Insights into the dynamics of mantle plumes from uranium-series geochemistry
Insights into the dynamics of mantle plumes from uranium-series geochemistry
复制标题
从铀系地球化学中洞察地幔柱的动力学
作者：
B. Bourdon;N. Ribe;A. Stracke;A. Saal;S. Turner
长期以来，夏威夷或冰岛等热点火山代表了地幔热柱的表面表现--地球岩石圈下炎热、浮力的上升区--最近成为争议的焦点。地幔热柱的存在与否，对于我们理解地幔的热力、动力学和成分演化是至关重要的。在这里，我们表明，在热点熔岩中测量的铀系不平衡表明，热点确实与热和浮力上升有关，而较弱(低浮力通量)的热点，如冰岛和亚速尔群岛，其特征是超额温度低于夏威夷等较强的热点。浮力通量和地幔温度之间的这种直接联系是地幔热柱存在的证据。
The long-standing paradigm that hotspot volcanoes such as Hawaii or Iceland represent the surface expression of mantle plumes—hot, buoyant upwelling regions beneath the Earth’s lithosphere—has recently been the focus of controversy. Whether mantle plumes exist or not is pivotal for our understanding of the thermal, dynamic and compositional evolution of the Earth’s mantle. Here we show that uranium-series disequilibria measured in hotspot lavas indicate that hotspots are indeed associated with hot and buoyant upwellings and that weaker (low buoyancy flux) hotspots such as Iceland and the Azores are characterized by lower excess temperatures than stronger hotspots such as Hawaii. This direct link between buoyancy flux and mantle temperature is evidence for the existence of mantle plumes.