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  • Articles  (33)
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  • 1
    Electronic Resource
    Electronic Resource
    Basalt and tonalite from the Amami Plateau, northern West Philippine Basin: New Early Cretaceous ages and geochemical results, and their petrologic and tectonic implications (2005)
    Melbourne, Australia : Blackwell Science Pty
    The @island arc 14 (2005), S. 0 
    Details
    ISSN: 1440-1738
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract  Basalts and tonalites dredged from the Amami Plateau in the northern West Philippine Basin have the geochemical characteristics of intraoceanic island arc rocks: low 87Sr/86Sr (0.70297–0.70310), intermediate 143Nd/144Nd (0.51288–0.51292), moderate light rare earth element (LREE) enrichment (La/Yb = 4.1–6.6) and high La/Nb (1.4–4.3). The incremental heating of hornblende from tonalites yielded well-defined plateaus and 40Ar/39Ar isochron ages of 115.8 ± 0.5 Ma and 117.0 ± 1.1 Ma, while plagioclase yielded disturbed Ar release patterns, with ages ranging from 70 to 112 Ma. Taken together, these results show that the Amami Plateau was formed by subduction-related magmatism in the Early Cretaceous period, earlier than indicated by prior K/Ar results. The results support tectonic models in which the West Philippine Basin was opened within a complex of Jurassic–Paleocene island arc terranes, which are now scattered in the northern West Philippine Basin, the Philippine Islands and Halmahera. The Amami Plateau tonalites and basalts have higher Sr/Y and lower Y and 87Sr/86Sr compared with younger tonalitic rocks from the northern Kyushu–Palau Ridge and the Tanzawa complex, which were formed by the subduction of the Pacific Plate beneath the Philippine Sea Plate. Based on the geochemical characteristics of the basalts, the Early Cretaceous subduction zone that formed the Amami Plateau may have been the site of slab melting, which suggests that a younger and hotter plate was being subducted at that time. However, the Amami tonalites were probably formed from basaltic magma by fractional crystallization or by partial melting of basaltic arc crust, rather than by melting of the subducted slab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1738.2005.00474.x
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  • 2
    Electronic Resource
    Electronic Resource
    Peeled or MASHed? (1991)
    [s.l.] : Nature Publishing Group
    Nature 350 (1991), S. 381-382 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] How magma is generated at convergent tectonic plate margins and what the source materials are, have long puzzled geologists. J-K P FIG. 1 Alternative explanations for the continental crustal signature in magmas from the northern SVZ: top, recyling of subduction eroded continental crust1; ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/350381a0
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  • 3
    Electronic Resource
    Electronic Resource
    A refractory HIMU component in the sources of island-arc magma (1992)
    [s.l.] : Nature Publishing Group
    Nature 360 (1992), S. 57-59 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Philippine Sea region was formed by three successive arc building and back-arc spreading phases, and is therefore ideal for studying the nature and relationship of arc and basin magma sources. Back-arc-basin basalts were erupted 65-40 million years before present (Myr BP) (West Philippine ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/360057a0
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  • 4
    Electronic Resource
    Electronic Resource
    Geochemical variations in Andean basaltic and silicic lavas from the Villarrica-Lanin volcanic chain (39.5° S): an evaluation of source heterogeneity, fractional crystallization and crustal assimilation (1989)
    Springer
