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Coneto |
Coneto Photos |
43-101 Technical Reports |
Santa Cruz |
Santa Cruz Photos |
43-101 Technical Reports
In June 2007, Orex Minerals Inc. entered into a joint venture with Silverex S.A. de C.V. for the continued exploration and production of gold and silver deposits on the Santa Cruz Property. Location and Property The Santa Cruz Project is located in northwestern Durango State, Mexico, in the heart of the prodigious "Silver Lake Trend." It is between the San Dimas (Tayoltita) Camp to the south, and the Topia Camp to the north, in the Sierra Madre Occidental mountains. The project consists of a group of contiguous parcels amounting to 21,000 hectares (52,000 acres) with more than 21 linear kilometers of silver and gold-bearing veins, the previously-operating Santa Cruz Mine, and a 50 tpd flotation mill complex. The property can be viewed in terms of three structural districts: The Western District (Jesus Maria -- La Christian -- Zambraneña -- La Perla -- El Carmen), the Eastern District (San Pablo -- La Fragua -- Orozco), and the Central District (Santa Cruz -- Guadalupe -- Veta Grande). History The Santa Cruz mining camp has a long history of production of silver, gold, lead, zinc and copper going as far back as the 1780's, when the operation was controlled by the Count of Zambrano. Stories relating to that time period report bonanza grades coming out of the Zambraneña Mine. In 1908, the Santa Cruz Mining Company was created, but its operations were intermittent, impeded due to the Mexican Revolution, and it stopped production in 1934. In 1967, the Dougherty family restarted operations in the Santa Cruz Mine under geologist Philip Beckley's direction, adding a 50 tpd floatation plant. Mr. Beckley's untimely death in 1983 lead to another halt in operations. The family of Victor Salas Gamero took over operations in 1985 and ran both the floatation plant and the Santa Cruz mine intermittently until 1996, and in 2002-03 through a private company - Minera Sisa S.A. de C.V.. In 2005, Minco PLC optioned the project and conducted mapping and broad spaced geochemical sampling, plus a short drilling program centered primarily in the Eastern and Central Districts. Minco did not extend road access to the Western District and the property was returned in 2006. Overall, the property has been privately held through most of the 20th century. The Eastern District and Central District have seen the bulk of the historic exploration and production, but still have exploration potential. The Western District shows excellent potential with visible surface veins bearing silver and gold. It is considered to be highly under-explored. Geologic Setting The Santa Cruz property is located in the western slope of a geological structural arch known as the Sierra Madre Occidental Mountains. It is a volcanic-dominated highland composed of Tertiary (Paleocene) to Quaternary (Pleistocene) sequences of andesite, dacite-rhyolite and basalt, resting on a basement of Cretaceous and earlier calcareous and metasedimentary rocks. This prominent arch extends from the US-Mexican border area to a transversal neovolcanic belt in central Mexico. The Cretaceous rocks are covered by a sequence of andesite tuff, flows and agglomerate of the Paleocene-Eocene aged "Lower Volcanic Series". This corresponds to the rocks exposed in the arroyos and is the main host rock for mineralized quartz veins. In the higher elevations, the "Lower Volcanic Series" is unconformably overlain by thick sequences of rhyolite and dacite ignimbrite, tuff and volcanic breccia of the "Upper Volcanic Series" of Oligocene age. The physiography of the project is rugged and partly dictated by underlying geology. Where the Upper Sequence Volcanics rhyolites are intact, there are highland plateau areas. These rhyolites form resistant cliffs. Streams and rivers have cut steep arroyos through to expose the underlying Lower Sequence Volcanics of mainly andesite. Most of the mineralized showings are in the 2,100 to 1,300 metres elevation, with deeper valleys cutting below 1,000 metres elevation. Eastern District. The Eastern District has multiple veins and structures, including San Pablo, a 22 m wide alteration zone, associated with a major regional shear, which has been projected over 2 km east-northeasterly along strike. Historic testing has yielded gold and silver in a series of old workings. La Fragua -- Orozco mineralized structure is also in the Eastern District. Variable thicknesses up to 19 metres over a strike length of 500 metres have been reported. Multiple veins exceed 6 kilometres in length. Central District. The Central District, which is the location of the Santa Cruz Mine, contains additional vein targets Guadalupe, Veta Grande, Buena Suerte, La Guadalupana and El Chino. More than 11 kms of veins run generally northeast and east-northeast striking and steeply dipping, with the