Valentin Troll - Academia.edu (original) (raw)

Papers by Valentin Troll

Research Square (Research Square), Feb 4, 2022

Bulletin of Volcanology, Jul 15, 2022

Elsevier eBooks, 2016

El Hierro, which is currently in its shield stage of evolution, provides an ideal starting point ... more El Hierro, which is currently in its shield stage of evolution, provides an ideal starting point to explain the progressive development of the typically long-lived Canary Islands. The island of El Hierro is the youngest (1.12 Ma), smallest (268 km 2 ), and westernmost of the Canaries. The most characteristic feature of the island is its truncated trihedral shape, with three convergent ridges of volcanic cones that are separated by wide, horseshoe-shaped embayments. The geology of El Hierro is representative of an oceanic island in the early stage of development. Most of the island is mantled by recent cinder cones and lavas, and it is barely incised by erosional canyons. The internal structure of the island, in turn, has been exhumed by gigantic landslides, revealing overlapping volcanic edifices that successively developed and then collapsed. These features provide one of the best possible geological scenarios to investigate the relationships between rift zones and giant lateral collapses in an oceanic shield volcano.

Elsevier eBooks, 2016

The Canary Islands, approximately 100 km off the African coast, display all features of an active... more The Canary Islands, approximately 100 km off the African coast, display all features of an active ocean island chain. Their origin is linked to a hot spot or plume that causes anomalously hot mantle material to intrude the African plate. The islands are dominated by mafic rocks and comprise uplifted submarine volcanic, subaerial shield volcanoes, and the remains of giant lateral collapses. Tenerife and Gran Canaria also display extensive felsic pyroclastic deposits. Teide on Tenerife (>3700 m), in the center of the island chain, is the emblematic volcano of the Canaries. For these reasons, the islands are a spectacular destination for volcanological field excursions and offer a deep and thorough insight into volcanic processes and ocean island evolution. This chapter provides an overview of the geology of the seven Canary Islands. Reference is made to the history of geological research in the region and to pioneering works of the past century, leading to a summary of the current literature and a review of the most modern geological concepts discussed for the archipelago.

O and C isotope study of Bastnas-type rare earth element mineralisation, Bergslagen, Sweden

Ancient cultures have frequently made use of stone surfaces to carve and engravesymbols, letters ... more Ancient cultures have frequently made use of stone surfaces to carve and engravesymbols, letters and messages for others. These petroglyphs usually have a lastingcharacter and are frequently preserved well beyond the survival of the culture thatproduced the petroglyphs. In this article we focus on the written and pictorial testimonyof the pre-Hispanic era of the island of El Hierro (Canary Islands, Spain), whichexploited a series of volcanic rock features to create a written testimony of theirpresence and their way of life. This specific cultural heritage has been adapted to thespecific geological features on the island and the emerging stone masonry skill of theaboriginal culture of the original islander, creating a unique and lasting record of theirability to use geological elements for cultural development.

