TephraNZ: a major- and trace-element reference dataset for glass-shard analyses from prominent Quaternary rhyolitic tephras in New Zealand and implications for correlation

Abstract. Although analyses of tephra-derived glass shards have been undertaken in New Zealand for nearly four decades (pioneered by Paul Froggatt), our study is the first to systematically develop a formal, comprehensive, open-access reference dataset glass-shard compositions tephras. These data will provide an important tool future studies identify and correlate tephra deposits associated petrological magma-related within beyond. Here we present foundation TephraNZ, selected Zealand. Prominent, rhyolitic, from Quaternary were identified, with sample collection targeting original type sites or locations where tephra's identification unequivocally known based on independent dating and/or mineralogical techniques. Glass extracted deposits, major- trace-element geochemical determined. We discuss detail reduction process used obtain results propose that follow similar protocol order gain comparable data. The contains 23 proximal 27 distal samples characterising 45 eruptive episodes ranging Kaharoa (636 ± 12 cal yr BP) Hikuroa Pumice member (2.0 0.6 Ma) six more caldera sources, most central Taup? Volcanic Zone. report 1385 major-element obtained electron microprobe (EMPA), 590 laser ablation (LA)-ICP-MS, individual shards. Using principal component analysis (PCA), Euclidean similarity coefficients, investigation, show chemical eruptions are commonly distinguished major elements, especially CaO, TiO2, K2O, FeOtt (Na2O+K2O SiO2/K2O), but not always. For those tephras signatures, some can be using trace elements (e.g. HFSEs: Zr, Hf, Nb; LILE: Ba, Rb; REE: Eu, Tm, Dy, Y, Tb, Gd, Er, Ho, Yb, Sm) ratios LILE/HFSE: Ba/Th, Ba/Zr, Rb/Zr; HFSE/HREE: Zr/Y, Zr/Yb, Hf/Y; LREE/HREE: La/Yb, Ce/Yb). Geochemistry alone cannot distinguish between following groups: (Unit Y post-?ruanui eruption sequence volcano) Waimihia S); Poronui C) Karapiti B); Rotorua Rerewhakaaitu; Kawakawa/?ruanui, Okaia. Other characteristics, including stratigraphic relationships age, separate all these otherwise-similar except Karapiti. Bimodality caused K2O variability newly identified Poihipi Tahuna compositions, sourced Centre (TVC) Mangakino (MgVC) separated bivariate plots SiO2/K2O vs. Na2O+K2O. derived Kapenga Centre, Whakamaru MgVC, they overlap Okataina volcanic centres. Specific lower than heterogeneous bimodal making them easier fingerprint geochemically.