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Milagro Mine, Cerro Pichao, Tafí del Valle Department, Tucumán, Argentina

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Latitude & Longitude (WGS84): 26° 21' 16'' South , 66° 3' 15'' West
Latitude & Longitude (decimal): -26.35444,-66.05417
Köppen climate type:Cwc : Cold subtropical highland climate or subpolar oceanic climate with dry winters
Name(s) in local language(s):Mina Milagro

Pegmatite worked for muscovite during the 1960s and 1970s.

Pegmatitic Body:
Between the veins of the region pegmatitics stands located on the right bank of the Pichao River in its upper 500 metres water down the Milagro mine. It is discordant with the schistosity of the metamorphic rock and presents a course North 15 degrees East, which is in general of all the pegmatites of the area. It's a body of irregular 4 meters of power in its part wider, with a visible a couple of meters extension, losing in the metamorphic rock.
The rock box is a shale injected with a high content of Biotite, not presenting alteration strong in contact, which is on the other hand sharp.
It's a zoned pegmatite with more or less coarse texture whose exterior area is dominated by the feldspar, in addition to abundant black tourmaline(Var: Schorl) levels of fracturing of the feldspar are stuffed with pinched in the form of fine aggregate. Towards the interior of the body decreases the plagioclase, appearing an aggregate consisting of quartz with packages of Muscovite constituting veins of filling of the feldspars.
Below middle of grain more bulk than the previous, still pink feldspar microcline its main component. There were veins of quartz of the kernel replace the feldspar of very frequently.
The presence of minerals like Beryl, tourmaline and uranium, as well as mica which constituted the commercially exploitable area of this body were sporadically observed in this area contact with the kernel.
The Uraninite is presented in the form of dark nodules and vacuoles within the feldspar, accompanied by Uranophane and Kasolite.
The Kaolinite only appears as the vacuoles of feldspar Microcline alteration in the vicinity of the Uraninite.
The Chalcosite is presented as veins of few centimeters included in feldspar(Albite-Anorthite Series), altered to Malachite in some sectors.
The Spodumene found in small quantities, partially altered, and bearer of micro crystals of Red Garnet and Emerald variety Beryl, dendrites of manganese in part of its surface.

Mineral List

13 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

541 - 1000 Ma

ID: 1376474
Neoproterozoic intrusive and metamorphic terranes

Age: Neoproterozoic (541 - 1000 Ma)

Comments: Mixtures of metamorphic and intrusive or plutonic rocks, tracts known as crystalline, migmatitic terranes, moderately to highly metamorphosed rocks of unknown origin with or without intrusions. This classification is inherently prone to variable interpretation, as other compilers might distinguish some packages by their metamorphic or gneissic protoliths, and the associated age ranges may be more variable.

Lithology: Intrusive and metamorphic terranes

Reference: Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d. [18]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

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Angelelli, Víctor (1961), El Berilo en la República Argentina. Comisión Nacional de Energía Atómica. Informe Nº 60. Buenos Aires.

Porto, Juan C. (1961), Informe sobre una inspección a las pegmatitas de Alto Cazadero y Cueva Bazán, Sierras de Quilmes. Tucumán. Dirección Prov. de Minas. Inédito. Tucumán.

Peña, Hugo A. (1965), Las Pegmatitas Micacíferas del Cerro Pichao, Colalao del Valle, Dpto. Tafí. Informe inédito de la Dirección Prov. de Minas, Tucumán.

Peña, Hugo A. (1965), Las pegmatitas micacíferas de las sierras de Quilmes o El Cajón, Dpto. de Tafí (Tucumán).

Kihien, Alfredo (1968), Estudio geológico y petrográfico del cuerpo granítico de Loma Colorada, Colalao del Valle, Dpto. de Tafí (Tucumán). Dpto. de Geología del Instituto Miguel Lillo. Trabajo de Seminario. Tucumán (inédito).

Peña, Hugo A. (1970), La presencia de minerales de Uranio en una pegmatita de la sierra de Quilmes o El Cajón, Provincia de Tucumán.

Tauber Larry, R. J. (1973). Visita a la pegmatita de Mina "Milagro", Cerro Pichao, Departamento Tafí del Valle", Provincia de Tucumán. Informe personal.

Tauber Larry, Raúl J. (2008). Visita a la pegmatita de Mina "Milagro", Cerro Pichao, Departamento Tafí del Valle", Provincia de Tucumán. Informe personal.

Acta Geológica Lilloana volume (tomo) XI:5. Fundación e Instituto Miguel Lillo, Universidad Nacional de Tucumán.

Tauber Larry, R. J. (2013). Visit to the area in November 2013.

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