Lithium isotope fractionation in magmatic systems : constraints from in situ δ7Li determinations on magmatic minerals by femtosecond-laser ablation-MC-ICP-MS

Investigations on the fractionation of stable metal isotopes to characterize mass flux at high temperatures have been proven to be a powerful tool during the past years. In this study, high precision in situ analyses on Li isotope ratios were performed on reference glasses and natural olivines at low concentration levels by femtosecond-laser ablation multi collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) in order to investigate the fractionation of Li isotopes during magma evolution. The analytical technique was tested by analyzing a series of reference glasses in situ and cross calibrating them with published values acquired by other methods (solution nebulization MC-ICP-MS, SIMS and TIMS). The results of this methodical investigation showed that operating the plasma at relatively cool conditions (900 W) largely suppresses matrix-dependent isotope effects in the plasma. In order to achieve the best precision for concentrations ranging from 2 to 10 µg/g a detector combination of an ion counter for the determination of 6Li and a faraday cup equipped with a 1013 Ω amplifier for 7Li was applied. Precise and accurate measurements of δ7Li with ~2 ‰ (2 σ) analytical uncertainty were performed on reference glass T1-G (δ7LiT1 G = 1.6-2.4 ‰). The fractionation of Li isotopes on the outcrop and mineral scale were investigated in this study. Bulk Li isotope analyses of an outcrop over a length of ~50 m in the French Massif Central showed that on the outcrop scale the isotopic composition varied between +2.1 and +3.3 ±2.0 ‰. The measured δ7Li-values coincide with the range of unaltered volcanic whole-rock suites worldwide (+2.0 to +5.0 ‰) and the value determined for the bulk silicate Earth (+3.5 to +4.0 ‰). A systems analysis was performed in order to determine melt reservoirs for two locations of distinct geotectonic settings (ocean intra-plate (Tenerife, Canary Islands, Spain) and volcanic island arc (Kluchevskoy volcano, Kamchatka peninsula, Russia)). Reservoirs of varying primitive grade in a volcanic plumbing system were determined and the passage way of crystals could be retraced by forsterite and Li contents. Diffusion of Li was modeled to be 1.4–2.5 times faster than that of the Mg-Fe diffusion couple, which is significantly less than the diffusivity determined in experimental studies. Chemically and isotopically zoned olivines from a continental intra-plate setting (Massif Central, France) were analyzed regarding their Li isotope composition along profiles from rim to core. Variations in the Mg-Fe and Li isotopic composition revealed a diffusive origin of the zoning, and Li gives insight into a second diffusive event, which remains hidden in Mg-Fe. Profiles of the first diffusive event were modeled with fixed time scales, based on Mg-Fe inter-diffusion, acquired by Oeser et al. (2015), for the residence time in a magma reservoir. The model again resulted in lower diffusion coefficients for Li diffusion in olivine, than those determined in experimental studies. A second, relatively short-lived, diffusive re-equilibration episode was assumed to be caused by the degassing of the magma and concomitant Li decrease in the melt with no effect on Mg-Fe distribution

Reconstruction of volcano-tectonic processes in interplay with sedimentary deposition in the Gulf of Naples (Italy) using a seismoacoustic dataset

The Campi Flegrei caldera (CFc) has been considered as one of the world's most active calderas, proven by recent episodes of unrest. As a future eruption could affect nearly 2.5 million people, understanding eruption mechanisms and dynamics is of paramount importance to reliably assess volcanic hazards and risks. In this thesis, the offshore sector of the CFc is investigated based on high-resolution multichannel reflection seismic data, including the first semi-3D multichannel seismic survey of a large collapse caldera. The main outcomes of the current thesis are presented in three novel and comprehensive evolutionary models addressing (1) a 3D reconstruction of the tectono-sedimentary variability in the Gulf of Naples half-graben with respect to volcanism during the past one million years, (2) the conceptual formation of the Campi Flegrei nested-caldera complex, and (3) the 3D post-caldera evolution of the CFc. These findings represent a significant advancement towards understanding the genesis and evolution of the CFc as well as the tectonic formation of the Gulf of Naples half-graben basin and its influence on volcanism

