Kurile island-arc volcanism: structural and petrological aspects

Role of subducted sediments in the genesis of Kurile-Kamchatka island arc basalts: Sr isotopic and elemental evidence.

“…In conse quence, the origin of K-K parental magmas has been sought by melting of the sub-arc mantle (Bailey et al, 1989;Avdeiko et al, 1991;Kersting and Arculus, 1995). Bailey et al (1989) argued that the K-K sub-arc mantle had passed through a three-stage evolution: (a) formation of depleted, lherzolitic mantle, (b) contamination by alkali and alkali earth elements during fluid metasomatism and (c) a later, deeper contamination by a melt with alkalic affinities.…”

“…From frontal to rear arc settings, basalt types and their derivative series change from low-K20 to high-K20 varieties and from tholeiitic to calcalkaline and even occasionally alkaline vari eties. Along the arc, front-arc volcanic rocks change from low-K20 varieties in the southern to medium-K20 varieties in the northern Kuriles (Popolitov and Volynets, 1982;Bailey et al, 1989;Avdeiko et al, 1991).…”

Geochemistry and solute fluxes of volcano-hydrothermal systems of Shiashkotan, Kuril Islands

“…10) instead of the triangle for the Na-KMg geothermometry of thermal waters of Shiashkotan (Giggenbach, 1988;Taran et al, 1998). Points for coastal springs are plotted within the area of partial equilibrium, whereas all acidic waters are plotted close to the average for the Shiashkotan rock (Avdeiko et al, 1991). Except for one point, Na/K ratios for the coastal springs are slightly lower than that for seawater (~29), indicating some re-equilibration.…”

Hydrogen isotopes in hornblendes and biotites from Quaternary volcanic rocks of the Kamchatka-Kurile arc.

“…In at least two of them (5485, Khangar, and AA-1023, Amanina, marked on the SD-H20 plot, Fig. 2), the water loss is the result of the partitioning of OH-F-C1 between minerals *Number of site for dredged submarine rocks (Avdeiko et al, 1992 The lack of correlation of SD and H20 is not surprising; the data scatter can be the result of many superimposed factors, including the regional and local heterogeneity of the magmatic fluid composition and the rate of magma degassing during ascent and eruption. Alteration (dehydra tion) of Hb probably does not play a significant role; points with the lowest water content fall in the main range of SD variation.…”

“…Aqueous fluids derived from the dehydration of subducted oceanic crust play an important role in the process of magma generation (Delaney and Helgeson, 1978;Tatsumi et al, 1986;Tatsumi, 1989;Othman et al, 1989;Peacock, 1990;Avdeiko et al, 1992;Giggenbach, 1992;Stolper and Newman, 1994). The participation of recycled oceanic water in the generation of arc magmas is suggested by the following observations: (1) There is an enrichment in deuterium of high-temperature magmatic gases from island arc volcanoes (Sakai and Matsubaya, 1977;Mizutani, 1978;Taran et al, 1987Taran et al, , 1989Taran et al, , 1995Symonds et al, 1990; *Present address: Instituto de Geofisica, UNAM, 04510, Coyocan, Mexico Giggenbach, 1992;Chiodini et al, 1995) over that commonly ascribed to mantle-derived water (e.g., Taylor and Sheppard, 1986); (2) there is also an enrichment in deuterium in amphiboles from is land arc volcanic rocks (Graham et al, 1982;Taran et al, 1989;Deloule et al, 1991;Miyagi and Matsubaya, 1992); and (3) there is a high pre eruptive water content in subduction zone mag mas (Harris and Anderson, 1984;Johnson et al, 1994) and high initial D/H ratios as estimated for closed or open system degassing models (Taylor et al, 1983;Taylor, 1986;Newman et al, 1988).…”