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Reginal
Geology
 The
San Simon Project is located in the Precambrian
Shield of northeastern Bolivia. It is an extension of
the Central Brazil Shield and a geotectonic extension of the
Amazonic Craton believed to have consolidated during the Trans-Amazonic
Orogeny which ended around 1700 Ma (million years). The shield
was affected by two younger orogenies, those of San Ignacio
(~1300 Ma) and Sunsas (~1000 Ma).
The major part of the shield area is underlain by a sequence
of schists, gneisses and granulites of Lower to Middle Proterozoic
age (2,500 to 1,300 Ma) with over 10,000 m thickness.
The San Simon project concessions cover a plateau that rises
up to 300 m above the late Tertiary lateritic Amazonian peneplain.
The plateau is made up of the Proterozoic Serranía
San Simón Group of a low to high grade greenshist facies
metamorphic arenaceous sequence. The group is divided into
the lower El Cerrito Argillite Formation (300-350 m thick),
the middle El Colorado quartzite formation (1,300-1,350 m
thick) and the upper Bonanza metagreywacke formation (1,600-1,650
m thick).
The Bonanza Formation is deposited in alternating high and
low energy shallow water, shallow depressions and paleotrough
features in an oxygenated environment. Local fine lamina with
sulphides and carbonates are deposited in stagnant water under
anaerobic conditions. Intraformational conglomerates indicate
shoaling and temporary withdrawal of the water followed by
desiccation and cracking of the surficial muds. Fragments
within the sediments suggest an origin from a gneissic basement,
volcanic successions and banded iron formation.
The paleocurrents during deposition for the group are principally
from the north. Both the El Cerrito and El Colorado Formations
had a northwest source of the sediments while the Bonanza
Formation had a northeast source. The main metallogenic feature
is late kinematic gold mineralization in the schist belt.
It includes banded iron formations, shear hosted quartz +/-
carbonate gold veins and sediment hosted gold. |
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