An Earth–Moon silicon isotope model to track silicic magma origins
An Earth–Moon silicon isotope model to track silicic magma origins
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DOI：
10.1016/j.gca.2015.07.005
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发表时间：
2015-10
影响因子：
5
通讯作者：
F. Poitrasson;T. Zambardi
中科院分区：
文献类型：
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作者：
F. Poitrasson;T. Zambardi
陆地和月球火成岩的对比表明，从玄武岩到花岗岩和斜长岩，Si同位素组成随着岩石sio2浓度和（或）构造硅酸盐含量的变化，虽然重同位素显著富集，但略有变化。这被解释为全球火成岩分异过程的结果，导致岩石中构造硅酸盐的数量增加。这种熔体聚合程度的增加与硅同位素组成的增加之间的关系在月球岩石中尤为明显。然而，陆地的趋势则更为分散。考虑到硅同位素对水岩相互作用的敏感性，更不稳定的陆地趋势很可能揭示了月球上没有发生的水的参与。因此，硅同位素似乎反映了过铝浅花岗岩来源中存在粘土矿物等低温水岩相互作用产物。相反，一些安山岩的重硅同位素组成可能反映了俯冲带和（或）俯冲前海洋地壳与重同位素海水相互作用的流体输入。
A comparison between terrestrial and lunar igneous rocks reveals that Si isotope compositions become slightly, though significantly enriched in heavy isotopes from basalts to granites and anorthosites as a function of the rock SiO2concentration and/or tectosilicate content. This is interpreted as the result of a global igneous differentiation process that leads to an increased amount of tectosilicates in the rocks. This relationship of increasing degree of melt polymerization with increasingly heavy silicon isotope composition is particularly apparent in lunar rocks. The terrestrial trend, however, is more scattered. Given the sensitivity of Si isotopes to water–rock interactions, it is likely that the more erratic terrestrial trend reveals the involvement of water that does not occur on the Moon. Hence, Si isotopes appear to reflect the occurrence of low temperature water–rock interaction products, like clay minerals, in the source of peraluminous leucogranites. Conversely, the heavy silicon isotope composition of some andesites possibly trace the input of fluids involved in subduction zones and/or interaction of the oceanic crust with isotopically heavy seawater before subduction.