SEG – Student Chapter - Universidad Nacional de Colombia

SEG – Student Chapter - Universidad Nacional de Colombia
Medellín Campus (Facultad de Minas)
FIELD TRIP TO THE WORLD CLASS DEPOSITS OF NORTHERN OF CHILE
(25 January – 10 February of 2014) - Report
Group photo of the field trip participants at the Escondida Mine. Back row (left to right): Sebastián Builes,
Santiago Gil, Albert Monterroza, Jhon Sepúlveda, Jorge Julián Restrepo, Esteban Moná, and two students
practitioners who accompanied us. Next down row (left to right): Carolina Amaya, Norbey Arcila, Paola Hoyos,
Oswaldo Ordónez. Next down row (left to right): David Muñoz, Paula Pacheco, Sabina Vahos, Sara Marín,
Leidy Gaviria. Who hold the banner – Front row (left to right): Sebastián Barbosa and Adriana Blanco.
Appreciating the sponsorship of the field trip
Itinerary
Day
Activities
25 Jan (Sat)
Travel from Medellín to Antofagasta (Chile) with stop in Lima (Perú)
26 Jan (Sun)
Travel from Antofagasta to Calama
27 Jan (Mon)
28 Jan (Tue)
29 Jan
(Wed)
30 Jan (Thu)
31 Jan (Fri)
Visit to the Chuquicamata mine (Porphyry-Cu deposit) - Codelco Norte,
Laguna Cejar (Salar de Atacama) and Valle de La Luna (Moon Valley)
Visit to the El Tesoro mine (Exotic-Cu and porphyry-Cu deposits) and
Esperanza mine (Porphyry-Cu deposit) - Antofagasta Minerals
Visit to the Escondida mine (Porphyry-Cu deposit) - BHP Billiton
Overnight
Calama
Calama
Antofagasta
Antofagasta
Visit to the Candelaria mine (IOCG deposit) - Freeport-McMoran Copper and Tierra Amarilla
Gold
(near to Copiapó)
Visit to the Museo Minero de Tierra Amarilla (mining museum), San José
Tierra Amarilla
mine (famous for the 33 miners) and Orbicular Granite (Natural Santuary) (near to Copiapó)
1 Feb (Sat)
Travel from Tierra Amarilla to La Serena
La Serena
2 Feb (Sun)
Geological transect along the Elqui River Valley
La Serena
3 Feb (Mon)
4 Feb (Tue)
Visit to the El Indio - Tambo (High sulfidation gold deposits - mine closure) Barrick Gold
Visit to the Mina Escuela El Brillador (Cu-deposit - school mine) - La Serena
University, and the 26 de Agosto mine (Cu-deposit) - Compañía Minera San
Gerónimo
La Serena
La Serena
5 Feb (Wed)
Visit to Carmen de Andacollo mine (Porphyry-Cu deposit) -Teck
La Serena
6 Feb (Thu)
Travel from La Serena to Valparaíso
Valparaíso
7 Feb (Fri)
Travel from Valparaíso to Santiago
Santiago
8 Feb (Sat)
Enjoy time in the capital city
Santiago
9 Feb (Sun)
Enjoy time in the capital city
Santiago
10 Feb
(Mon)
Return trip to Medellín
Map of field trip
Coordinates table of visited places
Place visited
Chuquicamata mine
Valle de La Luna (Moon Valley)
Laguna Cejar (Salar de Atacama)
El Tesoro mine
Esperanza mine
Escondida mine
Candelaria mine
Museo Minero de Tierra Amarilla
San José mine
Natural Sanctuary Orbicular Granite
El Indio-Tambo mine closure
Mina Escuela El Brillador (school mine)
Carmen de Andacollo mine
Latitude
22°21'35.89"S
22°55'17.39"S
23°30'49.08"S
23°25'42"S
23°32'28"S
24°17'05"S
27°30'44.34"S
27°29'49.53"S
27°09'27.04"S
26°58'19.91"S
29°44'52.32"S
29°48'45.90"S
30°15'30"S
Longitude
68°55'58.82"W
68°17'11.50"W
68°15'3.10"W
69°30'50"W
69°32'42"W
69°05'03"W
70°17'27.84"W
70°15'43.54"W
70°29'52.37"W
70°47'43.44"W
69°58'15.14"W
71°11'32.31"W
71°05'32"W
Field trip Participants
Name
Carolina Amaya López
Norbey Arcila Quintero
Type
Undergrade Student
Undergrade Student
Undergrade Student Juan Sebastián Barbosa Mejía
Secretary
Undergrade Student Adriana Marcela Blanco Palacio
Vicepresident
Undergrade Student Juan Sebastián Builes Carvajal
President
Undergrade Student
Leidy Gaviria Montes
Undergrade Student
Santiago Gil Cardona
Undergrade Student Paola Andrea Hoyos Giraldo
Treasurer
Undergrade Student
Sara Paulina Marín López
Undergrade Student
Juan Esteban Moná Graciano
Undergrade Student
David Muñoz Román
Paula Andrea Pachecho Sintura Undergrade Student
Undergrade Student
Jhon Alexis Sepúlveda Higuita
Undergrade Student
Laura Sabina Vahos Agudelo
Geology Teacher Oswaldo Ordóñez Carmona
Academic Fellow
Jorge Julián Restrepo Álvarez
Geology Teacher
Albert Eduardo Monterroza Ríos
Industry manager
Company
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
e-mail
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
[email protected]
[email protected]
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
U. Nacional de Colombia
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
U. Nacional de Colombia
Gran Colombia Gold
[email protected]
[email protected]
[email protected]
[email protected]
1. INTRODUCCIÓN
At the beginning of 2014, it was conducted the “GEOLOGICAL-MINER FIELD TRIP TO
THE WORLD CLASS DEPOSITS OF NORTHERN OF CHILE” of SEG – Student Chapter
of Universidad Nacional de Colombia – Sede Medellín (Facultad de Minas) (which is
composed by undergrade students of Geological Engineering) ([email protected]),
that took place in the largest world mines of Cu-Mo and Au in the northern of Chile, touring
an area of approximately 2000 km in north-south direction.
