2022
|
Ellis, B. S., Szymanowski, D., Harris, C., Tollan, P. M. E., Neukampf, J., Guillong, M., Cortes-Calderon, E. A., Bachmann, O. Evaluating the potential of rhyolitic glass as a lithium source for brine deposits (Article de journal) Dans: Economic Geologists, vol. 117, no. 1, p. 91–105, 2022. @article{Ellis_etal2022_2,
title = {Evaluating the potential of rhyolitic glass as a lithium source for brine deposits},
author = {B. S. Ellis and D. Szymanowski and C. Harris and P. M. E. Tollan and J. Neukampf and M. Guillong and E. A. Cortes-Calderon and O. Bachmann},
doi = {10.5382/econgeo.4866},
year = {2022},
date = {2022-01-01},
journal = {Economic Geologists},
volume = {117},
number = {1},
pages = {91--105},
abstract = {Lithium is an economically important element that is increasingly extracted from brines accumulated in continental basins. While a number of studies have identified silicic magmatic rocks as the ultimate source of dissolved brine lithium, the processes by which Li is mobilized remain poorly constrained. Here we focus on the potential of low-temperature, post-eruptive processes to remove Li from volcanic glass and generate Li-rich fluids. The rhyolitic glasses in this study (from the Yellowstone-Snake River Plain volcanic province in western North America) have interacted with meteoric water after emplacement as revealed by textures and a variety of geochemical and isotopic signatures. Indices of glass hydration correlate with Li concentrations, suggesting Li is lost to the water during the water-rock interaction. We estimate the original Li content upon deposition and the magnitude of Li depletion both by direct in situ glass measurements and by applying a partition-coefficient approach to plagioclase Li contents. Across our whole sample set (19 eruptive units spanning ca. 10 m.y.), Li losses average 8.9 ppm, with a maximum loss of 37.5 ppm. This allows estimation of the dense rock equivalent of silicic volcanic lithologies required to potentially source a brine deposit. Our data indicate that surficial processes occurring post-eruption may provide sufficient Li to form economic deposits. We found no relationship between deposit age and Li loss, i.e., hydration does not appear to be an ongoing process. Rather, it occurs primarily while the deposit is cooling shortly after eruption, with $delta$18O and $delta$D in our case study suggesting a temperature window of 40textdegree to 70textdegreeC.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lithium is an economically important element that is increasingly extracted from brines accumulated in continental basins. While a number of studies have identified silicic magmatic rocks as the ultimate source of dissolved brine lithium, the processes by which Li is mobilized remain poorly constrained. Here we focus on the potential of low-temperature, post-eruptive processes to remove Li from volcanic glass and generate Li-rich fluids. The rhyolitic glasses in this study (from the Yellowstone-Snake River Plain volcanic province in western North America) have interacted with meteoric water after emplacement as revealed by textures and a variety of geochemical and isotopic signatures. Indices of glass hydration correlate with Li concentrations, suggesting Li is lost to the water during the water-rock interaction. We estimate the original Li content upon deposition and the magnitude of Li depletion both by direct in situ glass measurements and by applying a partition-coefficient approach to plagioclase Li contents. Across our whole sample set (19 eruptive units spanning ca. 10 m.y.), Li losses average 8.9 ppm, with a maximum loss of 37.5 ppm. This allows estimation of the dense rock equivalent of silicic volcanic lithologies required to potentially source a brine deposit. Our data indicate that surficial processes occurring post-eruption may provide sufficient Li to form economic deposits. We found no relationship between deposit age and Li loss, i.e., hydration does not appear to be an ongoing process. Rather, it occurs primarily while the deposit is cooling shortly after eruption, with $delta$18O and $delta$D in our case study suggesting a temperature window of 40textdegree to 70textdegreeC. |
Neukampf, J., Laurent, O., Tollan, P., Bouvier, A. S., Magna, T., Ulmer, P., France, L., Ellis, B. S., Bachmann, O. Degassing from magma reservoir to eruption in silicic systems : The Li elemental and isotopic record from rhyolitic melt inclusions and host quartz in a Yellowstone rhyolite (Article de journal) Dans: Geochimica et Cosmochimica Acta, vol. 326, p. 56–76, 2022. @article{Neukampf_etal2022,
