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Geology of the Jicarilla mining district, Lincoln County, New Mexico — Summary

— Virginia T. McLemore, New Mexico Bureau of Geology and Mineral Resources, Socorro, NM 87801

Introduction

NAm
Figure 1. Extent of the North American Cordilleran alkaline-igneous belt.

The Jicarilla mining district is one of several mining districts associated with alkaline igneous rocks in the Lincoln County porphyry belt in central New Mexico. The Lincoln County porphyry belt (LCPB) is part of the North American Cordilleran alkaline-igneous belt (Fig. 1) and, in New Mexico, the North American Cordilleran alkaline-igneous belt extends from the Sangre de Cristo Mountains near Raton, southward to the Cornudas Mountains, east of El Paso, Texas (McLemore, 2018a). Significant mineral production, especially gold, has come from deposits spatially associated with Tertiary alkaline-igneous rocks in the New Mexico alkaline-igneous belt (McLemore, 2001, 2015). These mineral deposits in New Mexico have been referred to as Great Plains Margin (GPM) deposits by North and McLemore (1986, 1988) and McLemore (1996, 2001, 2015). Alternative classifications by other workers include Au-Ag-Te veins (Cox and Bagby, 1986; Bliss et al., 1992; Kelley, 1995; Kelley et al., 1995, 1998), alkalic-gold or alkaline-igneous related gold deposits (Fulp and Woodward, 1991a; Thompson, 1991; Bonham, 1988; Mutschler et al., 1985, 1991; Richards, 1995), porphyry gold deposits, and Rocky Mountain gold province.

The Jicarilla district (also known as the Ancho district) is in the Jicarilla Mountains in Lincoln County (Fig. 2). The district is accessed via U.S. Highway 54, approximately 20 miles northeast of Carrizozo on Jicarilla Road, a gravel county road. The area is rural, part of the Lincoln National Forest, and a few ranches are located within several miles of the district. The Jicarilla Mountains consist of rough terrain with steep slopes, narrow canyons and mountain peaks. Elevations in the district range from 6800 to 7800 ft.

NMGPM
Figure 2. Mining districts related to the North American Cordilleran alkaline-igneous belt (GPM or Great Plains Margin deposits), Rio Grande rift, calderas, and other Eocene-Miocene mining districts in New Mexico (McLemore, 2015, 2018).

The geology and mineralization of the Jicarilla mining district has been described in several reports (Ryberg, 1968; Johnson, 1972; Seagerstrom and Ryberg, 1974; North and McLemore, 1986; McLemore et al., 1992). The area is currently being mapped and sampled by the author and results reported here are preliminary. The purpose of this project is to (1) update McLemore et al. (1992), (2) describe the magmatic activity and gold resources within the Jicarilla district, (3) present some hypotheses on the origins of these mineral deposits, (4) present new age dates of the igneous rocks, (5) understand the relationship of the placer gold deposits to the vein deposits, and (6) understand the relationship of the Jicarilla district with magmatic activity and mineralization in the North American Cordilleran alkaline-igneous belt.

Geology

The predominant intrusive rock in the district is a porphyritic dacite and granodiorite to monzonite, intruded by a variety of dikes, sills, and laccoliths. Mafic xenoliths are common locally in the intrusive coarse-grained granodiorite. New, unpublished ages of igneous rocks from the Jicarilla Mountains in the northern Lincoln County porphyry belt range from 39.45±0.02 and 40.72±0.04 Ma, which is one of the oldest GPM districts (40Ar/39Ar, V.T. McLemore, report in progress).

The igneous rocks in the Jicarilla Mountains are subalkaline to alkaline, metaluminous to peraluminous. The samples plot as I or S type granites and plot within the VAG and active continental margin. The samples have linear, slightly enriched LREE chondrite-normalized patterns, with no europium anomaly. Initial strontium isotopes and neodymium isotopes are similar to other GPM districts (0.70565-0.70578, Allen and Foord, 1991).

Mineral deposits

Three types of deposits have been identified in the Jicarilla Mountains, as defined by McLemore (1996, 2015, 2018a) and McLemore and Lueth (2017):

  • GPM polymetallic, epithermal to mesothermal veins
  • GPM iron skarns and replacement deposits
  • Placer gold deposits.

