37 CRITICAL MINERAL DEPOSITS AND ORE SYSTEMS OF THE NORTHEAST

This session will showcase new findings pertaining to critical mineral resources and hydrothermal-magmatic ore systems across the northeast. We welcome submissions involving fieldwork, geochemical, petrologic, geochronologic, and other approaches from micro- to macroscopic scales.

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Room 25

Copper Isotopic Evidence From Native Copper Occurrences in the Newark Basin

Paper number: 37-7
Program: Technical Sessions
Time: 10:00 AM – 10:20 AM

Authors

  • Michael DiMaio Presenting Author
    Dept. Earth and Planetary Sciences, Rutgers University, Piscataway, NJ
  • Linda Godfrey
    Dept. Earth and Planetary Sciences, Rutgers University, Piscataway, NJ
  • Ryan Mathur
    Juniata College Dept Geology, Huntingdon, PA
  • John Puffer
    Department of Earth and Environmental Sciences, Rutgers University, Newark, NJ

Abstract

Here we present new copper isotopic data bearing on the origin of some historic Triassic red-bed hosted copper mines in the Newark Basin and, by extrapolation, similar deposits in the Hartford, Gettysburg and Culpepper basins.  The principal ore minerals are chalcocite and native copper.  Most published interpretations of their origins propose significant sedimentary controls with precipitation of copper from hypogene solutions forced by the reducing conditions found at organic enriched levels and at the base of very thick flood basalt flows and hornfels adjacent to diabase feeder dikes and sills. We acknowledge minor association with organic material, particularly fossil plants, for some deposits in the Newark Basin. However, the new copper isotopic data from native copper samples indicates an igneous source for the copper with minimal δ65Cu fractionation for multiple mineral deposits near or at the base of basalt flows. Preliminary data show an avg δ65Cu = 0.05‰ (n=4) from the Chimney Rock deposit in the Newark basin. Copper isotope data closely overlaps with those of Keweenawan copper mineralization that is also associated with thick flood basalt flows. The new data supports a USGS “Basaltic Cu” or “Hornfel” model; not a sediment hosted model and involves deuteric circulation of hot copper bearing fluids through and at the base of flows and shallow intrusions and precipitation of copper upon cooling near the margins. The origin of these copper deposits may hint to the fertility of correlated mafic intrusions in Large Igneous Provinces in the Central Atlantic Magmatic Province and subsequently exploration of intrusion related Cu-Ni magmatic deposits.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411371

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