Project "Lemuria".
The placer gold deposit is located on a mountain slope 700 km south of Santiago, the capital of Chile. There are two fields, El Oso and Antonina, with combined area 300 ha, together called project Lemuria.
History and technical characteristics of the field.
The gold placer was found in the valley of a small river in 2009. The river is 5-6 m wide and up to 80 cm deep. Geophysical surveys showed a river and a terrace alluvial deposits up to 20 m thick along with borders of an ore deposit.
More exploration and test drilling put thickness of placer sand in the current river channel at up to 8 m and in the paleochannel up to 20 m.
HMS of the channel deposits indicated presence of gold, its content looked to be approximately 10 g/m3.
On the surface pilot mining of the channel deposit put the average placer gold content at 9 g/m3; by the laws of geology, deep content should be several times higher.
The right bank has not been studied, but has two tributaries with placer gold. They start from the same mountain as the main river, but descend from its opposite shore and join the river at a spot within the borders of the gold field.
Georadar Ltda performed geophysical studies and coring, the samples were analyzed in ALS lab in Santiago.
We invited specialists from CJSC Primorzoloto to take samples of the placer sand and analyze them in a Moscow lab.
Test production was conducted on the surface for the alluvial deposit. Average gold content was
10 g/m3.
Overall, the following was established about the placer gold:
The gold-bearing plot is 200 m wide and 3000 m long.
The placer sand is 8-20 m thick.
Gold content is 5 g/m3.
Estimated size of the P1 type gold deposit is 24.0 tons, c.p.
Gold ore:
In 2016 geophysical studies examined the ore body and showed that it lies at the depth of 20 m and is 30 m thick. Gold ore was found everywhere in the 300 ha plot.
This puts the volume of ore at 90 mln m3.
Exact gold content is unknown, but weathering crusts (where the ore body reaches the surface) contain at least 5 g/m3. Taken together, the ore body should contain significantly more gold than the placer sand.
General geophysical studies.
On section 4 level 4 geologically corresponds to the alluvial sand facie.
Level 4 is the most waterlogged and its bottom corresponds to the local erosion base level.
Auger drilling to 10 m with samples taken every 1.0 m showed Arcosic sand, probably the alluvial sand facie, but not certainly (no balled material). It may also be the sand facie of residual granite here.
