Crustal construction of a volcanic arc, wide‐angle seismic results from the western Alaska Peninsula

摘要: [1] Results from the 1994 Aleutian Seismic experiment delineate basic oceanic arc crustal architecture, constrain magmatic flux rates and bulk composition, address questions of continental genesis. Here we present results a transect across protocontinental crust westernmost Alaska Peninsula (line A3) compare this structure to purely farther west. Arc is similar along these two transects. Magmatic accretion occurs at top bottom preexisting as 5- 10-km-thick upper carapace low velocity (2-5.8 km s -1 ) volcaniclastics, flows small plutons, mafic lower underplate (∼7.0 variable thickness, for maximum thickness of,25-30 km. Lateral gradients high velocities (>7.5 beneath forearc suggest dominantly vertical above focused melt source underlain by little but rather partially intruded and/or serpentinized mantle. The ratio volume ∼1, total implies ∼67 3 m.y. , more than twice previous estimates global productivity. thinner crust, it lacks massive tonalitic characteristic continents. An interpreted accumulation material midcrustal depths on line A3 has ∼6.4 suggesting an intermediate composition. Accretionary complex terranes consisting accumulations type would thus have compositions crust.