Petrogenetic Processes near OSCs and Transforms Inferred from the Chemistry of Seamount Lavas: Constraints on the Deep Thermal Structure and Processes beneath EPR Offsets

热地幔物质上涌在一个广泛的区域下活动 像东太平洋海隆（EPR）这样的山脊融化， 岩浆供给狭窄的轴向新火山带， 近轴海山 了解热结构、地幔 流动模式、熔体生成位置、管道和储存 宽亚轴带内的几何形状对于 了解活动海脊的岩浆供应和构造过程 波峰 这项研究将补充正在进行的EPR轴向研究 通过整合新海山岩石学的结果， 研究，以便构建一个更全面， 的热结构和岩石成因下广泛的 亚轴带 EPR轴附近的活动海山位于 沿轴深度最小值和偏移（OSC和转换）。 的 前一种类型已经得到了很好的研究，这些研究提供了一些 轴流与海山相互作用的可检验假设 成岩作用 相比之下，偏移的海山 没有系统的研究。 这项研究提出了一个30天的 调查和取样25座海山（87 疏浚）在各种构造环境中的OSC和转换， 完成对样品的岩石学/地球化学研究。 本研究的目的是化学表征 并利用这些数据来测试半个 关于海山在偏移处的起源， 地幔流动和熔融过程，以及岩浆供应几何学。 EPR及其周围的地下深处。 岩石成因 对海山熔岩的解释将与 对同生演化的解释，EPR轴 岩浆，以获得更广泛的了解岩石成因构造 在EPR之下发生的过程。 这项研究的目的是 以最小化空间/时间相关性的潜在问题。

Hot mantle material upwelling in a broad zone beneath active ridge crests like the East Pacific Rise (EPR) melts to provide magmas feeding the narrow axial neovolcanic zone plus active near-axis seamounts. Knowledge of the thermal structure, mantle flow patterns, melt-generation sites, and conduit and storage geometry within the broad subaxial zone is important for understanding magma supply and tectonic processes at active ridge crests. This study will complement on-going studies of EPR axial processes by integrating the results of new seamount petrologic study in order to construct a fuller, more comprehensive picture of the thermal structure and petrogenesis beneath the broad subaxial zone. Active seamounts near the EPR axis occur at along-axis depth minima and offsets (OSCs and transforms). The former type are well-studied and these studies provide several testable hypotheses for the interaction of axial and seamount petrogenetic processes. In contrast, seamounts at offsets have received no systematic study. Proposed in this study is a 30-day seabeam/dredging program to survey and sample 25 seamounts (87 dredges) in various tectonic settings at OSCs and transforms and to complete a petrologic/geochemical study of the samples. The goals of this study are to chemically characterize the lavas of seamounts at offsets and to use that data to test half a dozen discrete hypotheses for the origin of seamounts at offsets, mantle flow and melting processes, and magma supply geometry at depths beneath the EPR and its surroundings. The petrogenetic interpretation of the seamount lavas will be combined with interpretations for the origin and evolution of coeval, EPR axial magmas to gain a broader understanding of petrogenetic-tectonic processes occurring beneath the EPR. The study has been designed to minimize potential problems of spatial/temporal correlation.