Basalts subduction zones

Basalts (subduction zone, Alaid Volcano, Kamchatka, Russia, 2... 

Basalts (subduction zone, Indian Heaven, Washington, USA, 2 samples)... 

Basalts (subduction zone, Klychevskoi Volcano, Kamchatka, Russia) Basalts (subduction zone, Simcoe, Washington, USA, 2 samples) Basalts (subduction zone, Tolbachik Volcano, Kamchatka, Russia) Basalts to basaltic andesites (subduction zone, Central America, 19 samples)... 

These different sites of hydrothermal and ore-forming activity may have resulted from the mode of subduction of the Pacific Plate. Mariana-type subduction (characterized by a steep angle of subduction and back-arc basin formation Uyeda and Kanamori, 1979) during middle Miocene caused WNW-ESE extension, submarine hydrothermal activity, thick accumulation of bimodal (basaltic and dacitic) volcanic activity (Green tuff) and Kuroko-type formation (Shikazono and Shimizu, 1993). Plio-Pleistocene Chilean-type subduction (shallow-dipping subduction zone, E-W compression Uyeda and Kanamori, 1979) and oblique subduction of the Pacific Plate beneath the North American Plate led to uplift and expansion of land area, subaerial hydrothermal activity accompanied by meteoric water circulation, subaerial andesitic volcanic activity and formation of vein-type deposits. 

Poll S, Schmidt MW (1995) H2O transport and release in subduction zones experimental constraints on basaltic and andesitic systems. J Geophys Res 100 22,299-22,314 Pyle DM, Ivanovich M, Sparks RSJ (1988) Magma-cumulate mixing identified by U-Th disequilibrium dating. Nature 331 157-159... 

The first studies of Li isotopes in subduction zones concentrated on young convergent margin lavas. Moriguti and Nakamura (1998b) reported correlated Li isotope and fluid-mobile element (notably boron) concentration variations in the Izu arc, southeastern Japan (8 Li = +1.1 to +7.6), consistent with significant incorporation of Li from altered oceanic crust into arc lava sources (Fig. 6). A similar trend has been reported in samples of basalts and basaltic andesites from Mt. Shasta, California (5 Li = +2.5 to +6.5 Magna et al. 2003). 

Nishio Y, Sasaki S, Gamo T, Hiyagon H, Sano Y (1998) Carbon and helium isotope systematics of North Fiji basin basalt glasses carbon geochemical cycle in the subduction zone. Earth Planet Sci Lett 154 127-138... 

Basaltic andesites to andesites (subduction zone, Southern Volcanic Zone, Chile, 6 samples)... 

Tatsumi Y., Sakuyama M., Fukuyama H., and Kushiro I. (1983) Generation of arc basalt magmas and thermal structure of the mantle wedge in subduction zones. J. Geophys. Res. 88, 5815-5825. 

Ono S. (1998) Stability limits of hydrous minerals in sediment and mid-ocean ridge basalt compositions implications for water transport in subduction zones. J. Geophys. Res. 103, 18253-18267. 

Anderson A. T. (1982) Parental basalts in subduction zones implications for continental evolution. J. Geophys. Res. 87, 7047-7060. 

Using average MORE or the range of compositions of oceanic basalts (e.g., Hofmann, 1988 Chapter 3.13 and http //petdb.ldeo.columbia.edu Lehnert et al., 2000), the fluxes derived here can be applied to determine the average compositions of oceanic crust that is subducted and recycled into the mantle. These compositions thus influence the composition of subduction zone magmas (see Chapter 3.18) and bear on the chemical mass balance of the mantle. 

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