Mercury ores from the New Idria Mining District, California: geochemical and stable isotope studies

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90349-8· OSTI ID:6938597

Boctor, N Z; Shieh, Y N; Kullerud, G

The mercury ores of the New Idria Mining District are composed of metacinnabar and cinnabar with minor amounts of stibnite and iron disulfides. Metacinnabar from the main ore zone at the New Idria Mine contains Fe as a major impurity, whereas that from the CO veins contains both Se and Fe in solid solution. The impurity content varies within the same specimen and within individual crystals as well and demonstrates lack of chemical equilibrium. Most of the pyrite and marcasite crystallized earlier than cinnabar and in rare cases contain nuclei of framboidal pyrite. Pyrite and marcasite crystallized as discrete phases, and the latter does not show evidence of transition to pyrite. Dolomite shows normal marine carbonate delta/sup 18/O and delta/sup 13/C values. Quartz displays delta/sup 18/O ranging from 18.5 to 21.5 per thousand, distinctly lower than the associated dolomites, suggesting that the two minerals may have formed at two different stages. The range of delta/sup 34/S values for metacinnabar overlaps with that of cinnabar. The delta/sup 34/S for pyrite ranges from 3.1 to 13.0 per thousand; pyrite with framboidal nuclei shows the highest delta/sup 34/S values. The sulfur isotope data also suggest the lack of isotopic equilibrium. The source of C in the ore-forming fluids was marine carbonates leached from the Franciscan sediments. The source of S is uncertain because of lack of knowledge of the isotopic composition of total sulfur. It is likely that mixed sources of sulfur leached from sulfides in the host rocks and magmatic sulfur are involved.

• Research Organization: Carnegie Institution of Washington, Washington, DC (USA)
• OSTI ID: 6938597
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:6; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALIFORNIA
CARBON
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
CINNABAR
DOLOMITE
ELEMENTS
FEDERAL REGION IX
GEOCHEMISTRY
IRON COMPOUNDS
IRON SULFIDES
ISOTOPE RATIO
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MARCASITE
MERCURY
MERCURY COMPOUNDS
MERCURY SULFIDES
METALS
MINERALOGY
MINERALS
NONMETALS
NORTH AMERICA
ORE COMPOSITION
ORES
OXYGEN COMPOUNDS
PYRITE
SULFIDE MINERALS
SULFIDES
SULFUR
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
USA