Isotope geochemistry of volcanic rocks from the Barton Peninsula, King George Island, Antarctica

C, O, H, S and Sr isotopes were investigated to characterize the isotopic composition of the Paleocene-Eocene volcanic rocks in Barton Peninsula, King George Island, Antarctica. The analyzed samples of volcanic rocks cover a range from basalt to andesite. The delta C-13 and delta O-18 values of calcite in volcanic rocks range from -7.5aEuro degrees to -3.2aEuro degrees and 0.4aEuro degrees to 5.1aEuro degrees, respectively. The homogenous delta C-13(cal) and depleted delta O-18(cal) values relative to primary magmatic values reflect the effect of high temperature alteration of volcanic rocks. The delta O-18 of volcanic rocks ranges from -1.1aEuro degrees to 7.2aEuro degrees, and the majority of values are significantly lower than those of primary magmatic values. The low delta O-18(WR) values are compatible with high temperature alteration. The initial values of Sr-87/Sr-86 of volcanic rocks span a narrow range from 0.703 312 to 0.703 504 which belong to the present mid-oceanic ridge basalt. The values of Sr-87/Sr-86 of volcanics in the Barton Peninsula are similar to those determined in the Fildes Peninsula, King George Island. The delta D-WR and H2O contents of volcanic rocks range from -74aEuro degrees to -66aEuro degrees and 0.67 wt.% to 2.74 wt.%, respectively. The higher delta D-WR and H2O wt.% of volcanic rocks relative to fresh basalts also result from high temperature alteration. Sulfur isotope compositions of the volcanic rocks range from -12.5aEuro degrees to -7.0aEuro degrees; these values may represent fractionation accompanying partial oxidation of magmatic S or incorporation of some bacteriogenic sulfide. The low S contents and negative correlation with C and H2O reflect the formation of calcite and breakdown of sulfide as a result of high temperature water-rock interaction.