NEW PETROLOGY AND GEOCHRONOLOGY OF THE WEST CHINA PEAK COMPLEX OF THE IRONSIDE MOUNTAIN BATHOLITH, KLAMATH MOUNTAINS, CA

The Klamath Mountains Province of NW California (KMP) consists of a series of shallowly east-dipping, thrust-bounded slices composed of Neoproterozoic to Cretaceous marine sedimentary and volcanic rocks and associated mafic to ultramafic crystalline rocks. The thrust sheets successively young from east to west, and are interpreted as accreted oceanic terranes. Middle Jurassic to Early Cretaceous calc-alkaline plutons form distinctive belts within the KMP and are helpful markers to establish the accretionary history of bedrock terranes, as well as the Paleozoic through Tertiary tectonic and structural history of the region. The largest plutonic complex in the Klamaths is the 700 sq-km Ironside Mountain Batholith located in the Western Hayfork terrane and represents crustal derived plutonism that pre-dates the Nevadan Orogeny by 20Ma, based on distinct isotopic signatures (e.g., Barnes et al., 1992). Previous work in the Ironside Mountain batholith included detailed petrography primarily in the central part of the batholith, and one radiometric age (~170Ma) from the central region (Wright and Fahan, 1988).

In this work, we present a detailed geochronological and petrographic study in order to understand the magmatic origin, composition, and timing of emplacement of the West China Peak Complex (WCPC) of the Ironside Mountain batholith. The WCPC is thought to be concentrically zoned, ranging compositionally from hornblende gabbro to monzodiorite, four petrographic samples (Barnes et al., 2006). We present a detailed transect of 8 samples along a 2.5 km transect from edge to center of the pluton complex. In addition we present one new zircon U-Pb radiometric age from the WCPC, in order to constrain crystallization age of the WCPC, and understand its chronology in context of Ironside Mountain Batholith plutonism. Placing the WCPC chronology will contribute to a detailed understanding of pre-Nevadan tectonism and magmatism in the Klamath Mountain Province.

Session No. 79--Booth# 282

T132. Undergraduate Research Posters Showcasing Research by 2YC and 4YCU Geoscience Students (Posters)

Sunday, 22 October 2017: 9:00 AM-5:30 PM

Halls 4EF (Washington State Convention Center)

Geological Society of America Abstracts with Programs. Vol. 49, No. 6
doi: 10.1130/abs/2017AM-299414

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