorillonite, which are derived from the volcanic materials. Except for Eu, the abundances of REE and boron are very high at the boundary bed.In the above study, the terrestrial factors, i. e. volcanic eruption, paleo-geographic changes etc., have primarily been considered as the external cause of organic extinction by the end of Permian. |
| TIAN Shu-gang.1991.THE TERRESTRIAL CAUSE OF ORGANIC EXTINCTION BY THE END OF PERMIAN[J].Acta Geoscientica Sinica,12(1):167-178. |
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