Establishing a reference profile for fast-spreading oceanic crust: Petrology and geochemistry of the "Wadi Gideah" cross section in the Oman ophiolite

覆盖地球大部分的快速扩张的海洋地壳被认为是层状的和均匀的。尽管船舶研究付出了巨大的努力，但基于自然样品的完整的现代化学/岩石学剖面仍然缺失。为了通过快速扩张的海洋地壳建立参考剖面，本研究对阿曼白垩纪蛇绿岩地壳剖面进行了地球化学/岩石学调查，该剖面被认为是陆地上快速扩张的海洋岩石圈的最佳例子。为此，在Wadi Tayin地块的Wadi Gideah取样了一个完整的剖面（辉长岩、岩脉、玄武岩），代表了大约6.5公里的快速扩张的海洋地壳。在本项目中，我们重点进行了(1)岩石学和物相分析研究；(2)体积分析表征；(3)硫循环定量分析；(4)利用Sr和O同位素表征热液蚀变随深度的演化。这一剖面在地壳成分的完整性以及将获得的分析数据的质量和一致性方面将是独一无二的。因此，它非常适合促进我们对地壳吸积过程和快速扩张海洋地壳初级和次级地球化学旋回演化的认识。最后，阿曼参考剖面为综合海洋钻探计划（IODP）在1256站点（赤道太平洋）的钻探提供了科学支持，该站点目前的孔将于2011年深入辉长岩地壳。

Fast-spreading oceanic crust covering a large part of our planet is regarded as layered and homogenous. In spite of tremendous efforts by ship-based research, a complete modern chemical/petrological profile based on natural samples is still missing. In order to establish a reference profile through fast-spreading oceanic crust, the present study aims to perform a geochemical/petrological investigation of a crustal section in the Cretaceous ophiolite of Oman, which is regarded as the best example of fast-spreading oceanic lithosphere on land. For this, a complete section (gabbros, dikes, basalts) representative of approximately 6.5 km of fast-spreading oceanic crust was sampled at the Wadi Gideah in the Wadi Tayin massif. Within this project we focus on (1) petrography and phase analytical studies, (2) bulk-analytical characterization, (3) quantifying sulfur cycling and (4) characterizing the evolution of hydrothermal alteration with depth by using Sr and O isotopes. This profile will be unique in terms of completeness of the crustal components and quality and coherence of analytical data to be obtained. Hence, it is well-suited for advancing our understanding of crustal accretion processes and the evolution of primary and secondary geochemical cycles at fast-spreading oceanic crust. Finally, the Oman reference profile provide scientific support for the drilling of the Integrated Ocean Drilling Program (IODP) at Site 1256 (equatorial Pacific) where the deepening of the present hole down into the gabbro crust is scheduled for 2011.