Book contents
- Frontmatter
- Contents
- Preface
- Sensitivity of teleseismic body waves to mineral texture and melt in the mantle beneath a mid-ocean ridge
- Evidence for accumulated melt beneath the slow-spreading Mid-Atlantic Ridge
- An analysis of variations in isentropic melt productivity
- A review of melt migration processes in the adiabatically upwelling mantle beneath oceanic spreading ridges
- Rift-plume interaction in the North Atlantic
- The ultrafast East Pacific Rise: instability of the plate boundary and implications for accretionary processes
- Seafloor eruptions and evolution of hydrothermal fluid chemistry
- Controls on the physics and chemistry of seafloor hydrothermal circulation
- Where are the large hydrothermal sulphide deposits in the oceans?
- Sea water entrainment and fluid evolution within the TAG hydrothermal mound: evidence from analyses of anhydrite
- Thermocline penetration by buoyant plumes
- Crustal accretion and the hot vent ecosystem
- Biocatalytic transformations of hydrothermal fluids
- Index
Sensitivity of teleseismic body waves to mineral texture and melt in the mantle beneath a mid-ocean ridge
Published online by Cambridge University Press: 04 August 2010
- Frontmatter
- Contents
- Preface
- Sensitivity of teleseismic body waves to mineral texture and melt in the mantle beneath a mid-ocean ridge
- Evidence for accumulated melt beneath the slow-spreading Mid-Atlantic Ridge
- An analysis of variations in isentropic melt productivity
- A review of melt migration processes in the adiabatically upwelling mantle beneath oceanic spreading ridges
- Rift-plume interaction in the North Atlantic
- The ultrafast East Pacific Rise: instability of the plate boundary and implications for accretionary processes
- Seafloor eruptions and evolution of hydrothermal fluid chemistry
- Controls on the physics and chemistry of seafloor hydrothermal circulation
- Where are the large hydrothermal sulphide deposits in the oceans?
- Sea water entrainment and fluid evolution within the TAG hydrothermal mound: evidence from analyses of anhydrite
- Thermocline penetration by buoyant plumes
- Crustal accretion and the hot vent ecosystem
- Biocatalytic transformations of hydrothermal fluids
- Index
Summary
Seismic energy propagating through the mantle beneath an oceanic spreading centre develops a signature due both to the subaxial deformation field and to the presence of melt in the upwelling zone. Deformation of peridotite during mantle flow results in strong preferred orientation of olivine and significant seismic anisotropy in the upper 100 km of the mantle. Linked numerical models of flow, texture development and seismic velocity structure predict that regions of high anisotropy will characterize the subaxial region, particularly at slow-spreading mid-ocean ridges. In addition to mineral texture effects, the presence of basaltic melt can cause travel-time anomalies, the nature of which depend on the geometry, orientation and concentration of the melt. In order to illustrate the resolution of subaxial structure that future seismic experiments can hope to achieve, we investigate the teleseismic signature of a series of spreading centre models in which the mantle viscosity and melt geometry are varied. The P-wave travel times are not very sensitive to the geometry and orientation of melt inclusions, whether distributed in tubules or thin ellipsoidal inclusions. Travel time delays of 0.1–0.4 s are predicted for the melt distribution models tested. The P-wave effects of mineral texture dominate in the combined melt-plus-texture models. Thus, buoyancy-enhanced upwelling at a slow spreading ridge is characterized by 0.7–1.0 s early P-wave arrival times in a narrow axial region, while the models of plate-drivenonly flow predicts smaller advances (less than 0.5 s) over a broader region. In general S-wave travel times are more sensitive to the melt and show more obvious differences between melt present as tubules as opposed to thin disks, especially if a preferred disk orientation exists.
- Type
- Chapter
- Information
- Mid-Ocean RidgesDynamics of Processes Associated with the Creation of New Oceanic Crust, pp. 1 - 16Publisher: Cambridge University PressPrint publication year: 1999