The field trip started from the named II Region of Antofagasta, more specifically from the
city of Calama, where we visited the world class Cu deposit of Chuquicamata, and places
of geological interest like the Valle de la Luna (also known as Moon Valley) and Laguna
Cejar (Salar de Atacama). Continuing the trip to the south visiting the El Tesoro and
Esperanza mines, the porphyry Cu-Mo operated by Minera Escondida, the IOCG of
Minera Candelaria, the Museo Minero of Tierra Amarilla, San José mine where 33 miners
were trapped in 2010, Natural Sanctuary Orbicular Granite, besides we realize a
geological transect from La Serena to Pisco-Elqui municipality along the Elqui River Valley,
and visited the mine closure of the El Indio epithermal deposit, El Brillador school mine of
the La Serena University, and Carmen de Andacollo porphyry-Cu mine, among others,
and finally we were enjoyning the beautiful city of Santiago.
These deposits are part of the named seven metallogenic belts, which include porphyry
Cu-Mo, IOCG, high sulfidation, exotic-Cu, and other deposits types referenced by authors
of great international stature as Maksaev, Sillitoe, Perelló, and others, and evidencing the
great metallogenic potential of this western region of South America.
2. REGIONAL GEOLOGY
The geodynamic processes in northern of Chile and their lithological signatures are
preserved since the lower Paleozoic, upper Paleozoic and Jurassic times, until the present
day. In the lower and upper Paleozoic, the sedimentary basins were formed in continental
platforms environments, which were affected directly by syn-depositional metamorphism
(due to the separation and collision of Gondwana with the supercontinent Laurentia and
Báltica), which gives rise to the rocks that constitute the basement of northern Chile and
basically comprises schists of low to medium grade. Precambrian rocks have not been
report in the northern of Chile (Bahlburg, 1997). For the end of Permian age, the
Panthalassa Ocean was an active subduction margin, forming volcano-sedimentary and
plutonic rocks, until the end of the Paleozoic, where the proto-Andean orogeny began.
There is a sedimentary, volcanic and plutonic record of subduction of the Pacific plate
beneath the South American plate from Jurassic time until now (Coira, 1982). Thus, in
northern of Chile, there are igneous plutonic and volcanic rocks, the latter, interbedded
with sedimentary rocks of transitional and continental environments. Plutons of
granodioritic composition of Jurassic age are found in the Coastal Cordillera, being older
the eastern ones than the western ones; this phenomenon is because of the tectonic
erosion in the trench. The volcano-sedimentary sequences are composed of different
kinds of pyroclastic fragments and sandy and coarser sediments. In the Cenozoic, is
where the mainly intrusive bodies are mineralized which correspond to porfidic rocks of
Paleogene and Neogene ages (Damm, 1981). These plutons intruded sedimentary rocks
which where mineralized by fluids by ending stages of the magmatism. Eolic, alluvial and
transgressive marine sediments, represents Quaternary units that are mainly the cover of
Cenozoic rocks.
3. ESTRUCTURAL GEOLOGY
In the northern Chile (between 21° and 27° S), where was developed the magmatic arc of
Paleogene, are located two of the mayor fault systems of the country. The structural
pattern is determined by a series of blocks spaced apart by a fault system with orientation
NNE that constitutes the fault systems of Domeyko and to the west along to the Coastal
Cordillera, the fault system of Atacama (scielo.org.ar; 2014).
