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Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California

The Compass: Earth Science Journal of Sigma Gamma Epsilon

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Abstract

The northernmost occurrences of extensive, glaciated exposures of the Sierra Nevada batholith occur in the Donner Lake-Cisco Grove area of the northern Sierra Nevada. The plutonic rocks in this area, which are termed here the Castle Valley plutonic assemblage, crop out over an area of 225 km2 and for the most part are shown as a single undifferentiated mass on previously published geological maps. In the present work, the plutonic assemblage is divided into eight separate intrusive units or lithodemes, two of which each consist of two separate plutons. Compositions are dominantly granodiorite and tonalite, but diorite and granite form small plutons in places. Spectacular examples of comb layering and orbicular texture occur in the diorites. U-Pb zircon ages have been obtained for all but one of the main units and range from ~120 to 114 Ma, indicating that the entire assemblage was emplaced in a narrow time frame in the Early Cretaceous. This is consistent with abundant field evidence that many of the individual phases were intruded penecontemporaneously. The timing of emplacement correlates with onset of major Cretaceous plutonism in the main part of the Sierra Nevada batholith farther south. The emplacement ages also are similar to isotopic ages for gold-quartz mineralization in the Sierran foothills west of the study area, suggesting a direct genetic relationship between the voluminous Early Cretaceous plutonism and hydrothermal gold mineralization.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California
Series title:
The Compass: Earth Science Journal of Sigma Gamma Epsilon
Volume
74
Issue:
3
Year Published:
1998
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
The Compass: Earth Science Journal of Sigma Gamma Epsilon
First page:
69
Last page:
76