Boron Isotopic Composition of the Oceanic Crust

海水硼的同位素组成（11B/10 B）较高， 相对于新鲜的地幔衍生岩石富集（~40/mil）。 初步工作表明，这种浓缩主要是 结果大同位素分馏与 海洋地壳的变化。 此外，硼 蚀变地壳的同位素组成主要是 海水硼似乎与地幔不同， 可以由组成上不同的域组成。 作为 结果表明，硼同位素具有很大的潜力 为了阐明一些地球化学和地球物理的 与大洋地壳变化有关的问题。 这些包括俯冲挥发分在岛弧中的作用， 洋岛火山作用，热液流体演化 以及海水/地壳交换的长期变化。 海水/大洋地壳硼同位素交换的研究 具体目标如下：1）确定分布 蚀变地壳中的硼和硼同位素，2） 量化硼的净通量和同位素组成 从海水中提取到海洋地壳中; 3） 开发必要的背景数据， 未来开发硼同位素作为诊断工具， 对热液系统的研究。

The isotopic composition of seawater boron (11B/10B) is highly enriched (~40 per mil) relative to fresh mantle derived rocks. Initial work indicates that this enrichment is primarily the result of large isotopic fractionations associated with the alteration of the oceanic crust. In addition, the boron isotopic composition of the altered crust is dominated by seawater boron that appears to be distinct from the mantle and may be composed of compositionally distinct domains. As a result, it appears that boron isotopes have a great potential for elucidating a number of geochemical and geophysical problems associated with the alteration of the oceanic crust. These include the role of subducted volatiles in island-arc and ocean island volcanism, the evolution of hydrothermal fluids and secular changes in seawater/crust exchange. This study of seawater/oceanic crust boron isotope exchange has the following specific goals: 1) to determine the distribution of boron and boron isotopes within the altered crust, 2) to quantify the net flux and isotopic composition of boron extracted from seawater into the oceanic crust and 3) to develop the essential background data that are required for the future exploitation of boron isotopes as a diagnostic tool in the study of hydrothermal systems.