No abstract

This paper presents the preliminary results regarding the lithostratigraphy, petrography and petrology of James Ross Island Volcanic Group dominating the Lachman Crags and Cape Lachman lava-fed deltas in the Ulu Peninsula, James Ross Island north-eastern Antarctic Peninsula. Studied lava-fed deltas were produced via Late Miocene to Pleistocene sub-marine and sub-glacial volcanism and made up four main lithofacies: a- bottomset pillow lavas, peperites and associated volcanoclastic/siliciclastic deposits; b- foreset-bedded hyaloclastite breccias; c- intrusions (feeder dykes, sills, and plugs) and d- topset subaerial lavas. Collectively these lithofacies record the transition from an effusive subaqueous to an effusive subaerial eruption environment. All lava samples and dykes from bottomset, foreset and topset lava-fed delta associations are olivine-phyric alkali basalts and are mineralogically and geochemically homogeneous. These eruptive products display significant enrichments in alkali contents and have ocean island basalt (OIB)-type, intra-plate geochemical signatures characterized by enrichments in all highly to moderately incompatible trace elements relative to basaltic rocks from ocean ridge settings. Volcanic products from a number of different eruptive periods display limited variations in major and trace element relative abundances, indicating derivation from a relatively homogeneous mantle source. The results of quantitative modelling of geochemical data is consistent with the view that the primary melts from which these mafic alkaline rocks were originated are the products of relatively small degrees (~3-7%) of partial melting of a volatile-bearing, metasomatized mantle source. The magmatism is likely the result of extension-driven mantle upwelling.

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Fulgurites have been documented in geological deposits from throughout Earth's history. They have also been assigned a potential role in prebiotic chemistry as a source of reactants. Fulgurites are generated in nature by cloud-to-ground lightning strikes. The unpredictability in space and time of the occurrence of lightning events has limited the investigation of both the mechanisms by, and the conditions under, which fulgurites form. A laboratory-based approach can ameliorate this. Here, we describe experimentally generated fulgurites generated from Laacher See volcanic ash. We employ a DC source with a trigger-pulse setup in a high voltage laboratory, whose capabilities enable experimental conditions that correspond closely to the electrical characteristics of natural lightning strikes. The experimentally generated fulgurites closely resemble naturally-occurring fulgurites in both state and texture. These experimental investigations yield a high reproducibility of the characteristic of fulgurites generated under well-constrained conditions, enabling some inferences to be made regarding the processes involved in the generation of fulgurites in nature. This work provides a basis for a systematic characterization of experimental fulgurites and the characteristic of lightning discharges.

Fulgurites have been documented in geological deposits from throughout Earth's history. They have also been assigned a potential role in prebiotic chemistry as a source of reactants. Fulgurites are generated in nature by cloud-to-ground lightning strikes. The unpredictability in space and time of the occurrence of lightning events has limited the investigation of both the mechanisms by, and the conditions under, which fulgurites form. A laboratory-based approach can mitigate these limitations. Here, we describe experimentally generated fulgurites generated from Laacher See volcanic ash. We employ a DC source with a trigger-pulse setup in a high voltage laboratory, whose capabilities enable experimental conditions that correspond closely to the electrical characteristics of natural lightning strikes. The experimentally generated fulgurites closely resemble naturally-occurring fulgurites in both state and texture. These experimental investigations yield a high reproducibility of the characteristic of fulgurites generated under well-constrained conditions, enabling some inferences to be made regarding the processes involved in the generation of fulgurites in nature. This work provides a basis for a systematic characterization of experimental fulgurites and the characteristic of lightning discharges.