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THE MOBILIZATION OF LARGE ION LITHOPHILE ELEMENTS (LILES) IN CHONDRITES BY CHEMICAL ALTERATION IN ANTARCTICA: IMPLICATIONS FROM LU-HF AND SM-ND ISOTOPE SYSTEMATICS AND THE DISTRIBUTION OF LILES BY USING LA-ICP-TOF/MS

THURSDAY NOVEMBER 21 - 4 PM

RYOGA MAEDA
AMGC, VRIJE UNIVERSITEIT BRUSSEL

ABSTRACT: The isotope systematics of Lu-Hf and Sm-Nd are known to be important chronometers and tracers for chemical differentiation processes and have been applied to not only terrestrial but also extraterrestrial materials. More than 55000 meteorites have been collected from Antarctica, hot deserts and even where we live so far; more than half of all meteorites has been found in Antarctica. However, the relative mobility of large ion lithophile elements (LILEs) during weathering in cold and hot deserts poorly understood, especially in terms of isotope. In this study, therefore, the results of Lu-Hf and Sm-Nd isotope systematics in Antarctic chondrites are examined in a methodical manner and the distribution of trace elements in those samples is investigated by using LA-ICP-TOF/MS.
According to the results of Lu-Hf and Sm-Nd isotope systematics in Antarctic chondrites we obtained, 176Hf/177Hf and 143Nd/144Nd ratios in nearly all samples are within ranges of literature values using falls. However, 176Lu/177Hf and 147Sm/144Nd ratios in many samples are much higher than ranges of the literature values, while those ratios in samples from hot deserts are lower than the ranges because of a typical terrestrial weathering. In addition, many LILEs including rare earth elements and Hf are distributed in crucks in samples considerably based on trace elemental maps obtained by using LA-ICP-TOF/MS. Therefore, the shifts of 176Lu/177Hf and 147Sm/144Nd ratios in Antarctic chondrites may be explained by a chemical alteration in Antarctica.

BIO: Ryoga Maeda is a doctoral researcher at the AMGC group of Vrije Universiteit Brussel (VUB). He obtained a bachelor’s and master’s degrees in chemistry at Tokyo Metropolitan University, studying the distribution of rare earth elements, Th and U in R chondrite by using a chemical leaching technique. His PhD study is conducted at VUB, Université Libre de Bruxelles and Ghent University, and includes the comparative petrographic, geochemical, and isotopic characterization of various Antarctic meteorites using various state-of-the-art analytical techniques (ICP-OES, Q-ICP-MS, MC-ICP-MS, TIMS, micro-XRF, SEM-EDS, EPMA and LA-ICP-TOF/MS) to combine both bulk wet chemistry and in-situ measurements.

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