HR: 0800h
AN: V51A-1464    [Abstracts]
TI: The Cause of Recurring OIB Stages: Insights From the Evolution of Jasper Seamount
AU: * Konter, J G
EM: jkonter@ucsd.edu
AF: SIO-UCSD, 9500 Gilman Dr, San Diego, 92093
AU: Staudigel, H
EM: hstaudig@ucsd.edu
AF: SIO-UCSD, 9500 Gilman Dr, San Diego, 92093
AU: Blichert-Toft, J
EM: jblicher@ens-lyon.fr
AF: ENS-Lyon, 46 allee dItalie, Lyon, 69364
AU: Hanan, B B
EM: bhanan@mail.sdsu.edu
AF: SDSU, 5500 Campanile Dr, San Diego, 92182
AU: Polve, M
EM: polve@lmtg.obs-mip.fr
AF: Univ Paul Sabatier, 14 Ave E Belin, Toulouse, 31400
AU: Davies, G
EM: gareth.davies@falw.vu.nl
AF: Vrije Univ, De Boelelaan 1085, Amsterdam, 1081 HV
AU: Shimizu, N
EM: nshimizu@whoi.edu
AF: WHOI, Clark Lab 102, Woods Hole, 02543
AB: Ocean island geochemical data display a cycle of characteristic eruptive stages that is repeated along the island chain. Such a cycle consists of stages showing subsequent waxing and waning of the total volumes of melt produced, and the degree of melting in these stages. Furthermore, the cycle often includes a period of volcanic quiescence before the last phase of minor rejuvenated volcanism. The different stages are accompanied by a systematic evolution in isotopic signatures where the most depleted magmas are produced during the initial and final stages in many ocean island chains. The consistent association of volcanic stages, melting process and isotopic fingerprints of the respective source regions suggests a causal relationship between melting process and source region composition. We argue here that mantle dynamics and physics of melting cause the waxing and waning cycle of melt volumes and melt fractions. The type and sequence of melting is controlled by the particular component of a plum-pudding mantle that crosses its solidus during upwelling and thereby determines the isotopic signature. The initial small volumes of melt of within plate volcanoes are probably largely produced by volatile-assisted melting that can tap a wide range of mantle components with their respective isotopic compositions. The large volumes of the main stage shields systematically deplete the lower temperature solidus enriched plums in the mantle sources with their corresponding isotope signatures. Later stage melts then draw from a residual mantle that is depleted in the most fertile plums and therefore produce more depleted source compositions. A period of volcanic quiescence is caused when either the fertile plums are depleted or the upwelling starts to flow out laterally. Subsequent rejuvenation of volcanism is likely controlled by another process than sequential melting of different plum-types during decompression. This follows from the age range of the entire eruptive cycle, which exceeds the time spent over a potential plume conduit, given reasonable plate velocities and estimations of plume diameter. A possible explanation for this stage is decompression melting and/or melt extraction as a result of lithospheric flexure related to the construction of a new volcano at the leading tip of the chain.
Jasper Seamount, part of the Fieberling-Guadalupe chain, plays a key role in shaping our understanding of ocean island geochemistry by substantiating the Hawaiian correlation of volcanic stages, sequential melting, stage-specific source signatures and consistent flexure characteristics. The similarity in geochemical evolution between Jasper and Hawaii suggests that the observed cycle is independent of the volume of produced melt, which agrees with sequential melting of a plum-pudding source (broadly following Phipps Morgan and Morgan, 1999). We propose here that the Hawaiian/Fieberling-Guadelupe cycle serves as a type example for within plate volcanoes, whose age progression matches plate motion, and which represent ``true'' mantle plumes.
DE: 1025 Composition of the mantle
DE: 1033 Intra-plate processes (3615, 8415)
DE: 1040 Radiogenic isotope geochemistry
DE: 3037 Oceanic hotspots and intraplate volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005