Petrogenesis of lavas from Detroit Seamount: Geochemical differences between Emperor Chain and Hawaiian volcanoes

Abstract

[1] The Hawaiian Ridge and Emperor Seamount Chain define a hot spot track that provides an 80 Myr record of Hawaiian magmatism. Detroit Seamount ($76 to 81 Ma) is one of the oldest Emperor Seamounts. Volcanic rocks forming this seamount have been cored by the Ocean Drilling Program at six locations. Only tholeiitic basalt occurs at Site 884 on the eastern flank and only alkalic basalt, probably postshield lavas, occurs at Sites 883 and 1204 on the summit plateau. However, at Site 1203 the basement core (453 m penetration) includes four thick flows of pahoehoe alkalic basalt underlying $300 m of volcaniclastic rocks interbedded with submarine erupted tholeiitic basalt. The geochemical characteristics of these alkalic lavas indicate that phlogopite was important in their petrogenesis; they may represent preshield stage volcanism. The surprising upward transition from subaerial to submarine eruptives implies rapid subsidence of the volcano, which can be explained by the inferred near-ridge axis setting of the seamount at $80 Ma. A near-ridge axis setting with thin lithosphere is also consistent with a shallow depth of melt segregation for Detroit Seamount magmas relative to Hawaiian magmas, and the significant role for plagioclase fractionation as the Detroit Seamount magmas evolved in the crust. An important long-term trend along the hot spot track is that 87 Pb. We speculate that rejuvenated stage lavas and Detroit Seamount lavas sample a depleted mantle component, intrinsic to the plume, over the past 80 Myr.

Lithospheric control on geochemical composition along the Louisville Seamount Chain

“…(b) Zr/Nb versus La/Yb for the LSC lavas and Hawaiian shield, post‐shield and post‐erosional lavas (note that the LSC lavas display some similarity to the Hawaiian post‐shield lavas). Data for Hawaii are from Huang et al [2005], Shafer et al [2005], Yang et al [2003] and Pietruszka and Garcia [1999].…”

“…Intraplate volcanoes built on young, thin oceanic lithosphere close to spreading centers appear to erupt lavas with relatively depleted compositions. For example, the oldest Emperor seamounts were constructed on thin oceanic lithosphere close to a spreading center, and their comparatively depleted incompatible element compositions have been ascribed to either ‘plume‐ridge interaction’ [ Keller et al , 2000] or a ‘lithospheric lid’ effect [ Frey et al , 2005; Huang et al , 2005; Regelous et al , 2003; Shafer et al , 2005]. Osbourn Guyot was built closest to the fossil Osbourn Trough spreading center, and by analogy with the Emperor seamounts, an effect on the composition of lavas of the oldest Louisville seamounts could be expected.…”

Constraints on past plate and mantle motion from new ages for the Hawaiian‐Emperor Seamount Chain

“…A near‐ridge origin for Detroit Seamount is supported by the depleted trace element and isotopic compositions of Detroit lavas, which changed drastically over this 6 Myr period. The oldest 82 Ma ODP Site 884 lavas have the most depleted compositions approaching those of Pacific mid‐ocean ridge basalt [ Keller et al ., ; Regelous et al ., ], whereas younger Detroit lavas from ODP Sites 883 and 1203 have less extreme compositions, but are nevertheless more depleted than those of all other Hawaiian lavas, consistent with melting off axis, beneath young, thin oceanic lithosphere at 76 Ma [ Huang et al ., ; Frey et al ., ]. Moreover, the only part of the Emperor Chain that is smooth, almost isostatically compensated and hence almost not visible in the gravity image, indicating that it erupted on a spreading ridge, is between Detroit and Meiji seamounts.…”

Ancient carbonate sedimentary signature in the Hawaiian plume: Evidence from Mahukona volcano, Hawaii

“…Lavas forming the 0 to 80 Ma volcanoes along the age progressive Hawaiian‐Emperor hot spot track show both temporal and spatial isotopic heterogeneity [e.g., Roden et al , 1994; Lassiter and Hauri , 1998; Keller et al , 2000; Regelous et al , 2003]. Detailed studies indicate that the isotopic heterogeneity of Hawaiian‐Emperor lavas is not a result of assimilation of oceanic lithosphere [e.g., Eiler et al , 1996], but rather reflects geochemical heterogeneity within the Hawaiian plume [ Lassiter and Hauri , 1998; Blichert‐Toft et al , 1999; 2003; Abouchami et al , 2000; Frey et al , 2005; Huang et al , 2005a], with the exception that the assimilation of oceanic lithosphere into erupted Hawaiian lavas may be important in some West Maui and Kilauea lavas [ Gaffney et al , 2004; Garcia et al , 2008]. The intrinsic isotopic heterogeneity of the Hawaiian plume has been interpreted in part as a manifestation of recycled, ancient oceanic lithosphere (including sediments) in the plume [e.g., Hauri , 1996; Lassiter and Hauri , 1998; Blichert‐Toft et al , 1999; Jackson and Dasgupta , 2008].…”