|
Red Mountain |
|
|
Arizona, USA |
| Main commodities:
Cu
|
|
 |
|
|
 |
Super Porphyry Cu and Au
|
IOCG Deposits - 70 papers
|
All papers now Open Access.
Available as Full Text for direct download or on request. |
|
|
The Red Mountain copper deposit is located in the Patagonia Mountains of Santa Cruz County, ~5 km southeast of the town of Patagonia and 84 km SSE of Tucson in Arizona, USA (#Location: 31° 30' 10"N, 110° 43' 22"W).
For details of the regional setting see the record for the Hermosa - Taylor zinc-silver-lead deposit which is located ~5 km to the SSE.
The Red Mountain deposit comprises i). hypogene porphyry copper mineralisation at depths of >1000 m beneath surface, associated with a concealed quartz-monzonite intrusive complex of unknown size and extent; ii). hypogene enargite rich mineralisation occurring near surface, associated with pyritic phyllic and argillic alteration zones within the volcanic lithocap above the porphyry; and iii). a supergene profile and multiple chalcocite rich sulphide enrichment blankets within the near surface zone of pyrite-rich phyllic alteration (Corn, 1975; Titley, et al., 1989). The overall alteration/mineralisation system is believed to be centred on a caldera subsidence structure which was associated with explosive volcanism and sub-volcanic intrusive activity. This latter assumption is reinforced by an arcuate zone of dykes, intrusive breccias and subsidence structures (Corn, 1975).
Mineralisation is dated at around 62 Ma, based on associated alunite. The blind, possibly Paleocene age, intrusive breccias and monzonite to quartz-monzonite intrusions which form the core of the hydrothermal system, occur as irregular bodies, sills and dykes and are only known from deep drilling. These intrusions penetrate a strongly fractured volcanic lithocap which has been subjected to acid-sulphate and advanced argillic alteration of a dacite to quartz-latite (rhyodacite) and rhyolite tuff volcanic succession, overlying thick andesites and lower still, conglomerates. The upper tuffs are around 500 m thick, and are estimated at 'around 60 Ma' in age. The underlying andesites comprise an upper 500 m of andesites and trachy-andesites, underlain by a further 500 m of interlayered andesite, felsite and banded hornfels. The pre-ore andesitic volcanic rocks have been dated at about 72 Ma and are considered as late Cretaceous to lower Tertiary in age. This entire sequence has been intruded by sills and dykes of monzonite and quartz-monzonite porphyry which in deep drill holes within the mineralised area account for 25 to 30% of the rock intersected below the upper tuffaceous volcanics (Bodnar and Beane, 1980; Titley, et al., 1989).
Closely contiguous with the intrusive centre are a few mines that have taken complex base and precious metal ores from veins and replacement bodies in volcanic rocks. Mn-Ag mineralisation in carbonate rocks is also known from two sites to the south. Multiple Laramide intrusion in closely spaced centres in the district leaves uncertain the relationship of the base metal mines to any specific intrusion, one of which lies several kilometres to the SSW (Bodnar & Beane, 1980; Titley, et al., 1989).
Red Mountain stands out as the most striking feature in the district, with over 800 m of relief above the surrounding mountains. It is composed of erosionally resistant, highly altered tuffs. It is brightly coloured with jarositic staining from oxidised sulphides in its cap. Virtually all of the rocks exposed on the mountain are part of the late Cretaceous to lower Tertiary volcanic succession, mainly andesites, trachy-andesite and tuffs which extend in outcrop for several kilometres around the deposit. The north-west side of the mountain is cut by a north-east trending fault. The destructive effects of pervasive advanced argillic alteration, coupled with destructive acid weathering are seen in most outcrops and render rock identification in outcrop difficult. Most of the top of the system is in the upper tuff unit and the pyroclastic nature of this rock is sometimes revealed in ghost textures (Titley, et al., 1989).
According to Corn (1975), both the mineralisation and the alteration at Red Mountain exhibit concentric zoning patterns centred on the area of monzonite and quartz-monzonite porphyry intrusions. Surface exposure reflects a zonal pattern of alteration and mineralisation, centred on an area of phyllic alteration (silica flooded, alunite-pyrophyllite-pyrite bearing rocks) and Cu-Mo mineralisation that is surrounded successively by zones of pyritic-argillic alteration and propylitic andesites. The effects of hydrothermal alteration are evident over an area with a diameter of 11 to 13 km. Vertical zoning in alteration mineralogy appears to be related to a gradual increase in sulphur content from low sulphur K-silicate alteration at depth, through weak K-silicate alteration to sulphur rich, phyllic assemblages near the surface. The lateral and vertical zoning is also reflected in the distribution of Pb, Zn, Mo and Cu minerals both in the zone of pervasive disseminated sulphides and within the exterior veins of the propylitic alteration zone (Corn, 1975; Titley, et al., 1989).
