Boron Isotopic Composition of the Troodos Ophiolite

特罗多斯蛇绿岩的硼同位素组成

• 批准号: 8904443
• 负责人: Arthur Spivack
• 金额: $ 4.25万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1991-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8904443&HistoricalAwards=false
• 关键词: Boron; Isotopic; Composition; Troodos; Ophiolite

Hydrothermal reactions at mid-ocean ridges have a profound influence on the chemical and isotopic composition of seawater and the oceanic crust, involving chemical fluxes of many elements exceeding those from global river discharge. Despite its importance, fundamental aspects of these hydrothermal processes such as the extent of reaction at various temperatures and fluid flow paths are not well constrained. In addition, subduction of the altered crust results in the reinjection of elements derived from the hydrosphere back into the mantle. The bulk chemical transfer rates and the chemical signature of these recycled materials is poorly constrained. Recently it has been demonstrated that there are large boron isotopic fractionations associated with the alteration of the oceanic crust (Spivack and Edmond, 1987). This exchange exerts a primary control on the boron isotopic composition of seawater (~40 per mil enriched in the 11B/10B ratio relative to continental and oceanic igneous rocks|) and imparts a boron isotopic signature to the crust that should be useful as a tracer of subducted volatiles, and diagnostic in evaluating the nature of hydrothermal processes including fluid reaction histories, temperatures of reaction and flow paths. We propose to conduct a boron isotope study of the Troodos ophiolite that is aimed at two goals: 1) establishing a first order boron isotope profile for the altered oceanic crust and 2) developing the background data required for the future exploitation of boron isotopes in the study of hydrothermal systems. To these ends we intend to determine (B) and 11B in whole rocks and vein separates that are mineralogically and chemically well characterized. Alteration temperatures and fluid evolution wii be constrained by oxygen and strontium isotope data.

大洋中脊的热液反应具有深刻的 对海水化学和同位素组成的影响 和海洋地壳，涉及许多元素的化学通量 超过了全球河流排放量。 尽管 这些热液过程的重要性、基本方面 例如在不同温度和流体条件下的反应程度 流动路径没有被很好地约束。 此外， 蚀变的地壳导致元素的重新注入， 从水圈回到地幔 散装化学品 转移率和这些回收的化学签名 材料受到很差的约束。 最近的研究表明， 与蚀变有关的硼同位素分馏 海洋地壳（Spivack和Edmond，1987年）。 本所 对硼同位素组成起主要控制作用， 海水（相对于11B/10 B比值， 陆洋火成岩|）并赋予硼 地壳的同位素特征， 俯冲挥发物的示踪剂，并在评估 包括流体反应在内的热液过程的性质 历史、反应温度和流动路径。 我们建议对特罗多斯进行硼同位素研究 蛇绿岩，旨在两个目标：1）建立一个第一 蚀变洋壳的有序硼同位素剖面; 发展未来所需的背景数据 硼同位素在热液研究中的应用 系统. 为了这些目的，我们打算确定（B）和11 B， 从矿物学上来说， 化学性质良好。 温度变化和 流体演化受氧和锶的制约 同位素数据