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  • 1
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    The Indus-Yarlung Suture, Southern Tibet (1996)
    In:  Geowissenschaften, New York, August, vol. 14, no. 7-8, pp. 317-319, pp. B03403, (ISSN: 1340-4202)
    Details
    Publication Date: 1996
    Keywords: Plate tectonics ; Geol. aspects ; China ; Meissner
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    What is the Origin of Widespread Cenozoic Intraplate Volcanism on the New Zealand Microcontinent?. 1st Plume Project Workshop "Plume-like instabilities in the upper mantle beneath Europe" (2006)
    In:  Ottrott, France
    Details
    Publication Date: 2006
    Keywords: TF VIII ; Task Force VIII ; Baby plumes in Central Europe
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    BIBLIOGRAPHY ILP
  • 3
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    Seismic mapping of crustal structures beneath the Indus-Yarlung Suture, Tibet (1997)
    In:  The European Journal of Geoscience, Kunming, China, 3-4, vol. 9, no. 1, pp. 42-46, pp. B05301, (ISSN: 1340-4202)
    Details
    Publication Date: 1997
    Keywords: Seismics (controlled source seismology) ; Deep seismic sounding (espec. cont. crust) ; China ; Meissner
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Compositional variation and 226Ra-230Th model ages of axial lavas from the southern Mid-Atlantic Ridge, 8°48′S (2015)
    Wiley
    Details
    Publication Date: 2015-12-19
    Description: We present geological observations and geochemical data for the youngest volcanic features on the slow-spreading Mid-Atlantic Ridge at 8°48'S that shows seismic evidence for a thickened crust and excess magma formation. Young lava flows with high sonar reflectivity cover about 14 km 2 in the axial rift and were probably erupted from two axial volcanic ridges each of about 3 km in length. Three different lava units occur along an about 11 km long portion of the ridge, and lavas from the northern axial volcanic ridge differ from those of the southern axial volcanic ridge and surrounding lava flows. Basalts from the axial rift flanks and from a pillow mound within the young flows are more incompatible element depleted than those from the young volcanic field. Lavas from this volcanic area have 226 Ra- 230 Th disequilibria model ages of 1,000 and 4,000 years whereas the older lavas from the rift flank and the pillow mound, but also some of the lava field, are older than 8,000 years. Glasses from the northern and southern ends of the southern lava unit indicate up to 100°C cooler magma temperatures than in the center and increased assimilation of hydrothermally altered material. The compositional heterogeneity on a scale of 3 km suggests small magma batches rising vertically from the mantle to the surface without significant lateral flow and mixing. The observations on the 8°48'S lava field support the model of low frequency eruptions from single ascending magma batches that has been developed for slow-spreading ridges. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Origin of Indian Ocean Seamount Province by shallow recycling of continental lithosphere (2011)
    Springer Nature
    Details
    Publication Date: 2011-12-01
    Description: Origin of Indian Ocean Seamount Province by shallow recycling of continental lithosphere Nature Geoscience 4, 883 (2011). doi:10.1038/ngeo1331 Authors: K. Hoernle, F. Hauff, R. Werner, P. van den Bogaard, A. D. Gibbons, S. Conrad & R. D. Müller The origin of the Christmas Island Seamount Province in the northeast Indian Ocean is enigmatic. The seamounts do not form the narrow, linear and continuous trail of volcanoes that would be expected if they had formed above a mantle plume. Volcanism above a fracture in the lithosphere is also unlikely, because the fractures trend orthogonally with respect to the east–west trend of the Christmas Island chain. Here we combine 40Ar/39Ar age, Sr, Nd, Hf and high-precision Pb isotope analyses of volcanic rocks from the province with plate tectonic reconstructions. We find that the seamounts are 47–136 million years old, decrease in age from east to west and are consistently 0–25 million years younger