0000000000615050
AUTHOR
M. Molzahn
Os, Sr, Nd, Pb, O isotope and trace element data from the Ferrar flood basalts, antarctica: evidence for an enriched subcontinental lithospheric source
Os, Sr, Nd, Pb and O isotopes and trace element data are reported for basaltic andesite and andesite whole rocks and, in part, for selected mineral separates from the Jurassic Ferrar flood basalt province. Radiogenic Sr (> 0.709), unradiogenic Nd (εNd= −3 to −5), and radiogenic Pb isotopes, as well as low Nb/La ratios of 0.4 – 0.6 and Nb/La ratios between 0.45 and 0.6 are found for all rocks including our most primitive sample (Mg# = 71.9). This indicates involvement of either continental crust or enriched lithospheric mantle in magma genesis. 187Re/188Os correlates strongly with 187Os/188Os, with an age of 172 ± 5 Ma, in agreement with published Arsingle bondAr data. Initial 187Os/188Os of…
Constraints on the Cretaceous thermal event in the Transantarctic Mountains from alteration processes in Ferrar flood basalts
Abstract K–Ar and 40 Ar/ 39 Ar incremental-heating analyses on apophyllite formed during hydrothermal alteration of volcanic rocks from the Ferrar Supergroup in North Victoria Land, Antarctica, provide strong evidence for hydrothermal events during mid-Cretaceous time. A last event has been dated at 96.7±0.6 Ma. Variable older ages between 112 and 125 Ma are interpreted as mixed ages of hydrothermal events or may be caused by disturbances of the Ar–Ar system. The Rb–Sr isotope system of the apophyllites is not applicable to dating because a large portion of the Sr is radiogenic and because of Rb-mobility in the crystal structure. Secondary mineralogy suggests a temperature for alteration be…
Geochemical evolution of rift magmas by progressive tapping of a stratified mantle source beneath the Ross Sea Rift, Northern Victoria Land, Antarctica
Abstract Source compositions of Neogene-Quaternary volcanic rocks from the McMurdo Volcanic Group of the Ross Sea Rift in Northern Victoria Land, Antarctica are constrained by NdSrPb isotopes and trace element ratios in near-primary basalts. The rocks erupted along the western rift margin (Victoria Land Basin) and the western rift shoulder (Transantarctic Mountains). Near-primary basalts show no evidence of crustal contamination, suggesting that their initial NdSrPb isotopes reflect the composition of their mantle sources. The initial isotope ratios of near-primary basalts range from about 87 Sr 86 Sr = 0.70281 to 0.70504 and 143 Nd 144 Nd = 0.51269 to 0.51291 (ϵNd(t) = 1.3–5.5). The 20…