坦博拉火山大喷发之谜——来自西藏榴辉岩的新启示

西藏松多榴辉岩系典型的古洋壳俯冲产物。通过岩相学观察与热力学计算，证实了西藏古洋壳俯冲时经历了还原反应，俯冲洋壳中Fe3+和S6+等物质被还原成Fe2+和S2-，在俯冲通道内释放出富含CO2和H2S的流体。后者因密度低，从俯冲通道上升至岛弧火山之下的岩浆房中，最终通过火山喷发的方式排放至大气圈。因此认为，深俯冲的印度洋洋壳在地球深部也经历了相似的还原反应，将俯冲洋壳表层的硫酸盐转变为含硫流体，再通过坦博拉火山喷发的方式释放出来。现今洋壳持续俯冲，地球深部的还原反应持续进行，新生成的含硫流体正源源不断地汇聚于岛弧火山之下的岩浆房之中，因此，未来坦博拉式火山爆发是大概率事件。

A great eruption of Tambora mystery: Insights from the Tibetan eclogites

Songduo eclogites within the Tibetan regions are typical products of subduction of ancient oceanic crust, and thus studied in details in this paper. Petrographic observations and thermodynamic calculation confirm that the Songduo eclogites have experienced reduction reaction during the oceanic subdution. Fe3+ and S6+ were reduced to Fe2+ and S2- , respectively, releasing the fluids enriched in CO2 and H2S in the subduction channel. The CO2 and H2S-rich fluids were subsequently transferred into the overlying mantle wedge, and partially released into the atmosphere through the arc volcanoes. Therefore, it is regarded that the currently deep subduction of India oceanic crust experienced similar reduction reactions in deep earth. The sulfur is liberated from the buried surface sulphates into the sulfur-bearing fluids, and released into the atmosphere through the Tambora-like volcanoes. Today, the oceanic subduction and reduction reactions continued, and then, the newly-formed sulfur-bearing fluids continuously sunk in the magma chambers beneath the island arc volcanoes. Therefore, the tambora-like volcanic eruption is a high probability event happening in the near future.