High- and low-temperature alteration of ultramafic oceanic crust: Mineralogy, geochemistry and isotope characteristics of hydrothermal systems at the Mid Atlantic Ridge between 14° and 15°N

热液矿床可能是超镁铁岩-海水反应或玄武岩-海水反应的结果。先前对缓慢扩张脊的研究表明，除了玄武岩外，超基性岩石通常占上部海洋地壳的很大比例。这些超镁铁质岩石部分至完全蛇纹岩化，表明热液流体与上地幔岩性的反应是一个共同的过程。本项目旨在对大西洋中脊15 - 20断裂带正南的Logatchev地区的蛇纹岩超镁铁质热液系统进行取样。与玄武岩热液系统相比，高温和低温超镁铁质系统的存在导致了次生矿物学的显著差异。我们的主要目的是研究块状和粘土样品的矿物学、地球化学和同位素组成，以量化与蛇纹石化有关的化学变化。由此，我们希望更好地界定海水与下地壳/上地幔之间的反应在全球岩石圈-海水交换中的意义。为了实现这些目标，我们将在14°45′n和15°05′n之间使用RV Meteor从15.1进行船基采样。至13.2.2004 （M60/3）。

Hydrothermal deposits may be created as a result of either ultramafic rock-seawater or basalt-seawater reactions. Previous studies of slow-spreading ridges indicate that in addition to basalts ultramafic rocks often make up a significant proportion of the upper oceanic crust. These ultramafic rocks are partially to completely serpentinized, indicating that reaction of hydrohtermal fluids with upper mantle lithologies is a common process. The present projekt aims to sample the serpentinized ultramafic-hosted hydrothermal systems in the Logatchev field region directly south of the Fifteen-twenty Fracture Zone at the Mid-Atlantic Ridge. The occurrence of both high- and low-temperature ultramafic-hosted systems leads to pronounced differences in the secondary mineralogy when compard to basalt-hosted hydrothermal systems. Our main aims are to study the mineralogical, geochemical and isotopic composition of bulk and clay samples to quantify the chemical changes related to serpentinization. From this we hope to better define the significance of reactions between seawater and lower crust/upper mantle in global lithosphere-seawater-exchange. To achieve these aims we will have a ship-based sampling of the Mid Atlantic Ridge between 14°45'N and 15°05'N using the RV Meteor from 15.1. to 13.2.2004 (M60/3).