Geochemistry of volcanic rocks in Barton and Weaver peninsulas, King George Island, Antarctica: Implications for arc maturity and correlation with fossilized volcanic centers

Abstract

We investigated geochemical characteristics of the Paleocene-Eocene volcanic rocks in Barton and Weaver peninsulas, King George Island, Antarctica. Volcanic rocks are predominantly tholeiitic, and show geochemical properties typical for island arc volcanism. The volcanic rocks can be subdivided into three groups based on the differences of geochemistry and regional distribution. The group 1 rocks are distributed in Weaver Peninsula and in the central part of Barton Peninsula. They show relatively mafic compositions (basalts to basaltic andesites) with the lowest level of total REEs. The group 2 rocks are widely distributed in Barton Peninsula, and show intermediate compositions (basaltic andesites to andesites) with the highest LILE/HFSE and LREE/HREE ratios. The group 3 rocks occur as intermediate dikes or plugs along the southern coast of Barton Peninsula. They generally show similar compositions to those of the group 2, but have smaller LREE/HREE ratios. The parental magma of the group 1 seems to be most depleted among three groups, whereas that of the group 2 rocks enriched in LILEs and LREEs. Predominance of tholeiite series rocks, general absence of the basement complex, and difficulty of identifying dual volcanic chains suggest that the Early Tertiary volcanism in King George Island occurred in an immature island arc without thickened continental-type crust. Geochemical correlations between volcanic rocks and fossilized volcanic vents suggest that volcanic groups can be linked with vents: the group 1 with Weaver Nunatak, and the group 2 with Three Brothers Hill, Florence Nunatak and/or Czajkowski Needle. However, the group 3 seems to be correlative with the Chottaebawi plug (the Narebski Point), or represent distinct dike swarms.