Melting and dynamic metasomatism of mixed harzburgite + glimmerite mantle source: Implications for the genesis of orogenic potassic magmas

Förster, Michael W.; Prelević, Dejan; Schmück, Harald R.; Buhre, Stephan; Veter, Marina; Mertz‐Kraus, Regina; Foley, Stephen F.; Jacob, Dorrit E.

doi:10.1016/j.chemgeo.2016.08.037

Cited by 60 publications

(37 citation statements)

References 45 publications

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“…The coexistence of MORB-type basaltic and extremely enriched felsic volcanic rocks in the Trollhøtta basin implies that the mantle source below this basin was extremely heterogeneous, with highly metasomatized mantle domains adjacent to pristine, unaltered asthenospheric mantle. This would be in accordance with the model of Foley (1992), who suggested that mantle metasomatism may produce distinct networks of altered veins consisting of clinopyroxene and mica between unaltered peridotite (see also Spandler & Pirard 2013;Förster et al 2017). In such a scenario, both veins and unaltered peridotite domains could be tapped during separate but near-contemporaneous melting events, producing the extremely contrasting volcanic rocks of the Trollhøtta-Kinna basin.…”

Section: Accepted Manuscriptsupporting

confidence: 85%

Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

Dalslåen

Gasser

Grenne

et al. 2020

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The late Neoproterozoic to Palaeozoic Iapetus Ocean developed between Laurentia, Baltica, Siberia and Gondwana. Its Palaeozoic closure history is recorded by volcano-sedimentary successions within the Caledonian orogen of Scandinavia, the British Isles and Newfoundland. We present new lithological, geochemical and geochronological data relevant for the Iapetan closure history from the hitherto poorly known Trollhøtta-Kinna basin (central Norwegian Caledonides). This basin consists of alternating siliciclastic rocks, MORB, and felsic volcanic rocks highly enriched in e.g. Th, U and LREE. Rhyolites from the stratigraphically upper part are dated by zircon U-Pb TIMS to 473.3 ± 1.0 and 472.4 ± 0.7 Ma. Detrital zircon spectra indicate deposition after ~480 Ma, with sediments derived from composite Cambro-Ordovician and Archean to Neoproterozoic landmass(es), possibly the Laurentian margin or a related microcontinent. The peculiar bimodal volcanic association is interpreted as an intermittent phase of marginal basin rifting, derived from a heterogeneous mantle source previously metasomatized by continental material. The tectonic mechanisms behind rifting could be slab retreat and/or break-off, or far-field tectonic forces within the Iapetan realm. Comparison of this basin with other Iapetus-related, similarly-aged volcanosedimentary successions along the Caledonian-Appalachian orogen indicate that the bimodal MORB and highly enriched rocks reflect a palaeotectonic setting hitherto unknown in the orogen. Supplementary material: Analytical results for detrital zircon analyses.

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Section: Accepted Manuscriptsupporting

confidence: 85%

Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

Dalslåen

Gasser

Grenne

et al. 2020

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“…In the future, more experimental work is needed to further investigate the interaction between blueschist and mantle peridotite. When blueschist‐derived melts hybridize with mantle peridotite, the reaction zone would have great potential to produce phlogopite‐rich metasomatic assemblages (“metasomes”) that could sequester substantial amounts of trace elements and provide potassium enrichment seen widely in postcollisional orogenic volcanic rocks (Foley, 1992; Förster et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

The Role of Blueschist Stored in Shallow Lithosphere in the Generation of Postcollisional Orogenic Magmas