The Domeyko fault systems have orientation NNE and a long history of transcurrent
movements, both sinistral and dextral (scielo.org.ar; 2014). The Cu-Mo porphyry deposits
located on the western side of these fault systems are the representation of zone of
weakness cortical that was an important role during the later stages of the Andean
evolution.
The Atacama fault systems are the most important structures of the southern Andes
(Artenorte.cl; 2014).Its activity began during the Mesozoic with sinistral displacement
movements. Its topographical expression in the Coastal Mountains was reactivated during
the Cenozoic.
Fig 1: Schematic structural map of northern of Chile showing the location of the Atacama fault and Domeyko
fault and porphyry deposits associated with the latter (scielo.org.ar; 2014).
4. METALLOGENIC BELTS IN CHILE
There are recognized seven metallogenic belts of porphyry of Cu - Mo and Epithermal Au
deposits, their ages range from the Carboniferous to Pliocene, will be described below
(Maksaev, V. 2001; Camus, F. 2003; Sillitoe, R. Perelló, J. 2005):
A belt of upper Carboniferous to Triassic is extent for 1500 km along the Domeyko
Cordillera where eleven porphyry systems have been identified, which have suffered
erosion and are not economically exploitable showing a weak secondary enrichment; the
belt of Jurassic occur in the westernmost zone of the Coastal Cordillera. The most
important correspond to districts of Cu-stratabound deposits hosted in Jurassic volcanic
rocks of northern of Chile. There are also copper vein systems hosted by upper Jurassic
plutons; the belt of lower Cretaceous is located in the eastern flank of the Coastal
Cordillera, the bodies associated to the mineralization are porphyries of tonalitic and
dacitic compositions, there are also Cu-stratabound, Fe-deposits (magnetite-apatite) and
the IOCG deposits are related to Atacama fault system; the belt of upper Cretaceous is
located between Copiapó and Rancagua, and include mesothermal Au-Ag veins, base
metal deposits and epithermal deposits; the belt of Paleocene – lower Eocene in
comparison with the belt of cretaceous this show most amount of Cu, Mo and Au. The
larger volume of copper are located in the north end and in the youngest deposits (52 Ma),
between the 24-26° S the porphyry systems lose their continuity and are replaced by HS
or LS deposits; the belt of upper Eocene – lower Oligocene extents for more than 1400
km along the Domeyko fault zone of transpressive behavior. This belt contains the major
amounts of copper of the world. The last event (34-31 ma) is the major Cu mineralization;
in the belt of Neogene the volcanic activity occurred in 4 stages: the first of 26-22 Ma has
associated the epithermal systems; the second between 20-17 Ma is characterized by low
volcanic activity, follow by a third period between 16-11 Ma of intense volcanism
associated with epithermal systems, and finally the fourth stage between 11-5 Ma is
associated with Cu-Mo porphyry deposits.
Fig 2: Metallogenic belts of Chile (Modified from Sillitoe and Perelló, 2005).
5. GEOLOGICAL-MINERS SITES VISITED
5.1 Chuquicamata mine – Codelco Norte – Porphyry Cu-Mo – January 27th
Is the largest open pit copper mine of the world, and is located in the II Region of
Antofagasta (lat. 22°21'35.89"S, long. 68°55'58.82"W) at 16 km from the city of Calama on
the Domeyko Cordillera. It is part of the mining complex associated with Chuquicamata
Division along with Mina Sur and it is currently led by the state-owned Codelco. Their
name comes from indigenous communities “Chuquis” who lived in the area and obtained
native copper. The open pit measures are 5 km large, 3 km width and 1 km deep forming
an ellipse.
Chuquicamata is part copper porphyry deposits of the Eocene - Oligocene (40-32 Ma) belt
and his mineralization is subvertical slightly tilted to the west and is composed by Cu, Mo,
and Ag with minor amounts of Au. The deposit is located within the Domeyko fault system
and is represented by the Oeste fault, which divides to the east the ore body and to the
west the barren rock. There are early alterations located in the periphery of the deposit,
chloritic, bottom potassium and intense potassium, the latter is the most pervasive and is
the mineralization with major content of copper and molybdenum, expressed in
chalcopyrite and bornite, it also have quartz and molybdenum veins. The late alterations
are located to the west of the deposit, obey to the action of the Oeste fault and consist of
pervasive sericitic-quartz and intense potassium relict. In the late hydrothermal part,
supergen basins are generated with greater concentrations. The mine had oxides, but
these have been already exploited, currently only processed in Mina Sur, and they have
resources for a year, it should be noted that the oxides of Mina Sur are exotic generated
by gravitational fluid migration.