Journal of Volcanology and Geothermal Research

<p>Magma production, storage, and migration beneath volcanic ocean islands has been... more <p>Magma production, storage, and migration beneath volcanic ocean islands has been a matter of controversy and a multitude of methods are currently used to unravel magma evolution,  storage and migration processes. Here we report on a temporal sequence of lava samples<sup>1, 2</sup> spanning the entirety of the 2021 La Palma eruption (19/09 to 13/12) for which time-series seismic information is also available. Based on the seismic data, initial tephrite lavas were likely drawn from a storage level at or just above the Moho (10-15 km depth), with increasing contributions from a deeper reservoir (>20 km depth) that delivered more primitive basanite lava as the eruption progressed. Early tephrite lava compositions changed rapidly during the first few weeks of the eruption and show significant oxygen isotopic variability (δ18O = +4.9 to 5.8‰), with some samples requiring a low-δ18O component. Later basanite lavas are compositionally less variable after day 20 of the eruption and show a narrower range in oxygen isotopes (δ18O = +5.3 to 5.7‰), close to Atlantic MORB values and similar to values from other historical eruptions and to earlier values recorded from the Cumbre Vieja volcanic system. The larger variability in δ18O in the early lavas is associated with significantly more radiogenic 187Os/188Os and the presence of amphibole and frequent gabbroic micro-xenoliths. Interaction with high-T altered Jurassic oceanic crustal gabbros and basalts with high-time-integrated Re/Os and variable δ18O could be an explanation for the initially wider variations in oxygen isotopes. This is in line with the seismic evidence that indicates the early lavas had been stored at (sub-)Moho levels within the Jurassic oceanic crust at ca. 8-15 km below the island prior to eruption. Later erupted magmas derive from a deeper, upper mantle storage level (>20 km depth) and have had little to no interaction with the igneous and sedimentary portions of the Mesozoic ocean crust, thus providing a useful estimate of primitive mantle δ18O values for the Western Canary Islands.</p><p> </p><p><sup>1</sup>Carracedo J.C., Troll V.R., Day J.M.D., Geiger H., Aulinas Junca, M., Soler V., Deegan F.M., Perez-Torrado F.J., Gisbert G., Gazel E., Rodríguez-González, A., and Albert H. (2022) The 2021 eruption of the Cumbre Vieja Volcanic Ridge on La Palma, Canary Islands. Geology Today 38: 94-107. </p><p><sup>2</sup>Day J.M.D., Troll V.R., Aulinas M., Deegan F.M., Geiger H., Carracedo J.C., Pinto G.G., and Perez-Torrado F.J. (2022) Mantle source characteristics and magmatic processes during the 2021 La Palma eruption. Earth and Planetary Science Letters 597: 117793.</p>

Goldschmidt2022 abstracts, 2022

Czech Polar Reports

This study focuses on determining the trace element composition in olivine from olivine tholeiiti... more This study focuses on determining the trace element composition in olivine from olivine tholeiitic basalts sampled in Iceland during the 2022 Meradalir eruption of the 2021-ongoing Fagradalsfjall Fires. The chemistry of Meradalir olivine is characteristic for a volcanic origin where olivine crystals represent the product of crystallisation. Olivine from the Meradalir basalt magma falls within the field characteristic for the melting of a dominantly peridotitic mantle source. However, the data show that the 2022 Meradalir olivine crystalized from a compositionally more evolved magma than olivine from the preceding 2021 Geldingadalir eruption of the Fagradalsfjall Fires.

Nature Communications

The basalts of the 2021 Fagradalsfjall eruption were the first erupted on the Reykjanes Peninsula... more The basalts of the 2021 Fagradalsfjall eruption were the first erupted on the Reykjanes Peninsula in 781 years and offer a unique opportunity to determine the composition of the mantle underlying Iceland, in particular its oxygen isotope composition (δ18O values). The basalts show compositional variations in Zr/Y, Nb/Zr and Nb/Y values that span roughly half of the previously described range for Icelandic basaltic magmas and signal involvement of Icelandic plume (OIB) and Enriched Mid-Ocean Ridge Basalt (EMORB) in magma genesis. Here we show that Fagradalsfjall δ18O values are invariable (mean δ18O = 5.4 ± 0.3‰ 2 SD, N = 47) and indistinguishable from “normal” upper mantle, in contrast to significantly lower δ18O values reported for erupted materials elsewhere in Iceland (e.g., the 2014–2015 eruption at Holuhraun, Central Iceland). Thus, despite differing trace element characteristics, the melts that supplied the Fagradalsfjall eruption show no evidence for 18O-depleted mantle or in...

