Title

An experimental petrologic study of basalts from selected formations of the deccan traps, India

Document Type

Thesis

Degree

Master of Science (MS)

Department

Geosciences

First Advisor's Name

Guautam Sen

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Andrew Macfarlane

Third Advisor's Name

Rosemary Hickey-Vargas

Date of Defense

7-26-1999

Abstract

Crystallization experiments were performed at one-atmosphere pressure and Quartz- Fayalite-Magnetite (QFM) buffer conditions on tholeiitic basalts from Ambenali and Bushe formations of the Deccan Traps. The sequence and chemistry of the experimentally produced phase assernblages are in general agreement with the observed petrographic and geochemical variation of the natural Ambenali samples. When Bushe and Ambenali basalts are plotted on a cpx-ol-qz diagram, Ambenali plots close to the ol+aug+pl+l pseudo-cotectic whereas Bushe basalts define the pigeonite liquidus field which is somewhat different from that inferred by Grove and Bryan (1983) for midoceanic ridge basalts (MORBs). The difference can be ascribed to the different bulk composition of the starting materials used in the present experiments. Although ol → ol+ aug are near liquidus assemblages in the experiments on Neral at QFM, natural samples from this formation are rnostly aphyric. This may indicate that (1) the within-chamber crystal sorting processes were extremely efficient so that the crystals were totally removed from the melt prior to their eruption, or (2) the lavas erupted at super-liquidus temperatures (i.e., carried superheat).

Identifier

FI15101490

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