Unraveling the sequence of serpentinization reactions:: petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209, Site 1274)
Unraveling the sequence of serpentinization reactions:: petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209, Site 1274)
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DOI：
10.1029/2006gl025681
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发表时间：
2006-07-06
影响因子：
5.2
通讯作者：
Humphris, Susan E.
中科院分区：
文献类型：
--
作者：
Bach, Wolfgang;Paulick, Holger;Humphris, Susan E.
[1]详细的结构，矿物化学和岩石物理学研究的结果揭示了在洋中脊逆蛇纹化过程中的流体-岩石反应途径约束不良。均匀亏损的方辉橄榄岩和纯橄榄岩从大西洋中脊在15度N显示静态蛇纹岩化的可变程度。他们揭示了一个简单的反应序列：橄榄石的蛇纹石化和发展的一个典型的网状结构与蛇纹石水镁石网格边缘，然后更换橄榄石网格中心的蛇纹石和水镁石。残留橄榄石上的蛇形网眼边缘缺乏磁铁矿。相反，岩石中完全蛇纹化的区域显示出丰富的磁铁矿。我们建议，低流体通量的蛇纹石化的橄榄石，蛇纹石和铁水镁石的蛇纹石化的后期阶段，在更开放的系统条件下，形成磁铁矿的铁水镁石的故障。对这一系列反应的建模可以解释岩石磁化率和颗粒密度的协变。
[1] The results of detailed textural, mineral chemical, and petrophysical studies shed new light on the poorly constrained fluid-rock reaction pathways during retrograde serpentinization at mid-ocean ridges. Uniformly depleted harzburgites and dunites from the Mid-Atlantic Ridge at 15 degrees N show variable extents of static serpentinization. They reveal a simple sequence of reactions: serpentinization of olivine and development of a typical mesh texture with serpentine-brucite mesh rims, followed by replacement of olivine mesh centers by serpentine and brucite. The serpentine mesh rims on relic olivine are devoid of magnetite. Conversely, domains in the rock that are completely serpentinized show abundant magnetite. We propose that low-fluid-flux serpentinization of olivine to serpentine and ferroan brucite is followed by later stages of serpentinization under more open-system conditions and formation of magnetite by the breakdown of ferroan brucite. Modeling of this sequence of reactions can account for covariations in magnetic susceptibility and grain density of the rocks.