<p>Iceland has the largest variety of subglacially formed volcanic edifices... more <p>Iceland has the largest variety of subglacially formed volcanic edifices worldwide, given the extensive glacial cover during the Pleistocene and its frequent volcanic activity. As substantial parts of the volcanic zones are presently ice-covered, eruptions beneath glaciers are common.</p><p> </p><p>Phreatomagmatic activity and flood deposits have been hypothesised for shallow subglacial fissure eruptions, at or within a glacial margin. However, to date, no historical examples that did not immediately break through the ice, resulting in dry magmatic activity, have been directly observed. Also, at dynamic ice-margin settings, no extensive resultant formations from shallow subglacial fissure eruptions formed in older historic eruptions have been studied until now. </p><p> </p><p>The final fissure from the 1783–84 CE Laki basaltic flood lava event in the Síða highlands of Iceland, fissure 10, provides a perfect natural laboratory to understand the eruptive dynamics of a shallow subglacial or intraglacial fissure eruption. Fissure 10 is a 2.5 km long formation, which constitutes the final phase of activity on the 29 km long Laki crater row, formed as eruptive activity from the Laki eruption propagated under Síðujökull, an outlet glacier from the Vatnajökull ice-cap. The resultant eruptive sequences display evidence of the increasing influence of ice when traced along strike from SW to NE, with the eruption transitioning to a predominantly phreatomagmatic phase with increasing degrees of lateral confinement. The sequence is dominated by volcanoclastic units, formed by multiple phreatomagmatic and magmatic phases suggestive of fluctuating water levels, intercalated with hackly jointed intrusions, hackly jointed lobate lava flows and debris flows. Repeating units of agglutinated spatter and spatter-fed lava flows cap the sequence, suggesting decreasing influence of external water with stratigraphic height and towards the end of the fissure’s eruptive activity. A thin layer of glacial till coats the top of the fissure 10 sequences. The margin of Síðujökull has since fully receded from the formation.</p><p> </p><p>Our model for the eruptive dynamics of the northern Laki fissure 10 formation is based on field mapping, a drone photogrammetry survey, petrological observations and EMP analysis of glassy tephra and lava selvages to gain a full understanding of the activity and how eruptive activity progressed. The Laki eruption benefits from a wealth of previous studies on the magmatic phases from the other 9 subaerially eruptive fissures, to the SW of fissure 10, allowing for the effects of the glacier on this fissure’s activity to be isolated and defined.</p><p> </p><p>Fissure 10 allows for an approximate reconstruction of the ice margin and glacier slope at the time of eruption, adding valuable information on the extent of the glaciers in SW-Vatnajökull in the late 18<sup>th</sup> century, and during the Little Ice Age. These shallow subglacially erupted deposits are the only fully accessible intraglacial eruptive vents, from a known historical eruption, on Earth. Detailed mapping and petrological analysis of deposits like these is important for interpreting landforms in paleo-ice margins, where transitional activity occurs.</p>

The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understand... more The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understanding of magmatic processes and formation of the earliest continental crust. Particularly significant is magma-crust interaction that can modify the composition of magma and the dynamics of volcanism. This thesis investigates silicic magma genesis on different scales in two ocean island settings. First, volcanic products from a series of voluminous Neogene silicic centres in northeast Iceland are investigated using rock and mineral geochemistry, U-Pb geochronology, and oxygen isotope analysis. Second, interfacial processes of magma-crust interaction are investigated using geochemistry and 3D X-ray computed microtomography on crustal xenoliths from the 2011-12 El Hierro eruption, Canary Islands.The results from northeast Iceland constrain a rapid outburst of silicic magmatism driven by a flare of the Iceland plume and/or by formation of a new rift zone, causing large volume injection of bas...

Mineralogical Magazine, 2018

ABSTRACTThe Icelandic crust is characterized by low δ18O values that originate from pervasive hig... more ABSTRACTThe Icelandic crust is characterized by low δ18O values that originate from pervasive high-temperature hydrothermal alteration by18O-depleted meteoric waters. Igneous rocks in Iceland with δ18O values significantly higher than unaltered oceanic crust (~5.7‰) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjörður Eystri, Northeast Iceland, that show whole-rock δ18O values between +2.9 and +17.6‰ (n= 6), placing them among the highest δ18O values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show δ18O whole-rock values between +3.7 and +7.8‰ (n= 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n= 4) show δ18O values between +4.9 and +18.7‰, whereas pyroxene (n= 4) shows overall low δ18O values of +4.0 to +4.2‰, consistent with regional rhyolite values. In combination with the evidence from mineralo...

