ABSENCE OF AN ALUMINOUS PHASE IN THE UPPER PART OF THE EARTHS LOWER MANTLE
ABSENCE OF AN ALUMINOUS PHASE IN THE UPPER PART OF THE EARTHS LOWER MANTLE
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DOI：
10.1038/370131a0
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发表时间：
1994-07-14
期刊：
影响因子：
64.8
通讯作者：
IRIFUNE, T
中科院分区：
文献类型：
--
作者：
IRIFUNE, T
最近的高压实验（1-3）表明，地球的下地幔是由MgSiO 3和CaSiO 3钙钛矿，（Mg，Fe）O镁橄榄石，和少量但重要的铝相，如镁铝榴石或未识别的富铝相。然而，镁铝榴石的稳定性和任何这种铝相的性质是与下地幔矿物学有关的有争议的问题（4-7）。在这里，我报告的相变发生在地幔组合物的压力从23至28 GPa（相当于类似于650-770公里的深度在地幔）的实验研究。结果表明，当压力大于26 GPa（>720 km深度）时，镁铝榴石完全转变为钙钛矿结构。Al 2 O3主要存在于MgSiO 3钙钛矿中，在较高的压力下没有观察到单独的铝相，从而得出地球下地幔的上部仅由两种钙钛矿和镁橄榄石组成的结论。
RECENT high-pressure experiments(1-3) suggest that the Earth's lower mantle is composed of MgSiO3 and CaSiO3 perovskites, (Mg, Fe)O magnesiowustite, and a minor but significant amount of aluminous phases, such as majorite garnet or an unidentified Al-rich phase. The stability of majorite garnet and the nature of any such aluminous phase, however, are controversial issues relevant to the mineralogy of the lower mantle(4-7). Here I report an experimental study of the phase transformations that occur in a pyrolite mantle composition with increasing pressure from 23 to 28 GPa (equivalent to similar to 650-770 km depth in the mantle). The results demonstrate that majorite garnet completely transforms to perovskite structures at pressures above 26 GPa (>720 km depth). Al2O3 is accommodated mainly in MgSiO3 perovskite, and no separate aluminous phase was observed at higher pressures, leading to the conclusion that the upper part of the Earth's lower mantle is composed only of two perovskites and magnesiowustite.