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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Melting of carbonated pelites at 2.5-5.0 GPa, silicate-carbonatite liquid immiscibility, and potassium-carbon metasomatism of the mantle
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Melting of carbonated pelites at 2.5-5.0 GPa, silicate-carbonatite liquid immiscibility, and potassium-carbon metasomatism of the mantle

机译：2.5-5.0 GPa的碳酸钙质岩融化，硅酸盐-碳酸盐岩液体不混溶以及地幔的钾-碳交代作用

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Melting experiments on a Fe-rich carbonate-saturated petite were performed at 850-1300 degrees C and 2.5-5.0 GPa to define melting relations, melt compositions, and the conditions under which carbonates remain residual. In the selected fertile bulk composition, 30 wt.% potassic granite (2.5 GPa) or phonolite (5.0 GPa) melt is generated at the fluid-absent solidus. The temperature of the latter increases from 900 degrees C at 2.4 GPa to 1070 degrees C at 5.0 GPa. Phengite+quartz/coesite control initial silicate melting and melt productivity through the reaction phengite+quartz/coesite+ clinopyroxene+calcite= silicate melt+kyanite+garnet, which leaves most of the Fe-Mg-calcite in the residue. Na remains compatible in clinopyroxene (D-Na(cpx/melt)=3.1 to 7.3 at the fluid-absent solidus), resulting in silicate melts with K2O/Na2O wt-ratios of 5.8-8.6. Such highly potassic carbonated silicate melts represent ideal metasomatic agents for the source mantle of group II kimberlites. From 3.7 to 5.0 GPa, Fe-Mg-calcite disappears only through the formation of Ca-carbonatite at 1100 degrees C. The experiments provide a possible source for Ca-carbonatites in combination with alkaline granitic to phonolitic melts at temperatures unlikely to be achieved during ongoing subduction. Large scale carbonate transfer to the subarc mantle can thus only be achieved when burying rates slow considerably down or subducted crust becomes incorporated into the mantle. Consequently, it is likely that carbonates will not be extensively mobilized in a typical subarc region, thus extending and confirming earlier results from subsolidus studies (Connolly, J.A.D., 2005. Computation of phase equilibria by linear programming: a tool for geodynamic modelling and its application to subduction zone decarbonation. Earth Planet. Sci. Lett. 236, 524-541.), that >70-80% of the subducted carbonate will bypass the volcanic arc region and get buried to larger depths.
机译：在850-1300摄氏度和2.5-5.0 GPa的富铁碳酸盐饱和小岩上进行熔融实验，以定义熔融关系，熔融成分和碳酸盐残留的条件。在选定的肥沃的块状组成中，在无流体固相线处生成了30 wt。％的钾质花岗岩（2.5 GPa）或方沸石（5.0 GPa）熔体。后者的温度从2.4 GPa时的900摄氏度增加到5.0 GPa时的1070摄氏度。变质铁矿+石英/褐铁矿通过反应变质石+石英/褐铁矿+斜辉石+方解石=硅酸盐熔体+蓝晶石+石榴石来控制硅酸盐的初始熔融和熔体生产率，这将大部分Fe-Mg-方解石留在残留物中。 Na仍可与斜发rox共存（在无流体固相时D-Na（cpx / melt）= 3.1至7.3），硅酸盐熔体的K2O / Na2O重量比为5.8-8.6。这种高钾的碳酸硅酸盐熔体代表了II类金伯利岩的地幔的理想的交代剂。从3.7至5.0 GPa，Fe-Mg方解石仅通过在1100摄氏度下形成Ca碳酸盐而消失。该实验提供了Ca碳酸盐与碱性花岗石到音石质熔体结合的可能来源，而在此温度下不可能达到该温度。持续的俯冲。因此，只有当埋藏速度大大减慢或俯冲的地壳并入地幔中时，才能将大量的碳酸盐转移到弧下地幔中。因此，碳酸盐可能不会在典型的亚弧区域广泛地流动，从而扩展并证实了亚固相线研究的早期结果（Connolly，JAD，2005年。通过线性规划进行相平衡计算：地球动力学建模及其应用工具）到俯冲带脱碳（地球行星，科学，236页，524-541）），> 70-80％的俯冲碳酸盐将绕过火山弧区域并被埋入更深的深度。

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