Effect of Water on Olivine Stability in Tholeiites and the Production of Silica-Saturated Magmas in the Island-Arc Environment
Effect of Water on Olivine Stability in Tholeiites and the Production of Silica-Saturated Magmas in the Island-Arc Environment
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DOI：
10.1086/627871
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发表时间：
1973-05
期刊：
影响因子：
--
通讯作者：
I. Nicholls;A. .. Ringwood
中科院分区：
文献类型：
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作者：
I. Nicholls;A. .. Ringwood
橄榄石拉斑玄武岩和SiO2饱和拉斑玄武岩的实验结果表明，在溶解度极限范围内加入水可显著提高橄榄石稳定的最大压力。在上地幔深处，苦橄质岩浆在干燥条件下起源，橄榄岩的水饱和部分熔融可以产生$$SiO2 $$-饱和拉斑玄武岩液体。这种含水量大于5%的岩浆除非在很浅的深度从残余地幔中分离出来，否则在上升到地球表面的过程中至少会破碎橄榄石，从而产生石英拉斑玄武岩或玄武安山岩。岛弧拉斑玄武岩系列的玄武岩和玄武安山岩的地球化学是兼容的起源涉及橄榄石分馏从原始的贫橄榄拉斑玄武岩岩浆。这些岩浆从橄榄岩地幔中开始部分熔融和分离的位置将受到下行洋壳岩石圈脱水所产生的水的控制。
Experimental crystallization of olivine tholeiite and $$SiO_{2}$$-saturated tholeiite compositions has demonstrated that addition of water up to the limit of solubility markedly increases the maximum pressure of olivine stability. At depths within the upper mantle from which picritic magmas originate under dry conditions, water-saturated partial melting of peridotite can produce $$SiO_{2}$$-saturated tholeiite liquids. Unless they segregate from residual mantle at very shallow depths, magmas of this type with water contents >5% must fractionate at least olivine during ascent to the earth's surface, thus yielding quartz tholeiites or basaltic andesites. The geochemistry of basalts and basaltic andesites of the island-arc tholeiitic series is compatible with origin involving olivine fractionation from primitive olivine-poor tholeiite magmas. The sites of initiation of partial melting and segregation of these magmas from peridotite mantle will be controlled by availability of water from dehydration of downgoing oceanic lithosphere.