11-1 Petrographic and Geochemical Analysis of Highland Lakes California in Relation to Surrounding Volcanic Centers

Session: Applications of Igneous Petrology, Geochemistry, and Geochronology to Understanding Earth and Other Planetary Systems (Posters)

Poster Booth No.: 75

Presenting Author:

Joe Constantino

Authors:

Constantino, Joe¹, Fidler, Mary Kate², Dixon, Joe³, McNelly, Sloane⁴

(1) Geology, Clemson, Clemson, South Carolina, USA, (2) Geology, Clemson, Clemson, SC, USA, (3) Geology, Clemson, Clemson, SC, USA, (4) Geology, Clemson, Clemson, SC, USA,

Abstract:

            The area surrounding Highland Lakes in the central Sierra Nevada, California, exposes abundant volcanic and hypabyssal intrusive rocks. It sits south of the Ebbetts Pass Volcanic Center west of the northern tip of the Sierra Crest-Little Walker Volcanic Center. Despite its proximity to these two well documented Neogene Sierran volcanic centers, the rocks at Highland lakes are minimally documented and the lithologic diversity is poorly constrained. This study aimed to identify the lithologies present at Highland Lakes using whole-rock geochemical data from X-ray fluorescence (XRF) analysis and petrographic observations from hand samples and thin sections. These data were then compared to previously published geochemical data from the Ebbetts Pass and Sierra Crest-Little Walker volcanic centers. To then evaluate whether the Highland Lakes rocks are compositionally similar to or distinct from those volcanic systems. Samples were collected from dikes, plugs, and large clasts within volcanic debris flows with an emphasis on obtaining the freshest, least altered material. XRF results indicate that the samples range from approximately 57 to 73 wt% SiO₂, suggesting predominantly intermediate to felsic compositions. Most samples were classified as andesite though a select few dikes fell within the compositional range of dacite to rhyodacite. Variation diagrams of major element oxides vs. SiO₂ reveal linear arrays, suggesting that either mixing of magma sources or varying degrees of crustal assimilation played a role in the chemical evolution of these magmas. Comparison with volcanic and intrusive rocks from both the Ebbetts Pass and Sierra Crest-Little Walker volcanic centers shows compositional similarity between the samples of Highland Lakes and Ebbetts Pass, though some differences between the two datasets are present. Both these sites host primarily andesitic rocks but also host more felsic compositions. Though the Sierra Crest-Little Walker volcanic center also hosts andesites, it lacks felsic rocks and is characterized by an abundance of basalt and basaltic andesites – compositions which are absent from Highland Lakes. From this, we conclude that the Neogene magmatism at Highland Lakes may be related to the volcanism of the Ebbetts Pass Volcanic Center.  

 

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

doi: 10.1130/abs/2026SE-13681

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