Hydration Crystallization Reactions between Anhydrous Minerals and Hydrous Melt to Yield Amphibole and Biotite in Igneous Rocks: Description and Implications
Hydration Crystallization Reactions between Anhydrous Minerals and Hydrous Melt to Yield Amphibole and Biotite in Igneous Rocks: Description and Implications
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DOI：
10.1086/422670
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
J. S. Beard;P. C. Ragland;T. Rushmer
中科院分区：
文献类型：
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作者：
J. S. Beard;P. C. Ragland;T. Rushmer
某些含水岩浆的结晶作用可以部分地通过含水熔体与无水矿物之间的反应来模拟，从而产生含水矿物。这些反应（本文称为“水合结晶”）是平衡的、不一致的、无蒸汽的结晶反应，是脱水-熔融反应的逆反应。水合结晶的主要岩相学证据是部分反应和再吸收的辉石和氧化物矿物，其上覆盖着角闪石和黑云母。水化结晶作用可以将轻度含水（高达102wt%H2O）岩浆的含水量缓冲在低于饱和度的值，可以想象到结晶作用的完成，因此与“所有岩浆都达到水饱和”的格言相矛盾。即使这种缓冲作用在整个结晶过程中不持续，发生这些不一致反应的岩浆的水含量也会比没有发生这些不一致反应的岩浆的水含量低。无论它们是否排除蒸汽饱和，平衡水化结晶反应控制了许多含水岩体的晚期岩浆演化。
The crystallization of some hydrous magmas can be modeled, in part, via the reaction between hydrous melt and anhydrous minerals to yield hydrous minerals. The reactions (herein termed “hydration crystallization”) are equilibrium, incongruent, vapor‐absent crystallization reactions, the reverse of dehydration‐melting reactions. The principal petrographic evidence for hydration crystallization is partially reacted and resorbed pyroxene and oxide minerals mantled by amphibole and biotite. Hydration crystallization can buffer the water content of mildly hydrous (up to ∼2 wt% H2O) magmas at values below saturation, conceivably to the completion of crystallization, thus contradicting the maxim that “all magmas go to water saturation.” Even if the buffering effect does not persist throughout the crystallization history, water contents of magmas in which these incongruent reactions occur will remain lower than magmas in which they have not. Whether they preclude vapor saturation, equilibrium hydration crystallization reactions control the late magmatic evolution of many hydrous plutons.