The mine produces approximately 800.000 ton/day of mineral and 850 tonnes Cu/day,
generally extracting sulfides of copper and molybdenum with grades of 1.4 and 0.1%
respectively. Currently the resources in the district are about 17.287 billion of tonnes. The
fine copper of Chuquicamata is with 99, 9% of purity, and they produced a copper cathode
of 165 kg that is obtained using electrochemical processes, the cathode has a retail value
of approximately USD $1100. Throughout the process the mine spends about 2000 liters
per second of water that comes from underground mountain water. This water recycle
occurs in the thickeners, and get to use a drop 9 times before it evaporates. Having more
thickeners increases the efficiency of the mine, compared to other mines in Chile, despite
being an older mine. Regarding energy, annually they used 3 GW, which is almost 20% of
spend in Chile for a year. For this supply of energy, they used coal, thermoelectric energy
(primarily) and oil.
The method of exploitation is changing from open pit to Block Caving (underground),
because currently the mine is producing 400,000 tonnes of waste rock, and since it
increases the cost and distance that must be reached to find mineralization, it generates
higher costs. The beginning of underground exploitation will be in 2018 has a lifespan
approximately until 2060.
Fig 3: A) Intense potassic alteration; B) Molybdenite veinlet; C) Exploitation advance; D) Copper cathode.
Fig 4: A) Group photo at lookout of the Chuquicamata Mine; B) Open pit; C) Beneficiation plant.
5.2 Valle de La Luna (Moon Valley) – January 27th
The Moon Valley is located in the II Region of Antofagasta (lat. 22°55'17.39"S, long.
68°17'11.50"W) at 13 km from San Pedro de Atacama inside of the Salt Cordillera and in
the edge of Salar de Atacama.
About the geology of the zone, there are Paleozoic sedimentary marine rocks; that during
the Cretaceous began to raise in the seabed, leaving the basin between the Andes
Cordillera and Domeyko Cordillera, a huge lake with saline water that slowly evaporated,
then the fluvial and eolian erosion modified the landscape. The Sal Cordillera, which is the
most remarkable of Moon Valley scenic features, is a relief generated by successive
folding the salt flat background. It consists of sedimentary rocks with salt and gypsum
outcrops; in the saline efflorescence minerals are gypsum, anhydrite, halite and other
sulfates, borates and carbonates (Monumentos. cl, 2014).
Fig 5: A); B) Different views of the Moon Valley.
5.3 Laguna Cejar (Salar de Atacama) – January 27th
It is located within the Salar de Atacama in the II Region of Antofagasta (lat.
23°30'49.08"S, long. 68°15'3.10"W) between the Andes Cordillera to the east and the
Domeyko Cordillera to the west at 17 km from San Pedro de Atacama.
The deposition of evaporites in the basin of the Salar de Atacama has lasted at least since
the Oligocene. The stratigraphically lower levels, which constitute the Salt Cordillera, have
been folded and exposed from the middle Miocene tectonic block that controls the entire
structure of the Salar de Atacama. There are two large units in the Salar de Atacama: the
core and the marginal zone. The core consists of 90% of porous halite impregnated with
rich interstitial brine in Li, K, Mg and B; around the core, the marginal zone consists of fine
salt saline sediments, rich in sulfates. The authors state that the high salt load of the feed
water is not from residual brines, because there are also other sources such as the
alteration of volcanic rocks minerals, oxidation of sulfur and sulfide of other mineralized
bodies. This suggests that most of the Li, K, Mg and S components have a common origin.
Since Li and B are almost always associated with volcanism, it can be inferred for all these
components primarily a volcanic origin, either by hydrothermal fluids or alteration of
volcanic rocks, as it has been described in northern of Chile (Hugo Alonso, 1996).
Fig 6: A) Anhydrite crystals; B) Side view of Laguna Cejar; C) Group photo.
5.4 El Tesoro Mine – Antofagasta Minerals – Exotics-Cu and Porphyry Cu –
January 28th
The deposit is located in the II Region of Antofagasta (lat 23°25'42" S, long 69°30'50" W)
at 200 km northeast of Antofagasta. Currently the mine has three open pits, Tesoro
Central, Tesoro Noreste and Mirador and it is dedicated to a mining exploitation and
production of copper cathodes.
The mine is located on the porphyry copper belt of the Eocene - Oligocene (42-31 Ma),
which represents the largest known concentrations of copper in the world. The geology is
characterized by the presence of stratified sedimentary rocks that have been intruded by
porphyritic rocks. The Mirador pit is a Cu-porphyry deposit and the others pits are
associated with exotic mineralization that consists in atacamite, chrysocolla, copper wad
and copper pitch in sub-horizontally gravel layers. Its origin is due to the Cu-rich solutions
that migrate through paleochannel from one type porphyry copper deposit exposed on the
surface and is spatially associated with the Domeyko fault system.