title = {Degassing from magma reservoir to eruption in silicic systems : The Li elemental and isotopic record from rhyolitic melt inclusions and host quartz in a Yellowstone rhyolite},
author = {J. Neukampf and O. Laurent and P. Tollan and A. S. Bouvier and T. Magna and P. Ulmer and L. France and B. S. Ellis and O. Bachmann},
doi = {10.1016/j.gca.2022.03.037},
year = {2022},
date = {2022-01-01},
journal = {Geochimica et Cosmochimica Acta},
volume = {326},
pages = {56--76},
abstract = {Lithium and hydrogen are volatile elements which diffuse rapidly in crystals and melt, making them powerful geochemical tools to reconstruct geological processes that take place on short time scales, such as syn- and post-eruptive degassing. Although the dynamics of hydrogen are fairly well understood to better constrain such processes, the assessment of Li behaviour within the magma reservoir relevant for ascent-related degassing still lacks detailed evaluation. Here, the first in situ Li concentrations and isotopic compositions (using SIMS analysis) of rhyolitic quartz-hosted, naturally glassy and crystallised melt inclusions (MIs) and groundmass glass (Mesa Falls Tuff, Yellowstone) are used to reconstruct Li elemental and isotopic evolution in the magma reservoir. Lithium concentrations in quartz-hosted glassy MIs (10--61 ppm) from a fallout deposit overlap with their groundmass glass (32--46 ppm) and their host quartz (8--15 ppm). Crystallised MIs from a later erupted flow pumice clast sample have higher Li concentrations (8--190 ppm) compared to the groundmass glass (32--51 ppm) and their host quartz (15--24 ppm). Lithium content in quartz from the early erupted sample is relatively homogenous, whereas it is up to a factor of two higher and heterogeneous in the later erupted sample, with a simultaneous increase in Li versus a decrease in H towards crystal rims. The d7Li difference (expressed as D7LiMI--glass) between MIs (-8.0texttenthousand to + 12.3texttenthousand) and groundmass glass (+9.0texttenthousand to + 20.5texttenthousand) of two pyroclastic deposits reaches up to 29texttenthousand. Glassy MIs are internally heterogeneous in d7Li and Li abundance. The cores of the glassy MIs record the d7Li of the least modified melt during entrapment and the data distribution can be modelled by equilibrium fractionation between the melt and vapour phase during early opensystem degassing in the magma reservoir. Late degassing during eruption triggers Li--H diffusional exchange between quartz and melt, as the degassing of H2O and the accompanying pressure change trigger H diffusion out of the host quartz and the MIs, which is charge balanced by inward Li diffusion. This results in the modification of Li contents in quartz and d7Li values in the rims of the glassy MIs. Crystallised MIs reflect the loss of H2O from the MIs and the resulting enrichment of Li during the crystallisation. Additionally, the variations of d7Li in the groundmass glass can be explained through modelling by kinetic fractionation between the melt and vapour during late stage open-system degassing linked with magma ascent.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lithium and hydrogen are volatile elements which diffuse rapidly in crystals and melt, making them powerful geochemical tools to reconstruct geological processes that take place on short time scales, such as syn- and post-eruptive degassing. Although the dynamics of hydrogen are fairly well understood to better constrain such processes, the assessment of Li behaviour within the magma reservoir relevant for ascent-related degassing still lacks detailed evaluation. Here, the first in situ Li concentrations and isotopic compositions (using SIMS analysis) of rhyolitic quartz-hosted, naturally glassy and crystallised melt inclusions (MIs) and groundmass glass (Mesa Falls Tuff, Yellowstone) are used to reconstruct Li elemental and isotopic evolution in the magma reservoir. Lithium concentrations in quartz-hosted glassy MIs (10--61 ppm) from a fallout deposit overlap with their groundmass glass (32--46 ppm) and their host quartz (8--15 ppm). Crystallised MIs from a later erupted flow pumice clast sample have higher Li concentrations (8--190 ppm) compared to the groundmass glass (32--51 ppm) and their host quartz (15--24 ppm). Lithium content in quartz from the early erupted