Plume-related association of Cretaceous oceanic basalts of eastern Kamchatka: compositions of spinel and parental magmas

• Main Authors: Portnyagin, Maxim, Savel'ev, D. P., Hoernle, Kaj
• Format: Article in Journal/Newspaper
• Language: English
• Published: MAIK 2005
• Subjects: Pacific; Kamchatka
• Online Access: https://oceanrep.geomar.de/id/eprint/1650/; https://oceanrep.geomar.de/id/eprint/1650/1/Portnyagin-2005-Petrology.pdf; http://www.maik.rssi.ru/cgi-bin/search.pl?type=abstract&name=petreng&number=6&year=5&page=571

Cretaceous rocks comparable to mid-oceanic ridge and oceanic island basalts were described in ophiolite association of the Cape Kamchatskii, Eastern Kamchatka (Fedorchuk et al., 1989). New data on the composition of these basalts, their spinels, and melt inclusions in them are presented in this paper. Spinel from olivine–plagioclase basalts corresponds in composition to that of mid-oceanic ridge tholeiites (Mg# = 0.57−0.82, Cr# = 0.33–0.55, TiO2 = 0.03–0.85 wt %). High-K alkali basalts include less magnesian and chro- mian (Mg# = 0.57–0.70, Cr# = 0.23–0.30), but Ti-rich (TiO2 = 0.60–0.86 wt %) spinel. Low Cr# and very low Fe3+ contents of spinel distinguish the studied rocks from island-arc basalts of Eastern Kamchatka. Melt inclu- sions in spinel from plagioclase–olivine basalts have tholeiitic low-alkali (Na2O = 0.8–2.5 wt %, K2O = 0.01−0.09 wt %), high-Ca (CaO = 13–15 wt %), and low-Ti (TiO2 = 0.2–1.2 wt %) composition. Chlorine con- centrations are extremely low in the melt inclusions (Cl < 0.005 wt %), while S contents are high (S = 0.12 ± 0.03 wt %). Concentrations of incompatible elements in inclusions (La = 0.3–1.2 ppm, Sr = 27–70 ppm, Zr = 13–21 ppm) are systematically lower than in typical oceanic tholeiites. The melts are selectively enriched in K, Sr, and Ba relative to REE in the N-MORB-normalized trace-element spectra. Participation of plume com- ponent in the formation of the Late Cretaceous rift-related basalts of the Pacific Ocean, which are incorporated now in ophiolite association of the Cape Kamchatskii, is inferred from indicative rock assemblage and compo- sition of primitive melts and spinel.