The mine has a capacity of processing of 9 Mt of ore/year and 75 thousand tons of
cathodes/year. The actual resources are 220 Mt of Cu (Camus, 2003).
Fig 7: A) Group photo at lookout of the Tesoro Central pit; B) Group photo with a dump truck of 300 ton; C)
Tesoro Central open pit.
5.5 Esperanza Mine – Antofagasta Minerals – Porphyry Cu – January 28th
Esperanza mine is located in the II Region of Antofagasta (lat. 23°32'28"S, long.
69°32'42"W) at 167 km northeast of Antofagasta, and 100 km southwest of Calama, in the
eastern part of the Municipality of Sierra Gorda.
The porphyry body is located in the metallogenic belt of Eocene to Oligocene associated
with the Domeyko fault system, this intruding Jurassic andesites and Cretaceous marine
sediments, the intrusive mineralized body is elongated in the N30E direction; structurally
the deposit has two main structures, the Túnel fault and Esperanza fault, the latter is the
west limit of mineralization. The alterations presents are propylitic and potassium, as
predominantly, the mineralization is pyrite, chalcopyrite, some oxides of Cu, and bornite.
The mine belongs to Antogafasta Minerals by 70% and 30% at Marubeni Corporation, this
site extracts Cu-Au and the operation began in 2008 and has reserves of 583 Mt grading
0.55% Cu, 1.22 g/t Au, and produce 314,000 tonnes/year, 190,000 tonnes fine-Cu/year,
and 15,000 Oz Au/year. The operation is done in open pit and the material is transported
to the plant by means of a conveyor belt of 4 km to the stock pile, there to the sack
grinders and the grinder balls, then is taken to float, finely continuous to the thickeners and
the pasta obtained is carried by pipeline 145 km to the port of Minera Esperanza. This is
the first large scale mine that implemented from the beginning of its operations sea water
100% of the process, pick up at the Michilla port and transporting it by 141km to the mine,
although it is an expensive technology is an innovative method contributing to the
environment and ore beneficiation process.
Fig 8: A) Esperanza Open pit; B) Stock pile; C) Potassic alteration; D) Veinlets in Esperanza porphyry.
5.6 Escondida Mine – BHP Billiton – Porphyry Cu-Mo – January 29th
The Minera Escondida deposit is a Cu-Mo porphyry located in the Domeyko Cordillera in II
Region of Antogafasta (lat. 24°17'05" S, long. 69°05'03" W) about 140 km SE of the city of
Antofagasta, in a vast arid plain between 3000-3200 m above sea level. The Escondida
mine has approximately 4500 m large, 2500 m width and 750 m of deep. This mining
operation grouped two mines: Escondida and Escondida Norte.
The systems are associated with bimodal volcanism between late Eocene to early
Oligocene that gives rise to porphyritic intrusive complex. The Cu-mineralization is marked
by the presence of bornite and chalcopyrite. The structures are represented by a series of
NS faults associated with Domeyko fault zone (Camus, 2003). The alterations consist in
the development of one late magmatic potassium phase (associated with propilitic,
silicification and potassic alterations, with magnetite, chalcopyrite and bornite) which
bounds the margins to a more pervasive propylitic of great extent (includes chlorite-sericite
and quartz-sericite alteration with chalcopyrite, pyrite and molybdenite) and advanced
argillic alteration (represented by the acid-sulfate alteration, with quartz, pyrophyllite and
alunite as mineral association). Some exploration projects like Pampa Escondida,
Escondida Este and Chimborazo have been developed in the last year with excellent
results and maybe in a future one of this will be extracted.
This mining operation is run by BHP Billiton, which owns 57.5% of the company, and has
been developing since 1991. As regards the commodities operated by that company, it
can be mentioned that the copper extracted by the company is equivalent to 6% of world
copper production and 20% of Chilean production, highlighting that exploited 1.4 million
tons of material per day of which 400,000 are copper minerals. Annually, the production is
850,000 tons of refined copper in concentrate and 180,000 ounces of Au approximately. In
addition the company realizes a leaching extraction and electrowinning that allows you to
produce 140,000 tonnes of copper cathodes/year (Camus, 2003).
Fig 9: A) Escondida Porphyry; B) Molybdenite veinlet; C) Atacamite in supergene enrichment zone; D)
Alteration models (extract from presentations); E) Enrichment zones (extract from presentations).
Fig 10: A) Blasting at the Escondida open pit; B) Group photo at lookout in the pit.
5.7 Candelaria Mine – Freeport-McMoran Copper and Gold - IOCG – January 30th
The mine is located in the III Region of Atacama near the town of Tierra Amarilla at 22 km
from Copiapó (lat 27°30'44.34"S, long 70°17'27.84"W), currently exploited Cu and Au by
open pit and also with underground method.
