Mine detail: Big Horn Mine

Previously called ''

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Location

Lat / long:

34.35639, -117.74361

Resource(M)

Primary:	Gold
Secondary:	Silver
Tertiary:	Copper, Lead, Zinc, Arsenic
Ore:	Gold, Pyrite, Chalcopyrite, Galena, Arsenopyrite
Gangue:	Schist, Gneiss, Andesite
Orebody form:	Tabular; gold mineralization occurs within a zone of brecciation and cataclasite formation along the gently northwest-dipping Vincent Thrust fault zone. Disseminated gold occurs in the Pelona Schist near the Vincent Thrust.
Discovery year:	1891

Production

Operation type:	Underground
Deposit type:	Hydrothermal vein and replacement
Production size:	Medium
Development status:	Past Producer

Geology

Host rock:	San Gabriel Gneiss, Pelona Schist
Host type:	Amphibolite,Cataclasite,Schist,Gneiss
Associated type:	Gneiss,Schist,Quartz Monzonite,Volcanic Rock (Aphanitic)
Structure:	Vincent Thrust fault; San Andreas Fault; Punchbowl Fault, San Gabriel Fault; northwest striking normal faults in Big Horn Mine area; regional arching of the San Gabriel Mountains basement complex and Vincent Thrust along a northwest-trending axis in the region around the Big Horn Mine.
Tectonic:	Back-arc thrust belt The Big Horn Mine is located near the crest of the San Gabriel Mountains, an east-west trending range along the southwest side of the San Andreas Fault in the central part of the Transverse Range Province of southern California. Uplift of the range began a few million years ago and is still going on as a product of convergence between the North American and Pacific Plates along the bend in the San Andreas Fault. It was accomplished by reverse faulting along the southern range margin and broad arching across the interior and northern margin, with uplift extending northeastward across the San Andreas Fault. The relatively simple pattern and style of uplift are superimposed upon the complex structure of rocks exposed within the range (Ehlig, 1981, pg.254)
Alteration processes:	Silicification Pyritization Carbonatization

References

DEP	10310697
Reference	{Deposit:: Portions of various unpublished reports and reports from various Internet websites, contained in CGS Minefile Folder No. 330-3745.}{Deposit:: Clark, W. B., 1988, Mount Baldy District in Gold Districts of California, Sesquicentennial Edition, California Gold Discovery to Statehood: CGS (formerly CDMG) Bulletin 193, Page 174.}{Deposit:: Conrad, R. L., and Davis, T. E., 1977, Rb/Sr Geochronology of cataclastic rocks of the Vincent thrust, San Gabriel Mountains, southern California [abstract]: Geol. Soc. America Abstracts with Programs, v. 9, no. 4, p. 403-404.}{Deposit:: Ehlers, E. G. and Blatt H., 1980, Petrology: Igneous, Sedimentary, and Metamorphic: W. H. Freeman and Co., San Francisco, 732 p.}{Deposit:: Ehlig, P. L., 1981, Origin and tectonic history of the basement terrane of the San Gabriel Mountains, central Transverse Ranges; in Ernst, W. G., Editor, 1981, The tectonic development of California, Rubey Volume I: Prentice-Hall, Inc., Englewood Cliffs, New Jersey 07632, Pages 253-283.}{Deposit:: Hamann, W. E., 1985, Geology and geochemistry of the Big Horn gold mine, San Gabriel Mountains, southern California: M.S. Thesis, University of California Los Angeles (UCLA).}{Deposit:: Inspiration Mines, Inc., 1985, Big Horn Mine Feasibility Report.}{Deposit:: Jones, A. G., 1983a, Report on the Gig Horn Mine for Harbour Management Ltd.}{Deposit:: Miller, C. C., Jr., 1938, Report on Big Horn Mine, Los Angeles County, California, owned by Fenner Mines, Inc., 15 pages (The date of the report is written in pencil on the front of the report; the report is contained in CGS Minefile Folder No. 330-3745.)}{Deposit:: Miller, F. K., and Morton, D. M., 1977, Comparison of granitic intrusions in the Pelona and Orocopia schists, southern California: U.S. Geol. Survey Jour. Res., v. 5, p. 643-649.}{Deposit:: Ristorcelli, Steve, January 15, 1988, Summary report and recommendations on the big Horn property, Los Angeles County, California: report prepared for Centurion Minerals, Ltd. And contained in the CGS (formerly CDMG) Minefile archives.}{Deposit:: Shelton, J. S., 1955, Glendora volcanic rocks, Los Angeles basin, California: Geol. Soc. America Bull., v. 66, p. 45-90.}{Deposit:: Van Nort, S. D., 1986, Report on the big Horn Mine - An Evaluation of Recent Exploration - for Great Pacific Resources.}
Reporter	Schruben, Paul G., Hill, Robert L.