sample is relatively homogenous, whereas it is up to a factor of two higher and heterogeneous in the later erupted sample, with a simultaneous increase in Li versus a decrease in H towards crystal rims. The d7Li difference (expressed as D7LiMI--glass) between MIs (-8.0texttenthousand to + 12.3texttenthousand) and groundmass glass (+9.0texttenthousand to + 20.5texttenthousand) of two pyroclastic deposits reaches up to 29texttenthousand. Glassy MIs are internally heterogeneous in d7Li and Li abundance. The cores of the glassy MIs record the d7Li of the least modified melt during entrapment and the data distribution can be modelled by equilibrium fractionation between the melt and vapour phase during early opensystem degassing in the magma reservoir. Late degassing during eruption triggers Li--H diffusional exchange between quartz and melt, as the degassing of H2O and the accompanying pressure change trigger H diffusion out of the host quartz and the MIs, which is charge balanced by inward Li diffusion. This results in the modification of Li contents in quartz and d7Li values in the rims of the glassy MIs. Crystallised MIs reflect the loss of H2O from the MIs and the resulting enrichment of Li during the crystallisation. Additionally, the variations of d7Li in the groundmass glass can be explained through modelling by kinetic fractionation between the melt and vapour during late stage open-system degassing linked with magma ascent. |
Wolzlaw, J. F., Bastian, L., Guillong, M., Forni, F., Laurent, O., Neukampf, J., Sulpizio, R., Chelle-Michou, C., Bachmann, O. Garnet petrochronology reveals the lifetime and dynamics of phonolitic magma chambers at Somma-Vesuvius (Article de journal) Dans: Science Advances, vol. 8, p. eabk2184, 2022. @article{Wolzlaw_etal2022,
title = {Garnet petrochronology reveals the lifetime and dynamics of phonolitic magma chambers at Somma-Vesuvius},
author = {J. F. Wolzlaw and L. Bastian and M. Guillong and F. Forni and O. Laurent and J. Neukampf and R. Sulpizio and C. Chelle-Michou and O. Bachmann},
doi = {10.1126/sciadv.abk2184},
year = {2022},
date = {2022-01-01},
journal = {Science Advances},
volume = {8},
pages = {eabk2184},
abstract = {Somma-Vesuvius is one of the most iconic active volcanoes with historic and archeological records of numerous hazardous eruptions. Petrologic studies of eruptive products provide insights into the evolution of the magma reservoir before eruption. Here, we quantify the duration of shallow crustal storage and document the evolution of phonolitic magmas before major eruptions of Somma-Vesuvius. Garnet uranium-thorium petrochronology suggests progressively shorter pre-eruption residence times throughout the lifetime of the volcano. Residence times mirror the repose intervals between eruptions, implying that distinct phonolite magma batches were present throughout most of the volcano’s evolution, thereby controlling the eruption dynamics by preventing the ascent of mafic magmas from longer-lived and deeper reservoirs. Frequent lower-energy eruptions during the recent history sample this deeper reservoir and suggest that future Plinian eruptions are unlikely without centuries of volcanic quiescence. Crystal residence times from other volcanoes reveal that long-lived deep-seated reservoirs and transient upper crustal magma chambers are common features of subvolcanic plumbing systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Somma-Vesuvius is one of the most iconic active volcanoes with historic and archeological records of numerous hazardous eruptions. Petrologic studies of eruptive products provide insights into the evolution of the magma reservoir before eruption. Here, we quantify the duration of shallow crustal storage and document the evolution of phonolitic magmas before major eruptions of Somma-Vesuvius. Garnet uranium-thorium petrochronology suggests progressively shorter pre-eruption residence times throughout the lifetime of the volcano. Residence times mirror the repose intervals between eruptions, implying that distinct phonolite magma batches were present throughout most of the volcano’s evolution, thereby controlling the eruption dynamics by preventing the ascent of mafic magmas from longer-lived and deeper reservoirs. Frequent lower-energy eruptions during the recent history sample this deeper reservoir and suggest that future Plinian eruptions are unlikely without centuries of volcanic quiescence. Crystal residence times from other volcanoes reveal that long-lived deep-seated reservoirs and transient upper crustal magma chambers are common features of subvolcanic plumbing systems. |