than the underlying oceanic crust, consistent with formation near a mid-ocean ridge. The seamounts also exhibit an enriched geochemical signal, indicating that recycled continental lithosphere was present in their source. Plate tectonic reconstructions show that the seamount province formed at the position where West Burma began separating from Australia and India, forming a new mid-ocean ridge. We propose that the seamounts formed through shallow recycling of delaminated continental lithosphere entrained in mantle that was passively upwelling beneath the mid-ocean ridge. We conclude that shallow recycling of continental lithosphere at mid-ocean ridges could be an important mechanism for the formation of seamount provinces in young ocean basins.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 6
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    Arc-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-01-29
    Description: Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench-normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge or eroded fore-arc complexes but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated (63-190 mm yr(-1)) and are comparable to the magnitude of subducting Cocos plate motion (approximately 85 mm yr(-1)). Trench-parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hoernle, Kaj -- Abt, David L -- Fischer, Karen M -- Nichols, Holly -- Hauff, Folkmar -- Abers, Geoffrey A -- van den Bogaard, Paul -- Heydolph, Ken -- Alvarado, Guillermo -- Protti, Marino -- Strauch, Wilfried -- England -- Nature. 2008 Feb 28;451(7182):1094-7. doi: 10.1038/nature06550. Epub 2008 Jan 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SFB 574, University of Kiel, Wischhofstrasse 1-3, Kiel 24148, Germany. khoernle@ifm-geomar.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18223639" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 7
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    Petrogenesis of a late-stage calc-alkaline granite in a giant S-type batholith: geochronology and Sr–Nd–Pb isotopes from the Nomatsaus granite (Donkerhoek batholith), Namibia (2021)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2023-07-19
    Description: The late-tectonic 511.4 ± 0.6 Ma-old Nomatsaus intrusion (Donkerhoek batholith, Damara orogen, Namibia) consists of moderately peraluminous, magnesian, calc-alkalic to calcic granites similar to I-type granites worldwide. Major and trace-element variations and LREE and HREE concentrations in evolved rocks imply that the fractionated mineral assemblage includes biotite, Fe–Ti oxides, zircon, plagioclase and monazite. Increasing K2O abundance with increasing SiO2 suggests accumulation of K-feldspar; compatible with a small positive Eu anomaly in the most evolved rocks. In comparison with experimental data, the Nomatsaus granite was likely generated from meta-igneous sources of possibly dacitic composition that melted under water-undersaturated conditions (X H2O: 0.25–0.50) and at temperatures between 800 and 850 °C, compatible with the zircon and monazite saturation temperatures of 812 and 852 °C, respectively. The Nomatsaus granite has moderately radiogenic initial 87Sr/86Sr ratios (0.7067–0.7082), relatively radiogenic initial εNd values (− 2.9 to − 4.8) and moderately evolved Pb isotope ratios. Although initial Sr and Nd isotopic compositions of the granite do not vary with SiO2 or MgO contents, fSm/Nd and initial εNd values are negatively correlated indicating limited assimilation of crustal components during monazite-dominated fractional crystallization. The preferred petrogenetic model for the generation of the Nomatsaus granite involves a continent–continent collisional setting with stacking of crustal slices that in combination with high radioactive heat production rates heated the thickened crust, leading to the medium-P/high-T environment characteristic of the southern Central Zone of the Damara orogen. Such a setting promoted partial melting of metasedimentary sources during the initial stages of crustal heating, followed by the partial melting of meta-igneous rocks at mid-crustal levels at higher P–T conditions and relatively late in the orogenic evolution.
