U–Pb Zircon Geochronological and Petrologic Constraints on the Post-Collisional Variscan Volcanism of the Tiddas-Souk Es-Sebt des Aït Ikko Basin (Western Meseta, Morocco)

The NE–SW trending Tiddas Souk Es-Sebt des Ait Ikko (TSESDAI) basin, located at 110 km southeast of Rabat, in the region of Khmesset between the village of Tiddas Souk Es-Sebt des Ait Ikko, is the third largest late Palaeozoic continental trough in the northern Central Moroccan Meseta. It is a ~20 km long and ~2–3 km wide basin, comprising mainly mixed volcano-sedimentary reddish-purple continental Permian rocks laying with an angular unconformity on Visean deep marine siliciclastic sediments and unconformably overlain by the Triassic and Cenozoic formations. In this study we aim to better determine the age of Permian volcanics and their chemical and mineralogical characteristics, as well as assess the provenance of inherited zircons, thus contributing to the understanding of the late stages of the Variscan orogeny in Morocco. The standard volcanic succession includes the following terms: (i) andesites, lapilli tuffs and andesitic ash deposits; (ii) accumulations of rhyolitic lavas; (iii) lapilli tuffs and rhyolitic ash (formation F1); (iv) flows and breccias of dacites; (v) andesite flows; and (vi) basaltic flows. The various volcanic and subvolcanic studied rocks display calc-alkaline-series characteristics with high contents of SiO2, Al2O3, CaO, MgO, and relatively abundant alkalis, and low contents of MnO. In the classification diagram, the studied facies occupy the fields of andesites, trachy-basalts, dacites, trachydacites, and rhyolites and display a sub-alkaline behavior. These lavas would be derived from a parental mafic magma (basalts) produced by partial fusion of the upper mantle. Specific chemical analyses that were carried out on the mineralogical phases (biotite and pyroxene) revealed that the examined biotites can be classified as magnesian and share similarities with the calc-alkaline association-field, while the clinopyroxenes are mainly augites and plot on the calc-alkaline orogenic basalt field. Andesites and dacites of TSESDAI show similarities with the rocks of the calc-alkaline series not linked to active subduction and which involve a continental crust in their genesis. The existence of enclaves in the lavas of the TSESDAI massif; the abnormally high contents of Rb, Ba, Th, and La; and the systematic anomalies in TiO2 and P2O5 indicate also a crustal contamination mechanism. Three magmatic episodes are distinguished with two episodes that correspond to an eruptive cycle of calc-alkaline andesites and rhyolites followed by a basaltic episode. The SHRIMP U–Pb geochronologic data of zircons recovered from the rhyolite dome of Ari El Mahsar in TSESDAI basin show a Concordia age of 286.4 ± 4.7 Ma interpreted to date the magmatic crystallization of this dome. Thus, the rhyolite likely belongs to the third magmatic episodes of TSESDAI.

Machine learning thermobarometry and chemometry using amphibole and clinopyroxene: a window into the volcanic roots of an arc volcano (Mount Liamuiga, Saint Kitts)

The physical and chemical properties of magma govern the eruptive style and behaviour of volcanoes. Many of these parameters are linked to the storage pressure and temperature of the erupted magma, and melt chemistry. However, reliable single-phase thermobarometers and chemometers which can recover this information, particularly using amphibole chemistry, remain elusive. We present a suite of single-phase amphibole and clinopyroxene thermobarometers and chemometers, calibrated using machine learning. This approach allows us to intimately track the range of pre-eruptive conditions over the course of a millennial eruptive cycle on an island arc volcano (Saint Kitts, Eastern Caribbean). We unpick the story of Mount Liamuiga, a stratovolcano that pops its upper-crustal (2 kbar), dacitic cork at the beginning of the Lower Mansion Series eruptive sequence. This permits a progressive increase in the thermal maturity of the magma arriving at the surface from the middle to upper crust (2 – 5.5 kbar) through time. The temperature increase correlates well with matrix plagioclase chemistry, which itself displays a remarkable progression to less evolved (more anorthitic) composition in time. We find that amphibole is a reliable themobarometer (SEE = 1.4 kbar; 40 ˚C), at odds with previous studies. We suggest it is the regression strategy, as opposed to the abject insensitivity to pressure, that has hindered previous calibrations of amphibole only thermobarometers. By recognising this, we have constructed a high-resolution, quantitative picture of the magma plumbing system beneath an arc volcano.

Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde

<p>Cape Verde archipelago is a cluster of several volcanic islands arranged in a westward opening horseshoe shape located in the Atlantic Ocean, between 550 and 800 km-west of the coast of Senegal (Africa). Fogo Island is located in the southwest of the archipelago, and as main feature is a 9-km-north to south wide collapse caldera opened toward the east, within Pico do Fogo volcano rises 2,829 m.a.s.l. Pico do Fogo crater has an area of 0.142 km<sup>2</sup> and its characterized by a fumarolic field composed by low and moderate temperature fumaroles, with temperatures around 95ºC and reaching 400ºC respectively. The last eruption of Fogo volcanic system took place between November 2014 and February 2015, when four new eruptive vents were formed, and destroyed partially the villages of Portela and Bangaeira (Silva et. al., 2015) forcing the evacuation of 1,300 inhabitants. In this work we present the temporal evolution of <sup>3</sup>He/<sup>4</sup>He isotopic ratio, <sup>3</sup>He and <sup>4</sup>He emission and thermal energy released data measured from March 2007 to November 2018 in the crater of Pico do Fogo. In all the studied temporal evolutions, we can observe two main increases in the above parameters, the first in early 2010, suggesting a magmatic intrusion, and the second several months before the eruption onset. We have also observed that changes in the <sup>3</sup>He emission might be accompanied by a significant increase in thermal output if the system is in an eruptive cycle. Our results confirm <sup>3</sup>He emission studies are highly reliable indicator of imminent volcanic eruption and constitute a powerful tool to monitor the activity of volcanic areas around the world.</p><p>Silva et al., (2015), Geophysical Research Abstracts Vol. 17, EGU2015-13378, EGU General Assembly.</p>

