Sæmundur Ari Halldórsson

Sæmundur Ari Halldórsson
University of Iceland | HI · Nordic Volcanological Center

PhD

About

52
Publications
10,871
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931
Citations
Additional affiliations
March 2014 - present
University of Iceland
Position
  • Research Associate
September 2008 - March 2014
University of California, San Diego
Position
  • Student

Publications

Publications (52)
Article
Full-text available
Recent Icelandic rifting events have illuminated the roles of centralized crustal magma reservoirs and lateral magma transport1–4, important characteristics of mid-ocean ridge magmatism1,5. A consequence of such shallow crustal processing of magmas4,5 is the overprinting of signatures that trace the origin, evolution and transport of melts in the u...
Article
Full-text available
We measured the N concentrations and isotopic compositions of 44 samples of terrestrial potassic and micro- and meso-porous minerals and a small number of whole-rocks to determine the extent to which N is incorporated and stored during weathering and low-temperature hydrothermal alteration inMars surface/near-surface environments. The selection of...
Article
Icelandic basalts have low oxygen isotope (δ18O) values compared to other ocean island localities. While this observation is often ascribed to the assimilation of low-δ18O crust, a low-δ18O mantle beneath Iceland has also been suggested. To discern crustal from mantle-derived signals, high-quality in-situ and bulk crystal δ18O measurements have bee...
Article
The compositions of ocean island basalts (OIB) can record signatures of ancient subducted crust that has been recycled through the mantle. Based on their radiogenic isotope, major and trace element compositions, several geochemically-extreme mantle compositions are suggested to host components of recycled crust. Barium (Ba) stable isotopes can serv...
Conference Paper
Volcanoes in Iceland are supplied by excess mantle melting caused by interaction between the mid-Atlantic ridge and a deep-rooted mantle plume. Geochemically, this plume-ridge interaction is expressed in erupted basalt as a wide range of radiogenic isotope and trace element signatures reflecting variable mixtures between the upper mantle source of...
Article
We compile a new geochemical database (Icelandic Volcanic rocks Isotopic Database, IVID) which includes previously reported ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ¹⁷⁶Hf/¹⁷⁷Hf, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, ¹⁸⁷Os/¹⁸⁸Os and ³He/⁴He data and major and trace element concentrations measured in Icelandic volcanic rocks. Isotopic compositions were evaluated and...
Article
Stable sulfur isotope ratios of mid-ocean ridge and ocean island basalts (MORBs and OIBs) preserve unique information about early Earth processes and the long-term volatile cycles between Earth's mantle and the surface. Icelandic basalts present ideal material to examine the oldest known terrestrial mantle reservoir, accessed through a deep-rooted...
Article
Volatile-rich fluids are believed to play a key role in the metasomatic enrichment of the East African sub-continental lithospheric mantle (SCLM), but limited data is available on key volatile tracers such as CO2 and N2. We report new CO2 and N2 isotope and relative abundance data in exceptionally gas-rich mantle peridotite and pyroxenite xenoliths...
Article
Full-text available
Significance We report the discovery of anomalously high ³ He/ ⁴ He in “cold” geothermal fluids of central Panama, far from any active volcanoes. Combined with independent constraints from lava geochemistry, mantle source geochemical anomalies in Central America require a Galápagos plume contribution that is not derived from hotspot track recycling...
Preprint
Full-text available
Enriched mantle heterogeneities are widely considered to be generated through subduction, but the connections between specific subducted materials and the chemical signatures of mantle heterogeneities are not clearly defined. Boron is strongly isotopically fractionated at the surface and traces slab devolatilization, making it a potent tracer of pr...
Article
Full-text available
The element mercury (Hg) can develop large mass-independent fractionation (MIF) (Δ199Hg) due to photo-chemical reactions at Earth's surface. This results in globally negative Δ199Hg for terrestrial sub-aerially-derived materials and positive Δ199Hg for sub-aqueously-derived marine sediments. The mantle composition least affected by crustal recyclin...
Article
Carbon dioxide emissions from active subaerial volcanoes represent 20–50% of the annual global volcanic CO2 flux (Barry et al., 2014). Passive degassing of carbon from the flanks of volcanoes, and the associated accumulation of dissolved inorganic carbon (DIC) within nearby groundwater, also represents a potentially important, yet poorly constraine...
Article
Full-text available