Verzahnung von Data Stewardship und Data Science – Wege und Perspektiven

Data Science ermöglicht die Gewinnung von Erkenntnissen aus komplexen, hochdimensionalen Daten und wird daher als Schlüsseldisziplin unserer Zeit und zentrales Element der datenintensiven Forschung angesehen. Das Fundament dafür bilden gut kuratierte, FAIRe Daten, gewährleistet durch ein nachhaltiges Forschungsdatenmanagement bzw. Data Stewardship. Dementsprechend verspricht eine enge Abstimmung und systematische Verzahnung von Data Science und Data Stewardship im Forschungsprozess eine signifikante Effizienzsteigerung und maximale Wertschöpfung aus Daten. Das mit Unterstützung des Landes Bremen aufgebaute Data Science Center (DSC@UB) der Universität Bremen bietet dafür bestmögliche Rahmenbedingungen. Als zentrale, interdisziplinäre Infrastruktur für die datenintensive Forschung dient es als Ort für den fachübergreifenden Austausch und stellt essentielle Services zur Unterstützung von Forschenden bereit. Darüber hinaus ermöglicht das DSC die forschungsnahe Ansiedlung von Data Scientists und Data Stewards, die Wissenschaftler:innen im gesamten Datenlebenszyklus und in enger Zusammenarbeit unterstützen sollen. Dies soll (1) die FAIRe Bereitstellung von Daten, (2) einen möglichst großen Erkenntnisgewinn aus Daten, und (3) die Optimierung von Prozessen und Abläufen im Umgang mit Daten nachhaltig gewährleisten, wodurch neue Innovationsmöglichkeiten geschaffen werden

Multi-Stage Magma Evolution in Intra-Plate Volcanoes: Insights From Combined in situ Li and Mg–Fe Chemical and Isotopic Diffusion Profiles in Olivine

Understanding the timescales of magma evolution and ascent is essential for interpreting geophysical monitoring signals from active volcanoes. In this study, we explore the potential of diffusion-driven Li concentration and isotope zoning profiles recorded by magmatic olivine crystals to unravel time scales of magma evolution processes. Lithium is a fast-diffusing element and may provide the opportunity to investigate changes in magma composition during magma ascent, shortly before eruption. Lithium chemical and isotopic profiles were determined in olivines from two localities in the Massif Central volcanic region (France) that have previously been investigated for their Fe–Mg isotope systematics. The combined investigation of isotopic and chemical profiles makes it possible to distinguish between crystal growth and diffusion events. Extremely low δ7Li-values down to −30.7‰ (relative to the commonly used Li isotope standard IRMM-16) in the crystal core regions and elevated values at crystal rims (δ7Li ∼8 to 10‰), along with increasing concentrations from cores (∼3 to 1 μg/g) toward rims (12 to 6 μg/g) were found. The shape and orientation of both the chemical and isotopic profiles indicate that they were dominantly generated by Li diffusion into and within the olivine grains during magmatic differentiation. While Mg–Fe isotope and major element profiles have been modeled by a single diffusion event (Oeser et al., 2015), concentration and isotope profiles of Li indicate that a second diffusion event took place, that was not recorded by the Mg–Fe exchange diffusion couple. The first diffusion event was interpreted as reflecting the residence of the olivine crystals in a magma chamber. As diffusion coefficients for Fe–Mg exchange diffusion are very well determined, the time scales of this event are likely best quantified by Mg–Fe isotopic exchange diffusion modeling (Oeser et al., 2015). This event probably also generated the low δ7Li observed in olivine cores. Comparing the length of the Mg–Fe and Li profiles could thus be used to determine the less well-known diffusion coefficients of Li in the studied olivine crystals. The findings of this study indicate that Li diffusion at low Li concentration levels, as typically observed in natural olivine, may be not as fast as previously thought. The second diffusion event might represent a short-lived event, such as degassing, related to the ascent of the magma and/or magma cooling after emplacement of the lava. Such a process would only affect Li, which, in contrast to the refractory elements Fe and Mg, is volatile during degassing. The findings of this study show that, according to their different diffusion rates and physiochemical properties, the combined use of spatially resolved Li and Mg–Fe chemical and isotopic diffusion profiles, is a powerful tool to model even multi-stage evolution processes in magmatic systems. © Copyright © 2020 Steinmann, Oeser, Horn and Weyer