Contributions to Mineralogy and Petrology, 2017

Research Square (Research Square), Feb 4, 2022

Bulletin of Volcanology, Jul 15, 2022

Elsevier eBooks, 2016

El Hierro, which is currently in its shield stage of evolution, provides an ideal starting point ... more El Hierro, which is currently in its shield stage of evolution, provides an ideal starting point to explain the progressive development of the typically long-lived Canary Islands. The island of El Hierro is the youngest (1.12 Ma), smallest (268 km 2 ), and westernmost of the Canaries. The most characteristic feature of the island is its truncated trihedral shape, with three convergent ridges of volcanic cones that are separated by wide, horseshoe-shaped embayments. The geology of El Hierro is representative of an oceanic island in the early stage of development. Most of the island is mantled by recent cinder cones and lavas, and it is barely incised by erosional canyons. The internal structure of the island, in turn, has been exhumed by gigantic landslides, revealing overlapping volcanic edifices that successively developed and then collapsed. These features provide one of the best possible geological scenarios to investigate the relationships between rift zones and giant lateral collapses in an oceanic shield volcano.

Elsevier eBooks, 2016

The Canary Islands, approximately 100 km off the African coast, display all features of an active... more The Canary Islands, approximately 100 km off the African coast, display all features of an active ocean island chain. Their origin is linked to a hot spot or plume that causes anomalously hot mantle material to intrude the African plate. The islands are dominated by mafic rocks and comprise uplifted submarine volcanic, subaerial shield volcanoes, and the remains of giant lateral collapses. Tenerife and Gran Canaria also display extensive felsic pyroclastic deposits. Teide on Tenerife (>3700 m), in the center of the island chain, is the emblematic volcano of the Canaries. For these reasons, the islands are a spectacular destination for volcanological field excursions and offer a deep and thorough insight into volcanic processes and ocean island evolution. This chapter provides an overview of the geology of the seven Canary Islands. Reference is made to the history of geological research in the region and to pioneering works of the past century, leading to a summary of the current literature and a review of the most modern geological concepts discussed for the archipelago.

O and C isotope study of Bastnas-type rare earth element mineralisation, Bergslagen, Sweden

Ancient cultures have frequently made use of stone surfaces to carve and engravesymbols, letters ... more Ancient cultures have frequently made use of stone surfaces to carve and engravesymbols, letters and messages for others. These petroglyphs usually have a lastingcharacter and are frequently preserved well beyond the survival of the culture thatproduced the petroglyphs. In this article we focus on the written and pictorial testimonyof the pre-Hispanic era of the island of El Hierro (Canary Islands, Spain), whichexploited a series of volcanic rock features to create a written testimony of theirpresence and their way of life. This specific cultural heritage has been adapted to thespecific geological features on the island and the emerging stone masonry skill of theaboriginal culture of the original islander, creating a unique and lasting record of theirability to use geological elements for cultural development.