Cortes-Calderon, E. A., Ellis, B. S., Mark, D. F., Neukampf, J., Wolff, J. A., Ulmer, P., Bachmann, O. Generation and Field Relations of Low-$delta$18O Silica-Undersaturated and Mildly Saturated Alkaline Magmas: a Case Study from the Fataga Group, Gran Canaria (Article de journal) Dans: Journal of Petrology, vol. 00, p. 1–22, 2022. @article{Cortes-Calderon_etal2022,
title = {Generation and Field Relations of Low-$delta$18O Silica-Undersaturated and Mildly Saturated Alkaline Magmas: a Case Study from the Fataga Group, Gran Canaria},
author = {E. A. Cortes-Calderon and B. S. Ellis and D. F. Mark and J. Neukampf and J. A. Wolff and P. Ulmer and O. Bachmann},
doi = {10.1093/petrology/egac090},
year = {2022},
date = {2022-01-01},
journal = {Journal of Petrology},
volume = {00},
pages = {1--22},
abstract = {The origins of felsic low-$delta$18O melts (\< +5.5 texttenthousand) are usually attributed to assimilation of high-temperature hydrothermally altered (HTHA) rocks. Very few alkaline (silica undersaturated and/or peralkaline) examples are known. Here, we classify the Miocene Fataga Group in Gran Canaria, a silica-undersaturated to mildly saturated alkaline volcanic sequence consisting of trachytic to phonolitic extra-caldera ignimbrites and lavas, as a new low-$delta$18O felsic locality. We provide new mineral, glass and bulk geochemical data linked to a well-constrained stratigraphy to assess the processes involved in the magma reservoir that fed the Fataga eruptions. New high-precision single crystal feldspar 40Ar/39Ar ages of the study area span 13.931 textpm 0.034 Ma to 10.288 textpm 0.016 Ma. Fractional crystallisation at shallow depths of sanidine/anorthoclase, biotite, augite/diopside, titanite, ilmenite and titanomagnetite is the main driving process to produce phonolitic magmas from trachytic melts. Evidence of mafic hotter recharge is not found in the field, but some units exhibit trachytic compositions characterised by positive Eu/Eu* anomalies and high Ba contents, interpreted as melts of feldspar-dominated cumulates, the solid remnants of fractional crystallisation. Hence, recharge magmas halted in the crystal mush and provided the heat needed to sustain cumulate melting and volcanic activity. This cumulate signature might be lost if fractional crystallisation continues before the eruption. The interplay among meteoric water, the caldera-fault system, intra-caldera ignimbrites (Mog\'{a}n Group) and the Fataga magma reservoir favoured assimilation of up to ca. 30% of HTHA rocks. Such assimilation is variable through time and recorded by $delta$18Omelt values down to +4.73 texttenthousand. We did not find any direct relation between assimilation and silica saturation of the Fataga volcanic deposits.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The origins of felsic low-$delta$18O melts (< +5.5 texttenthousand) are usually attributed to assimilation of high-temperature hydrothermally altered (HTHA) rocks. Very few alkaline (silica undersaturated and/or peralkaline) examples are known. Here, we classify the Miocene Fataga Group in Gran Canaria, a silica-undersaturated to mildly saturated alkaline volcanic sequence consisting of trachytic to phonolitic extra-caldera ignimbrites and lavas, as a new low-$delta$18O felsic locality. We provide new mineral, glass and bulk geochemical data linked to a well-constrained stratigraphy to assess the processes involved in the magma reservoir that fed the Fataga eruptions. New high-precision single crystal feldspar 40Ar/39Ar ages of the study area span 13.931 textpm 0.034 Ma to 10.288 textpm 0.016 Ma. Fractional crystallisation at shallow depths of sanidine/anorthoclase, biotite, augite/diopside, titanite, ilmenite and titanomagnetite is the main driving process to produce phonolitic magmas from trachytic melts. Evidence of mafic hotter recharge is not found in the field, but some units exhibit trachytic compositions characterised by positive Eu/Eu* anomalies and high Ba contents, interpreted as melts of feldspar-dominated cumulates, the solid remnants of fractional crystallisation. Hence, recharge magmas halted in the crystal mush and provided the heat needed to sustain cumulate melting and volcanic activity. This cumulate signature might be lost if fractional crystallisation continues before the eruption. The interplay among meteoric water, the caldera-fault system, intra-caldera ignimbrites (Mogán Group) and the Fataga magma reservoir favoured assimilation of up to ca. 30% of HTHA rocks. Such assimilation is variable through time and recorded by $delta$18Omelt values down to +4.73 texttenthousand. We did not find any direct relation between assimilation and silica saturation of the Fataga volcanic deposits. |
