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San Dimas District - Tayoltita |
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Durango, Mexico |
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Ag Au
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Super Porphyry Cu and Au
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The Tayoltita epithermal vein system deposit is located in the San Dimas mining district on the western edge of the Sierra Madre Occidental in Durango Province, Mexico.
The Tayoltita mine exploited a series of major veins distributed over a 2 x 5 km area north of the the town of Tayoltita. Mining commenced in the mid 1700's and has continued sporadically to the present with the production of around 300 tonnes of gold and 15 000 tonnes of Ag.
The oldest rocks in the San Dimas area are a sequence of Cretaceous to Tertiary andesitic and rhyolitic volcanics (the Lower Volcanic Series) which are intruded by the large composite Sinaloa Batholith which ranges in age from100 Ma on the western margin to 45 Ma on the east, and in composition from quartz-diorite to quartz-monzonite. Mineralisation is found on the eastern margin of this batholith and has been timed at shortly after the intrusion of the final stages of the intrusive. Following a period of quiescence a second pulse of volcanics from 32 to 23 Ma blanketed the area with 1500 to 2500 m of mainly rhyolitic ignimbrites and ash flow tuffs.
Virtually all of the mineralisation in the district is within the Lower Volcanic Series. The uppermost unit in this sequence is a 140 to 200 m thick andesite flow known as the Productive andesite. Andesite stocks with an almost identical appearance are also found in the district and are believed to have been intrusive equivalents of the flows. Most of the mineralisation in the district is hosted by the Productive andesite and the intrusive andesite stocks.
The main structural elements of the district are a series of major post ore NNW trending normal faults with offsets of the order of 1 to 3 km. The majority of the veins formed along NNE to east-west faults. Individual veins are 2 to 3 m thick, but may locally reach 25 m in width. Some 70% of the production in the San Dimas district has come from the Tayoltita mine.
Ore grade mineralisation in the veins is generally concentrated in a position corresponding to where the individual vein cuts a particular horizon in the enclosing stratigraphy. This interval, the "ore horizon", has a 300 to 600 m vertical extent and can be projected from vein to vein to predict where ore will occur. Within the "ore horizon" mineralised veins contain shoots and contorted bands. The ore is contained in the second of three pulses of quartz. The third pulse is by far the most voluminous, but is usually barren. The ore bearing second phase is accompanied by pyrite, galena, sphalerite and chalcopyrite, with electrum and argentite, and alteration of chlorite, adularia, rhodonite, albite and calcite.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1994.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Conrad M E, O Neal J R, Petersen U 1995 - The relation between widespread 18 O depletion patterns and precious metal mineralization in the Tayoltita Mine, Durango, Mexico: in Econ. Geol. v90 pp 322-342
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Conrad M E, Petersen U, ONeil J R 1992 - Evolution of an Au-Ag-producing hydrothermal system: The Tayoltita Mine, Durango, Mexico: in Econ. Geol. v87 pp 1451-1474
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Horner J T, Enriquez E 1999 - Epithermal precious metal mineralization in a strike-slip corridor: the San Dimas district, Durango, Mexico: in Econ. Geol. v94 pp 1375-1380
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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