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  • 2015-2019  (6)
  • 2016  (6)
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  • 2015-2019  (6)
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  • 1
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    Evolution of magma chambers generating the phonolitic Cão Grande Formation on Santo Antão, Cape Verde Archipelago (2016)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 327 . pp. 436-448.
    Details
    Publication Date: 2019-02-01
    Description: Highlights • Individual evolution of temporal and spatial co-existing magma suites • Determination of pre-eruptive magma chamber conditions of the Cão Grande Formation magma chambers • Cão Grande Formation phonolite magmas typically reach H2O-saturation prior to the eruption. Abstract The Cão Grande Formation (CGF) on the western plateau of Santo Antão is a sequence of four phonolitic tephras (Canudo Tephra, Cão Grande I Tephra, Cão Grande II Tephra and Furninha Tephra) produced by highly explosive eruptions that alternatingly originated from a basanitic - phonolitic and a nephelinitic - phonolitic magmatic system. Detailed stratigraphy and petrological investigations of each unit are used to demonstrate the unusual situation that two distinct highly evolved magmas differentiated contemporaneously in separate magmatic systems. Chemical thermobarometry suggests that both magmatic systems not only temporally co-existed, but also that their magma chambers resided close to each other at 7 to 16 km depth, beneath the western plateau of Santo Antão. However, the distinct melt and magma compositions indicate that both systems evolved independently. The only interaction between both magmatic systems was an injection of magma from the nephelinitic - phonolitic magmatic system into the Cão Grande II Tephra (CG II) phonolitic reservoir, which is associated to the basanitic - phonolitic magmatic system. Compositional zonations in the tephra deposits indicate that the eruptions of the CGF tapped stratified magma reservoirs that mainly resulted from crystal accumulation generating downward increasing magma density. However, the CG II tephras also show a significant gradient in melt (glass) compositions. Magmas of the Canudo Tephra (CT) and the Cão Grande I Tephra (CG I) were H2O-saturated and their eruptions were probably triggered by fluid overpressure in the magma chamber. On the other hand, the CG II magma was H2O-undersaturated; we therefore assume that the injection of the hot nephelinitic - phonolitic magma system-type melt/magma triggered the eruption. The zoned deposit of the Furninha Tephra (FT) indicates mafic magma replenishment into a phonolitic reservoir directly prior to the eruption, thus providing a probable triggering mechanism. The new magma chamber models and thermobarometric results for the four CGF units provide constraints for hazard assessments, because similar events may occur in the future considering the longevity of the CGF magma systems.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.jvolgeores.2016.09.016
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 17 (11). pp. 4641-4668.
    Details
    Publication Date: 2019-02-01
    Description: We studied the tephra inventory of 18 deep sea drill sites from six DSDP/ODP legs (Legs 84, 138, 170, 202, 205, 206) and two IODP legs (Legs 334 and 344) offshore the southern Central American Volcanic Arc (CAVA). Eight drill sites are located on the incoming Cocos plate and ten drill sites on the continental slope of the Caribbean plate. In total we examined ∼840 ash-bearing horizons and identified ∼650 of these as primary ash beds of which 430 originated from the CAVA. Correlations of ash beds were established between marine cores and with terrestrial tephra deposits, using major and trace element glass compositions with respect to relative stratigraphic order. As a prerequisite for marine-terrestrial correlations we present a new geochemical data set for significant Neogene and Quaternary Costa Rican tephras. Moreover, new Ar/Ar ages for marine tephras have been determined and marine ash beds are also dated using the pelagic sedimentation rates. The resulting correlations and provenance analyses build a tephrochronostratigraphic framework for Costa Rica and Nicaragua that covers the last 〉8 Myr. We define 39 correlations of marine ash beds to specific tephra formations in Costa Rica and Nicaragua; from the 4.15 Ma Lower Sandillal Ignimbrite to the 3.5 ka Rincón de la Vieja Tephra from Costa Rica, as well as another 32 widely distributed tephra layers for which their specific region of origin along Costa Rica and Nicaragua can be constrained.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2016GC006503
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Alkalic marine tephra layers at ODP Site 1241 - Major explosive eruptions from an oceanic volcano in a pre-shield stage? (2016)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 328 . pp. 96-104.