Journal of Volcanology and Geothermal Research

<p>Magma production, storage, and migration beneath volcanic ocean islands has been... more <p>Magma production, storage, and migration beneath volcanic ocean islands has been a matter of controversy and a multitude of methods are currently used to unravel magma evolution,  storage and migration processes. Here we report on a temporal sequence of lava samples<sup>1, 2</sup> spanning the entirety of the 2021 La Palma eruption (19/09 to 13/12) for which time-series seismic information is also available. Based on the seismic data, initial tephrite lavas were likely drawn from a storage level at or just above the Moho (10-15 km depth), with increasing contributions from a deeper reservoir (>20 km depth) that delivered more primitive basanite lava as the eruption progressed. Early tephrite lava compositions changed rapidly during the first few weeks of the eruption and show significant oxygen isotopic variability (δ18O = +4.9 to 5.8‰), with some samples requiring a low-δ18O component. Later basanite lavas are compositionally less variable after day 20 of the eruption and show a narrower range in oxygen isotopes (δ18O = +5.3 to 5.7‰), close to Atlantic MORB values and similar to values from other historical eruptions and to earlier values recorded from the Cumbre Vieja volcanic system. The larger variability in δ18O in the early lavas is associated with significantly more radiogenic 187Os/188Os and the presence of amphibole and frequent gabbroic micro-xenoliths. Interaction with high-T altered Jurassic oceanic crustal gabbros and basalts with high-time-integrated Re/Os and variable δ18O could be an explanation for the initially wider variations in oxygen isotopes. This is in line with the seismic evidence that indicates the early lavas had been stored at (sub-)Moho levels within the Jurassic oceanic crust at ca. 8-15 km below the island prior to eruption. Later erupted magmas derive from a deeper, upper mantle storage level (>20 km depth) and have had little to no interaction with the igneous and sedimentary portions of the Mesozoic ocean crust, thus providing a useful estimate of primitive mantle δ18O values for the Western Canary Islands.</p><p> </p><p><sup>1</sup>Carracedo J.C., Troll V.R., Day J.M.D., Geiger H., Aulinas Junca, M., Soler V., Deegan F.M., Perez-Torrado F.J., Gisbert G., Gazel E., Rodríguez-González, A., and Albert H. (2022) The 2021 eruption of the Cumbre Vieja Volcanic Ridge on La Palma, Canary Islands. Geology Today 38: 94-107. </p><p><sup>2</sup>Day J.M.D., Troll V.R., Aulinas M., Deegan F.M., Geiger H., Carracedo J.C., Pinto G.G., and Perez-Torrado F.J. (2022) Mantle source characteristics and magmatic processes during the 2021 La Palma eruption. Earth and Planetary Science Letters 597: 117793.</p>

Goldschmidt2022 abstracts, 2022

Czech Polar Reports

This study focuses on determining the trace element composition in olivine from olivine tholeiiti... more This study focuses on determining the trace element composition in olivine from olivine tholeiitic basalts sampled in Iceland during the 2022 Meradalir eruption of the 2021-ongoing Fagradalsfjall Fires. The chemistry of Meradalir olivine is characteristic for a volcanic origin where olivine crystals represent the product of crystallisation. Olivine from the Meradalir basalt magma falls within the field characteristic for the melting of a dominantly peridotitic mantle source. However, the data show that the 2022 Meradalir olivine crystalized from a compositionally more evolved magma than olivine from the preceding 2021 Geldingadalir eruption of the Fagradalsfjall Fires.

Nature Communications

The basalts of the 2021 Fagradalsfjall eruption were the first erupted on the Reykjanes Peninsula... more The basalts of the 2021 Fagradalsfjall eruption were the first erupted on the Reykjanes Peninsula in 781 years and offer a unique opportunity to determine the composition of the mantle underlying Iceland, in particular its oxygen isotope composition (δ18O values). The basalts show compositional variations in Zr/Y, Nb/Zr and Nb/Y values that span roughly half of the previously described range for Icelandic basaltic magmas and signal involvement of Icelandic plume (OIB) and Enriched Mid-Ocean Ridge Basalt (EMORB) in magma genesis. Here we show that Fagradalsfjall δ18O values are invariable (mean δ18O = 5.4 ± 0.3‰ 2 SD, N = 47) and indistinguishable from “normal” upper mantle, in contrast to significantly lower δ18O values reported for erupted materials elsewhere in Iceland (e.g., the 2014–2015 eruption at Holuhraun, Central Iceland). Thus, despite differing trace element characteristics, the melts that supplied the Fagradalsfjall eruption show no evidence for 18O-depleted mantle or in...