Buena Suerte vein north-northwesterly striking. Western District. More than 4 kms of veins in the Western District are northwesterly striking and steeply dipping to the northeast. Various interpretations are presented in the historical reports. One has the Jesus Maria -- La Christian Vein and the Zambraneña -- La Perla - Carmen Vein as a part of the same structure, which would give the structure a greater than 2 km strike length. Alternate interpretations show the veins as parallel structures, with approximately 100 m spacing. Two additional veins further west have also been documented, El Cordon and El Creston Veins. Deposit Geology Santa Cruz contains multiple quartz vein structures of intermediate sulphidation epitermal type, extending over many kilometres. Principal elements of interest are silver, gold, copper, lead and zinc. Santa Cruz is considered to be an intermediate-sulphidation Ag-Au epithermal deposit camp typical of the Mexican silver belt. Mineralization at Santa Cruz is dominantly hosted in banded and smoky quartz veins and silicified breccias, but is also in pyritiferous shear zones. Silver is in the form of native silver and electrum (AgAu), as well as argentite (Ag2S), tetrahedrite ((Cu+/-Ag)12Sb4S13), tennantite ((Cu+/-Ag)12As4S13), pyrargerite -- ruby silver (Ag3SbS3) and stephanite (Ag5SbS4) (Hageman, 1911, Salas and Salas, 2006). It is tennantite -- tetrahedrite as a solid solution which is the dominant copper-bearing mineral in high grade zones. Sphalerite (ZnS) and galena (PbS) are the dominant zinc and lead minerals respectively. Sericite, calcite and minor amounts of the manganese carbonate mineral rhodochrosite (MnCO3) have been identified in the gangue minerals as well as quartz. Resources There are no current NI 43-101 compliant resources or reserves documented for the Santa Cruz camp. Most of the earlier mining operations followed the Mexican traditional approach of drifting on known showings. The following discussions come from observations on the property and historic records. Minerals such as native silver (Ag), electrum (AgAu), argentite (Ag2S), ruby silver (proustite Ag3AsS3 and pyrargyrite Ag3SbS3) and stephanite (Ag5SbS4) have all been documented at Santa Cruz and can carry very high precious metal values. Assays in historic references from various veins in all three districts have contained high precious metal values. There is strong potential for further discovery of high-grade mineralization in the Santa Cruz Camp. Eastern District: In the Eastern District, there are several old workings, with the largest being at Orozco and a more recent excavation at La Fragua. Narrow, high-grade tennantite veins in a large alteration zone are present at La Fragua and this is where a small scale hand-cobbing of sulphides operation was conducted for direct shipping material. Without further processing, sacks of rock containing Cu-Ag-Au, comparable in grade to a concentrate, were sold to concentrate buyers for shipment to smelters in China. There are no historic resources for La Fragua and it remains a drill target area. Central District: In the Central District, the Santa Cruz Mine was the main focus of operations. Longitudinal sections have channel sampling data, with many samples exceeding 1,000 g/t silver and one sample yielding a high of 30,776 g/t silver. Reports for the mine show 17 development levels for a depth of 250 metres. Historic mining operations focused on a single ore shoot. Testing for additional shoots on this structure is a target for future drilling. Western District: The Western District, which has not been mined in recent years, has some +100 year old adits on Jesus Maria and Zambraneña. Historic reserves were estimated for these deposits in 1973 of approximately 5.6 million ounces of silver and 10,000 ounces of gold contained within 272,430 tonnes grading 1.1 g/t Au and 644 g/t Ag for a Silver Equivalent of 711 g/t using 60 to 1 gold/silver ratio with metallurgical recoveries and net smelter returns assumed to be 100% (see table below). These historic reserves are not compliant with NI 43-101. 
click to enlarge The historic estimates may be relevant and appear intact from an examination of the Jesus Maria adits. Zambraneña adits were caved in at the portals and access is being restored. A 'qualified person' (as defined in NI 43-101) has not done sufficient work to classify the historic estimate as current mineral resources, and Orex is not treating the historic estimate as current mineral resources, but as a guide to exploration. The historic estimate should not be relied upon until confirmed with further testing. Table 2. -- Historical Reserves Summary
Orex 2007 Sampling: The Western District, which will be a major target area for Orex, has vein structures traced for over 4 km strike length. The following sample results over true widths were obtained in 2007, confirming the gold and silver mineralization potential.
