Intraplate Volcanism: Conc Continuing the Discussion of Mantle Plumes in the Previous Two Issues, Alan D Smith Looks at Mantle Models
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Basaltic Continental Intraplate Volcanism As Sustained by Shear-Driven Upwelling
Geophysical Research Abstracts Vol. 14, EGU2012-3273-1, 2012 EGU General Assembly 2012 © Author(s) 2012 Basaltic continental intraplate volcanism as sustained by shear-driven upwelling M. D. Ballmer (1), C. P. Conrad (1), and E. I. Smith (2) (1) Department of Geology & Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA, (2) Department of Geoscience, University of Nevada Las Vegas, Las Vegas, Neveda 89154, USA While most volcanism on Earth occurs at plate boundaries, the study of intraplate basaltic volcanism may provide an opportunity to scrutinize the make-up and dynamics of the mantle. In continental settings, a range of mechanisms were proposed to sustain mantle decompression and hence to support such volcanism. These include mantle plumes, fertile melting anomalies, self-sustaining buoyant decompression melting, lithospheric dripping, and edge-driven small-scale convection. Recently, Conrad et al. showed that basaltic continental volcanism occurs more often where shear across the asthenosphere is greatest, and hence propose shear-driven upwelling (SDU) to support such volcanism1. SDU does not require density heterogeneity to drive convection, in contrast to other mechanisms. Rather, it develops when rapid shear across the asthenosphere meets lateral viscosity variation2. For example, in a case with a low-viscosity pocket in the mantle, asthenospheric shear is accommodated in a different manner across the pocket than across the ambient mantle. This contrast drives vertical flow close to the margins of the pocket, and may be sufficient to sustain decompression melting, particularly if the viscosity anomaly is supported by higher water contents or temperatures2. -
The Origin of Intraplate Volcanism on Zealandia C
Geophysical Research Abstracts, Vol. 10, EGU2008-A-11195, 2008 SRef-ID: 1607-7962/gra/EGU2008-A-11195 EGU General Assembly 2008 © Author(s) 2008 The Origin of Intraplate Volcanism on Zealandia C. Timm (1), K. Hoernle (1), R. Werner (2), F. Hauff (1), P. van den Boogard (1), J. White (3), N. Mortimer (4) (1) IFM-GEOMAR, Wischhofstr. 1-3, 24148 Kiel (2) Tethys Geoconsulting GmbH, Wischhofstr. 1-3, 24148 Kiel (3) Geology Department, University of Otago, PO Box 56, Dunedin 9015, NZ (4) Institute of Geological and Nuclear Sciences, PO Box 31-312, Lower Hut, NZ The origin of intraplate volcanism on continents is generally attributed to mantle plumes or continental rifting. Widespread intraplate volcanism has occurred on the pri- marily submarine New Zealand micro-continent Zealandia almost continuously since its separation from Gondwana approx. 100 Ma ago. This volcanism cannot be directly related to continental rifting and occurred during local periods of both extension and compression. The lack of extended volcanic belts with age progressions in the direc- tion and at the rate of plate motion is not consistent with the plume hypothesis. Volu- minous HIMU-type volcanism was associated with the Cretaceous rifting of Zealandia from Gondwana, consistent with suggestions that a mantle plume or plume head may have been involved in causing the separation of Zealandia from Gondwana (Story et al., 1999). After the “break-up” ∼84 Ma ago, Zealandia drifted ∼6,000 km to the NW. In contrast, lower volumes of eruptives were produced in the Cenozoic. Most mafic (MgO > 5 wt%) Cenozoic lavas define an array between the Cretaceous HIMU-type lavas and Pacific MORB on Sr, Nd, Pb and Hf isotope correlation diagrams, suggest- ing the involvement of the residual HIMU-type plume-type material and the depleted MORB source. -
MANTLE PLUMES and FLOOD BASALTS Scribedblob of Uniformtemperature, Rather Than Resultingfrom Startsat the Paranaflood Basalt Province,South America