<p>Iceland has the largest variety of subglacially formed volcanic edifices... more <p>Iceland has the largest variety of subglacially formed volcanic edifices worldwide, given the extensive glacial cover during the Pleistocene and its frequent volcanic activity. As substantial parts of the volcanic zones are presently ice-covered, eruptions beneath glaciers are common.</p><p> </p><p>Phreatomagmatic activity and flood deposits have been hypothesised for shallow subglacial fissure eruptions, at or within a glacial margin. However, to date, no historical examples that did not immediately break through the ice, resulting in dry magmatic activity, have been directly observed. Also, at dynamic ice-margin settings, no extensive resultant formations from shallow subglacial fissure eruptions formed in older historic eruptions have been studied until now. </p><p> </p><p>The final fissure from the 1783–84 CE Laki basaltic flood lava event in the Síða highlands of Iceland, fissure 10, provides a perfect natural laboratory to understand the eruptive dynamics of a shallow subglacial or intraglacial fissure eruption. Fissure 10 is a 2.5 km long formation, which constitutes the final phase of activity on the 29 km long Laki crater row, formed as eruptive activity from the Laki eruption propagated under Síðujökull, an outlet glacier from the Vatnajökull ice-cap. The resultant eruptive sequences display evidence of the increasing influence of ice when traced along strike from SW to NE, with the eruption transitioning to a predominantly phreatomagmatic phase with increasing degrees of lateral confinement. The sequence is dominated by volcanoclastic units, formed by multiple phreatomagmatic and magmatic phases suggestive of fluctuating water levels, intercalated with hackly jointed intrusions, hackly jointed lobate lava flows and debris flows. Repeating units of agglutinated spatter and spatter-fed lava flows cap the sequence, suggesting decreasing influence of external water with stratigraphic height and towards the end of the fissure’s eruptive activity. A thin layer of glacial till coats the top of the fissure 10 sequences. The margin of Síðujökull has since fully receded from the formation.</p><p> </p><p>Our model for the eruptive dynamics of the northern Laki fissure 10 formation is based on field mapping, a drone photogrammetry survey, petrological observations and EMP analysis of glassy tephra and lava selvages to gain a full understanding of the activity and how eruptive activity progressed. The Laki eruption benefits from a wealth of previous studies on the magmatic phases from the other 9 subaerially eruptive fissures, to the SW of fissure 10, allowing for the effects of the glacier on this fissure’s activity to be isolated and defined.</p><p> </p><p>Fissure 10 allows for an approximate reconstruction of the ice margin and glacier slope at the time of eruption, adding valuable information on the extent of the glaciers in SW-Vatnajökull in the late 18<sup>th</sup> century, and during the Little Ice Age. These shallow subglacially erupted deposits are the only fully accessible intraglacial eruptive vents, from a known historical eruption, on Earth. Detailed mapping and petrological analysis of deposits like these is important for interpreting landforms in paleo-ice margins, where transitional activity occurs.</p>

The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understand... more The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understanding of magmatic processes and formation of the earliest continental crust. Particularly significant is magma-crust interaction that can modify the composition of magma and the dynamics of volcanism. This thesis investigates silicic magma genesis on different scales in two ocean island settings. First, volcanic products from a series of voluminous Neogene silicic centres in northeast Iceland are investigated using rock and mineral geochemistry, U-Pb geochronology, and oxygen isotope analysis. Second, interfacial processes of magma-crust interaction are investigated using geochemistry and 3D X-ray computed microtomography on crustal xenoliths from the 2011-12 El Hierro eruption, Canary Islands.The results from northeast Iceland constrain a rapid outburst of silicic magmatism driven by a flare of the Iceland plume and/or by formation of a new rift zone, causing large volume injection of bas...

Mineralogical Magazine, 2018

ABSTRACTThe Icelandic crust is characterized by low δ18O values that originate from pervasive hig... more ABSTRACTThe Icelandic crust is characterized by low δ18O values that originate from pervasive high-temperature hydrothermal alteration by18O-depleted meteoric waters. Igneous rocks in Iceland with δ18O values significantly higher than unaltered oceanic crust (~5.7‰) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjörður Eystri, Northeast Iceland, that show whole-rock δ18O values between +2.9 and +17.6‰ (n= 6), placing them among the highest δ18O values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show δ18O whole-rock values between +3.7 and +7.8‰ (n= 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n= 4) show δ18O values between +4.9 and +18.7‰, whereas pyroxene (n= 4) shows overall low δ18O values of +4.0 to +4.2‰, consistent with regional rhyolite values. In combination with the evidence from mineralo...

Contributions to Mineralogy and Petrology, 2017