Volcanism at the Edge of the Hawaiian Plume: Petrogenesis of Submarine Alkalic Lavas from the North Arch Volcanic Field   总被引：5，自引：3，他引：2  

FREY  F. A.; CLAGUE  D.; MAHONEY  J. J.; SINTON  J. M. 《Journal of Petrology》2000,41(5):667-691

Submarine lavas erupted onto the Hawaiian arch 200–400km north of Oahu show that the areal extent of Hawaiian volcanismis much larger than previously recognized. The North Arch volcanicfield comprises 25 000 km² of  相似文献   

Magma Genesis and Mantle Heterogeneity in the Manus Back-Arc Basin, Papua New Guinea   总被引：5，自引：1，他引：5  

SINTON  JOHN M.; FORD  LORI L.; CHAPPELL  BRUCE; McCULLOCH  MALCOLM T. 《Journal of Petrology》2003,44(1):159-195

Geochemical data from back-arc volcanic zones in the Manus Basinare used to define five magma types. Closest to the New Britainarc are medium-K lavas of the island arc association and back-arcbasin basalts (BABB). Mid-ocean ridge basalts (MORB), BABB andmildly enriched T-MORB (transitional MORB) occur along the ManusSpreading Center (MSC) and Extensional Transform Zone (ETZ).The MSC also erupted extreme back-arc basin basalts (XBABB),enriched in light rare earth elements, P, and Zr. Compared withnormal MORB, Manus MORB are even more depleted in high fieldstrength elements and slightly enriched in fluid-mobile elements,indicating slight, prior enrichment of their source with subduction-relatedcomponents. Chemical variations and modeling suggest systematic,coupled relationships between extent of mantle melting, priordepletion of the mantle source, and enrichment in subduction-relatedcomponents. Closest to the arc, the greatest addition of subduction-relatedcomponents has occurred in the mantle with the greatest amountof prior depletion, which has melted the most. Variations inK₂O/H₂O indicate that the subduction-related component is bestdescribed as a phlogopite and/or K-amphibole-bearing hybridizedperidotite. Magmas from the East Manus Rifts are enriched inNa and Zr with radiogenic ⁸⁷Sr/⁸⁶Sr, possibly indicating crustalinteraction in a zone of incipient rifting. The source for XBABBand lavas from the Witu Islands requires a mantle componentsimilar to carbonatite melt. KEY WORDS: Manus back-arc basin, mantle metasomatism, magma generation  相似文献   

Equilibration History of the Basel Alpine-Type Peridotite, Red Mountain, New Zealand     

SINTON  JOHN M. 《Journal of Petrology》1977,18(2):216-246

The Red Mountain alpine peridotie forms the basal, dominantlyharzburgitic tectonite portion of an ophiolite suite in SouthIsland, New Zealand. Olivine and pyroxene Mg/Fe compositionsare constant for individual lithologies, but generally increasethrough the series harzburgite, orthopyroxenite, harzburgiticdunite, dunite. An olivine-clinopyroxene dominated transitionalperidotite along the western margin of the mass has more Fe-richsilicates than in the harzburgitic suite. Fe-Mg silicate-spinelrelationships and the distribution of Al between coexistingpyroxene and spinel indicate nearly complete post-layering equilibration.A partial re-equilibration is suggested by narrow compositionalrims on pyroxenes and spinel. Relative to the mineral cores,the rims show enhanced partitioning of Al into spinel relativeto pyroxene. The Fe-Mg relationships between silicates and spinel,and the compositional variations from cores to rims of pyroxenesand spinels indicate that the rims formed at lower temperaturesthan the mineral cores. This conclusion is supported by theapplication of several geothermometers, which give average temperaturesof equilibration and partial re-equilibration of 1000–1070?C and 920–1030 ?C, respectively. Pyroxene overgrowthson olivine probably represent pre-equilibration cooling phenomena.Equilibration pressures cannot be estimated with precision becauseRed Mountain pyroxenes have Al contents that vary as a functionof whole-rock Al₂O₃, and other compositional variables, as wellas of T and P of equilibration. The lack of plagioclase in theharzburgite tectonites, and the wide range of (Al/Cr)_spinelindicate equilibration at fairly high pressures, probably atdepths within the 25–80 km range. The transitional peridotiteprobably formed by re-equilibration of residual crystals withbasaltic melt at shallower (<25 km) depths, and is evidencesupporting the conclusion that the ultramafic and mafic partsof the ophiolite suite at Red Mountain represent complementaryparts of the same melting event.  相似文献