Isotope Geochemistry of Volcanic Rocks from the Barton Peninsula, King George Island, Antarctica

Abstract

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 δ13C and δ18O values of calcite in volcanic rocks range from -7.5‰ to -3.2‰ and 0.4‰ to 5.1‰, respectively. The homogenous δ13Ccal and depleted δ18Ocal values relative to primary magmatic values reflect the effect of high temperature alteration of volcanic rocks. The δ18O of volcanic rocks ranges from -1.1‰ to 7.2‰, and the majority of values are significantly lower than those of primary magmatic values. The low δ18OWR values are compatible with high temperature alteration. The initial values of 87Sr/86Sr 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 87Sr/86Sr of volcanics in the Barton Peninsula are similar to those determined in the Fildes Peninsula, King George Island. The δDWR and H2O contents of volcanic rocks range from - 74‰ to -66‰ and 0.67 wt.% to 2.74 wt.%, respectively. The higher δDWR 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 -12.5‰ to -7.0‰;these values may represent fractionation from basalt to andesite. The δ13C and δ18O values of calcite in volcanic rocks range from -7.5‰ to -3.2‰ and 0.4‰ to 5.1‰, respectively. The homogenous δ13Ccal and depleted δ18Ocal values relative to primary magmatic values reflect the effect of high temperature alteration of volcanic rocks. The δ18O of volcanic rocks ranges from -1.1‰ to 7.2‰, and the majority of values are significantly lower than those of primary magmatic values. The low δ18OWR values are compatible with high temperature alteration. The initial values of 87