14-8 The Mineralogy, Origin, and Economic Potential of Arsenide Five-Element Vein Deposits in the Black Hawk District, Burro Mountains, southwestern New Mexico

Session: Linking Mineral Resources and the Geologic Framework of North America: The USGS Earth Mapping Resources Initiative (Earth MRI) and Related Activities

Presenting Author:

Virginia McLemore

Authors:

McLemore, Virginia T¹, Cook, Robert², Kazemi Motlagh, Zohreh T³, Musser, Don T⁴, Hurtig, Nicole C. ⁵, Newcomer, Jakob T⁶, Chavez, William X. ⁷

(1) New Mexico Bureau of Geology and Mineral Resources, Socorro, New Mexico, USA, (2) Auburn University, Auburn, AL, USA, (3) New Mexico Tech, Socorro, NM, USA, (4) private, Silver City, New Mexico, USA, (5) New Mexico Tech, Socorro, New Mexico, USA, (6) New Mexico tech, Socorro, New Mexico, USA, (7) New Mexico Tech, Socorro, NM, USA,

Abstract:

Arsenide five-element vein deposits are mineralogically and texturally complex, low- to moderate-temperature, hydrothermal, structurally-controlled Ag-Co-Ni-Bi-As bearing carbonate vein systems with local minor to trace elements such as U, Cu, Pb, Zn, Sb, Hg and others. There are many subtypes or variations of this deposit type, since some elements do not occur at all localities. Nonetheless, five-element districts are being re-evaluated worldwide due to the significant quantities of critical minerals that these deposits host, especially Co and Ni, which are important components in batteries. The elements (i.e., Ag, Co, Ni, Bi, As) forming most five-element vein systems have different chemical properties and are not normally found together in other deposit types, which highlights the need for specific hydrothermal processes leading to the formation of this particular element association. Textures of five-element veins are not usual for open-space filling veins and include thin wires, fern-shaped dendrites of native metals (Ag, As, and Bi), herringbone Ag, and botryoidal masses. The dendritic textures common to most five-element veins are thought to have formed very quickly; dendritic pyrite forms in some deposits. Typically, these deposits are small, narrow (<2 m) and discontinuous, making exploration for new ore shoots challenging. Common gangue minerals include carbonates (calcite, siderite, ankerite, and dolomite) with minor barite, quartz, and fluorite.

The Black Hawk district in the Burro Mountains, New Mexico is one of the few localities of five-element veins in the U.S. Although production records are lost, it is estimated that > $1,000,000 was produced from the district from 1883 to 1893, when silver prices dropped due to the silver panic of 1893. Recent mapping, geochemistry, petrography, and drilling in the Black Hawk district have shown epithermal textures such as bladed quartz after calcite (indicative of boiling) and brecciation are common in the higher levels of the system. General paragenesis includes 1) early barren hydrothermal calcite-quartz stage with minor sulfides (pyrite, sphalerite), 2) Ni-Co-As-Ag arsenides and sulfarsenides hosted by carbonates with native Ag, 3) uraninite stage, 4) sulfide stage, 5) late calcite-dolomite-quartz veins, and 6) late dissolution and reprecipitation (supergene). Brecciation occurs throughout the middle to later stages. Mineralized samples contain up to 9970 ppm Ag, 8540 ppm As, 5690 ppm Co, 72,400 ppm Ni, 57 ppm Bi, 165 ppm Sb, and 32,600 ppm U.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10748

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