Accession Number : ADA331707

Title :   Mantle Upwelling, Melt Generation, and Magma Transport Beneath Mid-Ocean Ridges

Descriptive Note : Doctoral thesis

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF EARTH ATMOSPHERIC AND PLANETARYSCIENCES

Personal Author(s) : Magde, Laura

PDF Url : ADA331707

Report Date : JUN 1997

Pagination or Media Count : 145

Abstract : This thesis combines surface observations with laboratory studies and geodynamic modeling to study a variety of aspects of the oceanic crustal-production system. Modeling the crustal and mantle contributions to the axial gravity and topography observed at the East Pacific Rise shows that the retained melt fraction in the mantle is small (<3%) and is focused into a narrow column extending up to 70 km beneath the ridge axis. Even when the buoyant component of mantle flow is constrained to be two-dimensional, laboratory studies show that a segmented ridge will drive three-dimensional mantle upwelling. However, using reasonable numerical mantle parameters, it is difficult to induce large-amplitude three-dimensional mantle upwelling at the relatively short wavelength of individual segments (^ 50 km). instead, a simple model of three-dimensional melt migration shows that observed along-axis variations in crustal thickness can be explained by focusing of melt as it upwells through a more two-dimensional mantle flow field. At the Reykjanes Ridge, the melt appears to accumulate in small crustal magma chambers, before erupting in small batches to form numerous overlapping hummocky lava flows and small volcanoes, suggesting that crustal accretion may be a highly discontinous process.

Descriptors :   *EARTH CRUST, *EARTH MANTLE, THESES, TOPOGRAPHY, SEGMENTED, EAST PACIFIC RISE, OCEAN RIDGES, UPWELLING, MAGMA, GEODYNAMICS.

Subject Categories : Geology, Geochemistry and Mineralogy

Distribution Statement : APPROVED FOR PUBLIC RELEASE