    Details
    Publication Date: 2019-09-23
    Description: Highlights • Subplinian to Plinian eruptions from Cocos Island • Tectonically controlled melt ascent • Ocean island evolution without passing typical growth stages Abstract We report a series of fourteen marine tephra layers that are the products of large explosive eruptions of Subplinian to Plinian intensities and magnitudes (VEI 〉 4) from Cocos Island, Costa Rica. Cocos Island is a volcanic island in the eastern Central Pacific Ocean ~ 500 km offshore Costa Rica, and is situated on the northwestern flank of the aseismic Cocos Ridge. Geochemical fingerprinting of Pleistocene (~ 2.4–1.4 Ma) marine tephra layers from Ocean Drilling Project (ODP) Leg 202 Site 1241 using major and trace element compositions of volcanic glass shards demonstrates unequivocally their origin from Cocos Island rather than the Galápagos Archipelago or the Central American Volcanic Arc (CAVA). Cocos Island and the adjacent seamounts of the Cocos Island Province have alkalic compositions and formed on young (≤ 3 Ma) oceanic crust from an extinct spreading ridge bounded by a transform fault against the older and thicker crust of the aseismic Cocos Ridge. Cocos Island has six times the average volume of the adjacent seamounts although all appear to have formed during the 3–1.4 Ma time period. Cocos Island lies closest to the transform fault and we explain its excessive growth by melts rising from garnet-bearing mantle being deflected from the thick Cocos Ridge lithosphere toward the thinner lithosphere on the other side of the transform, thus enlarging the melt catchment area for Cocos Island compared to the seamounts farther away from the transform. This special setting favored growth above sea level and subaerial explosive eruptions even though the absence of appropriate compositions suggests that the entirely alkalic Cocos Island (and seamounts) never evolved through the productive tholeiitic shield stage typical of other Pacific Ocean islands, possibly because melt production rates remained too small. Conditions of magma generation and ascent resembled Hawaiian pre-shield volcanoes but persisted for much longer (〈 1 m.y.) and formed evolved, trachytic magmas. Therefore Cocos Island may be a unique example for a volcanic ocean island that did not pass through the typical growth stages.
    Type: Article , PeerReviewed
    Format: other
    Format: text
    DOI: 10.1016/j.jvolgeores.2016.10.009
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 17 (11). pp. 4585-4604.
    Details
    Publication Date: 2019-02-01
    Description: Pacific drill sites offshore Central America provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the Neogene. The temporal distribution of tephra layers established by tephrochonostratigraphy in Part 1 indicates a nearly continuous highly explosive eruption record for the Costa Rican and the Nicaraguan volcanic arc within the last 8 M.y. The widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large-magnitude explosive eruptions along the southern Central American Volcanic Arc (CAVA). We observe three pulses of enhanced explosive magmatism between 0-1 Ma at the Cordillera Central, between 1-2 Ma at the Guanacaste and at 〉3 Ma at the Western Nicaragua segments. Averaged over the long-term the minimum erupted magma flux (per unit arc length) is ∼0.017 g/ms. Tephra ages, constrained by Ar-Ar dating and by correlation with dated terrestrial tephras, yield time-variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion. The peak rate at 〉2.3 Ma near Osa particularly relates to initial Cocos Ridge subduction which began at 2.91±0.23 Ma as inferred by the 1.5 M.y. delayed appearance of the OIB geochemical signal in tephras from Barva volcano at 1.42 Ma. Subsequent tectonic re-arrangements probably involved crustal extension on the Guanacaste segment that favored the 2-1 Ma period of unusually massive rhyolite production.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2016GC006504
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The 12.4 ka Upper Apoyeque Tephra, Nicaragua: stratigraphy, dispersal, composition, magma reservoir conditions and trigger of the plinian eruption (2016)
    Springer
    Details
    Publication Date: 2023-11-08