The episodic growth of high-elevation orogenic plateaux is controlled by a series of geodynamic processes. However, determining the underlying mechanisms that drive plateau growth dynamics over geological history and constraining the depths at which growth originates, remains challenging. Here we present He-CO2-N2 systematics of hydrothermal fluids...
Presentation
Oxygen isotope ratios (δ18O) of Icelandic crustal rocks and neovolcanic lavas differ significantly from mantle values. δ18O values have been widely used to study the role of the crust in Icelandic basalt petrogenesis, either in the form of source contamination or as crustal contamination. The Bárðarbunga volcanic system in central Iceland is envisi...
Preprint
Stable sulfur isotope ratios of mid-ocean ridge and ocean island basalts (MORBs and OIBs) preserve unique information about early Earth processes and the long-term volatile cycles between Earth’s mantle and the surface. Icelandic basalts present ideal material to examine the oldest known terrestrial mantle reservoir, accessed through a deep-rooted...
Article
Full-text available
The timescales of magmatic processes within a volcanic system may be variable over a volcano’s geological history. Crystals reflect environmental perturbations under which they grew, and compositional gradients quenched inside crystals on eruption can be exploited to extract timescales of magmatic processes. Here, we use multi-element diffusion chr...
Article
Full-text available
Significance The recent discovery of anomalous ¹⁸² W signatures in modern, plume-derived hotspot lavas provides evidence for survival of domains in Earth’s interior since the early Hadean. Only lavas with ancient, high- ³ He/ ⁴ He signatures preserve anomalous ¹⁸² W signatures. However, it is not known why only high- ³ He/ ⁴ He lavas have anomalous...
Article
Full-text available
Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation ra...
Article
The depth(s) of magma storage reservoirs beneath active volcanic regions may change with time. Determining the rates and causes of millennial-scale changes in magmatic system architecture is critical for the development of realistic time-integrated models of crustal evolution. Here we examine a suite of samples from the exceptionally well-exposed B...
Article
Clinopyroxene–liquid geothermobarometry is a widely used tool for estimating the conditions under which mafic magmas are stored before they erupt. However, redox variability, sector zoning and disequilibrium crystallization present major challenges to the robust estimation of magma storage conditions. Moreover, most recent studies seeking to addres...
Article
Full-text available
Change history: In this Article, the original affiliation 2 was not applicable and has been removed. In addition, in the Acknowledgements there was a statement missing and an error in a name. These errors have been corrected online.
Article
Full-text available
Carbon and other volatiles in the form of gases, fluids or mineral phases are transported from Earth’s surface into the mantle at convergent margins, where the oceanic crust subducts beneath the continental crust. The efficiency of this transfer has profound implications for the nature and scale of geochemical heterogeneities in Earth’s deep mantle...
Article
Full-text available
The 2014–2015 Holuhraun fissure eruption provided a rare opportunity to study in detail the magmatic processes and magma plumbing system dynamics during a 6-month-long, moderate- to large-volume basaltic fissure eruption. In this contribution, we present a comprehensive dataset, including major and trace elements of whole-rock and glassy tephra sam...
Article
Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ¹⁸O values. Overall, Toba quartz cry...
Article
A number of processes have extensively modified original mantle source N isotope and relative abundance compositions - most significantly air interaction, crustal contamination in some instances, and possibly degassing-induced fractionation. Under the assumption that the starting 4He/40Ar∗ production ratio of Iceland mantle is identical to the depl...
Article
Full-text available
The hydrogen-isotope [deuterium/hydrogen (D/H)] ratio of Earth can be used to constrain the origin of its water. However, the most accessible reservoir, Earth’s oceans, may no longer represent the original (primordial) D/H ratio, owing to changes caused by water cycling between the surface and the interior. Thus, a reservoir completely isolated fro...
Article
We report new carbon dioxide (CO2) abundance and isotope data for 71 geothermal gases and fluids from both high-temperature (HT > 150 °C at 1 km depth) and low-temperature (LT < 150 °C at 1 km depth) geothermal systems located within neovolcanic zones and older segments of the Icelandic crust, respectively. These data are supplemented by CO2 data o...
Article
We report combined He-Ne-Ar isotope data of mantle-derived xenoliths and/or lavas from all segments of the East Africa Rift System (EARS). Plume-like helium isotope (3He/4He) ratios (i.e., greater than the Depleted MORB Mantle (DMM) range of 8 ± 1RA) are restricted to the Ethiopia Rift and Rungwe, the southernmost volcanic province of the Western R...
Article
