U-series Isotope Data on Lau Basin Glasses: the Role of Subduction-related Fluids during Melt Generation in Back-arc Basins   总被引：6，自引：2，他引：6  

PEATE  DAVID W.; KOKFELT  THOMAS F.; HAWKESWORTH  CHRIS J.; VAN CALSTEREN  PETER W.; HERGT  JANET M.; PEARCE  JULIAN A. 《Journal of Petrology》2001,42(8):1449-1470

New thermal ionization mass spectrometry U-series disequilibriumdata are presented for 24 basaltic to dacitic glasses from activespreading centres in the back-arc Lau Basin (SW Pacific), togetherwith additional inductively coupled plasma mass spectrometrytrace element analyses and Sr–Nd–Pb isotope data.Valu Fa Ridge samples, adjacent to the arc front, have highU/Th and (²³⁰Th/²³⁸U) <1, implying a recent (<<350ka) addition of a U-rich slab-derived fluid. The Valu Fa datacan be combined with existing ²³⁰Th–²³⁸U data for theCentral Tonga arc to infer a fluid addition event at  相似文献   

Causes of spatial compositional variations in Mariana arc lavas: Trace element evidence   总被引：3，自引：0，他引：3  

DAVID W.  PEATE & JULIAN A.  PEARCE 《Island Arc》1998,7(3):479-495

New inductively coupled plasma mass spectrometry (ICP-MS) trace element data are presented on a suite of arc lavas from the northern Mariana and southern Bonin island arcs. The samples were dredged from seamounts in the Central Island Province (CIP), the Northern Seamount Province (NSP) and the Volcano Arc (VA), and they range in composition from low-K tholeiites to shoshonites. Previous studies on these samples concluded that the primary compositional control was two-component mixing between a fluid-metasomatized mid-ocean ridge basalt (MORB) source and an enriched, ocean island basalt (OIB)-like, mantle component, with subducted sediment material playing a secondary role. However, the new trace element data suggest that the compositional variations along the Mariana arc can be better explained by the addition of spatially varying subduction components to a spatially varying mantle source. The data suggest that the subduction component in the CIP and VA is dominated by aqueous fluids derived from altered oceanic crust and a pelagic sediment component, while the subduction component in the NSP is dominated by more silicic fluids derived from volcanogenic sediments as well as from pelagic sediment and altered oceanic crust. The mantle wedge in the CIP and VA is depleted relative to a normal mid-ocean ridge basalt source by loss of a small melt fraction, while the mantle wedge in the NSP is enriched either by possible gain of a small melt fraction or addition of a sediment-derived melt. Because the subduction of seamounts controls the arc and back-arc geometries, so the concomitant variation between subducted material and mantle composition may be no coincidence. The high field strength element (HFSE) data indicate a high degree of melting (∼ 25–30%) throughout the arc, ∼ 10% of which may be attributed to decompression and ∼ 20% to fluid addition.  相似文献   

The Prinsen af Wales Bjerge Formation Lavas, East Greenland: the Transition from Tholeiitic to Alkalic Magmatism during Palaeogene Continental Break-up   总被引：2，自引：1，他引：2  

PEATE  D. W.; BAKER  J. A.; BLICHERT-TOFT  J.; HILTON  D. R.; STOREY  M.; KENT  A. J. R.; BROOKS  C. K.; HANSEN  H.; PEDERSEN  A. K.; DUNCAN  R. A. 《Journal of Petrology》2003,44(2):279-304

We present elemental and isotopic (Sr–Nd–Pb–Hf–Os–He)data on primitive alkalic lavas from the Prinsen af Wales Bjerge,East Greenland. Stratigraphical, compositional and ⁴⁰Ar–³⁹Ardata indicate that this inland alkalic activity was contemporaneouswith the upper parts of the main tholeiitic plateau basaltsand also post-dated them. The alkalic rocks show a marked crustalinfluence, indicating establishment of new magmatic plumbingsystems distinct from the long-lived coastal systems that fedthe relatively uncontaminated plateau basalts. The least contaminatedlavas have high ³He/⁴He isotope ratios (R/R_A 12·4–18·5),sub-chondritic ¹⁸⁷Os/¹⁸⁸Os_i (0·120–0·126),low  相似文献   

Early Cretaceous Basaltic and Rhyolitic Magmatism in Southern Uruguay Associated with the Opening of the South Atlantic   总被引：8，自引：0，他引：8  

KIRSTEIN  LINDA A.; PEATE  DAVID W.; HAWKESWORTH  CHRIS J.; TURNER  SIMON P.; HARRIS  CHRIS; MANTOVANI  MARTA S. M. 《Journal of Petrology》2000,41(9):1413-1438

The Early Cretaceous volcanic rocks of southern Uruguay comprisemafic and felsic volcanics. The position of these outcrops atthe southern edge of the Paraná–Etendeka continentalflood basalt province provides an opportunity to investigatepossible lateral variations in both mafic and more evolved rocktypes towards the margins of such an area of plume-related magmatism.The mafic lavas are divided into two compositionally distinctmagma types. The more voluminous Treinte Y Trés magmatype is similar to the low-Ti basalts of the Paraná floodbasalt province. The Santa Lucía magma type is a distinctand rare basalt type with ocean-island basalt type asthenosphericaffinities (high Nb/La, low ⁸⁷Sr/⁸⁶Sr_i). The felsic volcanicsare divided into two series, the Lavalleja Series and the AigüaSeries. The Lavalleja Series are chemically and isotopicallysimilar to the Paraná–Etendeka low-Ti rhyolites,and are considered to be related to the Treinte Y Tréslavas by extensive fractionation and crustal assimilation. TheAigüa Series have low ¹⁴³Nd/¹⁴⁴Nd_i and low ⁸⁷Sr/⁸⁶Sr_i andunlike the rhyolites of the Paraná, are interpreted asmelts of pre-existing mafic lower crust that subsequently underwentextreme fractionation. The differences observed in the felsicsuites may be linked to differences in the volumes of the associatedbasalts and the amounts of extension. KEY WORDS: South America; flood basalts; felsic volcanics; crustal melts; plume  相似文献