    Contributions to mineralogy and petrology 103 (1989), S. 361-386 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract At 39.5° S in the southern volcanic zone of the Andes three Pleistocene-recent stratovolcanoes, Villarrica, Quetrupillan and Lanin, form a trend perpendicular to the strike of the Andes, 275 to 325 km from the Peru-Chile trench. Basalts from Villarrica and Lanin are geochemically distinct; the latter have higher incompatible element abundances and La/Sm but lower Ba/La and alkali metal/La ratios. These differences are consistent with our previously proposed models involving: a) a west to east decrease in an alkali metal-rich, high Ba/La slab-derived component which causes an across strike decrease in degree of melting; or b) a west to east increase in the contamination of subduction-related magma by enriched subcontinental lithospheric mantle. Silicic and mafic lavas from the stratovolcanoes have overlapping Sr, Nd and O isotopic ratios. Silicic lavas also have geochemical differences that parallel those of their associated basalts, e.g., rhyolite from Villarrica has lower La/Sm and incompatible element contents than high-SiO2 andesite from Lanin. At each volcano the most silicic lavas can be modelled by closed system fractional crystallization while andesites are best explained by magma mixing. Apparently crustal contamination was not an important process in deriving the evolved lavas. Basaltic flows from small scoria cones, 20–35 km from Villarrica volcano have high incompatible element contents and low Ba/La, like Lanin basalts, but trend to higher K/Rb (356–855) and lower 87Sr/ 86Sr (0.70361–0.70400) than basalts from either stratovolcano. However all basalts have similar Nd, Pb and O isotope ratios. The best explanation for the unique features of the cones is that the sources of SVZ magmas, e.g., slab-derived fluids or melts of the subcontinental lithospheric mantle, have varying alkali metal and radiogenic Sr contents. These heterogeneities are not manifested in stratovolcano basalts because of extensive subcrustal pooling and mixing. This model is preferable to one involving crustal contamination because it can account for variable Sr isotope ratios and uniform Nd and Pb isotope ratios among the basalts, and the divergence of the cones from across-strike geochemical trends defined by the stratovolcanoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402922
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  • 5
    Electronic Resource
    Electronic Resource
    Temporal variation of isotope and rare earth element abundances in volcanic rocks from Guam: implications for the evolution of the Mariana Arc (1987)
    Springer
    Contributions to mineralogy and petrology 97 (1987), S. 497-508 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Volcanic rocks exposed on Guam were erupted during the Late Middle Eocene (Facpi Fm.), Late Eocene-Oligocene (Alutom Fm.) and Miocene (Umatac Fm.). Four magma series are recognized: the boninite series (44 m.y.b.p.), the tholeiite and calc-alkaline series, which were erupted along with boninite series lavas at 32–36 m.y.b.p. and high-K lavas of the Umatac Fm. (14 m.y.b.p.). Isotope and and rare earth element (REE) characteristics of the four magma series are distinct. Boninite series lavas have U-shaped REE patterns, relatively low 143Nd/144Nd (0.51294–0.51298), and high 206Pb/204Pb (19.0–19.2). Tholeiite series lavas are LREE (light REE) depleted, and have high 143Nd/144Nd (0.51304–0.51306) and low 206Pb/204Pb (18.4–18.5). Calc-alkaline series lavas have Sr, Nd and Pb isotope ratios similar to tholeiite series lavas, but flat to U-shaped REE patterns. Umatac Fm. lavas are strongly LREE-enriched, and have higher 87Sr/ 86Sr (0.70375–0.70380) and 207Pb/204Pb relative to 206Pb/ 204Pb than Facpi and Alutom Fm. lavas. Boninite and tholeiite series magmas, erupted in the position of the Palau-Kyushu Ridge, were probably derived from distinct mantle sources having OIB and N-MORB-like isotopic characteristics, together with fluids derived from subducted Pacific plate basalt. Calc-alkaline series lavas were most likely derived from the tholeiite series by extensive crystal fractionation, wallrock contamination and magma mixing. Lavas of the Umatac Fm., erupted in the position of the West Mariana Ridge, may include up to 2–3% subducted sediment, similar to some active Mariana arc lavas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375327
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  • 6
    Electronic Resource
    Electronic Resource
    Crustal xenoliths from Calbuco Volcano, Andean Southern Volcanic Zone: implications for crustal composition and magma-crust interaction (1995)
    Springer
    Contributions to mineralogy and petrology 119 (1995), S. 331-344 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Crustal xenoliths in the 1961 andesite flow of Calbuco Volcano, in the southern Southern Volcanic Zone (SSVZ) of the Andes, consist predominantly of pyroxene granulites and hornblende gabbronorites. The granulites contain plagioclase+pyroxene+magnetite±amphibole, and have pronounced granoblastic textures. Small amounts of relict amphibole surrounded by pyroxene-plagioclase-magnetite-glass symplectites are found in some specimens. These and similar textures in the gabbronorites are interpreted as evidence of dehydration melting. Mineral and bulk rock geochemical data indicate that the granulites are derived from an incompatible trace element depleted basaltic protolith that underwent two stages of metamorphism: a moderate pressure, high temperature stage accompanied by melting and melt extraction from some samples, followed by thermal metamorphism after entrainment in the Calbuco andesite lavas. High ɛNd T values (+4.0 to +8.6), Nd-isotope model ages of 1.7–2.0 Ga, and trace element characteristics like chondrite normalized La/Yb〈 and La/Nb≤1 indicate that the protoliths were oceanic basalts. Similar oceanic metabasalts of greenschist to amphibolite facies are found in the Paleozoic metamorphic belt that underlies the Chilean coastal ranges. Mineral and bulk rock compositions of the gabbronorite xenoliths indicate that they are cognate, crystallizing from the basaltic andesite magma at Calbuco. Crystallization pressures for the gabbros based on total Al contents in amphibole are 6–8 kbar. These pressures point to middle to lower crustal storage of the Calbuco magma. Neither granulite nor gabbro xenoliths have the appropriate geochemical characteristics to be contaminants of Calbuco andesites, although an ancient sedimentary contaminant is indicated by the lava compositions. The presence of oceanic metabasaltic xenoliths, together with the sedimentary isotopic imprint, suggests that the lower crust beneath the volcano is analogous to the coastal metamorphic belt, which is an accretionary complex of intercalated basalts and sediments that formed along the Paleozoic Gondwanan margin. If this is the case, the geochemical composition of the lower and middle crust beneath the SSVZ is significantly different from that of most recent SSVZ volcanic rocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286933
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  • 7
    Electronic Resource
    Electronic Resource
    Element and Sediment Accumulation Rates in the Florida Everglades (2000)
    Springer
    Water, air & soil pollution 122 (2000), S. 327-349 
    Details
    ISSN: 1573-2932
    Keywords: accumulation ; airborne flux ; bulk accumulation ; Florida Everglades ; major elements ; trace elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Sediment and element accumulationrates were determined in cores taken from two borrowcanals and a rockpit lake of known age in the FloridaEverglades. Bulk accumulation of ∼1 kg m-2 yr-1 is dominated by precipitatedcarbonate and lesser amounts of organic material. Acid-insoluble clastic input is 0.5–2% of the totalaccumulation except in a borrow canal close to alevee. The accumulation rate of Ca tracks bulkaccumulation of carbonate while Al and Fe track bulkaccumulation of fines. Trace elements Cu, Hg, Mn, andV accumulated at rates 2 to 10 times greater thanpublished airborne fluxes while Ni and Zn accumulationrates were similar to airborne fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005290900575
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  • 8
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    Geochemistry of volcanic glass from Oligocene detrital sediments at DSDP Site 296, Kyushu Palau Ridge: Interpreting the magmatic evolution of the early northern Izu–Bonin –Mariana Island Arc (2020)
    Wiley
    Details
    Publication Date: 2020-01-01
    Print ISSN: 1038-4871
    Electronic ISSN: 1440-1738
    Topics: Geosciences
    Published by Wiley
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  • 9
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    Implications of Eocene-age Philippine Sea and forearc basalts for initiation and early history of the Izu-Bonin-Mariana arc (2018)
    Elsevier
    Details
    Publication Date: 2018-05-01
    Print ISSN: 0016-7037
    Electronic ISSN: 1872-9533
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Elsevier
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  • 10
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    Age and geochemistry of volcanic clasts from DSDP Site 445, Daito Ridge and relationship to Minami-Daito Basin and early Izu-Bonin arc magmatism (2013)
    Elsevier
    Details
    Publication Date: 2013-07-01
    Print ISSN: 1367-9120
    Electronic ISSN: 1878-5786
    Topics: Geosciences
    Published by Elsevier
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