36-6 New U-Pb Age Data for Lights Creek Stock and Engels Gabbro, Plumas County, Northern California

Session: Cordilleran Mineral Systems: Interdisciplinary Perspectives on Critical Metal Ore Deposits (Posters)

Poster Booth No.: 24

Presenting Author:

Hannah Aird

Authors:

Aird, Hannah M¹, Pierce, Margaret C², Martinez-Contreras, Mauricio Israel³

(1) Department of Earth and Environmental Sciences, California State University, Chico, Chico, California, USA, (2) Department of Earth and Environmental Sciences, California State University, Chico, Chico, California, USA, (3) Department of Earth and Environmental Sciences, California State University, Chico, Chico, California, USA,

Abstract:

This study presents new U-Pb age data acquired across the Lights Creek Stock, a granitoid pluton in Plumas County, California. The Lights Creek stock and associated Engels hornblende gabbro host three iron oxide-copper-gold (IOCG) deposits, which were historically mined as part of the Plumas County Copper Belt. The stock was mapped in the 1970s as having igneous zoning, but reevaluation suggests that the mineralogic variation is due to varying degrees of hydrothermal alteration. New dates show that the western side of the stock (~188Ma) is older than the eastern portion (~185Ma), and that dioritic compositions were intruded concurrently with more silicic pulses of magma at ~186Ma. New dates of ~115Ma have also been acquired for the Engels gabbro, which hosts the Engels IOCG deposit. This shows that this small area of northern California experienced magmatism over a period of at least 70Ma, and suggests that the fluids causing the IOCG mineralization could have been produced by magmatic activity significantly younger than the host Lights Creek Stock.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.