Hydrogen isotope ratios in basaltic melt inclusions from Baffin Island and Iceland indicate Earth's primordial D/H ratio survives in the deep mantle.
Article
We studied to D/H ratio of the deep terrestrial mantle to determine if the Earths primordial hydrogen isotope composition was significantly different to that of the current surficial hydrosphere.
Article
We present the chemical and isotope (HeCN) characterization of active fumaroles and hydrothermal gases and waters from the summits and flanks of 19 volcanic centers along the western Sunda arc, Indonesia. Samples were collected over two field expeditions (1991 and 2010) and cover 13 volcanic centers in Sumatra, 5 in Java and one in Bali. In additio...
Article
We investigate the helium (3He/4He) and carbon (δ13C) isotope compositions and relative abundance ratios (CO2/3He) of gas samples together with the stable isotope compositions of dissolved carbon and sulfur and the oxygen and hydrogen isotopic compositions of the associated water phase from a number of geothermal fields located around Lake Van in e...
Article
The Indonesian island of Sumatra, located in one of the most active zones of the Pacific Ring of Fire, is characterized by a chain of subduction‐zone volcanoes which extend the entire length of the island. As a group of volcanic geochemists, we embarked upon a five‐week sampling expedition to these exotic, remote, and in part explosive volcanoes (S...
Article
Full-text available
We describe a new system for the simultaneous static triple-collection of nitrogen isotopes at the <10μcm3 STP [N2] (<1 × 10-5 cm3STP; <0.5 nmol) level using a modified VG-5440 noble gas mass spectrometer. The system consists of an internal N2-STD with aδ15N value of -0.11 ± 0.22 ‰ (1σ) calibrated against an air-standard (Air-STD). The N2-STD was m...
Article
We report helium isotope ratios (3He/4He) of lavas and tephra of the Rungwe Volcanic Province (RVP) in southern Tanzania. Values as high as 15RA (RA = air 3He/4He) far exceed typical upper mantle values, and are the first observation of plume-like ratios south of the Turkana Depression which separates the topographic highs of the Ethiopia and Kenya...
Conference Paper
Full-text available
We investigate helium isotope compositions and CO2/3He ratios of gas samples and stable isotope (oxygen, hydrogen, carbon and sulfur) compositions of water samples collected from various geothermal fields in eastern Anatolia. Most of sampling sites are located close to recently active volcanoes (e.g. Ararat, Tendürek, Süphan, Nemrut Caldera) around...
Article
P. H. BARRY1*, D. R. HILTON1, E. FÜRI1, S.A. HALLDÓRSON1, T.P. FISCHER2, K. GRONVOLD3 1 Scripps Institution of Oceanography, UCSD, La Jolla, California 92093, USA (*Correspondence: pbarry@ucsd.edu). 2University of New Mexico, Albuquerque, NM 87131, USA. 3University of Iceland, Askja, Sturlugata 7, IS-101, Reykjavik, Iceland Carbon dioxide (CO2) is...
Article
Helium isotope studies of the East African Rift System (EARS) suggest the involvement of a deep mantle plume(s) beneath the northern (Ethiopian) segment [1-3]. The highest 3He/4He (RA) signatures found to date show a close association with the greatest magma volumes erupted since the Early Cenozoic in the region. While the helium isotope characteri...
Article
We present new He–Ne data for geothermal fluids and He–Ne–Ar data for basalts from throughout the Icelandic neovolcanic zones and older parts of the Icelandic crust. Geothermal fluids, subglacial glasses, and mafic phenocrysts are characterized by a wide range in helium isotope ratios (3He/4He) encompassing typical MORB-like ratios through values a...
Article
Nitrogen isotope geochemistry can be used to identify sedimentary input (delta15N=+80/00) in volcanic arc systems, but its use as an indicator of deep mantle volatile contributions is limited. Consequently, we target the neovolcanic zones of Iceland where He isotope work has revealed a distinct region of elevated 3He/4He ratios (>20RA, where RA=air...
Article
The Thjorsa lava in South Iceland is an early Holocene fissure lava within the Bardarbunga volcanic system—the most productive segment of the Eastern Rift Zone during the Quaternary and Holocene. The lava has a volume of 25 km3 and is one of notably plagioclase-porphyritic early Holocene lava flows in Iceland.The possible genetic relationship betwe...
Article
The Thjorsa lava is a voluminous tholeiite fissure lava flow originating within the Bardarbunga volcanic system of the Eastern Rift Zone, Iceland. The lava contains a high content of xenocrysts of plagioclase and minor olivine. Detailed analytical work using electron microprobe reveals a very thin reaction rim surrounding the xenocryst. Individual...
Article
The Thjorsa lava in the Eastern Rift Zone (ERZ) in Southern Iceland erupted 8600 years ago. It is the largest Holocene fissure lava in Iceland with a total volume of 25 km3. It is one of several highly plagioclase-porphyritic tholeiitic fissure eruptions from the early Holocene. These porphyritic lavas belong to the Bardarbunga volcanic system whic...

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