30 Applications of Igneous Petrology, Geochemistry, and Geochronology to Understanding Earth and Other Planetary Systems

This session invites contributions that explore igneous systems through traditional and nontraditional methods. Studies that link crustal evolution, planetary formation, resource potential, and comparative planetology across temporal and spatial scales are especially encouraged.

Tuesday, 10 March 2026
1:30 PM - 3:30 PM
RCC, 104

Fluid Source Determination for Miocene Low Sulfidation Epithermal Deposits in the Northern Great Basin with Noble Gas Isotopes

Paper number: 30-7
Program: Technical Sessions
Time: 3:15 PM – 3:30 PM

Authors

Abstract

The origin of gold in low‑sulfidation deposits of the Northern Great Basin (NGB) remains debated, regarding the extent to which early Yellowstone hotspot magmatism contributed metals and volatiles to these systems. Although interpretations vary, multiple isotopic studies have pointed to a deep mantle‑derived component. Isotopic compositions of trace Pb alloyed with gold match signatures of the earliest Yellowstone plume basalts, suggesting a mantle derived component (Kamenov et.al., 2007). Re‑Os isotopic ratios from gold and electrum at the Sleeper and Fire Creek deposits further support a mantle origin distinct from crustal sources and comparable to the Columbia River Basalt Group (Hofstra and Creaser, 2009; Maria‑Benavides, 2018). Ar‑Ar ages of adularia from Florida Mountain (~15.35–15.95 Ma; Monroe, 2021) and Jumbo mine (16.52 ± 0.02 Ma; Davis, 2024) align with regional mineralization and the onset of Yellowstone hotspot activity recorded by the Steens Mountain Basalt at 16.58 ± 0.18 Ma. Noble gas isotopes can provide additional insight in evaluating mantle volatile contributions to these deposits. Melt inclusions in olivine from the Columbia River basalts contain elevated 3He/4He ratios (11.4 Ra), reflecting a deep plume source (Dodson et.al., 1997). Comparable mantle‑like helium signatures in fluid inclusions of ore and gangue minerals from high‑sulfidation deposits in SW Nevada suggest that mantle‑derived volatiles influenced ore‑forming fluids across the region. However, no noble gas-based fluid inclusion studies have directly constrained mantle involvement in NGB low‑sulfidation deposits, largely because suitable analytical techniques for noble gases particularly crushing and gas‑extraction methods remain limited and difficult to apply. Preliminary sequential crushing and argon‑isotope analyses of quartz fluid inclusions from the Trade Dollar mine, (Silver City District, Idaho) yield 40Ar/36Ar ratios of 303–322, indicating dominantly atmospheric signatures, underscoring the need for improved discrimination of trapped components. By integrating helium, neon, and argon isotopic data with existing geochronologic and radiogenic isotope constraints, we aim to determine whether mantle‑derived volatiles associated with early Yellowstone hotspot magmatism can be fingerprinted within NGB low‑sulfidation epithermal deposits, thereby advancing understanding of metal sources and fluid evolution in these economically significant systems. This study is projected to form a basis for improving analytical strategies for resolving noble‑gas signatures in fluid inclusions by refining analytical strategies that improve extraction, purification, and isotopic interpretation

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

doi: 10.1130/abs/2026SE-411788

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