Collaborative Research: Mantle Melting and Crustal Genesis at the Slowest Spreading Rate: A Petrological Investigation of Gakkel Ridge, Arctic Ocean

摘要OPP-99- 11795 MichaelOPP-99- 12162 DickOPP-99 - 12156 GrahamOPP-00- 00389 Langmuir加克尔海脊在全球洋脊系统中占据着独特而重要的地位，因为它是：1）扩张最慢的海脊; 2）最深的海脊; 3）唯一可以直接采样极地地幔成分的区域;（4）处于大陆岩石圈包围的独特构造环境中。 洋脊的走向垂直于扩张方向，这导致很少的转换偏移，它似乎是最冷的上地幔之上的脊。 这些特征的结合使得大量关于洋壳形成的假设得以验证。Gakkel海岭没有进行岩石学取样，主要是由于北冰洋的永久冰盖使得地球物理数据难以获得。 山脊上的常年冰层覆盖需要两艘破冰船协同工作，才能进行安全有效的探险。 最近的事态发展使取样考察成为可能。 从潜艇上收集的美国SCICEX测深、侧扫和重力数据为规划良好的采样方案提供了必要的背景数据。 作为对InterRIDGE计划努力的回应，德国同事已经为一个为期50天的两艘船的国际探险队准备了破冰船Polarstem，专门研究Gakkel Ridge。 美国还将提供一艘破冰船，即新的USCG希利号。 主要调查人员将沿着沿着600公里的加克尔山脊对玄武岩、橄榄岩和相关岩石进行取样。 对这些岩石的详细地球化学研究沿着地壳和岩石圈厚度的地球物理估计可以结合起来，产生在超缓慢扩张条件下洋壳形成的定量模型。 与此同时，在进行基底取样的同时，还将使用连接在挖掘（或取芯）钢丝和钻杆上的MAPR装置进行一次勘查，作为热液调查。 这次调查的目的是为今后沿沿着加克尔海岭进行热液和有关生物研究奠定基础。 最后，沿加克尔海岭沿着取样并对数据进行解释，将使人们对北冰洋地壳的构成及其对北冰洋化学的影响有一个基本的了解。

AbstractOPP-99-11795MichaelOPP-99-12162DickOPP-99-12156GrahamOPP-00-00389LangmuirThe Gakkel Ridge occupies a unique and important place within the global system of ocean ridges because it is: 1) the slowest spreading ridge; 2) the deepest ocean ridge; 3) the sole region where polar mantle compositions can be sampled directly; and 4) in a unique tectonic setting surrounded by continental lithosphere in close proximity. The Ridge's strike is perpendicular to spreading direction which results in very few transform offsets and it appears to be the ridge above the coldest upper mantle. This combination of characteristics permits a large number of hypotheses of ocean crust formation to be tested. The Gakkel Ridge has been unsampled petrologically, largely due the permanent ice cover of the Arctic Ocean that makes geophysical data difficult to obtain. This perennial ice cover over the Ridge will require two icebreakers working in tandem to mount a safe and effective expedition. Recent developments make a sampling expedition possible. The U.S. SCICEX bathymetry, sidescan and gravity data collected from a submarine provide the necessary background data to plan a good sampling program. German colleagues, in response to InterRIDGE planning efforts, have in place ice breaker, Polarstem, for a two-ship, 50-day international expedition dedicated to study of the Gakkel Ridge. The United States will also provide an icebreaker, the new USCG Healy. The Principal Investigators will sample basalts, peridotites, and related rocks along 600 km of the Gakkel Ridge. Detailed geochemical study of these rocks along with geophysical estimates of crustal and lithospheric thickness can be combined to generate quantitative models of oceanic crust formation under ultra-slow spreading conditions. Concurrently, with the basement sampling, a reconnaissance will be carried out as a hydrothermal survey using MAPR devices attached to the dredging (or coring) wire and rosettes. The survey would be designed to lay the groundwork for future hydrothermal and related biological studies along Gakkel Ridge. Finally, sampling along Gakkel Ridge and interpretation of the data will provide a basic understanding of the makeup of Arctic Ocean crust, and its influence on Arctic Ocean chemistry.