利用镁和氧同位素追踪俯冲过程中的碳酸盐-硅酸盐相互作用。
Tracing carbonate-silicate interaction during subduction using magnesium and oxygen isotopes.
机构信息
1] State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China [2] Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.
Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.
出版信息
Nat Commun. 2014 Nov 4;5:5328. doi: 10.1038/ncomms6328.
Subduction of carbonates and carbonated eclogites into the mantle plays an important role in transporting carbon into deep Earth. However, to what degree isotopic exchanges occur between carbonate and silicate during subduction remains unclear. Here we report Mg and O isotopic compositions for ultrahigh pressure metamorphic marbles and enclosed carbonated eclogites from China. These marbles include both calcite- and dolomite-rich examples and display similar O but distinct Mg isotopic signatures to their protoliths. Their δ(26)Mg values vary from -2.508 to -0.531‰, and negatively correlate with MgO/CaO ratios, unforeseen in sedimentary carbonates. Carbonated eclogites have extremely heavy δ(18)O (up to +21.1‰) and light δ(26)Mg values (down to -1.928‰ in garnet and -0.980‰ in pyroxene) compared with their protoliths. These unique Mg-O isotopic characteristics reflect differential isotopic exchange between eclogites and carbonates during subduction, making coupled Mg and O isotopic studies potential tools for tracing deep carbon recycling.
碳酸盐和碳酸质榴辉岩俯冲到地幔中，对将碳输送到地球深部起着重要作用。然而，俯冲过程中碳酸盐和硅酸盐之间发生了多大程度的同位素交换仍不清楚。在这里，我们报告了来自中国的超高压变质大理岩和包裹的碳酸盐榴辉岩的镁和氧同位素组成。这些大理岩包括富方解石和富白云石的例子，它们的氧同位素组成与原岩相似，但镁同位素组成不同。它们的 δ(26)Mg 值变化范围为-2.508 至-0.531‰，与 MgO/CaO 比值呈负相关，这在沉积碳酸盐中是没有预料到的。与原岩相比，榴辉岩具有极高的 δ(18)O（高达+21.1‰）和轻的 δ(26)Mg 值（石榴石中低至-1.928‰，辉石中低至-0.980‰）。这些独特的 Mg-O 同位素特征反映了俯冲过程中榴辉岩和碳酸盐之间的差异同位素交换，使耦合的 Mg 和 O 同位素研究成为追踪深部碳循环的潜在工具。
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