The Granite Aqueduct and Autometamorphism of Plutons
The Granite Aqueduct and Autometamorphism of Plutons
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DOI：
10.3390/geosciences10040136
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发表时间：
2020-04-01
期刊：
影响因子：
2.7
通讯作者：
Coleman, Drew S.
中科院分区：
文献类型：
--
作者：
Bartley, John M.;Glazner, Allen F.;Coleman, Drew S.
伊恩·卡迈克尔（Ian Carmichael）写道，一条“安山岩水道”将大量的水从俯冲带的岩浆源区输送到地球表面。不同的观察表明，俯冲带岩浆含有5重量%或更多的H2O。大多数水是从结晶侵入体中释放出来的，在接触变质作用和矿床成因中起着中心作用，但它也对深成岩石本身有重要影响。许多岩体是在百万年的时间尺度上自上而下逐渐形成的。早期形成的增量是后来增量的围岩;每个增量结晶时释放的热量和水在离开岩体之前通过较老的增量。水通过多种途径上升。热液脉记录了通过裂缝通道上升的过程。加州约塞米蒂国家公园中的管状通道位于细晶伟晶岩脉中或附近，细晶伟晶岩脉本身是含水晚期岩浆液体的产物。普遍的晶界渗透记录流体介导的subsolidus修改矿物成分和纹理。岩浆水的洪水携带了岩浆总热能的很大一部分，并以比传导快得多的速度传输该能量，从而增强了由增量岩体生长引起的波动的置入后热历史。俯冲带岩浆释放的水不仅对围岩的变质和成矿作用起着重要作用，而且对岩体本身的岩石学和热历史也起着重要作用。
Ian Carmichael wrote of an "andesite aqueduct" that conveys vast amounts of water from the magma source region of a subduction zone to the Earth's surface. Diverse observations indicate that subduction zone magmas contain 5 wt % or more H2O. Most of the water is released from crystallizing intrusions to play a central role in contact metamorphism and the genesis of ore deposits, but it also has important effects on the plutonic rocks themselves. Many plutons were constructed incrementally from the top down over million-year time scales. Early-formed increments are wall rocks to later increments; heat and water released as each increment crystallizes pass through older increments before exiting the pluton. The water ascends via multiple pathways. Hydrothermal veins record ascent via fracture conduits. Pipe-like conduits in Yosemite National Park, California, are located in or near aplite-pegmatite dikes, which themselves are products of hydrous late-stage magmatic liquids. Pervasive grain-boundary infiltration is recorded by fluid-mediated subsolidus modification of mineral compositions and textures. The flood of magmatic water carries a large fraction of the total thermal energy of the magma and transmits that energy much more rapidly than conduction, thus enhancing the fluctuating postemplacement thermal histories that result from incremental pluton growth. The effects of water released by subduction zone magmas are central not only to metamorphism and mineralization of surrounding rocks, but also to the petrology and the thermal history of the plutons themselves.