Wang

Foley

2020

JGR Solid Earth

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In regions with small ocean plates and continental blocks, such as the Mediterranean in the Cenozoic and modern Indonesia, many blueschists may be stored at shallow depth in the mantle lithosphere that is newly formed during the amalgamation of small continental blocks and oceans. Melting of these blueschists at low pressures in the mixed lithosphere of this type during postcollisional relaxation may be involved in the generation of postcollisional orogenic magmas. Here, we have conducted a series of melting experiments on three blueschist samples with differing protoliths at 800-850°C, 2 GPa to investigate phase relations, mineral compositions, and trace element partitioning (using laser ablation-inductively coupled plasma-mass spectrometry [LA-ICP-MS]/nanoscale secondary ion mass spectrometry [NanoSIMS]), including the first results for clinozoisite. Dacitic/rhyolitic melts (SiO 2 60 to 66 wt%) containing~13 wt% volatiles are produced in all runs. Mn-rich and Mn-poor almandine garnets exhibit distinct rare earth element (REE) distribution patterns, while Mn-rich garnets are effective preconcentrators of heavy REEs (HREEs) for later metamorphic processes. Melts produced from fluid-affected blueschists of terrigenous origin show the most large-ion lithophile element (LILE) enrichment, whereas those from terrigenous blueschists with no fluid history exhibit the lowest K/Th and Ba/Th and strongest Ce/Pb and Nb/U fractionations. Melts of blueschists derived from mid-ocean ridge basalt (MORB) have relatively consistent, MORB-like Ba/Th and Nb/U (~3) but the lowest Ce/Pb ratios (3.3). V/Sc and Zr/Hf ratios remain constant at ≥850°C regardless of the origin of the blueschist. Dehydration melting in new mantle lithosphere where blueschist is stored at shallow depth will significantly affect trace element behavior and should be considered carefully when examining chemical cycling and magmatism in postcollisional orogenic settings.

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“…Amphiboles are very useful for the investigation of mafic magma genesis, especially the ultrapotassic ones, in which amphibole is an early crystallizing phase (Foley 1992, Conceição and Green 2004, Förster et al 2017. Compositional variation in amphibole is strongly affected by changes in pressure, temperature, oxidation conditions, magma composition, and water activity (Scaillet and Evans 1999, Dalpé and Baker 2000, Rooney et al 2011.…”

Section: Discussionmentioning

confidence: 99%

Amphibole crystallization conditions as record of interaction between ultrapotassic enclaves and monzonitic magmas in the Glória Norte Stock, South of Borborema Province

et al. 2020

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The Glória Norte Stock (GNS) is made up of predominantly porphyritic biotite-amphibole-bearing quartz monzonite, enclosing a large number of microgranular mafic enclaves (MME). The GNS MME are fine-grained rocks with rounded and ellipsoid shapes that show sharp and gradational contacts with the host rocks, suggesting they coexisted with the host monzonite as magmas. The studied amphibole crystals of the two rock types are calcic and correspond to pargasite, edenite, and magnesium-hornblende. Their compositions are influenced by substitutions involving Al 3+ , Na + , Fe 2+ , Si 4+ and Mg 2+ ions, reflecting the decrease in temperature and the increase in oxygen fugacity. They present low Ti and Al contents, and varied Si content (6.2-7.7 apuf). The mg# values range from 0.48-0.84. Pressures for the crystallization of the MME amphiboles vary between 2.6 and 7.8 kbar and the temperatures of solidus and liquidus were estimated between 600-659 and 887-908°C, respectively. The early MME amphibole crystals with lower Si and Mg content were formed under high pressure (7.8 kbar) and temperature (908 °C). The presence of amphiboles with 862°C and 5 kbar in MME and GNS reflects that the interaction between these magmas occurred at 18 km of depth.

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Melting and dynamic metasomatism of mixed harzburgite + glimmerite mantle source: Implications for the genesis of orogenic potassic magmas

Cited by 60 publications

References 45 publications

Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

The Role of Blueschist Stored in Shallow Lithosphere in the Generation of Postcollisional Orogenic Magmas

Amphibole crystallization conditions as record of interaction between ultrapotassic enclaves and monzonitic magmas in the Glória Norte Stock, South of Borborema Province

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Melting and dynamic metasomatism of mixed harzburgite + glimmerite mantle source: Implications for the genesis of orogenic potassic magmas

Cited by 60 publications

References 45 publications

Early­­­­–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

Early­­­­–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

The Role of Blueschist Stored in Shallow Lithosphere in the Generation of Postcollisional Orogenic Magmas

Amphibole crystallization conditions as record of interaction between ultrapotassic enclaves and monzonitic magmas in the Glória Norte Stock, South of Borborema Province

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Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides

Early–Middle Ordovician sedimentation and bimodal volcanism at the margin of Iapetus: the Trollhøtta–Kinna Basin of the central Norwegian Caledonides