Ellis, B. S., Pimentel, A., Wolff, J. A., Etter, A., Cortes-Calderon, E. A., Harris, C., Mark, D. F., Neukampf, J., Bachmann, O. Geochemistry of the Pepom tephra deposits: The most recent intracaldera volcanism of Sete Cidades volcano, S~ao Miguel, Azores (Article de journal) Dans: Journal of Volcanology and Geothermal Research, vol. 50, p. 107673, 2022. @article{Ellis_etal2022,
title = {Geochemistry of the Pepom tephra deposits: The most recent intracaldera volcanism of Sete Cidades volcano, S~ao Miguel, Azores},
author = {B. S. Ellis and A. Pimentel and J. A. Wolff and A. Etter and E. A. Cortes-Calderon and C. Harris and D. F. Mark and J. Neukampf and O. Bachmann},
doi = {10.1016/j.jvolgeores.2022.107673},
year = {2022},
date = {2022-01-01},
journal = {Journal of Volcanology and Geothermal Research},
volume = {50},
pages = {107673},
abstract = {Many volcanoes have the ability to impact human infrastructure with explosive activity and understanding the processes of magma generation and conditions of storage in these systems remains a priority. The Sete Cidades volcano on the island of S~ao Miguel, Azores archipelago is exactly such a volcano lying only 12 km from the island’s capital city of Ponta Delgada and has been repeatedly active during the Holocene. Sete Cidades is the westernmost central volcano of S~ao Miguel and its most recent explosive volcanism produced the Pepom series of 17 trachytic pumice deposits that were erupted from vents within the caldera. These variably magmatic and phreatomagmatic eruptions involved trachytic magmas that represent the end point of a magmatic evolution dominated by crystal fractionation processes. The magmas contain a mineral assemblage dominated by feldspar, with biotite, clinopyroxene, FeTi oxides, amphibole, and trace apatite. Mineral thermometry and hygrometry reveal that the Pepom magmas were stored at temperatures of 789 textpm 23 textdegreeC to 894 textpm 20 textdegreeC under volatile-rich conditions (mostly \>5 wt% water). Intercalated within the trachytic pyroclastic succession are mafic products that were erupted from vents on the flanks of the volcano suggesting that the evolved, shallow magmatic system may be acting as a barrier to ascending mafic magmas. The Pepom tephra deposits represent trachytic magmas that show limited evidence for the involvement of feldspar-dominated cumulates as has been observed in other settings whereas the preceding, caldera-forming, Santa B\'{a}rbara eruption suggests such involvement. Despite the predominant role of fractionation in petrogenesis, the Pepom tephras formed from mildly low-$delta$18O magmas (4.1 to 5.6texttenthousand for trachyte) and as such require the addition of hydrothermally altered material. The cause of the low-$delta$18O values remains unknown, but low-$delta$18O, hydrothermally altered syenitic clasts found within deposits from the nearby Fogo volcano may be potentially analogues.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Many volcanoes have the ability to impact human infrastructure with explosive activity and understanding the processes of magma generation and conditions of storage in these systems remains a priority. The Sete Cidades volcano on the island of S~ao Miguel, Azores archipelago is exactly such a volcano lying only 12 km from the island’s capital city of Ponta Delgada and has been repeatedly active during the Holocene. Sete Cidades is the westernmost central volcano of S~ao Miguel and its most recent explosive volcanism produced the Pepom series of 17 trachytic pumice deposits that were erupted from vents within the caldera. These variably magmatic and phreatomagmatic eruptions involved trachytic magmas that represent the end point of a magmatic evolution dominated by crystal fractionation processes. The magmas contain a mineral assemblage dominated by feldspar, with biotite, clinopyroxene, FeTi oxides, amphibole, and trace apatite. Mineral thermometry and hygrometry reveal that the Pepom magmas were stored at temperatures of 789 textpm 23 textdegreeC to 894 textpm 20 textdegreeC under volatile-rich