Date of Award:

5-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

John Shervais

Committee

John Shervais

Committee

Anthony Lowry

Committee

Dennis Newell

Abstract

The Snake River Plain (SRP) in southern Idaho is one of the most well-preserved examples of continent-hotspot interaction available today. Geophysical studies have imaged a feature ~10 km thick at the base of the upper crust. This feature, termed the “mid-crustal sill complex” is likely a layered mafic intrusion. The study of layered mafic intrusions is important because it provides a link between deep plutonic processes and shallow volcanic processes. Investigation of the mid crustal sill complex will provide better understanding of the evolutionary process of SRP basalts.

This thesis investigates three xenoliths sampled from the Kimama drill core collected near Kimama ID, and three xenoliths sampled from a basalt quarry at Sid Butte, ID with the hypothesis that the xenoliths originated in a mid-to-lower crustal sill complex. Through geochemical investigation, the hypothesis was supported for the Kimama xenoliths and proved null for the Sid Butte xenoliths.

The investigation of these xenoliths supports the presence of layered mafic mid-to-lower crustal sill complexes beneath the SRP and its importance in the evolution of SRP basalts. Also, shallow subvolcanic magma chambers are added to the current model of crustal architecture of the SRP and their importance in the evolution of SRP basalts is highlighted.

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