Transition from a continental to an oceanic rift: geology and biogeochemistry of the Northern Red Sea

了解从大陆裂谷向海洋裂谷过渡的过程、海底扩张的最早阶段和被动边缘的形成，是地球科学中的一项重大挑战。我们通过一个关于红海裂谷北部地质和生物地球化学的研究项目来应对这一挑战。红海/亚丁湾/东非裂谷系统为研究大陆向海洋的裂谷过渡提供了理想的自然环境。我们建议与意大利科考船乌拉尼亚号进行为期35天的红海北部探险。其目标是研究(A)具有真正“大洋”地壳的最北端(想必是最年轻的)地壳及其向变薄/拉伸的大陆地壳的过渡；(B)横穿红海(Zabargad F.Z)的断裂带，在那里可以观察到大型海洋转型发展的最早阶段，目前向北延伸的红海大洋裂谷似乎对此产生了影响。这项工作将包括多波束、磁测量、重力和地震反射测量、岩石和沉积物采样以及轴向热液喷口周围的水采样。该项目除了处理和解释在海上获得的地球物理数据外，还将涉及一项关于火成岩和热液的地球化学的大型分析方案。这项工作将阐明从大陆裂谷向海洋裂谷过渡的构造和岩石学方面的问题，以及被动边缘的形成，还将解决胚胎海洋中的沉积问题和轴向热液单元中的生物地球化学问题。该项目意味着意大利、法国、德国和英国科学家和机构之间的合作。

Understanding the processes that occur during the transition from a continental to an oceanic rift, the earliest stages of seafloor spreading and the formation of passive margins is a major challenge in the Earth Sciences. We address this challenge with a research project on the geology and biogeochemistry of the northern Red Sea Rift. The Red Sea/Gulf of Aden/East African Rift system provides an ideal natural setting to study the continental to oceanic rift transition. We propose a 35 days expedition to the northern Red Sea with the Italian research vessel Urania. The objectives are to study (a) the northernmost (presumably youngest) throughs with truly "oceanic" crust, and their transition to thinned/stretched continental crust; (b) a fracture zone intersecting the Red Sea (Zabargad F.Z.), where the earliest stages in the development of the large oceanic transforms can be observed, and where the North-propagating Red Sea oceanic rift appears to impact at present. The work will include multibeam, magnetometric, gravimetric and seismic reflection surveys, rock and sediment sampling and water sampling aboxe axial hydrothermal vents. The project, in addition to processing and interpreting the geophysical data obtained at sea, will involve also a large analytical program on the geochemistry of igneous rocks and of hydrothermal fluids. The work will clarify tectonic and petrological aspects of the transition form continental to oceanic rift and of the formation of passive margins, and will also address problems of sedimentation in an embryonic ocean and of biogeochemistry in axial hydrothermal cells. The project implies collaboration among Italian, French, German and British scientists and Institutions.