In terms of geology, there are two domains, one sedimentary eastward and another
intrusive to the west. Candelaria is located at the base of the sedimentary domain, which
the andesitic volcanic rocks are folded and affected by structures. Westward intrusive
bodies (diorites and granodiorites of 119 Ma belonging to Copiapó batholith) provided the
mineralizing fluids through the reservoir structures. In terms of structural geology, the area
is dominated by north-south structures, associated with the Atacama fault system. The site
of Candelaria is located east of the fault zone. Candelaria is an IOCG deposit with the
mineralization age is estimated between 110 and 115 Ma by various methods and is
related to late fluids nearby intrusive bodies. Mineralization consists of magnetite,
chalcopyrite and pyrite, at the top of the deposit is presented pyrrhotite instead of pyrite.
The gold is contained in the inner structure of chalcopyrite and pyrite lesser extent, the ore
minerals occur in veinlets, breccia fillings and dissemination in intensely altered volcanic
rocks of the unit Punta Del Cobre Fm. The volcanic rocks of Candelaria mineralization
were affected by an early potassic alteration, a superimposed sodium-calcium alteration
later stage. A retrograde phase characterized by amphibolite, chlorite, epidote, sericite and
minor clinozoicite affected the whole and finally came up with the late introduction of Kfeldspar (post-mineralization) (Maksaev, V). Portions of Copiapó Batholith to the west are
marginally affected by intense sodium-calcium alteration possibly related to mineral
formation (Marschik & Fontboté, 2001).
The mine has a production of 200,000 tons/day, which corresponds to 70,000 ton ore Cu,
inferred resources of 121 Mt to 0.570% Cu, indicated resources 110 Mt at 0.594% Cu and
measured resources of 563 Mt to 0.679% Cu, reserves are 350 Mt of ore. The company is
controlled by U.S. Company Freeport-McMoran Copper & Gold and the finished product is
a concentrate of copper.
Fig 11: A) Mirmequític texture in potassic alteration and Cpy-Mgn veinlet of an IOCG; B) Specular hematite; C)
Breccia with chalcopyrite veinlets of Punta Del Cobre Fm. D) Garnet in hosted rock.
Fig 12: A) Open pit of Candelaria mine; B) Group photo at lookout in the pit.
5.8 Museo Minero de Tierra Amarilla (Mining museum) – January 31th
The Tierra Amarilla Mining Museum is located at km 17 km from Copiapó (lat.
27°29'49.53"S, long. 70°15'43.54"W), and was opened on 18 August 2011 in order to
gather and known parts and testimonials that illustrate representative aspects of life of
Atacama Region, providing visitors knowledge about the history of the region from its
mining vocation. The permanent exhibition shows minerals mined in national sites and
foreigners, fossils, historical objects, and models of each stage of the mining operations;
as well as the rescue of their historical heritage values, in order to contribute in a manner
relevant to knowledge and consolidation of regional identity. This place has large spaces
for recreation than and scientists seeking to find a face more social and academic of the
geology and mining (El Museo Minero de Tierra Amarilla; Page web Museo Minero de
Tierra Amarilla, 2014). On this visit we were accompanied by Mr. Alejandro Aracena who
is co-founder of the museum and who represents the mining culture in the Atacama
Region.
Fig 13: A) Atacamite; B) Group photo with Mr. Alejandro Aracena (we can see behind an orbicular granite); C)
Iron meteorite exhibited at the museum; D) Orbicule with magnetic core. E) Dendritic habit of pyrolusite F)
Group photo at the entrance of the Mining museum of Tierra Amarilla G) Calcantite.
5.9 San José Cu mine – January 31th
The San Jose mine was a mining operation located in the Copiapó Province in the III
Region of Atacama (lat. 27°09'27.04"S, long. 70°29'52.37"W) at 29 km northwest of the
Copiapó city and 33 km east of Caldera city. Its exploitation began around the mid
nineteenth century; in 1840 to August 5 of 2010 (date of the incident that left 33 miners
trapped). Although initially their production was silver, at the date of its closure on average
1,200 tons of copper per year were extracted. The mine is known for the incident that
happened on August 5 of 2010, where a collapse of 700,000 tons of material in the 300
level of the mine was produced at 5 km from the mine entrance, leaving 33 miners trapped
for 70 days. Until the "San Lorenzo” rescue operation on October 13 could reach the level
where they were trapped and finally free them.
Nowadays at the mine site, there is a memorial of the events that took place in the mine
from the moment of the collapse until the rescue of the 33 miners. In the museum you can
learn about the San Lorenzo operation, see parts of the elements that were used in the
work of search and rescue of the miners. The museum San Jose mine since then has
become a place open for interested, tourists and curious of what happened there (Díaz, F,
2013; InfoBae América, 2010 and La Torre de Babel, 2010).
