Farallon Blanco Mine, Sierra de La Ramada, Burruyacú Department, Tucumán, Argentina

Veins of Calcite of hydrothermal origin appears in the eastern slope of the Sierra of the Ramada, upper area of the River El Naranjito in the Burruyacú Department some 50 kilometres approximately from the city of San Miguel de Tucumán. All the veins meet searches made, carried out in the main the work of exploration in search of gold and silver ores, denounced as "Farallón Blanco".
It's veins of calcite on manifest schist slates, forming long streaks of variable power, since some as up over 11 meters, direction predominantly N.W. to S.E. and inclinations ranging from 86 ° to 40 °, discordant with the direction of the schist. The area is covered by thick vegetation, having noted the presence of at least 10 veins of calcite.
The result of analysis carried out indicate that the reefs are composed of calcium carbonate, sufficiently pure to produce good quality lime, being the quality of the ore of the main vein of lower percentage of calcium carbonate containing a certain percentage of silica and iron salts, in part also manganoan.
The work of exploration that made the mining Department of the National University of Tucumán, materialized to the deepening of a master well, to explore the Gold - Silver possibilities for the main vein of calcite.

Geological history:
"Farallón Blanco" is located on the eastern slope of the sierra of La Ramada, Department of Burruyacú, province of Tucumán. The sierra de La Ramada, along with the field, Medina and Nogalito form the so-called Sierras of the northeast of Tucuman, belonging to the subsystem Santa Barbara. The mountains consist of shale and Slate gray of the formation Medina of Precambrian age - eocambric and the granite stock Rodeo de Funes of the possible age Paleozoic. There are also El Cadillal formation reddish Cretaceous conglomerates. This unit is intercalated traquitas and basbelonging to the high complex high in the Salinas. The tertiary is represented by sandstones reddish (Loro river formation), pelites Green chalk, oolitic limestone ( Nio River formation), siltstones and reddish arcilitas and greenish (Salí river formation). Complete the Columbiana fanglomerates, conglomerates and deposits fluvial Quaternary terraced. The sierra de La Ramada is structurally a large Anticline whose core is formed by metamorphites of the formation Medina.Calcite veins are located at both sides of the Gorge of the River El Naranjito located in the metamorphites. Calcite in the form of veins and veins located in the metamorphic basement has address predominant WNW - ESE. There are two types (white and grey), differentiated by color and aspect to ultraviolet light. The main grain is sparry added with crystals of up 50 mm of form escalenoedric. It has been recognized by underground workings, approximately 90 m run with a thickness gave 1.5 m. The dominant position is 110 ° NE inclination 70 ° - 80 ° SW. In the area there are lots of veins of quartz in position matching or discordant with the main plane of cleavage of the metamorphites. Under the microscope the quartz has fragments extinction with black spots and reddish oxide of iron and manganese. Calcite veins pass through quartz. Is the little metal mineralization of gold, pyrite and chalcopyrite. Gold varies between 2 and 10 µ in some cases reaches 20µ, their edges are smooth, sharp or rounded. They are distributed both in the mass quartz and calcite. Pyrite is presented with oxides of manganese in aggregate irregular corroded edges. Chalcopyrite occurs in small individuals of size 10 to 20 µ. Found in veins of calcite with manganese oxide. Manganese is presents as pyrolusite and psilomelane. Existing mining tilling has been realized by the Department of mining Affairs of the Universidad Nacional de Tucumán. There are two main tasks: a vertical pique of 25 m of depth on the left bank of the El Naranjito River and horizontal galleries on the right bank totaling 145 m of development. Is considered that the mineralization of calcites it is carbonated solutions product that circulated by pre-existing fractures of the basement and hydrothermal fluids were possibly linked to the lowest of the branch saw magmatism and the gold content in the veins of calcite could have been remobilized of veins quartz.

Primary mineralization:
Calcite - Manganoan calcite - quartz - native gold - pyrite - chalcopyrite - Pyrolusite - Psilomelane - manganese oxides - iron oxides.

Mineral List

13 entries listed. 9 valid minerals.

References