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Memorial University Research Repository JOURNALOF GEOPHYSICAL RESEARCH, VOL. 106, NO. B2, PAGES 2047-2059, FEBRUARY 10, 2001 Mantleplumes and flood basalts: Enhanced melting fromplume ascent and an eclogitecomponent A.M. Leitch•, andG. F.Davies ResearchSchool of EarthSciences, Australian National University, Canberra, ACT Abstract.New numerical models of startingplumes reproduce the observed volumes and rates of floodbasalt eruptions, even for a plumeof moderatetemperature arriving under thick lithosphere. Thesemodels follow the growth of a newplume from a thermalboundary layer and its subsequent risethrough the mantle viscosity structure. They show that as a plumehead rises into the lower- viscosityupper mantle it narrows,and it isthus able to penetrate rapidly right to thebase of litho- sphere,where it spreadsas a thinlayer. This behavior also brings the hottest plume matehal to the shallowestdepths. Both factors enhance melt production compared with previous plume models. Themodel plumes are also assumed to containeclogite bodies, inferred from geochemistry to be recycledoceanic crust. Previous numerical models have shown that the presence of nonreacting eclogitebodies may greatly enhance melt production. it hasbeen argued that the eclogite-derived meltwould react with surroundingperidotite and refreeze; however, recent experimental studies indicatethat eclogite-derived melts may have reached the Earth's surface with onlymoderate or evenminor -
Mantle Plumes and Intraplate Volcanism Volcanism on the Earth
Mantle Plumes and Intraplate Volcanism Origin of Oceanic Island Volcanoes EAS 302 Lecture 20 Volcanism on the Earth • Mid-ocean ridges (>90% of the volcanism) – “constructive” plate margins • Subduction-related (much of the rest) – “destructive plate” margins • Volcanism in plate interiors (usually) – , e.g., Yellowstone, Hawaii not explained by the plate tectonic paradigm. Characteristics of Intra-plate Volcanoes • Not restricted to plate margins. • Occur at locations that are stationary relative to plate motions, “hot spots”(pointed out by J. T. Wilson, 1963). • Distinctive isotopic and trace element composition. Hot Spot Traces on the Pacific Ocean Floor The Mantle Plume Model • “ Hot spot” volcanoes are manifestations of mantle plumes: columns of hot rock rising buoyantly from the deep mantle – This idea proposed by W. J. Morgan in 1971. • Evidence – Maintain (almost) fixed positions relative to each other; i.e., they are not affected by plate motions – A number of “hot spots” are associated with “swells”, indicative of hot mantle below – Their magmas are compositionally distinct from mid-ocean ridge basalts and therefore must be derived from a different part of the mantle Current Mantle Plumes The Hawaiian Mantle Plume Age of Hawaiian Volcanism The Hawaiian “Swell” Plumes at the surface • In the last 100-200 km, the plume begins to melt. • Once it reaches the base of the lithosphere, it can no longer rise and spreads out. Isotopic Compositions of Oceanic Island Basalts • Nd and Sr isotope ratios 12 DMM distinct from MORB: 10 derived from separate MORB 8 reservoir which is less 6 depleted (and Society ε Nd 4 sometimes enriched) in HIMU incompatible elements. -
Volcanism in a Plate Tectonics Perspective
Appendix I Volcanism in a Plate Tectonics Perspective 1 APPENDIX I VOLCANISM IN A PLATE TECTONICS PERSPECTIVE Contributed by Tom Sisson Volcanoes and Earth’s Interior Structure (See Surrounded by Volcanoes and Magma Mash for relevant illustrations and activities.) To understand how volcanoes form, it is necessary to know something about the inner structure and dynamics of the Earth. The speed at which earthquake waves travel indicates that Earth contains a dense core composed chiefly of iron. The inner part of the core is solid metal, but the outer part is melted and can flow. Circulation (movement) of the liquid outer core probably creates Earth’s magnetic field that causes compass needles to point north and helps some animals migrate. The outer core is surrounded by hot, dense rock known as the mantle. Although the mantle is nearly everywhere completely solid, the rock is hot enough that it is soft and pliable. It flows very slowly, at speeds of inches-to-feet each year, in much the same way as solid ice flows in a glacier. Earth’s interior is hot both because of heat left over from its formation 4.56 billion years ago by meteorites crashing together (accreting due to gravity), and because of traces of natural radioactivity in rocks. As radioactive elements break down into other elements, they release heat, which warms the inside of the Earth. The outermost part of the solid Earth is the crust, which is colder and about ten percent less dense than the mantle, both because it has a different chemical composition and because of lower pressures that favor low-density minerals. -
