Remote Sensing of Hydrogen in Earth’s Mantle
Remote Sensing of Hydrogen in Earth’s Mantle
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DOI：
10.2138/rmg.2006.62.15
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发表时间：
2006
影响因子：
--
通讯作者：
S. Karato
中科院分区：
文献类型：
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作者：
S. Karato
众所周知，地球内部的氢在许多过程中发挥着关键作用。因此，推断氢的分布是我们研究地球动力学和演化的关键步骤。通常，氢的分布是从两种类型的样品在表面推断。首先，岩浆可能含有氢（水），并且在某些条件下，岩浆中的水含量可以在冷却时淬灭。在这些情况下，测量岩浆中的水含量为我们提供了一些关于源区氢（水）含量的限制（如果我们知道氢在岩浆和源岩之间的分配以及熔融程度）。其次，可以测量一些由岩浆搬运的捕虏体的氢含量。它们为捕虏体所在区域的氢含量提供了直接线索。然而，这些直接的岩石学方法有两个主要问题。首先，取样受到火山分布的限制，即使有携带地球内部岩石的火山，火山取样岩石的深度范围也有限（通常<200 km）。其次，不能保证在这些样品上测量的氢含量实际上代表这些样品来自的区域中的氢含量。例如，众所周知，氢很容易扩散，因此溶解在矿物中的氢可以在岩石的运输过程中扩散出来，或者相反，一块岩石可能在上升过程中获得额外的氢。溶解在矿物中的氢原子也可沉淀在矿物中形成流体包裹体或微观含水矿物。总之，从岩石样品中推断氢分布的直接方法具有主要局限性，并且替代方法，即，遥感氢含量从地球物理...
Hydrogen1 in Earth’s interior is known to play a key role in a number of processes. Consequently, inferring the distribution of hydrogen is a critical step in our study of dynamics and evolution of Earth. Usually, hydrogen distribution is inferred from two types of samples at the surface. First, a magma may contain hydrogen (water), and under some conditions the water content of the magma can be quenched upon cooling. In these cases, measurements of the water content of the magma provide us with some constraints on the hydrogen (water) content of the source region (if we know the partitioning of hydrogen between magmas and the source rocks, and the degree of melting). Second, hydrogen content of some xenoliths transported by magma can be measured. They provide a direct clue as to the hydrogen content in a region from which a xenolith has been carried. However, these direct, petrologic approaches have two major problems. Firstly, the sampling is limited by the distribution of volcanoes, and even if there are volcanoes that carry rocks from Earth’s interior, the depth extent that volcanoes sample rocks is limited (usually <200 km). Secondly, there is no guarantee that the hydrogen content that one measures on these samples actually represents the hydrogen content in a region where these samples came from. For example, hydrogen is known to diffuse very easily so hydrogen dissolved in minerals could diffuse out during the transport of a rock, or conversely, a piece of rock may acquire extra hydrogen during its ascent. Also hydrogen atoms dissolved in minerals may precipitate in the mineral to form fluid inclusions or micro-scale hydrous minerals. In summary, the direct method to infer the distribution of hydrogen from rock samples has major limitations, and an alternative approach, i.e., remote sensing hydrogen content from geophysical …