资源环境科技发展态势分析平台

Relationships between extensional tectonics and magmatism are ubiquitous in continental rifts and oceanic spreading centers. Yet few studies document interactions between extensional faults and mantle melts in volcanic arcs. We constrain the crustal structure of the extensional offshore Taupo Volcanic Zone (TVZ) from a marine multichannel and wide-angle seismic experiment. The TVZ crust thins from >26 km to similar to 18-19 km across similar to 50 km in the Bay of Plenty. Elevated P wave velocities in the lower crust indicate mafic additions. Magmatic sills between 4- and 15-km depth lie beneath listric normal faults in a similar to 40-km-wide active rift zone. P wave velocities in the middle and upper crust along the arc front are similar to 0.3-0.5 km/s slower than in the adjacent crust, indicating a possible thermal anomaly imparted by heat from magmatic intrusions. We propose that rifting in the offshore TVZ is partially compensated by intrusions and assisted by thermal weakening of the lithosphere.