14 Undergraduate Research (Posters)

Monday, 13 May 2002
1:30 PM - 5:30 PM

STRATIGRAPHY OF THE GOLDSTEIN PEAK PENDANT, WESTERN SIERRA NEVADA BATHOLITH, CA

Paper number: 14-14
Program: THEME SESSIONS
Time: 1:30 PM – 5:30 PM

Authors

Abstract

A two-km-thick, meta-volcano-sedimentary section of the Kings Terrane crops out ~60 km southeast of Fresno on Goldstein Peak in the central Sierra Nevada foothills. The northwest-trending, subvertically foliated pendant is surrounded by ~115 to 110 Mya tonalites, granodiorites and gabbros of the Early Cretaceous batholith. Within the pendant, a 0.5-km-thick, quartzofeldspathic amphibolite is sandwiched between two, relatively undeformed sections of biotite-quartzofeldspathic schist. The typically fine-grained, mafic to intermediate amphibolites are composed of hornblende and plagioclase feldspar with variable quartz modes. The clast shapes and geometry of clast swarms suggest that the amphibolite protoliths were subaqueous metavolcanic breccias, or hyaloclasites, cut by at least one discordant feeder dike. The surrounding biotite quartzofeldpathic schists are interlayered with quartzite and quartz pebble conglomerate, together consistent with the subaqueous deposition of siliciclastic sediments. Preliminary interpretation of stratigraphic top features, such as graded bedding in the conglomerates, suggests that the protolith section is younger to the west.

Metamorphism of the Goldstein Peak pendant occurred within the hornblende hornfels and/or pyroxene hornfels facies, as indicated by the presence of cordierite and the replacement of andalusite by sillimanite. Rare, 0.5-m-thick, garnet-biotite granite and biotite granite dikes intrude the western package of metasediments. Cuspate dike margins and curvilinear apophyses suggest that the dikes intruded prior to complete lithification of the sediments. U-Pb zircon dates of the granite dikes, as well as of a mafic feeder dike within the metavolcanic section, should help constrain the timing of volcanism, sedimentation, and tilting relative to Early Cretaceous plutonism and metamorphism.