Quantifying the thermal structure and hydrothermal fluid fluxes in the lower oceanic crust

量化下洋壳的热结构和热液流体通量

• 批准号: RGPIN-2016-04019
• 负责人: Gillis, Kathryn
• 金额: $ 2.91万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=651909
• 关键词: Quantifying; thermal; structure; hydrothermal; fluid

New ocean crust is built along mid-ocean ridges by submarine volcanic activity. Seawater migrates down into this new permeable crust, and is progressively heated as it circulates due the presence of magma at depth. Seawater-derived fluids are chemically modified as they migrate through the crust because they react with the rocks through which they are passing. When these fluids exit the seafloor they are enriched in metals and H2S, leading to the formation of economically important volcanic hosted massive sulfide deposits and providing nutrients for unique biological ecosystems. The chemical exchange between the oceans and the ocean crust acts to modify the composition of both. Within the broader earth system this exchange plays an important role in regulating the composition of the ocean and the inputs into subduction zones, which influences the composition of arc volcanoes and contributes to heterogeneity in the mantle.****A critical gap in our understanding of how the ocean crust is built and hydrothermally altered is related to the plutonic sequence that resides >2 km beneath the seafloor. At and near mid-ocean ridges, the interplay between magmatic intrusion and hydrothermal cooling and alteration controls the thermal and chemical evolution of the plutonic crust. To gain access to these critical rocks we take advantage of “tectonic windows,” where lower crustal exposures were unroofed by tectonic processes, thus bypassing the upper crust entirely. In the Pacific Ocean there are two such tectonic windows, Hess and Pito Deeps, and these are the only locations globally where these critical plutonic rocks have been mapped and sampled. Over the last 20+ years, I have participated in four submersible/ROV sampling cruises and led two international ocean drilling expeditions, leading to a globally unique sample suite for my proposed research. ****Over the next grant cycle, my research group will use this unique sample suite to test competing hypotheses for how crust is built at fast-spreading mid-ocean ridges by magmatic processes and subsequently cooled and altered by hydrothermal flow and reaction. We will also build a quantitative model for the magmatic and hydrothermal controls on the S and chalcophile element budget of the lower crust to expand our understanding of how the lower crust contributes to the global cycling of these elements.**

新海皮是通过海底火山活动沿着海洋中部山脊建造的。海水迁移到这种新的渗透地壳中，并且由于深度存在岩浆而循环时逐渐加热。海水衍生的液体通过外壳迁移而被化学修饰，因为它们与它们经过的岩石反应。当这些流体退出海底时，它们会富集金属和H2，从而形成经济重要的火山托管大量硫化物沉积物，并为独特的生物生态系统提供营养。海洋与海壳之间的化学交换作用，以修饰两者的组成。在更广阔的地球系统中，这种交换在确定海洋的组成和俯冲带的投入方面起着重要作用，这影响了弧火山的组成，并有助于地幔中的异质性。在山脊中部及其附近，岩浆入侵与水热冷却和改变之间的相互作用控制着丘脑外壳的热和化学演化。为了获得这些关键岩石，我们利用“构造窗户”的优势，在构造过程中，较低的地壳暴露是未盖的，因此完全绕过了上皮。太平洋有两个这样的构造窗户，即赫斯和皮托深处，这些是全球唯一在这些关键的岩石岩石被绘制和采样的地方。在过去的20多年中，我参加了四次潜水/ROV抽样巡游，并带领了两次国际海洋钻探探险，为我的拟议研究提供了全球独特的样本套件。 ****在下一个赠款周期中，我的研究小组将使用这个独特的样品套件来测试竞争假设，以通过岩浆过程在快速散布的中山脊上建造地壳，然后通过水热流和反应而冷却和改变。我们还将建立一个定量模型，以对下壳的S和豆科植物元素预算进行岩浆和热液控制，以扩展我们对下层外壳如何有助于这些元素的全球循环的理解。** **