Ancient Helium and Tungsten Isotopic Signatures Preserved in Mantle Domains Least Modified by Crustal Recycling
Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling Matthew G. Jacksona,1, Janne Blichert-Toftb,2, Saemundur A. Halldórssonc,2, Andrea Mundl-Petermeierd, Michael Bizimise, Mark D. Kurzf, Allison A. Pricea, Sunna Harðardóttirc, Lori N. Willhitea,g, Kresten Breddamh, Thorsten W. Beckeri,j, and Rebecca A. Fischerk aDepartment of Earth Science, University of California, Santa Barbara, CA 93106-9630; bLaboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon, CNRS, and Université de Lyon, 69007 Lyon, France; cNordVulk, Institute of Earth Sciences, University of Iceland, 102 Reykjavík, Iceland; dDepartment of Lithospheric Research, University of Vienna, 1090 Vienna, Austria; eSchool of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC 29208; fDepartment of Marine Chemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; gDepartment of Geology, University of Maryland, College Park, MD 20742; hRadiation Protection, Danish Health Authority, 2300 Copenhagen, Denmark; iInstitute for Geophysics, The Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713; jDepartment of Geological Sciences, The Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713; and kDepartment of Earth & Planetary Sciences, Harvard University, Cambridge, MA 02138 Edited by Albrecht W. Hofmann, Max Planck Institute for Chemistry, Mainz, Germany, and approved October 22, 2020 (received for review May 14, 2020) Rare high-3He/4He signatures in ocean island basalts (OIB) erupted Sr-Nd-Pb isotopic space, these four geochemical endmembers can at volcanic hotspots derive from deep-seated domains preserved in be used to define the apices of a tetrahedron (8) (Fig. -
Mantle Plumes
Geol. 655 Isotope Geochemistry Lecture 21 Spring 2007 ISOTOPIC EVOLUTION OF THE MANTLE IV THE ORIGIN OF MANTLE PLUMES AND THE COMMON COMPONENT IN PLUMES Determining how the various geochemical reservoirs of the mantle have evolved is among the most vexing problems in geochemistry. The principal observation to be explained is that mantle plumes in- variably have less depleted isotopic signatures than MORB, and the isotopic compositions of some in- dicate net enrichment in incompatible elements. As we saw in the previous lecture, mantle plumes were initially thought to consist of primitive mantle (e.g., Schilling, 1973). As we found, mixing be- tween primitive and depleted mantle can explain the Sr and Nd isotopic compositions of some plumes, but virtually none of the Pb isotope data can be explained this way, nor are the trace element composi- tions of OIB consistent with plumes being composed of primitive mantle. Indeed, although ‘primitive mantle’ has proved to be a useful hypothetical concept, no mantle-derived basalts or xenoliths have appropriate compositions to be ‘primitive mantle’ or derived from it. It is possible that no part of the mantle retains its original, primitive, composition (on the other hand, to have survived, primitive man- tle must not participate in volcanism and other such processes, so the absence of evidence for a primi- tive mantle reservoir is not evidence of its absence). Hofmann and White (1982) suggested mantle plumes obtain their unique geochemical signature through deep recycling of oceanic crust (Figure 21.1). Partial melting at mid-ocean ridges creates oce- anic crust that is less depleted in incompatible elements than the depleted upper mantle. -
Different Causes of the Delamination on the Example of Caucasus and Kyrgyz Tien Shan Collision Zones
