PRELIMINARY MINERALOGY OF THE VICTORIO DISTRICT, NEW MEXICO
Nelia W. Dunbar, Virginia T. McLemore
New Mexico Bureau of Geology and Mineral Resources, New Mexico Tech,
Socorro, NM, 87801
The Victorio mining district, located in the Victorio Mountains,
Luna County, hosts three types of deposits. These include carbonate-hosted
lead-zinc replacement, tungsten-beryllium-molybdenum skarn-vein-tactite,
and porphyry-type molybdenum deposits.
Most of the production from the district came from the carbonate-hosted
Pb-Zn replacement deposits that occur as oxidized replacements
and veins within Ordovician and Silurian dolomites and limestones.
The more productive deposits occur along faults or fractures that
strike N30-65°E and dip steeply east. Brecciation, dissolution,
and recrystallization of the dolomites are common in the vicinity
of the mineral deposits. Ore minerals include galena, smithsonite,
cerussite, and anglesite with rare sphalerite, galena, and chalcopyrite
in a gangue of quartz, calcite, and iron oxides. Lead typically
exceeds zinc and copper in abundance. Ore at the Rambler mine
averaged 12.5% Pb and 3.9% Zn. Gold assays range as high as 5,500
ppb Au. Carminite, kolfanite, adamite, vanadinite, and wulfenite
have also been reported (Beyer, 1997).
Drill cores collected in the vicinity of Victorio Mountains yield
mineralogically diverse samples and examples of what appear to
be skarn-associated vein and replacement-texture deposits, as
well igneous granite, were studied using the electron microprobe.
Using this instrument, textural relationships as well as quantitative
and qualitative chemical compositions of metal-bearing and gangue
minerals were investigated. A diverse mineral assemblage was found
the within the gangue minerals of the samples interpreted to represent
replacement-texture and vein skarn samples. Garnet, a wide compositional
range of pyroxenes, actinolite, serpentine, phlogopite, calcite,
quartz, talc, and fluorite were recognized. The assemblages present
in the samples that appear to be replacement-texture deposits
are indistinguishable from those that are veins, and are likely
to represent the same mineralization event. The mineral assemblage,
particularly the presence of serpentine, magnesian pyroxene, phlogopite,
and talc, and the absence of wollastonite and apatite suggests
that the Victorio Mountain skarn system should be classified as
magnesian, rather than calcic (e.g. Kwak, 1994). The presence
of fluorite further suggests that the skarn-related fluids were
F-rich. Mineralogy and textural relationships observed in both
replacement-texture and vein deposits suggest that remnants of
a primary, or prograde, skarn assemblage are present, as well
as a number of secondary, or retrograde phases. In one sample,
large (~1 cm) complexly zoned garnets, interpreted to be part
of a prograde skarn assemblage, are present in an open-space filling
vein. In a nearby part of the same sample, smaller garnets co-exist
with phlogopite, serpentine and talc, interpreted to be part of
a retrograde facies. Other samples record similar ranges of mineral
phases. In one case, delicate, fan-shaped masses of phlogopite
appear to have crystallized in open-space cavities, possibly related
to intragranular cavities formed during prograde skarn evolution.
Around and intergrown with the phlogopite, serpentine, a mineral
that would form at a late stage of prograde evolution than phlogopite,
is found. Hence, the replacement-texture and vein samples from
Victorio Mountains appear to record an extended history of skarn
formation, spanning a range of fluid concentrations and formation
temperatures.
A range of metal-bearing minerals are observed in the skarn-related
samples. These include euhedrel rods or masses of molybdenite,
masses of molybdenum-bearing scheelite, and an iron-sulphide.
The metal-bearing minerals more abundant in the vein samples
as compared to the replacement-texture samples. In some cases,
bands of concentrated metal-bearing phases are present along vein
margins, suggesting an interval of favorable conditions for ore
formation during the growth of the veins.
One sample of granite from the Victorio Mountain area was analyzed,
and appears to contain a normal mineral assemblage of quartz,
potassic feldspar, biotite, albite, and magnetite. However, in
addition to these phases, the granite contains abundant, pinkish,
manganese-rich garnets that include a high abundance of heavy
mineral inclusions as well as fluorite. These inclusions include
hafnium-rich zircon, and thorium-, uranium- and yttrium-rich allanite.
These phases appear to have crystallized from the granitic magma,
and may suggest that the Victorio Mountain granite may be been
anomalously enriched in heavy elements, as well as fluorine.
Molybdenite and scheelite have also been observed in the Victorio
granite.
The carbonate-hosted Pb-Zn replacement deposits in the Victorio
district are epithermal deposits as evidenced by ore textures,
ore controls, and correlations with similar carbonate-hosted replacement
deposits in southwestern New Mexico, which are also believed to
be epithermal. The skarn-vein-tactite and porphyry-type Mo deposits
are magmatic-hydrothermal deposits that appear to be related to
the Victorio Mountains granite as evidenced by ore textures and
similar mineralogy, metal associations, and alteration assemblages.
However, the relationship between the carbonate-hosted replacement
and skarn-porphyry-Mo deposits remains unknown. All three deposit
types may be genetically related, or more than one mineralization
event occurred forming the deposits at different times.
Selected minerals found in the Victorio mining district, Luna
County (from Holser, 1953; Griswold, 1961; DeMark, 1992; Northrop
and LaBruzza, 1996; Beyer, 1997; Gulf Minerals company reports;
this study). Minerals in bold are newly reported in this study.