GPM polymetallic, epithermal to mesothermal veins are mostly fissure pyrite-gold veins, narrow (less than 2 m wide), north- to northeast-trending, with variable gold and low amounts of copper, lead, and zinc sulfides. Quartz and calcite are rare in most veins, although silicification and clay alteration are common.

The GPM iron skarns and replacement deposits are found throughout the Jicarilla Mountains replacing Yeso and San Andres limestone and siltstone and are spatially associated with the igneous rocks. These deposits typically consist of magnetite, hematite, limonite, and martite in a gangue of calcite, quartz, fluorite, tremolite, actinolite, pyrite, phlogopite, and locally malachite, azurite, and chalcopyrite. The iron ore grade is typically less than 50%.

The Jicarilla district contains large resources of residual, alluvial, and stream placer gold deposits. These placers formed by weathering of the lode gold deposits and the dacite and granodiorite to monzonite porphyry, which underlies much of the area. The dacite and granodiorite to monzonite porphyry apparently contains fine-grained gold disseminated within the matrix. In the placers, gold appears to be controlled by reddish soil streaks within the alluvium above white clay lenses. The alluvium is very poorly sorted and consists of angular to rounded boulders, cobbles, and grains of the dacite and granodiorite to monzonite as well as pieces of magnetite-hematite derived from nearby iron-replacement deposits. Many active streams in the Jicarilla Mountains also contain small placer gold deposits. Recovery of the placer gold is difficult because of the fine grain size of the gold, abundance of clay, and lack of water.

Mineral-resource potential

The Jicarilla district has future mineral-resource potential for gold in veins, as described by McLemore et al. (1991) and McLemore (2018b). It is concluded that the mineral-resource potential is very high with a high level of certainty for placer gold and high with a moderate level of certainty for lode gold in the Jicarilla district. The mineral-resource potential is moderate with a high level of certainty for iron and low with a low level of certainty for molybdenum and tellurium in the Jicarilla district (McLemore, 2018b).