EGU2020-6412 https://doi.org/10.5194/egusphere-egu2020-6412 EGU General Assembly 2020 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Different causes of the delamination on the example of Caucasus and Kyrgyz Tien Shan collision zones. Irina Medved1,2,3, Ivan Koulakov2,3, and Mikhail Buslov1 1IGM SB RAS, Novosibirsk, Russian Federation ([email protected]) 2IPGG SB RAS, Novosibirsk, Russian Federation 3Novosibirsk State University, Novosibirsk, Russian Federation The causes of delamination of the mantle lithosphere in collision zones is actively debated in the scientific community. The main discussions are focused on the initiation of sinking of the continental lithosphere into the asthenosphere to a depth. Most scientists believe that such kind of immersion is impossible. However, there are several articles showing that this process is nonetheless taking place. For example Kay and Kay, (1993), Faccenda, Minelli, Gerya, (2009), Ueda et. al., (2012) and others propose various mechanisms of delamination, for example: eclogitization of the mafic layer of the lower crust, the effect of convection in the upper mantle, or gradual transition of the oceanic subduction into continental collision. Does the mantle part of the lithosphere sink into the mantle or spread laterally, as described in [for example, Deep Geodynamics, 2001; Bird, 1991; Schmeling and Marquart, 1991]? To answer these questions, we study deep structures beneath the Caucasus and Kyrgyz Tien Shan collision zones. The studies were carried out on the basis of multiscale seismic tomography methods: regional and global. This approach made it possible to study heterogeneities both in the crust and in the upper mantle. -
Large Igneous Provinces and the Mantle Plume Hypothesis
Large Igneous Provinces and the Mantle Plume Hypothesis Columnar jointing in a postglacial basalt flow at Aldeyarfoss, NE Iceland. PHOTO JOHN MACLENNAN Ian H. Campbell1 antle plumes are columns of hot, solid material that originate deep in the mantle, probably at the core–mantle boundary. Laboratory 1990) and aseismic ridges, like the Chagos–Lacadive Ridge, to the and numerical models replicating conditions appropriate to the M melting of a plume tail (Wilson mantle show that mantle plumes have a regular and predictable shape that 1963; Morgan 1971). allows a number of testable predictions to be made. New mantle plumes are predicted to consist of a large head, 1000 km in diameter, followed by a THE MANTLE PLUME HYPOTHESIS narrower tail. Initial eruption of basalt from a plume head should be preceded Convection in fluids is driven by by ~1000 m of domal uplift. High-temperature magmas are expected to buoyancy anomalies that originate dominate the first eruptive products of a new plume and should be concen- in thermal boundary layers. trated near the centre of the volcanic province. All of these predictions are Earth’s mantle has two boundary confirmed by observations. layers. The upper boundary layer is the lithosphere, which cools KEYWORDS: mantle plume, large igneous provinces, uplift, picrite through its upper surface. It even- tually becomes denser than the INTRODUCTION underlying mantle and sinks back into it, driving plate tectonics. The lower boundary layer is The plate tectonic hypothesis provides an elegant explana- the contact between the Earth’s molten iron–nickel outer tion for Earth’s two principal types of basaltic volcanism, core and the mantle. -
Diamonds Deliver the Dirt Dinosaurs Usually Found in Younger Sediments
NEWS AND VIEWS RESUME------ - - complexes such as [Mlll(bipy-h] rather may be regarded as 'expanded' ele Early bird than [M0 (bipyh). The niceties of this ments, in which the effective size of the How a routine re-examination of a ambiguity are of direct relevance, as the alkali metal atom has been increased - modest fossil reptile turned into a complex cation [Ru(bipyh)2+ plays a instead of finding the electron in one of search for the closest relatives of birds vital role in many chemical photoconver the valence orbitals of the metal ion it is is recounted by A. R. Milner and S. E. sion systems. The critical excited state found slightly out in the orbitals of the Evans in Palaeontology (34, 503-513; [Ru(bipy)3] 2+* is best described10 as directly bonded ligands. D 1991). Fragmentary material of charge-separated [Ru III(bipy h(bipy-) ]2 + •. Lisboasaurus estesi from Guimarota in Portugal, about 160 million years old, The new compound described by Lehn Edwin C. Constable is in the Cambridge originally described as from a lizard. and