Collaborative Research: Testing Models of Magmatic and Hydrothermal Segmentation: A 3-D Seismic Tomography Experiment at the Endeavour Ridge

在控制山脊过程的分段和强度方面，相互竞争的模型在地幔和地壳岩浆分段的规模、相对于火山段的热液喷发分布以及在岩浆和热液系统之间输送能量的热边界层的性质上存在分歧。最近在Juan de Fuca海脊奋进段下方发现的轴向岩浆室(AMC)反射体，以及海底深度、海脊形态和热液喷发沿轴线的系统变化，为检验相互矛盾的假说提供了理想的目标。该项目的科学目标是：(1)确定奋进山脊岩浆-热液系统的分段和强度是与岩浆供应有关，还是与地幔与地壳之间的岩浆管道有关，以及(2)约束奋进热液系统下面的热和岩浆结构，以了解能量转移的模式。活动震源地震层析成像实验使用三分量海底地震仪阵列，将沿着奋进海脊80公里长的部分成像地壳和最顶部地幔的三维地震结构。该实验将成像四个目标：(1)轴向高度(0至900 KYR)25公里范围内的地壳厚度变化；(2)扩张轴下方最高地幔的二维(即地图视图)结构；(3)地壳岩浆系统的三维结构；(4)奋进喷发场下方详细的三维浅层地壳热结构。成像结果将确定岩浆供应的近代历史、从地幔到地壳的熔体输送模式以及海底岩浆和热液系统的结构和分段。这些测量对于检验关于什么控制山脊岩浆和热液过程的强度的相互竞争的假设至关重要。

Competing models for controls on the segmentation and intensity of ridge crest processes are at odds on the scale of mantle and crustal magmatic segmentation, the distribution of hydrothermal venting with respect to a volcanic segment and the properties of the thermal boundary layer that transports energy between the magmatic and hydrothermal systems. The recent discovery of an axial magma chamber (AMC) reflector beneath the Endeavour segment of the Juan de Fuca ridge, as well as systematic along axis changes in seafloor depth, ridge crest morphology and hydrothermal venting provide an ideal target for testing conflicting hypotheses. The scientific objectives of this project are to: (1) Determine if the segmentation and intensity of the magma-hydrothermal systems at the Endeavour ridge are related to magma supply or to the magma plumbing between the mantle and crust, and (2) Constrain the thermal and magmatic structure underlying the Endeavour hydrothermal system in order to understand the patterns of energy transfer. An active source seismic tomography experiment, using an array of 64 three-component ocean-bottom seismometers, will image the 3-D seismic structure of the crust and topmost mantle along an 80-km-long section of the Endeavour ridge. The experiment will image four targets: (1) crustal thickness variations within 25 km of the axial high (0 to 900 kyr); (2) the 2-D (i.e., map view) structure of the uppermost mantle beneath the spreading axis; (3) the 3-D structure of the crustal magmatic system and (4) the detailed 3-D, shallow crustal thermal structure beneath the Endeavour vent field. The results of imaging will define the recent history of magma supply, the pattern of melt delivery from the mantle to the crust and the structure and segmentation of the subseafloor magmatic and hydrothermal systems. These measurements are essential to testing critically competing hypotheses for what regulates the intensity of ridge crest magmatic and hydrothermal processes.