A roadmap for amphibious drilling at the Campi Flegrei caldera: insights from a MagellanPlus workshop

Large calderas are among the Earth's major volcanic features. They are associated with large magma reservoirs and elevated geothermal gradients. Caldera-forming eruptions result from the withdrawal and collapse of the magma chambers and produce large-volume pyroclastic deposits and later-stage deformation related to post-caldera resurgence and volcanism. Unrest episodes are not always followed by an eruption; however, every eruption is preceded by unrest. The Campi Flegrei caldera (CFc), located along the eastern Tyrrhenian coastline in southern Italy, is close to the densely populated area of Naples. It is one of the most dangerous volcanoes on Earth and represents a key example of an active, resurgent caldera. It has been traditionally interpreted as a nested caldera formed by collapses during the 100–200 km3 Campanian Ignimbrite (CI) eruption at ∼39 ka and the 40 km3 eruption of the Neapolitan Yellow Tuff (NYT) at ∼15 ka. Recent studies have suggested that the CI may instead have been fed by a fissure eruption from the Campanian Plain, north of Campi Flegrei. A MagellanPlus workshop was held in Naples, Italy, on 25–28 February 2017 to explore the potential of the CFc as target for an amphibious drilling project within the International Ocean Discovery Program (IODP) and the International Continental Drilling Program (ICDP). It was agreed that Campi Flegrei is an ideal site to investigate the mechanisms of caldera formation and associated post-caldera dynamics and to analyze the still poorly understood interplay between hydrothermal and magmatic processes. A coordinated onshore–offshore drilling strategy has been developed to reconstruct the structure and evolution of Campi Flegrei and to investigate volcanic precursors by examining (a) the succession of volcanic and hydrothermal products and related processes, (b) the inner structure of the caldera resurgence, (c) the physical, chemical, and biological characteristics of the hydrothermal system and offshore sediments, and (d) the geological expression of the phreatic and hydromagmatic eruptions, hydrothermal degassing, sedimentary structures, and other records of these phenomena. The deployment of a multiparametric in situ monitoring system at depth will enable near-real-time tracking of changes in the magma reservoir and hydrothermal system

Rekonstruktion von vulkanisch-tektonischen Prozessen im Zusammenspiel mit sedimentärer Deposition im Golf von Neapel (Italien) basierend auf einem seismoakustischen Datensatz

The Campi Flegrei caldera (CFc) has been considered as one of the world's most active calderas, proven by recent episodes of unrest. As a future eruption could affect nearly 2.5 million people, understanding eruption mechanisms and dynamics is of paramount importance to reliably assess volcanic hazards and risks. In this thesis, the offshore sector of the CFc is investigated based on high-resolution multichannel reflection seismic data, including the first semi-3D multichannel seismic survey of a large collapse caldera. The main outcomes of the current thesis are presented in three novel and comprehensive evolutionary models addressing (1) a 3D reconstruction of the tectono-sedimentary variability in the Gulf of Naples half-graben with respect to volcanism during the past one million years, (2) the conceptual formation of the Campi Flegrei nested-caldera complex, and (3) the 3D post-caldera evolution of the CFc. These findings represent a significant advancement towards understanding the genesis and evolution of the CFc as well as the tectonic formation of the Gulf of Naples half-graben basin and its influence on volcanism

