Publication Date

Summer 2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Advisor

Robert Miller

Keywords

california, construction, crystal range, emplacement, pluton

Subject Areas

Geology

Abstract

Three Cretaceous plutons are investigated to determine their construction and emplacement histories, focusing on magmatic foliation patterns and contact relationships with each other and with the Jurassic metasedimentary host rocks of the Sailor Canyon Formation. The earliest Cretaceous Pyramid Peak granite is a leucocratic pluton with extensive co-magmatic diorite and granite-diorite hybrid rock. It contains a single NNW -striking magmatic foliation that probably reflects the regional stress field at the time of crystallization. The granite was constructed by multiple magmatic increments, though internal contacts are scarce in homogeneous parts of the pluton. Emplacement was accommodated by roof uplift, a modest degree of floor sinking, and the brittle transfer of host via stoping. The mid-Cretaceous Wrights Lake granodiorite is largely homogeneous, except near the margin, and has abundant microgranitoid enclaves and schlieren. This granodiorite has two overprinting magmatic foliations: a contact-parallel foliation that is interpreted to reflect filter pressing and/or flow of magma against the margin, and an east-west discordant foliation that reflects regional strain. Xenoliths of Sailor Canyon Formation and Pyramid Peak granite are common near the margin, demonstrating stoping. The markedly homogenous, weakly foliated Tyler Lake granodiorite has poorly exposed contacts and few conclusions could be made about its history, but brittle transfer of host probably played a role. Plutons in the region document a transition in the regional strain field between the early and middle Cretaceous.

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