Hydrous partial melting within the lower oceanic crust
Hydrous partial melting within the lower oceanic crust
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DOI：
10.1111/j.1365-3121.2005.00613.x
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发表时间：
2005-06
期刊：
影响因子：
2.4
通讯作者：
J. Koepke;S. Feig;J. Snow
中科院分区：
文献类型：
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作者：
J. Koepke;S. Feig;J. Snow
我们通过扫描电子显微镜研究了来自现代洋壳和蛇绿岩（东太平洋隆起，大西洋中脊，西南印度洋脊，阿曼蛇绿岩）的60多个大洋辉长岩，并在几乎所有样品中发现了微结构，表明水合部分熔融反应进行。特征共生体包括斜方辉石和角闪石镶边橄榄石和单斜辉石原生晶与强烈富集在钙长石中的新变斜长石密切接触。这与最近在900至1000 °C之间对各种天然辉长岩进行的水饱和熔融实验一致。在天然辉长岩中观察到的显微结构意味着富水流体在韧性状态下在晶界上的传播，导致含水部分熔融。因此，这类热液活动是在深海地壳内以极高的温度（900-1000 °C）进行的，没有裂缝系统，而裂缝系统是目前能够进行热液循环的模型的先决条件。
We studied more than 60 oceanic gabbros from the recent oceanic crust and from ophiolites (East Pacific Rise, Mid‐Atlantic Ridge, Southwest Indian Ridge, Oman ophiolite) by scanning electron microscopy and found in nearly all samples microstructures suggesting that hydrous partial melting reactions proceeded. The characteristic paragenesis consists of orthopyroxene and pargasite rimming olivine and clinopyroxene primocrysts in intimate contact with neoblastic plagioclase strongly enriched in anorthite. This is in agreement with recent water‐saturated melting experiments on a variety of natural gabbros between 900 and 1000 °C. The observed microtextures in the natural gabbros imply the propagation of water‐rich fluids on grain boundaries in a ductile regime causing hydrous partial melting. Thus, this type of hydrothermal activity proceeds within the deep oceanic crust at very high temperatures (900–1000 °C) without a crack system, a prerequisite in current models for enabling hydrothermal circulation.