Verzahnung von Data Stewardship und Data Science – Wege und Perspektiven

Data Science ermöglicht die Gewinnung von Erkenntnissen aus komplexen, hochdimensionalen Daten und wird daher als Schlüsseldisziplin unserer Zeit und zentralesElement der datenintensiven Forschung angesehen. Das Fundament dafür bilden gutkuratierte, FAIRe Daten, gewährleistet durch ein nachhaltiges Forschungsdatenmanagement bzw. Data Stewardship. Dementsprechend verspricht eine enge Abstimmung und systematische Verzahnung von Data Science und Data Stewardship imForschungsprozess eine signifikante Effizienzsteigerung und maximale Wertschöpfung aus Daten. Das mit Unterstützung des Landes Bremen aufgebaute Data ScienceCenter (DSC@UB) der Universität Bremen bietet dafür bestmögliche Rahmenbedingungen. Als zentrale, interdisziplinäre Infrastruktur für die datenintensive Forschungdient es als Ort für den fachübergreifenden Austausch und stellt essentielle Services zur Unterstützung von Forschenden bereit. Darüber hinaus ermöglicht das DSCdie forschungsnahe Ansiedlung von Data Scientists und Data Stewards, die Wissenschaftler:innen im gesamten Datenlebenszyklus und in enger Zusammenarbeit unterstützen sollen. Dies soll (1) die FAIRe Bereitstellung von Daten, (2) einen möglichstgroßen Erkenntnisgewinn aus Daten, und (3) die Optimierung von Prozessen und Abläufen im Umgang mit Daten nachhaltig gewährleisten, wodurch neue Innovationsmöglichkeiten geschaffen werden

Post-collapse evolution of a coastal caldera system: Insights from a 3D multichannel seismic survey from the Campi Flegrei caldera (Italy)

In this study we present the first 3D high-resolution multichannel seismic dataset from a (partly) submerged caldera setting, the Campi Flegrei caldera (CFc). Our work aims at examining the spatial and temporal evolution of the CFc since the last caldera-forming event, the Neapolitan Yellow Tuff (NYT, 15 ka) eruption. The main objectives are to investigate the caldera's shallow (< 200 m) subsurface structure and post-NYT-collapse (< 15 ka) deformational processes, the manifestation of magmatic and hydrothermal processes in the subsurface, as well as the volume, dispersal and explosivity of coastal post-collapse eruptions, thereby significantly advancing our current knowledge of the CFc. Our findings confirm the existence of a nested-caldera system comprising two caldera depressions bordered by an inner and a deeper (> 200 m) outer caldera ring-fault zone. The seismic data revealed that the NYT collapse occurred exclusively along the inner caldera ring-fault and that the related NYT caldera depression is filled with on average ~ 61 m of sediment deposited between 15 and 8.6 ka. The geometry of the inner ring-fault, consisting of four fault segments, seems to be strongly influenced by regional NW-SE and NE SW-trending faults. Furthermore, we found that the ring-faults have acted as pathway for the recent (< 3.7 ka) ascent of fluids (gases and liquids) and the emplacement of intrusions. We propose that the outer ring-fault zone, which likely formed in the course of the Campanian Ignimbrite (CI, 39 ka) eruption, has had the main control on the release and ascent of fluids. Overall, the caldera ring-faults represent key locations for the interconnection between the magmatic-hydrothermal systems and the surface and, thus, potentially represent future eruption sites as well as important fluid pathways during the recent unrest episodes. Furthermore, we reassessed the volume, dispersal, and explosivity of the post-collapse Nisida Bank (10.3–9.5 ka), Nisida Island (~ 3.98 ka), and Capo Miseno (3.7 ka) eruptions, yielding DRE values of 0.15 km3, 0.1 km3, and 0.08 km3, respectively, and an explosive magnitude of at least moderate-large scale (VEI 3). Our findings highlight that eruption volumes may be underestimated by 3 to 4 times if the submerged portion of a (partly) submerged caldera is not considered, implying severe consequences for the hazard and risk evaluation. The spatial response of the post-collapse (< 15 ka) depositional environment to volcanic activity, deformational processes and sea-level variations is presented in a comprehensive 3D evolutionary model