The Red Mountain alteration/mineralisation system exhibits two different types of hypogene Cu mineralisation. Enargite is associated with near surface, high pyrite, phyllic and pyrite-argillic alteration. Chalcopyrite occurs with both weak K-silicate and more intense K-silicate alteration at depth. Although not of ore grade, the enargite mineralisation provided a protore source for the Cu of the 'high level' chalcocite blanket. 'Ore grade' hypogene mineralisation occurs at depths of 1000 m or more beneath the surface. The zoning pattern is characterised by a gradual increase in the grade of Cu with depth within the zone of weak K-silicate alteration, and the upper parts of the main K-silicate zone (Corn, 1975).
Episodic uplift has produced four hematite rich zones reflecting four cycles of chalcocite blanket development and subsequent oxidation and leaching (S Titley, pers. comm., 1994). A supergene alunite from the uppermost (and presumably oldest) layer of hematite leached capping yielded an Oligocene age of 25.3 ±0.7 Ma.
Published resource figures are: 100 Mt @ 0.71% Cu (Total Resource, 1978, USBM)
570 Mt @ 0.63% Cu (Mutschler et al., 2004).
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.
Red Mountain
|
|
|
|
Bodnar RJ and Beane RE 1980 - Temporal and spatial variations in hydrothermal fluid characteristics during vein filling in preore cover overlying deeply buried porphyry copper-type mineralisation at Red Mountain, Arizona: in Econ. Geol. v75 pp 876-893
|
Corn, R.M., 1975 - Alteration-mineralization zoning, Red Mountain, Arizona: in Econ. Geol. v.70, pp. 1437-1447.
|
Graybeal, F.T., 1996 - Sunnyside A Vertically-Preserved Porphyry Copper System, Patagonia Mountains, Arizona: in SEG Newsletter No.26, p. 1, 10-14.
|
Graybeal, F.T., Moyer, L.A., Vikre, P.G., Dunlap, P. and Wallis, J.C., 2015 - Geologic map of the Patagonia Mountains, Santa Cruz County, Arizona: in U.S. Geological Survey, Open-File Report 2015-1023, 10p.
|
Lecumberri-Sanchez, Newton, P.C., Westman, E.C., Kamilli, R.J., Canby, V.M. and Bodnar, R.J., 2013 - Temporal and spatial distribution of alteration, mineralization and fluid inclusions in the transitional high-sulfidation epithermal-porphyry copper system at Red Mountain, Arizona: in J. of Geochemical Exploration v.125, pp. 80-93.
|
Long, K.R., 1995 - Production and reserves of Cordilleran (Alaska to Chile) porphyry copper deposits: in Pierce, F.W. and Bolm, J.G., (Eds.), 1995 Porphyry copper deposits of the American Cordillera: Tucson, Arizona Geological Society Digest, v.20, pp. 35-68.
|
Quinlan, J.L., 1986 - Geology and silicate-alteration zoning at the Red Mountain porphyry copper deposit, Santa Cruz County, Arizona: in Beatty, B. and Wilkinson, P.A.K., (Eds.), 1986 Frontiers in geology and ore deposits of Arizona and the Southwest: Arizona Geological Society Digest, v. 16, pp. 294-305.
|
Titley, S.R., 1993 - Characteristics of porphyry copper occurrence in the American Southwest: in Kirkham, R.V., Sinclair, W.D., Thorpe, R.I. and Duke, J.M., (Eds.), 1993 Mineral deposit modeling: Geological Association of Canada, Special Paper 40, pp. 433-464.
|
Vikre, P.G., Graybeal, F.T., Fleck, R.J., Batron, M.D. and Seedorff, E., 2014 - Succession of Laramide Magmatic and Magmatic-Hydrothermal Events in the Patagonia Mountains, Santa Cruz County, Arizona: in Econ. Geol. v.109, pp. 1667-1704.
|
|
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.
|
Top | Search Again | PGC Home | Terms & Conditions
|
|