Fig 14: A) SEG student group at the San José Mine; B) 33 flags belonging to the country of the miners that
were trapped inside the mine for 70 days (32 from Chile and 1 from Bolivia); C) Group photo with the flags
behind; D) “We are well in the shelter, the 33”, first sign of live received from miners; E) Tour guide explaining
the situation experienced by the 33 miners.
5.10
Natural Sanctuary Orbicular Granite – January 31th
This place is located in the III Region of Atacama (lat. 26°58'19.91"S, long 70°47'43.44"W)
belonging to the Commune Caldera. It is easily accessible and is situated 11 km north of
Caldera, near Rodillo beach. This outcrop is one of the few of this type of rock found in
Chile; it was discovered in 1961 by the Chilean geologist F. Ortiz. Given its unique
character, this site was declared “Nature Sanctuary” in 1981 and is protected by
conservation laws that apply to this type of monument (Sociedad Geológica de Chile,
2013).
The body, of Jurassic age, is dyke-like with an exposed surface area of approximately 375
m2, 15 m thick, 25 m long and is enclosed in tonalitic batholith. Both hosted rock and
orbicular body are cut by diabasic dykes. The surface ratio of matrix/orbicules is 35/65;
orbicules are mainly ellipsoidal with an average axis of 7 cm and are composed of a
quartz-diorite core and a single dark shell with a predominantly radial texture composed of
equal amounts of plagioclase and amphibole accompanied by lesser amounts of
clinopyroxene, biotite and magnetite. Non-orbicular inclusions in the orbicular body are
scare (Aguirre, Hervé, and Del Campo, 1976).
The petrogenesis of the orbicular body is explained based on two assumptions: a) Nonorbicular inclusions in the orbicular body and the core of orbicules correspond to hosted
rock xenoliths and, b) The shell of the orbicules and the matrix were generated form a
same magma during differentiation.
Fig 15: A) Contact between the tonalitic batholith and orbicular body; B); D) Orbicules; C) Triangular Orbicule;
E) Granite Orbicular outcrop.
5.11
Geological transect along the Elqui River Valley – February 2th
The Elqui River Valley occupies the northern sector of the IV Region of Coquimbo,
extending from 29°40'S to 32°10'S. Climatically located at the boundary between the
desert climate of northern Chile and central semi-arid climate of Chile ((Cabezas, Cepeda,
and Bodini, 2007) in Sanchéz and Morales, 1993).
The geology of the area is represented by pre-Tertiary intrusive rocks and Tertiary Quaternary sediments (gravel and sand), which are located in the flat areas. The large
existing terraces in the lower section of the valley favor agriculture and human settlement.
In this zone highlights the major crops of grapes to produce vine and pisco (VisitChile.com,
2012)
Fig 16: A) Volcanosedimentary sequence at the Elqui River Valley; B) Puclaro dam; D); E) Vineyard in the
semiarid climate; F) Grapes from a Fundo Los Nichos vineyard.
5.12
El Indio–Tambo – Barrick Gold – High sulfidation – February 3th
The El Indio – Tambo is located in the IV Region of Coquimbo in the Andes Cordillera (lat.
29°44'52.32"S, long. 69°58'15.14"W) at 160 km from the La Serena city at heights
between 4000 and 4500 m above sea level. Actually is property of Barrick Gold and is the
first voluntary mine closure in South America and it was exploited for 23 years (1979 –
2002) through open pits and tunnels with a production of 10 M oz Au at 10 g/t Au average
grade, 100 M oz Ag and 1 Mt Cu, and has been considered the classic high sulfidation AuAg-Cu vein deposit.
The world class deposit is located whitin the denominated Indio-Pascua epithermal belt
which is a metallogenic belt which contains large high sulfidation deposits like PascuaLama, Veladero, Indio, Tambo, etc, that are associated with a calc-alkaline volcanism
occurred between Miocene-Pliocene (12 – 7 Ma). The evolution of the epithermal system
is characterized by two main stages: alteration and mineralization. The hypogene vetiform
mineralization is hosted in acid volcanic rocks (Vacas Heladas Fm – Dacitic ignimbrites of
12 Ma) and grouped in two mineralizations stages: Cu and Au. The cupriferous stage is
reduced and is composed by enargite and chalcopyrite, and the auriferous stage is
oxidized and consists in veins filled by quartz, pyrite, and native gold. These
mineralizations stages is associated with alterations (pervasives in some cases) quartzsericite and advanced argilic characterized by alunite, barite, limolite, jarosite, etc. The
mineralization is structurally controlled by two mayors reverse-rigth lateral faults oriented
NNE with a dip 60° to NW (Bissig, 2001).
