Accession Number:

ADA573600

Title:

Deep Explosive Volcanism on the Gakkel Ridge and Seismological Constraints on Shallow Recharge at TAG Active Mound

Descriptive Note:

Doctoral thesis

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE JOINT PROGRAM IN APPLIED OCEAN SCIENCE AND ENGINEERING

Personal Author(s):

Report Date:

2013-02-01

Pagination or Media Count:

142.0

Abstract:

Seafloor digital imagery and bathymetric data are used to evaluate the volcanic characteristics of the 85 E segment of the ultraslow spreading Gakkel Ridge 9 mm yrexpn -1. Imagery reveals that ridges and volcanic cones in the axial valley are covered by numerous, small-volume lava flows, including a few flows fresh enough to have potentially erupted during the 1999 seismic swarm at the site. The morphology and distribution of volcaniclastic deposits observed on the seafloor at depths of 3800 m, greater than the critical point for steam generation, are consistent with having formed by explosive discharge of magma and COsub 2 from source vents. Microearthquakes recorded on a 200 m aperture seismometer network deployed on the Trans-Atlantic Geotraverse active mound, a seafloor massive sulfide on the Mid-Atlantic Ridge at 26 N, are used to image subsurface processes at the hydrothermal system. Over nine-months, 32,078 local microearthquakes Msub L -1 with single-phase arrivals cluster on the southwest flank of the deposit at depths 125 m. Microearthquakes characteristics are consistent with reaction-driven cracking driven by anhydrite deposition in the shallow secondary circulation system. Exit fluid temperatures recorded at diffuse vents on the mound during the microearthquake study are used to explore linkages between seismicity and venting.

Subject Categories:

  • Geology, Geochemistry and Mineralogy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE