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  • 1
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    The role and conditions of second-stage mantle melting in the generation of low-Ti tholeiites and boninites: the case of the Manihiki Plateau and the Troodos ophiolite (2017)
    Springer
    In:  Contributions to Mineralogy and Petrology, 172 (11-12, Article Nr. 104).
    Details
    Publication Date: 2020-02-06
    Description: High-Mg, low-Ti volcanic rocks from the Manihiki Plateau in the Western Pacific share many geochemical characteristics with subduction-related boninites such as high-Ca boninites from the Troodos ophiolite on Cyprus, which are believed to originate by hydrous re-melting of previously depleted mantle. In this paper we compare the Manihiki rocks and Troodos boninites using a new dataset on the major and trace element composition of whole rocks and glasses from these locations, and new high-precision, electron microprobe analyses of olivine and Cr-spinel in these rocks. Our results show that both low-Ti Manihiki rocks and Troodos boninites could originate by re-melting of a previously depleted lherzolite mantle source (20–25% of total melting with 8–10% melting during the first stage), as indicated by strong depletion of magmas in more to less incompatible elements (Sm/Yb 〈 0.8, Zr/Y 〈 2, Ti/V 〈 12) and high-Cr-spinel compositions (Cr# 〉 0.5). In comparison with Troodos boninites, the low-Ti Manihiki magmas had distinctively lower H2O contents (〈 0.2 vs. 〉 2 wt% in boninites), ~ 100 °C higher liquidus temperatures at a given olivine Fo-number, lower fO2 (ΔQFM 〈 + 0.2 vs. ΔQFM 〉 + 0.2) and originated from deeper and hotter mantle (1.4–1.7 GPa, ~ 1440 °C vs. 0.8–1.0 GPa, ~ 1300 °C for Troodos boninites). The data provide new evidence that re-melting of residual upper mantle is not only restricted to subduction zones, where it occurs under hydrous conditions, but can also take place due to interaction of previously depleted upper mantle with mantle plumes from the deep and hotter Earth interior.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    DOI: 10.1007/s00410-017-1424-3
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Ultramafic–Mafic Assemblage of Plutonic Rocks and Hornblende Schists of Shirshov Rise, Bering Sea, and Stalemate Ridge, Northwest Pacific: Geodynamic Interpretations of Geochemical Data (2018)
    Springer
    In:  Petrology, 26 (5). pp. 492-514.
    Details
    Publication Date: 2021-02-08
    Description: The paper presents data on plutonic and metamorphic rocks dredged during Cruise 249 of the German R/V Sonne to the Stalemate Ridge, Northwest Pacific Ocean and the Shirshov Rise, western Bering Sea. Dredges in the northwestern sector of the Stalemate Ridge and central portion of the Shirshov Rise show that the plutonic and metamorphic rocks obtained here are amazingly similar. Our petrologic and geochemical data led us to view the rocks as members of a mafic–ultramafic assemblage typical of cumulate portions of ophiolite complexes and backarc spreading centers. The plutonic complexes of the Shirshov Rise and Stalemate Ridge show similarities not only in the petrography and mineralogy of their protoliths but also in the character of their metamorphic transformations. Plutonic rocks from both areas display mineralogical evidence of metamorphism within a broad temperature range: from the high-temperature amphibolite facies to the greenschist facies. Relations between the index mineral assemblages indicate that the metamorphic history of plutonic complexes in the Stalemate Ridge and Shirshov Rise proceeded along a retrograde path. Hornblende schists accompanying the plutonic rocks of the Stalemate Ridge and Shirshov Rise are petrographically close to foliated amphibolites in subophiolitic metamorphic aureoles. Within the framework of geodynamic interpretations of our results, it is realistic to suggest that the examined plutonic complexes were exhumed from subduction zones of various age.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1134/S0869591118050077
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Constraining input and output fluxes of the southern Central Chile Subduction Zone: water, chlorine, sulfur (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 2129-2153.
    Details
    Publication Date: 2019-09-23
    Description: In this paper, we constrain the input and output fluxes of H2O, Cl and S into the southern-central Chilean subduction zone (31°S–46°S). We determine the input flux by calculating the amounts of water, chlorine and sulfur that are carried into the subduction zone in subducted sediments, igneous crust and hydrated lithospheric mantle. The applied models take into account that latitudinal variations in the subducting Nazca plate impact the crustal porosity and the degree of upper mantle serpentinization and thus water storage in the crust and mantle. In another step, we constrain the output fluxes of the subduction zone both to the subcontinental lithospheric mantle and to the atmosphere–geosphere–ocean by the combined use of gas flux determinations at the volcanic arc, volume calculations of volcanic rocks and the combination of mineralogical and geothermal models of the subduction zone. The calculations indicate that about 68 Tg/m/Ma of water enters the subduction zone, as averaged over its total length of 1,480 km. The volcanic output on the other hand accounts for 2 Tg/m/Ma or 3 % of that input. We presume that a large fraction of the volatiles that are captured within the subducting sediments (which accounts for roughly one-third of the input) are cycled back into the ocean through the forearc. This assumption is however questioned by the present lack of evidence for major venting systems of the submarine forearc. The largest part of the water that is carried into the subduction zone in the crust and hydrated mantle (accounting for two-thirds of the input) appears to be transported beyond the volcanic arc.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-014-1002-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    The age of Earth’s largest volcano: Tamu Massif on Shatsky Rise (northwest Pacific Ocean) (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (8). pp. 2351-2357.
    Details
    Publication Date: 2017-05-23
    Description: This study presents laser step-heating 40Ar/39Ar age determinations of basaltic lava samples from Tamu Massif, the oldest and largest edifice of the submarine Shatsky Rise in the northwest Pacific and Earth’s proposed largest volcano. The rocks were recovered during Integrated Ocean Drilling Program Expedition 324, which cored 160 m into the igneous basement near the summit of Tamu Massif. The analyzed lavas cover all three major stratigraphic groups penetrated at this site and confirm a Late Jurassic/Early Cretaceous age for the onset of Shatsky Rise volcanism. Lavas analyzed from the lower and middle section of the hole yield plateau ages between 144.4 ± 1.0 and 143.1 ± 3.3 Ma with overlapping analytical errors (2σ), whereas a sample from the uppermost lava group produced a significantly younger age of 133.9 ± 2.3 Ma suggesting a late or rejuvenated phase of volcanism. The new geochronological data infer minimum (average) melt production rates of 0.63–0.84 km3/a over a time interval of 3–4 million years consistent with the presence of a mantle plume.
    Type: Article , PeerReviewed
    Format: other
    Format: text
    DOI: 10.1007/s00531-014-1078-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Insights from trace element geochemistry as to the roles of subduction zone geometry and subduction input on the chemistry of arc magmas (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1929-1944.
    Details
    Publication Date: 2019-09-23
    Description: Subduction zones of continental, transitional, and oceanic settings, relative to the nature of the overriding plate, are compared in terms of trace element compositions of mafic to intermediate arc rocks, in order to evaluate the relationship between subduction parameters and the presence of subduction fluids. The continental Chilean Southern Volcanic Zone (SVZ) and the transitional to oceanic Central American Volcanic Arc (CAVA) show increasing degrees of melting with increasing involvement of slab fluids, as is typical for hydrous flux melting beneath arc volcanoes. At the SVZ, the central segment with the thinnest continental crust/lithosphere erupted the highest-degree melts from the most depleted sources, similar to the oceanic-like Nicaraguan segment of the CAVA. The northern part of the SVZ, located on the thickest continental crust/lithosphere, exhibits features more similar to Costa Rica situated on the Caribbean Large Igneous Province, with lower degrees of melting from more enriched source materials. The composition of the slab fluids is characteristic for each arc system, with a particularly pronounced enrichment in Pb at the SVZ and in Ba at the CAVA. A direct compositional relationship between the arc rocks and the corresponding marine sediments that are subducted at the trenches clearly shows that the compositional signature of the lavas erupted in the different arcs carries an inherited signal from the subducted sediments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-013-0917-1
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  • 6
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    Hafnium isotopic variations in East Atlantic intraplate volcanism (2011)
    Springer
    In:  Contributions to Mineralogy and Petrology, 162 (1). pp. 21-36.
    Details
    Publication Date: 2019-09-23
    Description: The broad belt of intraplate volcanism in the East Atlantic between 25° and 37° N is proposed to have formed by two adjacent hotspot tracks (the Madeira and Canary tracks) that possess systematically different isotopic signatures reflecting different mantle source compositions. To test this model, Hf isotope ratios from volcanic rocks from all individual islands and all major seamounts are presented in this study. In comparison with published Nd isotope variations (6 εNd units), 176Hf/177Hf ratios span a much larger range (14 εHf units). Samples from the proposed Madeira hotspot track have the most radiogenic Hf isotopic compositions (176Hf/177Hfm up to 0.283335), extending across the entire field for central Atlantic MORB. They form a relatively narrow, elongated trend on the Nd vs. Hf isotope diagram (stretching over 〉10 εHf units) between a depleted N-MORB-like endmember and a moderately enriched composition located on, or slightly below, the Nd–Hf mantle array, which overlaps the proposed "C" mantle component of Hanan and Graham (1996). In contrast, all samples from the Canary hotspot track plot below the mantle array (176Hf/177Hfm = 0.282943–0.283067) and form a much denser cluster with less compositional variation (~4 εHf units). The cluster falls between (1) a low Hf isotope HIMUlike endmember, (2) a more depleted composition, and (3) the moderately enriched end of the Madeira trend. The new Hf isotope data confirm the general geochemical distinction of the Canary and Madeira domains in the East Atlantic. Both domains, however, seem to share a common, moderately enriched endmember that has "C"-like isotope compositions and is believed to represent subducted, 〈1-Ga-old oceanic lithosphere (oceanic crust and possibly minor sediment addition). The lower 176Hf/177Hf ratio of the enriched, HIMU-like Canary domain endmember indicates the contribution of oceanic lithosphere with somewhat older recycling ages of 〉=1 Ga.
    Type: Article , PeerReviewed
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    Format: other
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    DOI: 10.1007/s00410-010-0580-5
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Two-stage evolution of mantle peridotites from the Stalemate Fracture Zone, northwestern Pacific (2013)
    Springer
    In:  Geochemistry International, 51 (9). pp. 683-695.
    Details
    Publication Date: 2017-11-06
    Description: This paper reports the results of a mineralogical study of 14 mantle peridotite samples dredged in 2009 from the eastern slope of the northwestern segment of the Stalemate Ridge in the northwestern Pacific during cruise SO201-KALMAR Leg 1b of the R/V Sonne. The sample collection included four serpentinized and silicified dunites and ten variably serpentinized lherzolites. The compositions of primary minerals (clinopyroxene, orthopyroxene, and spinel) change systematically from the lherzolites to dunites. Spinel from the lherzolites shows higher Mg# and lower Cr# values (0.65-0.68 and 0.26-0.33, respectively) compared with spinel from the dunites (Mg# = 0.56-0.64 and Cr# = 0.38-0.43). Clinopyroxene from the lherzolites is less magnesian (Mg# = 91.7-92.4) than clinopyroxene from dunite sample DR37-3 (Mg# = 93.7). Based on the obtained data, it was concluded that the lherzolites of the Stalemate Fracture Zone were derived by 10-12% near-fractional melting of a DMM-type depleted mantle reservoir beneath the Kula-Pacific spreading center. The dunites were produced by interaction of residual lherzolites with sodium- and titaniumrich melt and are probably fragments of a network of dunite channels in the shallow mantle. The moderately depleted composition of minerals clearly distinguishes the lherzolites from the strongly depleted peridotites of the East Pacific Rise and indicates the existence of slow-spreading mid-ocean ridges in the Pacific Ocean during the Cretaceous-Paleogene.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1134/S0016702913080028
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  • 8
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    Structure and evolution of the volcanic rift zone at São Lourenço peninsula, Madeira (2009)
    Springer
    In:  Bulletin of Volcanology, 71 (6). pp. 671-685.
