Collaborative Research: Hf and Pb Isotope Ratios in Seawater: Indicators of Paleo-Hydrothermal Activity

合作研究：海水中的Hf和Pb同位素比： 古热液活动标志 本研究旨在探讨铪和铅在海水中的行为 和热液系统，目的是利用同位素比率 海洋沉积物中的这些元素作为过去的指标 火山活动的速率海洋Hf和Pb同位素组成 表明这些海洋资源中 元素来自“地幔”来源：年轻的火山岩， 俯冲/造山带和洋中脊。 Hf和Pb是 因为它们在海洋中的停留时间不同，所以是互补的。 铪在海洋中的停留时间与海洋混合相似 时间，使其相对同位素均匀的整个 海洋.新的分析发展使得现在可以测量 Hf的含量和同位素组成在合理范围内， 天然沃茨的体积。 它的海洋化学现在可以更好地 定义了 铅在海水中的停留时间短， 来自大洋中脊的热液通量在局部占主导地位， 同位素组成，从而允许区域差异， 流量待定。 地幔通量变化的模型将是 基于同位素系统学， 和铅对海洋的影响有待明确。 组合 的Pb和Hf与Sr通量模型将有可能确定 过去地幔流向海洋的变化比 仅使用Sr是可能的。 这样就有可能 测试更快的扩张速度，火山活动速度， 和增加的地幔流到海洋是同义词， 与扩展速率变化的其他度量进行比较。这 反过来又将使全球地球化学模型的完善 其他元素的循环，如碳。

Collaborative Research: Hf and Pb Isotope Ratios in Seawater: Indicators of Paleo-Hydrothermal Activity This study is to investigate the behavior of Hf and Pb in seawater and hydrothermal systems with the goal of using the isotope ratios of these elements in marine sediments as indicators of the past rates of volcanism. The isotopic compositions of marine Hf and Pb indicate that large proportions of the oceanic inventory of these elements are derived from 'mantle' sources: young volcanic rocks of subduction/.orogenic zones and mid-ocean ridges. Hf and Pb are complementary because of their different oceanic residence times. Hf has a residence time in the oceans similar to ocean mixing times, making it relatively isotopically homogeneous throughout the oceans. New analytical developments make it now possible to measure the concentration and isotopic composition of Hf in reasonable volumes of natural waters. Its marine chemistry can now be better defined. Pb has a short residence time in seawater, and the hydrothermal flux from mid-ocean ridges locally dominates its isotopic composition, thus allowing regional variations in this flux to be determined. Models of mantle flux variations will be based on isotope systematics that allow the proportion of mantle Hf and Pb to the oceans to be determined unequivocally. Combination of Pb and Hf with Sr flux models will make it possible to define past changes in mantle fluxes to the oceans more accurately than has been possible by using Sr alone. It will then be possible to test the hypothesis that faster spreading rates, volcanism rates, and increased mantle fluxes to the oceans are synonymous by comparison with other measures of spreading rate variations. This in turn will allow a refinement of models of global geochemical cycles of other elements, such as carbon.