Jakub Sliwinski

The use of biotite trace element compositions for fingerprinting magma batches at Las Cañadas volcano, Tenerife

Accurate identification of individual volcanic events in the field is crucial for constraining eruption volumes and calculating recurrence intervals between eruptive episodes. Due to complexities of pyroclastic transport and deposition and intra-unit textural variability, such identification can be challenging. We present a novel method for fingerprinting ignimbrites via trace element chemistry (V, Co, Nb) in biotite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Using samples from the alkaline magmatic series of Tenerife, we are able to demonstrate (1) clustering of previously characterized units into distinct, homogeneous groups based on V, Co, and Nb concentrations in biotite, despite the presence of extreme variation and zonation in other trace elements (Ba, Sr, Rb) that indicate complex petrogenetic processes, and (2) biotite compositions are similar throughout a deposit and relatively independent of stratigraphic height or juvenile clast texture (crystal-rich vs crystal-poor). Our results show that trace elements in biotite can be used to fingerprint eruptions and correlate geographically separated volcanic deposits, including those preserved in offshore turbidite records.

Evidence for a spike in mantle carbon outgassing during the Ediacaran period

Long-term cycles in Earth’s climate are thought to be primarily controlled by changes in atmospheric CO2 concentrations. Changes in carbon emissions from volcanic activity can create an imbalance in the carbon cycle. Large-scale changes in volcanic activity have been inferred from proxies such as the age abundance of detrital zircons, but the magnitude of carbon emissions depends on the style of volcanism as well as the amount. Here we analyse U–Pb age and trace element data of detrital zircons from Antarctica and compare the results with the global rock record. We identify a spike in CO2-rich carbonatite and alkaline magmatism during the Ediacaran period. Before the Ediacaran, secular cooling of the mantle and the advent of cooler subduction regimes promoted the sequestration of carbon derived from decarbonation of subducting oceanic slabs in the mantle. We infer that subsequent magmatism led to the extensive release of carbon that may at least in part be recorded in the Shuram–Wonoka carbon isotope excursion. We therefore suggest that this pulse of alkaline volcanism reflects a profound reorganization of the Neoproterozoic deep and surface carbon cycles and promoted planetary warming before the Cambrian radiation.A spike of carbon-rich volcanism during the Ediacaran period identified in detrital zircon data may reflect a reorganization of the Neoproterozoic deep carbon cycle.

A continental arc tempo discovered in the Pacific-Gondwana margin mudpile?

The integration of detrital zircon age and trace element analyses provides a powerful tool with which to reconstruct continental arc evolution. Detrital zircons from the Ross-Delamerian orogen along the Pacific-Gondwana margin in north Victoria Land in Antarctica yield a broad 700–500 Ma U-Pb age population that shows a prominent period of activity centered at ca. 630–550 Ma. This activity is well correlated with the highest zircon Th/U and U/Yb ratios, suggesting an increase in lithospheric contribution coincident with fluid input from oceanic slab subduction, respectively. A low Yb/Gd ratio over this same period also suggests crustal thickening. Determination of zircon parent rock types using trace element proxies reveals the presence of previously unrecognized distinct pulses of granitoid activity that occur over tens of millions of years. Lulls between granitoid flare-ups overlap with increases in mafic-carbonatite-alkaline magma production, suggesting an influx of mantle or lower crustal melts during syn-subduction extension. A concomitant increase in the number of metamorphic zircons (U/Th > 10) and 40Ar/39Ar white mica cooling ages found during these extensional episodes suggest that significant thermal perturbations of the crust coincided with orogenic cooling, which was possibly influenced by uplift and exhumation.

LA-ICP-MS U-Pb zircon geochronology data of the Early to Mid-Miocene syn-extensional massive silicic volcanism in the Pannonian Basin (East-Central Europe)

This article provides LA-ICP-MS in-situ U-Pb zircon dates performed on single crystals from dacitic to rhyolitic ignimbrites of the Bükkalja Volcanic Field (Hungary, East-Central Europe) temporally covering the main period of the Neogene silicic volcanic activity in the Pannonian Basin. The data include drift-corrected, alpha dose-corrected, Th-disequilibrium-corrected, and filtered data for geochronological use. The data presented in this article are interpreted and discussed in the research article entitled “Early to Mid-Miocene syn-extensional massive silicic volcanism in the Pannonian Basin (East-Central Europe): eruption chronology, correlation potential and geodynamic implications” by Lukács et al. (2018) [1].

Learning Hedonic Games

Coalitional stability in hedonic games has usually been considered in the setting where agent preferences are fully known. We consider the setting where agent preferences are unknown; we lay the theoretical foundations for studying the interplay between coalitional stability and (PAC) learning in hedonic games. We introduce the notion of PAC stability — the equivalent of core stability under uncertainty — and examine the PAC stabilizability and learnability of several popular classes of hedonic games.