References

  1. Allen, M.S. and Foord, E.E., 1991, Geological, geochemical and isotopic characteristics of the Lincoln County porphyry belt, New Mexico:implications for regional tectonics and mineral deposits: New Mexico Geological Society, Guidebook 42, p. 97-113.
  2. Bliss, J.D., Sutphin, D.M., Moiser, D.L., and Allen, M.S., 1992, Au-Ag-Te veins associated with alkalic rocks: U.S. Geological Survey, Open-file report 92-208, 15 p.
  3. Cox, D.P. and Bagby, W.C., 1986, Descriptive models of Au-Ag-Te veins; in Cox, D. P., and Singer, D. A., eds., 1986, Mineral deposit models: U.S. Geological Survey, Bulletin 1693, p. 124.
  4. Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey, Bulletin 1693, 379 p.
  5. Johnson, M.G., 1972, Placer gold deposits of New Mexico: U.S. Geological Survey, Bulletin 1348, 46 p.
  6. Kelley, K.D., 1995, Au-Ag-Te vein deposits; in du Bray, E.A., ed., Preliminary compilation of descriptive geoenvironmental mineral deposit models: U.S. Geological Survey, Open-file report 95-831, p. 130-136.
  7. McLemore, V. T., 1991, Base-and precious-metal deposits in Lincoln and Otero Counties, New Mexico: New Mexico Geological Society, Socorro, Guidebook 42, p. 305-309.
  8. McLemore, V.T., 1996, Great Plains margin (alkaline-related) gold deposits in New Mexico; in Coyner, A.R. and Fahey, P.L., eds, Geology and ore deposits of the American Cordillera, Symposium Proceedings: Geological Society of Nevada, Reno, p. 935-950.
  9. McLemore, V.T., 2001, Silver and gold resources in New Mexico: New Mexico Bureau of Mines and Mineral Resources, Resource Map 21, 60 p.
  10. McLemore, V.T., 2015, Great Plains Margin (alkaline-related) gold deposits in New Mexico: twenty years later: Geological Society of Nevada, New concepts and discoveries, 2015 Symposium volume, p. 1305-1327.
  11. McLemore, V.T., 2017, Mining districts and prospect areas of New Mexico: New Mexico Bureau of Geology and Mineral Resources, Resource Map 24, 65 p., scale 1:1,000,000.
  12. McLemore, V.T., 2018a, Rare Earth Elements (REE) Deposits Associated with Great Plain Margin Deposits (Alkaline-Related), Southwestern United States and Eastern Mexico: Resources, 7(1), 8; 44 p., doi:10.3390/resources7010008; http://www.mdpi.com/2079-9276/7/1/8 link http://www.mdpi.com/2079-9276/7/1/8
  13. McLemore, V.T., 2018b, Mineral-resource Potential of proposed U.S. Bureau of Land Management exchange of lands with New Mexico State Land Office: New Mexico Bureau of Geology and Mineral Resources, Open-file Report OF-598, 152 p., https://geoinfo.nmt.edu/publications/openfile/details.cfml?Volume=598
  14. McLemore, V.T. and Lueth, V., 2017, Metallic Mineral Deposits; in McLemore, V.T., Timmons, S., and Wilks, M., eds., Energy and Mineral deposits in New Mexico: New Mexico Bureau of Geology and Mineral Resources Memoir 50 and New Mexico Geological Society Special Publication 13, 79 p.
  15. McLemore, V.T., Ouimette, M., and Eveleth, R. W., 1991, Preliminary observations on the mining history, geology and mineralization of the Jicarilla mining district, Lincoln County, New Mexico; in Barker, J.M., Kues, B.S, Austin, G.S., and Lucas, S.G., eds., Geology of the Sierra Blanca, Sacramento, and Capitan Ranges, New Mexico: New Mexico Geological Society, Guidebook 42, p. 311-316.
  16. Mutschler, F. E., Griffin, M. E., Stevens, D. S. and Shannon, S. S., Jr., 1985, Precious metal deposits related to alkaline rocks in the North American Cordillera-an interpretive review: Transactions Geological Society of South America, v. 88, p. 355-377.
  17. Mutschler, F. E., Mooney, T. C., and Johnson, D. C., 1991, Precious metal deposits related to alkaline igneous rocks-a space-time trip through the Cordillera: Mining Engineering, v. 43, p. 304-309.
  18. North, R.M., and McLemore, V.T., 1986, Silver and gold occurrences in New Mexico: New Mexico Bureau of Mines and Mineral Resources, Resource Map 15, 32 pp., scale 1:1,000,000.
  19. North, R.M., and McLemore, V.T., 1988, A classification of the precious metal deposits of New Mexico; in Bulk mineable precious metal deposits of the western United States Symposium Volume: Geological Society of Nevada, Reno, Symposium held April 6-8, 1987, pp. 625-660.
  20. Richards, J.P., 1995, Alkalic-type epithermal gold deposits—a review; in Thompson, J.F.H. (ed.), Magmas, fluids, and ore deposits: Mineralogical Association of Canada, Short Course Series, v. 23, p. 367-400.
  21. Ryberg, G.C., 1968, The geology of the Jicarilla Mountains, Lincoln County, New Mexico: M.S. thesis, University of New Mexico, Albuquerque, 144 p.
  22. Rytuba, J.J. and Cox, D.P., 1991, Porphyry gold: A supplement to U.S. Geological Survey Bulletin 1693: U.S. Geological Survey, Open-file Report 91-116, 7 p.
  23. Segerstrom, K., and Ryberg, G.C., 1974, Geology and placer-gold deposits of the Jicarilla Mountains, Lincoln County, New Mexico:U.S. Geological Survey, Bulletin 1308, 25 p.
  24. Thompson, T.B, 1991, Genesis of gold associated with alkaline igneous rocks (abstr.):Geological Society of America, Abstracts with Programs, v. 23, p. 99-100.
  25. Woolley, A.R., 1987, Alkaline rocks and carbonatites of the world, Part 1: North and South America: University of Texas Press, Austin.

Updated June 24, 2019