Experimental Determination of Boron Isotopic Fractionation Between Fluid and Silicate Melts

随着硼从硅酸盐熔体中流失到共存的水蒸气中，硼的同位素已被证明是相互分离的。由这项建议资助的工作将测量玄武岩、安山岩和花岗岩组成的熔体和各种流体之间的硼同位素分馏的量。液体将是水或二氧化碳，或它们的混合物。将对一系列温度进行研究，以模拟自然条件。硅酸盐熔体(岩浆)在生成、迁移和冷却(在地表或地表以下)过程中的演化通常涉及(在一个或另一个阶段)流体相的形成。本文提出的硼分馏实验数据将使一种新的稳定同位素体系应用于解开硅酸盐熔体的历史。一种特殊的应用是沿着火山弧形成的岩浆。对这些样品的研究有助于限制俯冲板块对这些熔体源区的不同贡献，并可以澄清岩浆上升过程中的脱气作用。

Hervig0106659The isotopes of boron have been shown to fractionate from one another as boron is lost from a silicate melt into coexisting water vapor. Work funded by this proposal will measure the amount of boron isotope fractionation between melts and a variety of fluids for melts of basaltic, andesitic, and granitic composition. Fluids will be water or carbon dioxide, or mixtures thereof. A range of temperatures will be studied to mimic natural conditions. The evolution of silicate melts (magmas) during generation, transport, and cooling (either at the surface of the earth or below) generally involves (at one stage or another) the formation of a fluid phase. The experimental data on boron fractionation proposed here will allow the application of a new stable isotope system to unraveling the history of silicate melts. A specific application is to magmas formed along volcanic arcs. Study of these samples can help constrain the varying contribution of the subducting slab to the source regions of these melts, and can clarify the effects of degassing during the ascent of magmas.