Sand River secures sizable Mexican land position

Sand River Resources (SRIV-C) has acquired a portfolio of 16 exploration projects, 14 of which are situated in Mexico.

The company’s premier exploration and development target is the Macocozac property in Mexico’s Zacatecas state. Sand River has signed a letter of intent with Minera Caopas, a private Mexican resource company, for an option to purchase a majority position in the property, which hosts the currently producing Tajos Arroyos Azules copper mine and a 2,250-tonne-per-day mill and concentrator.

The 1,167-ha Macocozac property is host to a copper-gold skarn and porphyry-copper system on the margin of a large Cretaceous-to-Tertiary-aged intrusive complex. The intrusives, which range from monzonite to granodiorite, invade Cretaceous-aged limestones. As a result, skarns, mantos and chimney deposits have formed around the periphery of the main intrusion.

Mineralized skarns occur in relation to intense stockwork veining that exhibits quartz, sericite and pyrite alteration.

Past and present mining and exploration has focused on the skarn mineralization, while the potential of igneous-hosted copper has been largely ignored.

At Tajos Arroyos Azules, a quartz-monzonite porphyry is surrounded by a garnet-pyrite-chalcopyrite-magnetite skarn. An unmineralized granodiorite intrusion is adjacent to the monzonite stock.

The mine hosts a sulphide resource of 14.6 million tonnes grading 1.04% copper and an additional 24 million tonnes of oxide copper ore and stockpiled ore at 0.7% copper. Skarn mineralization is open at depth, and to the south and west.

Porphyry-style mineralization around the mine covers an area of about 1.5 km by 300 metres. Previous drilling intersected up to 0.75% copper over 9 metres within the monzonite porphyry next to the skarn.

Sand River has initiated a 2,000-to-4,000-metre due diligence drilling program designed to test the skarn below the underground workings, as well as the porphyry-copper system.

Geology at the El Cobra prospect, situated about 2.5 km to the northwest of Tajo Azules, consists of quartz-sericite vein alteration along the margin of a granodiorite intrusion. Intense leaching and veining has essentially obliterated the original rock texture. The stockwork here, which covers an area of about 1 km by 500 metres, has not been extensively explored.

Several zinc-silver-gold replacement chimneys can also be found along the margin of the intrusive. Previous underground workings have exploited these zones.

Sand River and Spokane Resources (SKN-V) have formed an equal joint venture with a Mexican mining family under which they can earn up to a 75% interest in the Minerales project and up to an 85% interest in 11 other Mexican projects. The overall land package comprises 53 concessions in several of northern Mexico’s important mining districts.

The joint-venture partners have decided to focus their efforts on Minerales and three other polymetallic skarn systems: Piedras Verdes, Descubridora and Los Chinos.

* Minerales — The Minerales concession covers an area of 924 ha in the celebrated Santa Eulalia mining district, where mines have been in production for more than 350 years. The property includes the Minerales mine, and adjoins the active San Antonio and Buena Tierra mining concessions.

Production at the Minerales mine ceased in 1992 because of labor and financial problems. Mine workings include 22 levels and an estimated 500 km of tunnels reaching a depth of 800 metres. Prior to the closure, two years of production had been blocked out in four zones: 150,000 tonnes of zinc oxide grading 28% zinc; 1.1 million tonnes grading 2.7% zinc, 3.2% lead and 115 grams silver per tonne; 495,000 tonnes grading 8% zinc, 3.13% lead and 130 grams silver; and 200,000 tonnes grading 3.5% zinc, 4% lead and 140 grams silver. The total reserve weighs in at 1.9 million tonnes grading 6% zinc, 3.1% lead and 118 grams silver.

Sand River says the deposit is open to reserve expansion with further exploration and evaluation.

Away from the mine, up to 16 new targets have been identified on the property, and a mapping and sampling program is currently under way.

Geophysical surveys are also being planned to delineate the targets.

Sand River and Spokane are also interested in capitalizing on the mill tailings at Minerales. A study completed by BHP Minerals in 1991 estimated that the tailings held a resource of 6 million tonnes grading 2.28% zinc and 34 grams silver. The study, which was based on 13 drill holes, indicated that zinc recovery of up to 81% was possible using standard floatation methods.

Current investigations indicate a resource of 20 million tonnes with metal grades similar to those estimated in the BHP study, contained within an area measuring 800 metres by 250 metres and with an average depth of 45 metres.

An additional 18 drill holes will be put down on 100-metre centres and further metallurgical work will test solvent-extraction recoveries. Kilborn Engineering and McClelland Laboratories will be hired to conduct these studies.

* Piedras Verdes — The Piedras Verdes project is located 20 km west of Francisco Gold’s El Sauzal project, in the Sierra Madre range of western Chihuahua. The 748-ha project hosts a large copper-zinc-silver skarn system that can be followed over a strike length of about 3 km. The region has seen only limited exploration and development.

Piedras Verdes was recently in production, producing 50 tonnes per day from garnet-altered skarn at average grades of 6% copper, 2% zinc and 100 grams silver.

The joint venture has budgeted for geological mapping, ground geophysical surveys and follow up drilling.

* Descubridora — This project covers an area of about 2,567 ha on the city limits of Chihuahua. The region hosts several small gold and silver mines and prospect pits. Kennecott discovered skarn-related mineralization at Descubridora during a drilling program in 1992; its best intercept contained 11% zinc over 5 metres.

In the southern portion of the concession lies the Prieta mine, which produced gold from silicified zones within andesite and limestone. Kennecott put down 11 holes in a portion of this target and hit a 40-metre interval grading 1.5 grams gold per tonne.

Sand River and Spokane are the first companies to explore the area since Kennecott’s withdrawal in 1993. The partners intend to drill-test a large magnetic anomaly situated on the western portion of the claim block.

* Los Chinos — Los Chinos is situated just south of the New Mexican border and is adjacent to the Bismark mine, owned and operated by Penoles, a private Mexican company. The mine exploits a large zinc skarn system that contains an estimated 15 million tonnes grading 9% combined zinc and copper with silver and gold credits.

The 346-ha property was explored by Broken Hill Proprietary (BHP) during 1991 and 1992. BHP pulled 2,300 metres of core, with the best intercept being 8.6 metres grading 11% combined zinc and lead. Drilling confirmed that replacement-type mineralization existed on the northern flank of the intrusive complex. The joint venture believes that favorable potential exists to expand the Bismark mine deposit onto the Los Chinos property. The companies report that they have developed a positive working relationship with Penoles.

The current exploration program involves mapping, sampling and geophysical surveys, primarily in the area closest to the Bismark mine.

* Cerro del Fortuna — The Cerro del Fortuna property is situated in Sonora state, 30 km south of Mexico’s largest copper mine, Cananea. The Cananea mining district hosts several large open-pit and underground mines producing copper, silver, gold and zinc.

High-grade silver and gold veins hosted within andesitic volcanics can be found on the property. Sampling has indicated that the veins contain up to 933 grams silver and 6.2 grams gold per tonne.

To date, at least five veins have been identified at surface which can be traced along strike for over 1.5 km and are, on average, about 3 metres wide.

In addition, a stockwork zone has been identified associated with su
b-parallel mineralized veins.

Limited underground workings exploited the high-grade ore at Cerro del Fortuna during the 1800s, however, the region has not been subject to modern exploration techniques to determine the extent and controlling features of the mineralized zones.

Sand River and Spokane plan to initiate a mapping and sampling program, followed by a first-phase drilling program.