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

Gakkel Ridge在全球海洋脊系统中占有独特而重要的地位，因为它是：1)扩张最慢的脊；2)最深的洋脊；3)唯一可以直接采样极地地幔成分的区域；4)在一个被大陆岩石圈紧密包围的独特构造环境中。该脊的走向垂直于扩张方向，导致很少的变换偏移，看起来是在最冷的上地幔之上的脊。这些特征的结合使得大量关于海洋地壳形成的假设得以检验。由于北冰洋的永久冰层使得地球物理数据难以获得，所以Gakkel Ridge的岩石学样本一直未被采集。这片常年覆盖在山脊上的冰层需要两艘破冰船一起工作才能进行一次安全有效的探险。最近的发展使抽样考察成为可能。从潜艇上收集的美国sciex测深、侧扫描和重力数据为制定良好的采样计划提供了必要的背景数据。作为对InterRIDGE计划努力的回应，德国的同事们已经准备好了破冰船Polarstem，准备进行一次为期50天的国际考察，专门研究Gakkel Ridge。美国也将提供一艘破冰船，新的USCG Healy。首席研究人员将沿着Gakkel山脊600公里的地方对玄武岩、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以及地壳和岩石圈厚度的地球物理估计可以结合起来，产生超慢扩张条件下海洋地壳形成的定量模型。与此同时，在进行地下室取样的同时，将使用连接在疏浚（或取心）线和玫瑰花结上的MAPR装置进行一项作为热液调查的侦察。这次调查的目的是为今后在Gakkel Ridge进行热液和相关生物学研究奠定基础。最后，沿Gakkel Ridge取样和数据解释将提供对北冰洋地壳组成及其对北冰洋化学的影响的基本认识。

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.