    Details
    Publication Date: 2018-05-29
    Description: Ponta de São Lourenço is the deeply eroded eastern end of Madeira’s east–west trending rift zone, located near the geometric intersection of the Madeira rift axis with that of the Desertas Islands to the southeast. It dominantly consists of basaltic pyroclastic deposits from Strombolian and phreatomagmatic eruptions, lava flows, and a dike swarm. Main differences compared to highly productive rift zones such as in Hawai’i are a lower dike intensity (50–60 dikes/km) and the lack of a shallow magma reservoir or summit caldera. 40Ar/39Ar age determinations show that volcanic activity at Ponta de São Lourenço lasted from 〉5.2 to 4 Ma (early Madeira rift phase) and from 2.4 to 0.9 Ma (late Madeira rift phase), with a hiatus dividing the stratigraphy into lower and upper units. Toward the east, the distribution of eruptive centers becomes diffuse, and the rift axis bends to parallel the Desertas ridge. The bending may have resulted from mutual gravitational influence of the Madeira and Desertas volcanic edifices. We propose that Ponta de São Lourenço represents a type example for the interior of a fading rift arm on oceanic volcanoes, with modern analogues being the terminations of the rift zones at La Palma and El Hierro (Canary Islands). There is no evidence for Ponta de São Lourenço representing a former central volcano that interconnected and fed the Madeira and Desertas rifts. Our results suggest a subdivision of volcanic rift zones into (1) a highly productive endmember characterized by a central volcano with a shallow magma chamber feeding one or more rift arms, and (2) a less productive endmember characterized by rifts fed from deep-seated magma reservoirs rather than from a central volcano, as is the case for Ponta de São Lourenço.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00445-008-0253-7
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  • 9
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    Seamounts (2016)
    Springer
    In:  In: Encyclopedia of Marine Geosciences. , ed. by Harff, J., Meschede, M., Petersen, S. and Thiede, J. Springer, Dordrecht, pp. 754-760. ISBN 978-94-007-6239-4
    Details
    Publication Date: 2019-09-23
    Description: Seamounts are literally mountains rising from the seafloor. More specifically, they are “any geographically isolated topographic feature on the seafloor taller than 100 m, including ones whose summit regions may temporarily emerge above sea level, but not including features that are located on continental shelves or that are part of other major landmasses” (Staudigel et al., 2010). The term “guyot” can be used for seamounts having a truncated cone shape with a flat summit produced by erosion at sea level (Hess, 1946), development of carbonate reefs (e.g., Flood, 1999), or partial collapse due to caldera formation (e.g., Batiza et al., 1984). Seamounts 〈1,000 m tall are sometimes referred to as “knolls” (e.g., Hirano et al., 2008). “Petit spots” are a newly discovered subset of sea knolls confined to the bulge of subducting oceanic plates of oceanic plates seaward of deep-sea trenches (Hirano et al., 2006).
    Type: Book chapter , PeerReviewed
    Format: text
    DOI: 10.1007/978-94-007-6644-0_34-2
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  • 10
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    Contrasting compositional trends of rocks and olivine-hosted melt inclusions from Cerro Negro volcano (Central America): implications for decompression-driven fractionation of hydrous magmas (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1963-1982.
    Details
    Publication Date: 2017-05-23
    Description: Melt inclusions in olivine Fo83–72 from tephras of 1867, 1971 and 1992 eruptions of Cerro Negro volcano represent a series of basaltic to andesitic melts of narrow range of MgO (5.6–8 wt %) formed by ~46 wt % fractional crystallization of olivine (~6 wt %), plagioclase (~27 wt %), pyroxene (~13 wt %) and magnetite (〈1 wt %) from primitive basaltic melt (average SiO2 = 49 wt %, MgO = 7.6 wt %, H2O = 6 wt %) as it ascended to the surface from the depth of about 14 km. The crystallization occurred at increasing liquidus temperature from 1,050 to 1,090 °C in the pressure range from 400 to 50 MPa and was induced by release of mixed H2O–CO2 fluid from the melt at decreasing pressure. Matrix glass compositions fall at the high-Si end of the melt inclusion trend and represent the final stage of melt crystallization during and after eruption. The bulk compositions of erupted Cerro Negro magmas (tephras and lavas) range from high- to low-MgO (3–10 wt %) basalts, which form a compositional array crossing the trend of melt inclusions so that virtually no rock from Cerro Negro has composition akin to true melt represented by the inclusions. The variations of the bulk magma (rocks) and melt (melt inclusions) compositions can be generated in a dyke connecting a deep primitive magma reservoir with the Cerro Negro edifice. While the melt inclusions represent the compositional trend of instantaneous melts along the magma pathway at decreasing pressure and H2O content, occurrence of low-Mg to high-Mg basalts reflects the process of phenocryst re-distribution in progressively evolving melt. The crystallization scenario is anticipated to operate everywhere in dykes feeding basaltic volcanoes and can explain the predominance of plagioclase-rich high-Al basalts in island arc as well as typical compositional variations of magmas during single eruptions.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-012-0810-3
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