Historic Exploration Eastern District: The Eastern District includes San Pablo, a 22 m wide alteration zone, associated with a major regional shear, which has been projected over 2 km east-northeasterly along strike. Historic testing has yielded gold and silver in a series of old workings. Hole SC-1 (2005) contained an interval from 76.00 to 98.00 m for 22 m grading Ag 66.2 g/t, Au 0.27 g/t, Zn 1.22 %, Pb 0.23% and Cu 0.10%. Hole SC-2 (2005) contained an interval from 112 to 115 for 3 m grading Ag 464.3 g/t, Au 0.12 g/t, Zn 2.71%, Pb 0.66% and Cu 0.05%. High-grade tetrahedrite-tennantite has been selectively mined in the La Fragua -- Orozco mineralized structure in the Eastern District. The Santa Maria vein in La Fragua has historically reported channel samples grading Ag 707 g/t, Au 7.68 g/t, Cu 9.40%, over 2.50 metres. A weighted average of 5 intercept samples in 1996, over a 500 m strike length, yielded 4.55 m at Ag 162.6 g/t and Au 0.77 g/t. Some interpretations of the Eastern District suggest that the San Pablo and La Fragua -- Orozco may connect. Central District: On longitudinal sections, the Santa Cruz Mine has 17 levels extending for a depth of approximately 250 metres and along strike for 130 metres. This is interpreted to represent one ore-shoot, which was exposed in Santa Cruz creek. Information about the location and high-grade results from some underground sampling indicates that mineralization may still be present and projections of the Santa Cruz vein have not been drill tested, thus exploration potential is considered significant in the Central District. A brief surficial exploration program was conducted in 2005 in the Central and Eastern Districts under a joint venture between Minco PLC and Minera Sisa S.A. de C.V., including 2,700 metres of drilling. No drilling was conducted in the Western District. This program also included geological mapping and a broad scale soil sampling at 200 metre line spacing across most of the Eastern and Central Districts, highlighting several areas of anomalous silver, gold, copper, zinc and lead. Drilling was not specific enough to fully test the high-grade vein systems. Western District: The most under-explored area is the Western District, which had small scale production dating from before the Mexican Revolution (pre-1911), but has never been diamond drilled. Multiple veins exceed 4 kilometres strike length. Historic sampling reports many samples exceeding 1,000 g/t silver, including one at 110,000 g/t silver and 5,500 g/t gold, suggesting the presence of electrum (AgAu) in the system. Surface chip sampling conducted in 2007 confirmed the presence of gold and silver in the El Carmen, Zambraneña, La Christian and Jesus Maria areas of the Western District, including a high of 929.9 g/t silver and 13.15 g/t gold over 1.5 metres at surface. Exploration Objectives Orex's chief focus will be on the excellent exploration potential of the Santa Cruz Project. Each of the three structural districts has multiple vein targets totaling over 21 kilometre distances. The Eastern District and Central District have seen the bulk of the historic exploration and production, but still have exploration potential. The Western District is considered to be greatly under-explored. Historic records with many samples in the multiple kilograms of silver per tonne, plus gold, show the potential for native silver (electrum) in the veins from El Carmen -- La Perla -- Zambraneña -- La Christian -- Jesus Maria workings. This area deserves to be drill tested. A two phase exploration, geological mapping, sampling and diamond drilling exploration program, consisting of 20,000 meters, has been proposed for the 2009 season. The initial drilling will be for 3,000 metres starting in the Zambraneña workings area, then branching northwest toward La Perla and Carmen. Ortho-photography has been flown and surveying control stations have been prepared for topographic control. In addition, reconnaissance sampling and geological mapping in the Western and Eastern Districts has commenced, as well as the identification of drill targets. Current activities on-site consist of road and bridge repairs, as well as new road construction, to gain better access to Zambraneña. Twenty five kilometres of road repairs have also been completed to improve access in the Central and Eastern Districts. New road construction has now reached the Zambraneña (level 3 area) and construction of drill pads has commenced. Silverex is preparing access to the old Zambraneña adits. A 2009 Q2 start of drilling is anticipated. Maps
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