Publication Date

Fall 2023

Degree Type


Degree Name

Master of Science (MS)




Robert Miller; Jonathan S. Miller; Ellen P. Metzger


Of the four voluminous, normally zoned Late Cretaceous intrusive suites of the Sierra Nevada batholith, the >1,000 km², ~96-88 Ma Sonora Pass intrusive suite is the oldest, northernmost, and least studied. It contains the marginal, equigranular Kinney Lakes hornblende-biotite granodiorite and the inner, porphyritic Topaz Lake biotite granodiorite. From this research, the Lake Alpine granodiorite is now considered the outermost part of the Sonora Pass intrusive suite. The suite intruded Early Cretaceous plutons and metasedimentary rocks. The Kinney Lakes and Lake Alpine granodiorites were constructed by multiple phases, as were the plutonic host rocks. The granodiorites are marked by schlieren and mafic enclave swarms, particularly concentrated near margins. Accommodation of the Sonora Pass intrusive suite and the older plutons was facilitated by multiple material transfer processes, including stoping and ductile flow. Magmatic foliation in the study area is steep and lineations are down-dip. Foliations are either subparallel to contacts or parallel to the regional NW-strike. They record both internal magmatic processes and regional NE-SW shortening. Solid-state structures include well-developed foliations and lineations, and local ductile shear zones; some formed by the regional strain and others during emplacement.

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