He, Pb, Sr and Nd isotope constraints on magma genesis and mantle heterogeneity beneath young Pacific seamounts

A deep mantle source for high 3He/4He ocean island basalts (OIB) inferred from Pacific near‐ridge seamount lavas

“…No Pb isotopes are available for West Greenland lavas. The composition of the bulk silicate Earth (BSE) [Zindler and Hart, 1986] He higher than the canonical MORB value of 8 ± 1 R A [Graham, 2002], consistent with previous 3 He/ 4 He work on seamounts in the area [Graham et al, 1987[Graham et al, , 1988.…”

“…[11] Our results show that Pacific OIB-like seamount lavas [see also Graham et al, 1987Graham et al, , 1988 do not have the high 3 He/ 4 He signature of OIB. The Hawaiian-type MORB and E-MORB in our study area also have MORB-like 3 He/ 4 He ratios and this observation stands in marked contrast to the high 3 He/ 4 He ratios that characterize E-MORB along ridge segments near linear volcanic chains, e.g., Galapagos Spreading Center near the Galapagos Islands [Graham et al, 1993] and the southern EPR near the Easter Island chain [Poreda et al, 1993].…”

Geochemical and Nd‐Sr‐Pb isotopic evidence on the origin and geodynamic evolution of mid‐Cretaceous continental arc volcanic rocks of the Spences Bridge Group, south‐central British Columbia

“…Nd-Sr isotopic variation in SBG volcanic rocks (data corrected to an age of 100 Ma) relative to MORB and seamount basalts from the Juan de Fuca Ridge and East Pacific Rise (EPR) (Zindler et al 1984;Graham et al 1988), arc assemblages related to slab dehydration (Cascade arc: Leeman et al 1990;Borg et al 1997. Mariana arc: DePaolo andWasserburg 1977;White and Patchett 1984), adakitic assemblages (Setouchi high-Mg andesites: Shimoda et al 1998.…”

Isotope Geochemistry of Leg 129 Basalts: Implications for the Origin of the Widespread Cretaceous Volcanic Event in the Pacific

“…The isotopic compositions of Site 801 alkali basalts overlap with those of isolated seamounts formed near mid-ocean ridges (Zindler et al, 1984;Graham et al, 1988;Castillo and Batiza, 1989;Hegner and Tatsumoto, 1989). These seamounts are ubiquitous on the ocean floor (Batiza, 1982;Fornari et al, 1987;Smith and Jordan, 1988) although their formation and evolution apparently are strongly influenced by the tectonic and magma supply processes at mid-ocean ridges if the seamounts were formed on <lO-m.y.-old lithosphere (Fornari et al, 1987).…”