Type of deposit in parenthesis: 1-carbonate-hosted Pb-Zn replacement
deposits, 2-Be-Mo-W skarn-vein-tactite deposits, and 3-porphyry
Mo deposits.
| MINERAL | CHEMICAL FORMULA | MINERAL | CHEMICAL FORMULA |
| Pyrite (1, 2, 3) | FeS2 | Psilomelane (1, 2) | Mn oxide |
| Pyrrhotite (1, 2, 3) | FexS | Molybdenite (2, 3) | MoS2 |
| Marcasite (1, 2) | FeS2 | Powellite (2) | CaMoO4 |
| Sphalerite (1, 2) | (Zn, Fe)S | Scheelite (2) | CaWO4 |
| Galena (1, 2) | PbS | Magnetite (2, 3) | Fe3O4 |
| Calcite (1, 2, 3) | CaCO3 | Beryl (2, 3) | Be3Al2Si6O18 |
| Quartz (1, 2, 3) | SiO2 | Bismutite (2) | Bi2(CO3)O2 |
| Chalcopyrite (1, 2) | CuFeS2 | Bismuthinite (2, 3) | Bi2S3 |
| Wolframite (1, 2) | (Fe, Mn)WO4 | Galenobismutite (2, 3) | PbS4Bi2 |
| Bornite (1) | Cu5FeS4 | Helvite (2) | Mn4Be3(SiO4)3S |
| Wurtzite (1) | (Zn,Fe)S | Danalite (2) | Fe4Be3(SiO4)3S |
| Cerussite (1) | PbCO3 | Hübnerite (2) | MnWO4 |
| Anglesite (1) | PbSO4 | Beyerite (2) | (Ca, Pb)Bi2(CO3)2O2 |
| Gold (1) | Au | Chondrodite (2) | (Mg, Fe)5(SiO4)2(F, OH)2 |
| Argentite (1) | Ag2S | Humite (2) | (Mg, Fe)7(SiO4)3(F, OH)2 |
| Chlorargyrite (1) | AgCl | Clinohumite | (Mg, Fe)9(SiO4)4(F, OH)2 |
| Carminite (1) | PbFe2(AsO4)2(OH)2 | Scapolite (2) | (Na,Ca)4Al3-6Si6-9O24 (Cl,CO3,SO4) |
| Beudantite (1) | PbFe3(As,O4)(SO4)(OH)6 | Diopside (2) | CaMgSi2O6 |
| Bromargyrite (1) | AgBr | Fluorite (2, 3) | CaF2 |
| Kolfanite (1) | Ca2Fe3O2(AsO4)3?2H2O | Serpentine (2) | (Mg, Fe, Ni)3Si2O5(OH) |
| Adamite (1) | Tremolite (2) | Ca2(Mg,Fe)5Si8O22(OH)2 | |
| Vanadinite (1, 2) | Pb5(VO4)3Cl | Augite (2) | (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6 |
| Wulfenite (1, 2) | PbMoO4 | Talc (2) | Mg3Si4O10(OH)2 |
| Mimetite (1) | Pb5(AsO4)3Cl | Phlogopite (2) | KMg3Si3AlO10(F, OH)2 |
| Hemimorphite (1) | Zn4Si2O7(OH)2?H2O | Stolzite (2) | PbWO4 |
| Descloizite (1) | PbZn(VO4)(OH) | Rhodochrosite (3) | MnCO3 |
| Willemite (1) | Zn2SiO4 | Zircon (3) | ZrSiO4 |
| Smithsonite (1) | ZnCO3 | Allanite (3) | (Y, Ce, Ca)2(Al, Fe)3(SiO4)3(OH) |
| Aurichalcite (1) | (Zn, Cu)5(CO3)2(OH)6 | Tetrahedrite (2?) | (Cu,Fe)12Sb4S13 |
| Pyromorphite (1) | Pb5(PO4)3Cl | Cassiterite (2?) | SnO2 |
| Pyroxene (2) | (Ca,Fe,Li,Mg,Na)(Al,Cr,Fe,Mg,Mn)(Al,Si)2O6 | Garnet (2, 3) | (Mn, Mg, Fe, Ca)3(Al, Cr, Fe, Mn, Ti, V, Zr)2Si3O12 |
Beyer, J., 1997, A second New Mexico carminite locality, Victorio
Mountains, Luna County, New Mexico (abs.): New Mexico Geology,
v. 19, p. 26-27.
DeMark, 1992, New Mexico mineral locality index: Rocks and Minerals,
v. 67, p. 314-327, 330-331
Griswold, G. B., 1961, Mineral deposits of Luna County, New Mexico:
New Mexico Bureau of Geology and Mineral Resources, Bulletin 72,
157 p.
Holser, W. T., 1953, Beryllium minerals in the Victorio Mountains,
Luna County, New Mexico: American Mineralogist, v. 38, p. 599-611.
Kwak, T. A. P., 1994, Hydrothermal alteration in carbonate-replacement
deposits: ore skarns and distal equivalents; in Lentz, D. R.,
ed., Alteration and alteration processes associated with ore-forming
systems: Geological Association of Canada, Short Course Notes
v. 11, p. 381-402.
Northrop, S. A. and LaBruzza, F. A., 1996, Minerals of New Mexico:
University of New Mexico Press, Albuquerque, New Mexico, 356 pp.