IBIGEO   22622
INSTITUTO DE BIO Y GEOCIENCIAS DEL NOA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A preliminary characterization of the wasted metals enriched sediments in the abandoned mining treatment plant La Poma. Salta, Argentina
Autor/es:
CACCIABUE, LUCÍA; ARNOSIO, MARCELO; KIRSCHBAUM, ALICIA; PETTINARI, G.
Lugar:
Mendoza, Argentina
Reunión:
Congreso; 18th International Sedimentological Congress; 2010
Institución organizadora:
International Association of Sedimentologists
Resumen:
In the northwest of Argentina,
abandoned mines as well as mineral treatment plants where metals as Pb, Ag and
Zn were extracted and concentrated, represent a potential risk of acid mine
drainage (AMD) generation. The mineral treatment plant La Poma is located in Chorrillos, 17
km from San Antonio de
los Cobres village, Los Andes department, in Salta province. The old plant concentrated
the ore using a flotation chemical method. In 1986 the plant stopped working
and the waste from flotation process was left exposed to weathering. Furthermore, both infrastructure and machinery
were abandoned without any planning for its closure. Nowadays a huge volume of
mining tailings are present surrounding the closed plant. This material has
been eroded by the Tajamar
River, which pass through
the abandoned place. Near the river, light and yellowish salts precipitate. By X-ray
diffraction, a secondary sulfate dietrichite (Zn0.6Fe2+0.3Mn2+0.1Al2(SO4)422(H2O)) and
sulfides such as smythite (Fe2+6.75Ni2.25S11),
galene and pyrite were determinated. Tailings are composed of medium-fine grained
sand, grey-yellowish and green color, with friable consistency. None
sedimentary structure is observed. Quartz, feldspar and biotite were recognized
as main minerals, and zircon, hornblende, hematite and pyrite are abundant
accessory minerals. Some sediments deposited by the Tajamar river after
crossing the tailings were described. Three leves were recognized. The upper
level, 5 cm
thick, is fine grained sand, gray- greenish color. The minerals identified are quartz and feldspar,
hornblende, magnetite, pyroxene, zircon and tourmaline as accessories. Pyrite
is absent. The second level, 6
cm thick, is fine grained sand, dark green color. Rock
fragments, quartz, feldspar and altered biotite are present; the accessory
minerals identified are similar to the upper level. Pyrite is poor and it is
oxidized, which is coherent with the higher rate of weathering in this
transported materials instead of the static sediments in the
tailings. The lower level is composed of fine grained sand. Zircon, brownish
hornblende with magnetite, poor altered biotite, tourmaline and pyroxene were
determinated. Pyrite is absent. The occurrence of secondary minerals on
tailings surface is the result of dissolution of primary sulfides, transporting
and precipitation of salts due to evaporation. These soluble salts stay on the
surface until next rainy season, when they are disolved again.