关于现代浅海型海底热液活动的研究进展

Introduction to Modern Shallow-submarine Hydrothermal Activity

浅海型海底热液活动一般出现于海底火山顶部或者翼部,其所处的特殊地理位置是深海热液活动和陆上热泉的过渡地形。研究浅海型海底热液活动使我们更全面了解地球内部热量的缓慢散发形式。目前浅海型热液活动研究多侧重于流体、伴生气体、沉积物等方面:对于流体研究主要通过流体元素特征探讨流体源,虽然浅海热液活动流体在海底喷出,但流体主要组分有时是海水,有时是陆上大气水—海水只是作为少部分加入其中。对于伴生气体的研究表明:热液喷出时伴生气体组分多是火山气来源,火山气的加入导致热液流体酸性增强,使热液流体较容易淅沥出围岩中的元素,因此尽管浅海型热液流体流经路程短,但是流体中依然包含了较多物质,从而在海底表面沉淀沉积物,甚至可以形成烟囱体,由此可见浅海型热液活动与火山活动紧密相关。对于沉积物的研究显示浅海热液活动产生的沉积物组分简单,也有像深海热液活动中烟囱状沉积体的形成。沉积物对周围水域中元素浓度起到积极影响,如Fe、As含量等,这是热液流体与海水相互作用的结果。现代浅海型热液活动往往出现于近海岸处,距离人类生活较深海热液活动更加接近,所以浅海热液活动对周围环境影响的深度及广度应该成为下一步研究重点。

The shallow-submarine hydrothermal activities generally appear in the oceanic volcano crowns or flanks. The submerged flanks of island arc volcanoes provide an exceptional opportunity to study the essential differences and similarities between subaerial and submarine venting and the transition from one to the other. Studying the shallow-submarine hydrothermal activities makes us understand comprehensively how the heat of the Earth＇s interior diffuses slowly. At present the fluid, associated gas and deposits of shallow-submarine hydrothermal activities are the focuses of current researches. The fluid source is discussed by the fluid＇s elemental characteristics. The fluid of shallow-submarine hydrothermal activities on the seafloor could be either sea water or meteoric water. The study of shallow-submarine hydrothermal activities associated gases indicates that they are volcanic in origin and strengthen the acidity of hydrothermal fluid. The acidic fluid dissolves elements from the wall rock easily. Therefore, although the distance shallow-submarine hydrothermal fluid traveled is short, the fluid could contain high con- centration of dissolved matter. Thus, precipitates may be formed on the seabed surface, even chimney may occur. It suggests that the shallow-submarine hydrothermal activity has a close relationship with volcanic activity. The component of the deposit produced by the shallow-submarine hydrothermal activities is simple. The deposit influences positively the elemental concentration within the ambient waters, e.g. Fe, As, which is a result of the hydrothermal fluid and sea water mixing. Modern shallow-submarine seafloor hydrothermal activity generally occurs near shore, close to the area of human activities. The profundity and span of effect of shallow-submarine seafloor hydrothermal activities on the environment should be a major research focus.