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The Origin of Basalt and Cause of Melting Beneath East Antarctica as Revealed by the Southernmost Volcanoes on Earth

Reindel, Jenna L
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1542379105898001

Abstract Details

2018, Master of Science (MS), Bowling Green State University, Geology.
The southernmost volcanoes on Earth, Mt. Early and Sheridan Bluff, are two basaltic monogenetic volcanoes located 87°S at the head of the Scott Glacier, in the southern Transantarctic Mountains. The Early Miocene volcanoes lie ~1000 km from any other volcano and ~200 km from the shoulder of the West Antarctic Rift System (WARS), which is the foci of most Cenozoic alkaline volcanism in Antarctica. WARS is part of a larger diffuse alkaline magmatic province (DAMP) including volcanism in New Zealand and Australia. Dating by the 40Ar/39Ar method indicates that Mt. Early is older than previously determined and closer in age to Sheridan Bluff (~19 Ma). Basalts range in composition from alkaline (~6 wt. % Ne-normative) to subalkaline tholeiite (~6 wt. % Hy-normative). Tholeiite have higher ratios of Zr/Nb (9) than alkaline basalts (4) and have lower ratios of La/Yb (5), La/Lu (<50), and Gd/Yb (2) than alkaline basalts (20, 100-150, and ~3 respectively). Fractional crystallization, assimilation-fractional crystallization (AFC), and partial melting are tested as mechanisms to explain compositional variations. Crystal fractionation alone cannot explain the difference in composition. Modelling AFC on plots of Rb, Ba, and La/Nd versus TiO2 show that unrealistic bulk partition coefficients are required to explain the array of compositions using contaminates from the upper crust. I conclude that the coexistence of tholeiite and alkaline basalt is likely due to different degrees of partial melting. The basalts mirror partial melting trends for a common garnet lherzolite source on plots of La/Lu versus Nb/Yb. These models also suggest that tholeiite was produced by higher degrees of melting at shallower depths. Mt. Early and Sheridan Bluff basalt, especially tholeiite, are distinctive from DAMP basalt, having lower Ce/Pb (≤ 20), Gd/Yb (≤ 3) and lack K and Pb anomalies on normalized multi-element plots. Negative K anomalies are a prominent feature of DAMP basalt and are used to support amphibole-rich lithospheric sources. It is likely that the basalts from Mt. Early and Sheridan Bluff were derived from asthenosphere with little or no input from mantle lithosphere. Causes for volcanism in DAMP include passive extension, metasomatism and plumes. A recent viable mechanism for triggering volcanism in this region is lithospheric delamination and has been proposed based on geophysical evidence.
Kurt Panter, Dr. (Advisor)
Peter Gorsevski, Dr. (Committee Member)
Daniel Kelley, Dr. (Committee Member)
106 p.
Geochemistry; Geology; Petrology
geochemistry, volcanology, Antarctica, East Antarctica, basalt, alkaline basalt, subalkaline basalt, tholeiite, tholeiitic basalt, fractional crystallization, contamination, partial melting, lithospheric delamination

Recommended Citations

Citations

  • Reindel, J. L. (2018). The Origin of Basalt and Cause of Melting Beneath East Antarctica as Revealed by the Southernmost Volcanoes on Earth [Master's thesis, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1542379105898001

    APA Style (7th edition)

  • Reindel, Jenna. The Origin of Basalt and Cause of Melting Beneath East Antarctica as Revealed by the Southernmost Volcanoes on Earth. 2018. Bowling Green State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1542379105898001.

    MLA Style (8th edition)

  • Reindel, Jenna. "The Origin of Basalt and Cause of Melting Beneath East Antarctica as Revealed by the Southernmost Volcanoes on Earth." Master's thesis, Bowling Green State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1542379105898001

    Chicago Manual of Style (17th edition)

bgsu1542379105898001
288
© 2018, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.