    Description: Deutsche Forschungsgemeinschaft
    Description: Universität Hamburg (1037)
    Keywords: ddc:552.3 ; Nomatsaus granite ; Donkerhoek batholith ; Damara Orogen ; Radiogenic isotopes ; U–Pb monazite geochronology
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 8
    Electronic Resource
    Electronic Resource
    A Mid Cretaceous origin for the Galápagos hotspot: volcanological, petrological and geochemical evidence from Costa Rican oceanic crustal segments (1997)
    Springer
    Geologische Rundschau 86 (1997), S. 141-155 
    Details
    ISSN: 0016-7835
    Keywords: Key words Costa Rica ; Ophiolites ; Oceanic crust ; Hotspot ; Galápagos islands ; Volcanology ; Petrology ; Geochemistry ; Isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Quepos, Nicoya and Herradura oceanic igneous terranes in Costa Rica are conspicuous features of a Mid to Late Cretaceous regional magmatic event that encompasses similar terranes in Central America, Colombia, Ecuador and the Caribbean. The Quepos terrane (66 Ma), which consists of ol-cpx phyric, tholeiitic pillow lavas overlain by highly vesicular hyaloclastites, breccias and conglomerates, is interpreted as an uplifted seamount/ocean island complex. The Nicoya (∼90 Ma) and Herradura terranes consist of fault-bounded sequences of sediments, tholeiitic volcanics (pillow lavas and massive sheet flows) and plutonic rocks. The volcanic rocks were emplaced at relatively high eruption rates in moderate to deep water, possibly forming part of an oceanic plateau. Major and trace element data from Nicoya/Herradura tholeiites indicate higher melting temperatures than inferred for normal mid-ocean-ridge basalts (MORB) and/or a different source composition. Sr–Nd–Pb isotopic ratios from all three terranes are distinct from MORB but resemble those from the Galápagos hotspot. The volcanological, petrological and geochemical data from Costa Rican volcanic terranes, combined with published age data, paleomagnetic results and plate tectonic reconstructions of this region, provide strong evidence for a Mid Cretaceous (∼90Ma) age for the Galápagos hotspot, making it one of the oldest known, active hotspots on Earth. Our results also support an origin of the Caribbean Plate through melting of the head of the Galápagos starting plume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009938
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    Paper (German National Licenses)
    Fulltext
  • 9
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    New data of Cretaceous Pacific MORB from accretionary complexes in Kamchatka: Implications for the origin of depleted component in the Hawaiian hotspot lavas (Poster). EGU 3rd General Assembly (2006)
    In:  Vienna, Austria
    Details
    Publication Date: 2006
    Keywords: TF III ; Task Force III ; Lithosphere-Astenosphere Interactions
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    BIBLIOGRAPHY ILP
  • 10
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    Olivine Major and Trace Element Compositions in Southern Payenia Basalts, Argentina: Evidence for Pyroxenite-Peridotite Melt Mixing in a Back-arc Setting (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-23
    Description: Olivine major and trace element compositions from 12 basalts from the southern Payenia volcanic province in Argentina have been analyzed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The olivines have high Fe/Mn and low Ca/Fe and many fall at the end of the global olivine array, indicating that they were formed from a pyroxene-rich source distinct from typical mantle peridotite. The olivines with the highest Fe/Mn have higher Zn/Fe, Zn and Co and lower Co/Fe than the olivines with lower Fe/Mn, also suggesting contributions from a pyroxene-rich source. Together with whole-rock radiogenic isotopes and elemental concentrations, the samples indicate mixing between two mantle sources: (1) a pyroxene-rich source with EM-1 ocean island basalt type trace element and isotope characteristics; (2) a peridotitic source with more radiogenic Pb that was metasomatized by subduction-zone fluids and/or melts. The increasing contributions from the pyroxene-rich source in the southern Payenia basalts are correlated with an increasing Fe-enrichment, which caused the olivines to have lower forsterite contents at a given Ni content. Al-in-olivine crystallization temperatures measured on olivine–spinel pairs are between 1155 and 1243°C and indicate that the magmas formed at normal upper mantle (asthenospheric) temperatures of ~1350°C. The pyroxene-rich material is interpreted to have been brought up from the deeper parts of the upper mantle by vigorous asthenospheric upwelling caused by break-off of the Nazca slab south of Payenia during the Pliocene and roll-back of the subducting slab beneath Payenia. The pyroxene-rich mantle mixed with peridotitic metasomatized South Atlantic mantle in the mantle wedge beneath Payenia.
    Print ISSN: 0022-3530
    Electronic ISSN: 1460-2415
    Topics: Geosciences
    Published by Oxford University Press
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