Prospects of
application rocks

 

bulletZone Lago Alumine

 

> Features and industrial aptitude of the Granito Gris Lonco Luan

> Possibilities of exploitation and commercialization.

> Bibliographic references

 

bulletGranites and gabbros in the zone. Antecedents.

Excellent exposures of granites are located along the valley of the river Aluiné, on its left bank; they can also be found between the lake Ñorquinco and the main part of the ranch house Pulmarí. These are granitoids that are part of the Granodiorite Paso de Icalma, of fine to medium grains, in general of color light grey to bluish grey; they present granular hypidiomorphic to alliotromorphic textures, with plagioclase An 20-30, pertitic orthoclase and quartz. Between the mafites, the brownish red biotite is predominant over greenish blue hornblende. Within the accessories the following can be observed: apatite, titanite, zircon and epidote, with prehnite and clorite as biotite alteration. (Cucchi et al, 2006- in Danieli et al,2011)

From some of these outcrops, along the path that leads from Pulmarí to the lake Ñorquinco, several rock blocks were extracted from which at the time (decade of 1980) plates for the manufacturing of floors were obtained. These plates were commercialized in the regional market with the name of “Gris Pulmarí” (grey Pulmarí). The rocks generally present homogeneous color and texture, although the presence of xenolith or resisters of dark color is common, ranging from 1 to 15 cm. of diameter. Veins or small veins can also be observed and they are generally used by quarry workers as structural guides for extraction of blocks.

Crystalline rocks of black color are frequently present in these granitic outcrops; they are gabbros and micro-gabbros which are exposed in continue outcrops on both banks of the river Pulmarí, upstream from the lake Los Giles, and in the area of the quarry Granito Gris Lonco Luan Expte Nº 12782/87 owned by Minera Cordillera del Viento. It is important to mention that in front of the lake Verde, in lands of Corporación Interestadual Pulmarí a quarry called “María Juana” was installed for the extraction of blocks. Today inactive, the quarry is located on the south bank of the river Pulmarí, 46 kilometers away from Aluminé. It is possible to get to the site through the provincial Route Nº 11, and the exploitation fronts are at the side of this Route. Geology in the area of the quarry is quite simple, with gabbric facies within the Granodiorite Paso de Icalma. It is interpreted as a basic magma pulse of reduced size, emerging in the lowest part of the river valley as isolated bodies. (Cucchi et al, 2006). The outcrops are fractured as consequence of the physical weathering and the relaxation of the material after the glacial retreat (fracturing with deep angular design that originates blocks of small size, of bipyramidal shapes). This effect partially disappears at 2 meters deep, and from then on there is a very hard-fresh black rock.

The outcrop selected back then for the exploitation is an elongated body in direction NW-SE, of approximately 600 meters long and 300 meters wide, divided in smaller pieces by canyons that drain into the river Pulmarí. The estimated exploitation reserves are 135.000 m3, of which 46.000 were recovered until de end of the exploitation.

The following chart summarizes the main physical properties of these rocks, according to trials made in the research center called Centro de Investigación y tecnología aplicada a la Construcción INTI 1994. (in Danieli et al,2011)

 

Physical trial

Grey Pulmarí

Black Pulmarí

Density

2660 Kg/ m3

2869 Kg/m3

 

Absorption

0,20%

0,17%

Porosity

 

0,31%

 

 

0,26%

 

Abrasion

0,90 mm/1000 m

1,35mm/1000 m

Impact

500 mm

350 mm

Dilatation

7,2 x10-6 /1ºC

5,4x10-6 /1ºC

Compression

136,8 Mpa

172,1Mpa

Flexion

15,7 Mpa

19,6 Mpa

Frost resistance capacity

123,4 Mpa

160,5 Mpa

 

Physical features of granites and gabbros of Pulmarí

 

Due to meteoric alteration, there is partial deferrization of gabbros of biotites, augite and opaque minerals, which produces chromatic variations in the rocks and lack of competition. In polished plates this can be seen as oxidized brownish dots, a little bit clearer than the main color.

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