conditions (mostly >5 wt% water). Intercalated within the trachytic pyroclastic succession are mafic products that were erupted from vents on the flanks of the volcano suggesting that the evolved, shallow magmatic system may be acting as a barrier to ascending mafic magmas. The Pepom tephra deposits represent trachytic magmas that show limited evidence for the involvement of feldspar-dominated cumulates as has been observed in other settings whereas the preceding, caldera-forming, Santa Bárbara eruption suggests such involvement. Despite the predominant role of fractionation in petrogenesis, the Pepom tephras formed from mildly low-$delta$18O magmas (4.1 to 5.6texttenthousand for trachyte) and as such require the addition of hydrothermally altered material. The cause of the low-$delta$18O values remains unknown, but low-$delta$18O, hydrothermally altered syenitic clasts found within deposits from the nearby Fogo volcano may be potentially analogues. |
Wolff, J. A., Neukampf, J. Biotite as an indicator of post‑eruptive cryptic alteration in the Battleship Rock Ignimbrite, Valles Caldera, NM, USA (Article de journal) Dans: Bulletin of Volcanology, vol. 89, p. 99, 2022. @article{Wolff+Neukampf2022,
title = {Biotite as an indicator of post‑eruptive cryptic alteration in the Battleship Rock Ignimbrite, Valles Caldera, NM, USA},
author = {J. A. Wolff and J. Neukampf},
doi = {10.1007/s00445-022-01609-w},
year = {2022},
date = {2022-01-01},
journal = {Bulletin of Volcanology},
volume = {89},
pages = {99},
abstract = {The Battleship Rock Ignimbrite of the East Fork Member of the Valles Rhyolite (USA) consists of a variably welded compound cooling unit emplaced in the southern part of the Valles Caldera at 74 ka. At the type locality, the unit was deposited in a narrow paleocanyon and is glassy throughout, with little petrographic evidence for post-eruptive alteration. Biotites from different zones in the ignimbrite at this location, and associated lavas and fallout deposits of the East Fork Member, frequently exhibit low analytical totals (\< 94 wt%; by electron microprobe) that are correlated with potassium (K) depletion and enriched in lithium (Li). These variations between samples are systematically related to the welding profile of theignimbrite. Biotites with low totals are accompanied by groundmass glass with low $delta$18O, which requires high-temperature interaction with meteoric water. The low totals, K depletion, and Li enrichment are therefore attributed to a brief episodeof meteoric-hydrothermal alteration of the cooling tuff immediately following emplacement. The duration of the episode is estimated to be on the order of months or less, constrained by Cs, Rb, and Sr mobility in glass. Additional variations inglass and biotite chemistry are identified as primary, and offer an avenue to deciphering the complex event stratigraphy of the eruption, with implications for hazard potential of future rhyolitic eruptions from Valles Caldera.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The Battleship Rock Ignimbrite of the East Fork Member of the Valles Rhyolite (USA) consists of a variably welded compound cooling unit emplaced in the southern part of the Valles Caldera at 74 ka. At the type locality, the unit was deposited in a narrow paleocanyon and is glassy throughout, with little petrographic evidence for post-eruptive alteration. Biotites from different zones in the ignimbrite at this location, and associated lavas and fallout deposits of the East Fork Member, frequently exhibit low analytical totals (< 94 wt%; by electron microprobe) that are correlated with potassium (K) depletion and enriched in lithium (Li). These variations between samples are systematically related to the welding profile of theignimbrite. Biotites with low totals are accompanied by groundmass glass with low $delta$18O, which requires high-temperature interaction with meteoric water. The low totals, K depletion, and Li enrichment are therefore attributed to a brief episodeof meteoric-hydrothermal alteration of the cooling tuff immediately following emplacement. The duration of the episode is estimated to be on the order of months or less, constrained by Cs, Rb, and Sr mobility in glass. Additional variations inglass and biotite chemistry are identified as primary, and offer an avenue to deciphering the complex event stratigraphy of the eruption, with implications for hazard potential of future rhyolitic eruptions from Valles Caldera. |