    Description: Upper Apoyeque Tephra (UAq) was formed by a rhyodacitic plinian eruption in west-central Nicaragua at 12.4 ka BP. The fallout tephra was dispersed from a progressively rising plinian eruption column that became exposed to different wind speeds and directions at different heights in the stratosphere, leading to an asymmetric tephra fan with different facies in the western and southern sector. Tephra dispersal data integrated with geochemical compositions of lava flows in the area facilitate delimitation of the source vent to the south of Chiltepe Peninsula. UAq, Lower Apoyeque Tephra, Apoyeque Ignimbrite, and two lithic clasts in San Isidro Tephra together form a differentiation trend distinct from that of the younger tephras and lavas at Chiltepe Volcanic Complex in a TiO2 versus K2O diagram, compositionally precluding a genetic relationship of UAq with the present-day Apoyeque stratovolcano. Apoyeque Volcano in its present shape did not exist at the time of the UAq eruption. The surface expression of the UAq vent is now obscured by younger eruption products and lake water. Pressure-temperature constraints based on mineral-melt equilibria and fluid inclusions in plagioclase indicate at least two magma storage levels. Clinopyroxenes crystallised in a deep crustal reservoir at ~24 km depth as inferred from clinopyroxene-melt inclusion pairs. Chemical disequilibrium between clinopyroxenes and matrix glasses indicates rapid magma ascent to the shallower reservoir at ~5.4 km depth, where magnesiohornblendes and plagioclase fractionated at a temperature of ~830°C. Water concentrations were ~5.5 wt. % as derived from congruent results of amphibole and plagioclase-melt hygrometry. The eruption was triggered by injection of a hotter, more primitive melt into a water-supersaturated reservoir.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Format: text
    Format: text
    Format: other
    Format: text
    Format: other
    Format: text
    Format: text
    Format: other
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
    facet.materialart.
    Unknown
    The 12.4 ka Upper Apoyeque Tephra, Nicaragua: stratigraphy, dispersal, composition, magma reservoir conditions and trigger of the plinian eruption (2016)
    Details
    Publication Date: 2023-11-08
    Description: Highly-explosive plinian eruptions belong to the most devastating phenomena of volcanic activity. Upper Apoyeque Tephra (UAq), erupted in close vicinity of the Managua city region in west-central Nicaragua with two million inhabitants, was formed by a rhyodacitic plinian eruption at 12.4 ka BP. The fallout tephra was dispersed from a progressively rising plinian eruption column that became exposed to different wind speeds and directions at different heights in the stratosphere, leading to an asymmetric tephra fan with different facies in the western and southern sector. Tephra dispersal data integrated with geochemical compositions of lava flows in the area facilitate to delimit the source vent to the south of Chiltepe Peninsula. UAq, Lower Apoyeque Tephra, Apoyeque Ignimbrite, and two lithic clasts in San Isidro Tephra together form a trend distinct from that of the younger tephras and lavas at Chiltepe Volcanic Complex in a TiO2 versus K2O diagram, compositionally precluding a genetic relationship of UAq with the present-day Apoyeque Volcano. Apoyeque Volcano in its present shape did not exist at the time of the UAq eruption. The surface expression of the UAq vent is now obscured by younger eruption products and lake water. Pressure-temperature constraints based on mineral-melt equilibria indicate at least two magma storage levels. Clinopyroxenes crystallised in a deep crustal reservoir at ~24 km depth as inferred from clinopyroxene-melt inclusion pairs. Chemical disequilibrium between clinopyroxenes and matrix glasses indicate rapid magma ascent to the shallower reservoir at ~5.4 km depth, where magnesiohornblendes and plagioclase fractionated at a temperature of ~830°C. Water concentrations ranged at ~5.5 wt. % as derived from congruent results of amphibole and plagioclase-melt hygrometry. The eruption was triggered through injection of a hotter, more primitive melt into a water-supersaturated reservoir.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Poster
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