Mapping the Bubble Trap Feeding Eruptions of Strokkur Geyser, Iceland

<p>Geysers are characterized by regular eruptions of hot water fountains. Their internal system consists of a heat source at depth, an often complex crack system and a conduit linking it to the surface. The conduit and crack system is filled with water, steam and gases similar to a volcano. Bubble traps are sometimes and rarely mapped and alternative heat-driven models for geyser eruptions exist.</p><p>Using a multidisciplinary, dense and close network of video cameras, seismometers, water pressure sensors and a tiltmeter we studied pool geyser Strokkur in June 2018. These multidisciplinary observations and particle-motion based tremor locations enabled us to derive a schematic cross section describing the driving mechanisms and the fluid dynamic processes within the bubble trap, crack system and conduit. We imaged a bubble trap at 23.7+-4.4 m depth, 13 to 23 m west of the conduit. We divide the eruptive cycle into eruption, refilling of the conduit, gas accumulation in the bubble trap and a trail of bubbles from the bubble trap into the conduit where they collapse at depth and have gained novel insights in understanding the gas accumulation, migration and collapse in such hot geyser systems in different phases of the eruptive cycle.</p><p>The dataset of this experiment can be accessed here:</p><p><strong>- Eibl, E. P. S.</strong>, Müller, D., Allahbakhshi, M., Walter, T. R., Jousset, P., Hersir, G. P., Dahm, T., (2020) ' Multidisciplinary dataset at the Strokkur Geyser, Iceland, allows to study internal processes and to image a bubble trap.' GFZ Data Services. DOI: 10.5880/GFZ.2.1.2020.007</p><p>- <strong>Eibl, E. P. S.</strong>; Walter, T.; Jousset, P.; Dahm, T.; Allahbakhshi, M.; Müller, D.; Hersir, G.P. (2020): 1 year seismological experiment at Strokkur in 2017/18. GFZ Data Services. Other/Seismic Network. DOI:10.14470/2Y7562610816</p>

InSAR Imaging of White Island from 2014 to 2020: Insights into the 2019 Phreatic Eruption

<p>At 14:11 NZDT (01:11 UTC) on 9 December 2019, an explosive eruption (VEI=2) occurred on White/Whakaari Island in New Zealand’s northeast Bay of Plenty. The sudden eruption claimed 20 lives among the 47 tourists who were on the island at the time of the eruption. Several volcano-tectonic features overlap in the island such as a major caldera rim collapsing scarp to the west, a landslide, a crater lake and a large shallow hydrothermal system at the center, making complex the understanding of the eruption triggering factors. Here we use Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data from 3 different tracks (1 ascending and 2 descending) spanning the period of 2014-2020 to investigate the spatio-temporal surface deformation evolution of White Island in the years before the eruption. By analyzing the InSAR time-series displacements between the two eruptions of April 2016 and December 2019, at least 4 separate stages can be identified that possibly relate to different parts of the volcanic eruptive cycle:  1) During April 2016 - February 2018, the crater lake edge and the western sub-crater wall rapidly moved downslope at a rate of ~6 cm/yr, while the central sub-crater area uplifted at a rate of ~3 cm/yr; 2) From February 2018 to January 2019, both the western and the central sub-craters uplifted at a rate of ~5 cm/yr; 3) During  the following six months, from January 2019 to June 2019, the western sub-crater started moving downslope again at a rate of ~3 cm/yr, while the central sub-cater kept moving up at a rate of ~4 cm/yr; 4) And finally, during June 2019 - December 2019 (until the eruption), uplift occurred around the western sub-crater again at a similar rate as in the central sub-crater area (~ 4 cm/yr). Seismic records before the eruption show that approximately 500 volcanic earthquakes located at a depth of ~ 5 km occurred at the southwestern part of White Island on June 2019, that may point to a shallow level intrusion of new magma. This upcoming magma might then have pressurized the shallow hydrothermal system during the fourth-stage uplift. Modeling of the uplift during June 2019 to December 2019 indicates a shallow source located at only ~200 m below the surface in the vicinity of the crater lake, likely coinciding with the shallow hydrothermal system responsible for the final 2019 phreatic eruption.</p>

Sonification and Animation of Multivariate Data to Illuminate Dynamics of Geyser Eruptions

Sonification of time series data in natural science has gained increasing attention as an observational and educational tool. Sound is a direct representation for oscillatory data, but for most phenomena, less direct representational methods are necessary. Coupled with animated visual representations of the same data, the visual and auditory systems can work together to identify complex patterns quickly. We developed a multivariate data sonification and visualization approach to explore and convey patterns in a complex dynamic system, Lone Star Geyser in Yellowstone National Park. This geyser has erupted regularly for at least 100 years, with remarkable consistency in the interval between eruptions (three hours) but with significant variations in smaller scale patterns between each eruptive cycle. From a scientific standpoint, the ability to hear structures evolving over time in multiparameter data permits the rapid identification of relationships that might otherwise be overlooked or require significant processing to find. The human auditory system is adept at physical interpretation of call-and-response or causality in polyphonic sounds. Methods developed here for oscillatory and nonstationary data have great potential as scientific observational and educational tools, for data-driven composition with scientific and artistic intent, and towards the development of machine learning tools for pattern identification in complex data.