Strontium Isotopic Studies of the Ross Island Volcanics, Antarctica

• Main Author: Hajime Kurasawa
• Format: Report
• Language: English
• Published: Geochemical Research Section, Geological Survey of Japan 1975
• Subjects: Ross Island; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=821; http://id.nii.ac.jp/1291/00000821/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=821&item_no=1&attribute_id=18&file_no=1

The isotopic composition of strontium has been determined for samples from DVDP #1 and #2 from Ross Island. It covers the range of olivine basalt, titanaugite-hornblende basalt, hornblende-titanaugite trachy-basalt and hornblende trachyte. The ^<87>Sr/^<86>Sr ratio for the M. I. T. Eimer and Amend reagent SrCO_3 standard determined in our laboratory is 0.7079±0.0001. The basaltic rocks appear to be comagmatic with similar low initial ^<87>Sr/^<86>Sr ratios around 0.7035. This ratio is comparable with ratios of the other alkaline rock series of oceanic islands. The trachytes have initial ratios significantly higher than the basaltic rocks. Compared to the basaltic rocks, the trachytes are enriched in K, Si, Al, Na and Rb and depleted in Ca, Fe, Mg, Ti and Sr. Contamination by submarine sediments and/or by crustal rocks could explain the initial ^<87>Sr/^<86>Sr ratio, but it does not account for the peculiarities in chemistry which characterize the trachytes. The chemical characteristics of the trachytes and the initial ^<87>Sr/^<86>Sr ratio can be explained by deriving the trachytes from older igneous rocks due to partial melting of the latter's alkali feldspar-rich portion. However, this model raises problems regarding the nature of parental material.