Fluid Inclusions in Halite: Clues to the History of Seawater

拟议的研究计划旨在提高我们对过去600万年地球历史中海水化学演变的理解。为了实现这一目标，我们计划扩展我们的分析数据库，以分析海洋蒸发岩中盐岩盐（NaCl）中流体包裹体中盐水的化学成分。这些卤水中有许多是盐沉淀的溶液的样品。在海洋蒸发岩中，这些盐水大部分或全部来自海水；因此，它们的组成反映了盐沉淀时海水的组成。在许多情况下，这些盐水从海水中演化出来的过程是如此复杂，以至于从包裹体流体的组成中几乎无法获得关于母海水组成的信息。幸运的是，在一些海洋蒸发岩中，盐水的演变非常简单，因此，开始时海水的大部分化学成分可以被重建。迄今为止积累的数据表明，在过去600年中，海水的成分出奇地保守。目前这些数据仍然是零碎的。我们建议将其扩展到相当大的范围，并建立显生宙海水组成的相当完整的记录。

The proposed program of research is designed to improve our understanding of the chemical evolution of seawater during the last 600 m.y. of Earth history. To accomplish this, we plan to extend our analytical data base for the chemical composition of brines in fluid inclusions trapped in halite (NaCl) in marine evaporites. Many of these brines are samples of the solutions from which the salt precipitated. In marine evaporites these brines are largely or entirely derived from seawater; their composition therefore reflects the composition of seawater at the time of salt precipitation. In many instances the evolution of these brines from seawater has been so complicated, that little information regarding the composition of the parent seawater can be gained from the composition of the inclusion fluids. Fortunately, the evolution of the brines in some marine evaporites has been sufficiently simple, so that much of the chemistry of the starting seawater can be reconstructed. The data accumulated to date indicate that the composition of seawater has been surprisingly conservative during the past 600 m.y. At present these data are still fragmentary. We propose to extend them considerably, and to construct a reasonably complete record of the composition of seawater during the Phanerozoic Eon.