co-workers. provides a structural Centre for Molecular Recognition, University was model for this photoexcited state as well Chemical Laboratory, University of Cam Further study by R. Estes revealed the as challenging our preconceptions about bridge, Lensfield Road, Cambridge CB2 presence of socketed teeth, more the ionic state. These new compounds 1EW, UK. characteristic of archosaurs (crocodiles, MANTLE GEOCHEMISTRY ________________ dinosaurs and birds). Milner and Evans now show that Lisboasaurus most closely resembles the troodontids, a group of advanced, birdlike theropod Diamonds deliver the dirt dinosaurs usually found in younger sediments. -
Origin of Indian Ocean Seamount Province by Shallow Recycling of Continental Lithosphere
LETTERS PUBLISHED ONLINE: 27 NOVEMBER 2011 | DOI: 10.1038/NGEO1331 Origin of Indian Ocean Seamount Province by shallow recycling of continental lithosphere K. Hoernle1*, F. Hauff1, R. Werner1, P. van den Bogaard1, A. D. Gibbons2, S. Conrad1 and R. D. Müller2 The origin of the Christmas Island Seamount Province in the 5° S Outsider Seamount Sumatra northeast Indian Ocean is enigmatic. The seamounts do not Java form the narrow, linear and continuous trail of volcanoes 53 Investigator Rise Bali that would be expected if they had formed above a mantle Vening-Meinesz 1,2 3 Cocos- plume . Volcanism above a fracture in the lithosphere is also Keeling Volcanic Province 10° S unlikely, because the fractures trend orthogonally with respect Islands 4¬44 Christmas Island 64 70 65 85 105 to the east–west trend of the Christmas Island chain. Here 56 71 94 40 39 we combine Ar= Ar age, Sr, Nd, Hf and high-precision Pb 47 64 81 107 97 112 104 136 Argo isotope analyses of volcanic rocks from the province with plate 90 95 115 Basin tectonic reconstructions. We find that the seamounts are 47– 47 102 115 Volc. 15° S Prov. 136 million years old, decrease in age from east to west and are Cocos-Keeling Eastern Wharton Basin consistently 0–25 million years younger than the underlying Volc. Prov. Volcanic Province oceanic crust, consistent with formation near a mid-ocean 7 cm yr¬1 ridge. The seamounts also exhibit an enriched geochemical 95° E 100° E 105° E 110° E 115° E signal, indicating that recycled continental lithosphere was present in their source. -
The Role of Crustal Recycling During the Assembly of the Supercontinent
The role of crustal recycling during the assembly of the supercontinent NUNA: Geochemical and isotopic constraints from felsic magmatism in the Makkovik Province, Labrador. Alana M. Hinchey Geological Survey, Department of Natural Resources, Government of Newfoundland and Labrador, *(e-mail: [email protected]) Summary The Makkovik Province of Labrador documents the early stages of the Great Proterozoic Accretionary Orogen recording part of the amalgamation of the supercontinent NUNA. During this supercontinent amalgamation, most continental crustal growth occurred in a relatively short period of time between 1900 and 1800 Ma. Insight into the assembly of NUNA is preserved in the felsic rocks from the Aillik Domain of the Makkovik Province. Major and trace element lithogeochemical signatures indicate compositions typical of “A-type‟ rhyolites and granites. Extended trace and rare earth element patterns are typical of the compositions of melts derived by partial melting of sialic crust, with strongly negative Nb and Ti anomalies; typical of crustal derived melts related either to the subduction processes or to crustal contamination processes. The trace element ratios, such as high La/Yb(PM) and Zr/Y ratios, are indicative of a low degree of partial melting at high temperatures (~850 - 900 oC) where garnet and amphibole were stable in the residue. The felsic volcanic rocks and synvolcanic intrusions have εNd(T) values that range from -0.86 to -4.62, with T(DM) model ages that range from 2160 Ma to 2775 Ma, suggesting derivation by partial melting sialic crust of predominantly Late Archean to Paleoproterozoic age. The neodymium crustal index (NCI) indicates a crustal neodymium contribution ranging from 31% to 61%, with an average of 46%, suggesting an equal amount of recycling of crust relative to the addition of juvenile crust during the derivation of the felsic rocks.