For the mining factor, Barrick Gold encouraged a pioneer initiative in the Chilean mining to
make the decision to close the mine according to high environmental and social standards,
implementing a program to give sustainability in agricultural regions (grape crops) and in
nearby cities (La Serena and Coquimbo), investing about USD 80 million. The Closure
Plan include two phases, the first include the demolition, rehabilitation, surface water
management (construction of canal of 5 km for the Malo River), and the second consist in
the physical and chemical monitoring of instalations, water sources, etc (Galleguillos, 2007
and http://barricksudamerica.com/cierre-el-indio/).
Fig 17: A) Enargite – Cpy vein; B) Alunite vein and tectonic breccia; C) Baritine; D) Alunite; E) Vuggy silica; F)
Native sulfur from steam heated zone.
Fig 18: A) El Indio closure mine; B) Artificial canal for the Malo River; C) Group photo with the Tambo mine
behind.
5.13
El Brillador School Mine – La Serena University – February 4th
The school mine El Brillador is located in the IV Region of Coquimbo (lat. 29°48'45.90"S,
long. 71°11'32.31"W) at 23 km from La Serena city. It belongs to La Serena University and
is sed for academic purposes where students will make their practices in underground
mining operation with emphasis ventilation, fortification, drilling and rock fragmentation,
metallurgy, basic mining and rock mechanics, as well as training services in risk
prevention activities in plant and mine.
It is represented by deposits of Cu (chalcopyrite, bornite, chalcocite, covellite, malachite,
atacamite, chrysocolla) that are hosted in a volcanosedimentary sequence, intrusive rocks
and hornfels. In the Brillador district, bodies of hydrothermal alteration are developed in
NW faults, besides in stratabound deposits and veins.
The mine was initially operated by Indians and later managed and operated by French
businessman Charles Lambert, in the nineteenth century. Today, the 26 de Agosto mine is
operated by the San Geronimo Mining Company, through lease from the 620 m to the
surface, which together with other mines processed 25,000 tonnes of copper oxides per
month and produces about 9,000 tonnes per year of copper sulfate.
Fig 19: A) Group photo in the El Brillador entrance; B) Fortification with rockbolts; C) Capacitation area with
wood doors fortification; D) Mineralized breccia; E) Calcantite mineralization.
Fig 20: A) Atacamite vein; B) 26 de Agosto open pit.
5.14
Carmen de Andacollo – Minera Teck – Porphyry Cu – February 5th
The mining company Carmen de Andacollo is located in the IV Region of Coquimbo (lat.
30°15'30" S, long. 71°5'32" W) about 55 km south east of La Serena. The district lies
within the watershed of Andacollo and is part of porphyry copper belt of Cretaceous age.
The geology of the area roughly consists of a lower volcanic unit, with mostly andesites
porphyritic, an upper volcanic unit which presents tuffs which due to its porosity allowed
the flow of mineralized solutions, a unit of intrusive rocks formed by dacite porphyry and
rhyolitic related to copper mineralization, a unit of breccia (Brecha Hermosa), and a unit of
undifferentiated rocks which we cannot tell what kind of rock it is due to the degree of
alteration present. In Carmen de Andacollo mine it is possible to observe all kind of
alterations like alteration chlorite-epidote, biotite alteration, albitic alteration, K-feldspar
alteration, quartz-sericite alteration, and kaolin-smectite-barite-siderite-montmorillonite
alterations.
The Carmen Andacollo deposit has a hybrid genesis influenced by a porphyry copper
deposit and linked by one stratabound. It is also affected by a fault system with NE
direction like as Andacollo fault and the Beautiful fault, among others. The generation of
the deposit was a result of a series of events, starting with the extensive structural
configuration, the intrusion of porphyritic dacite dikes with all alterations that besides
solutions mineralizing invasion generated through Hermosa and Andacollo faults, and it
presents an ascent of hydrothermal that strongly affects the Brecha Hermosa and
moderately toba. Later activation of structural systems is recorded, causing a strong
tectonism on the Brecha Hermosa. The late porphyry intrusion "El Culebrón" and andesitic
porphyry and finally a rise of late hydrothermal solution and the development of supergene
alteration.
The operation is an open pit mine and produces both porphyry copper cathodes (20.000
ton/year) and copper concentrate body of hypogene portion of the deposit (80.000
ton/year). The reserves of the supergene leacheable part of the deposit 7,247 Mt of 0.42 %
Cu, and the total mineral reserves of Carmen de Andacollo is 476,610 Mt of 0.35 % Cu
0.12 g/t Au (TECK-Carmen de Andacollo, 2012).
Fig 21: A); B) Carmen de Andacollo pit; C); D) Dust control by water sprayers trucks.
Fig 22: A) Group photo with the open pit behind; B) Group photo with sedimentation pool behind; C)
Beneficiation plant.
6. ACKNOWLEDGEMENTS
The field trip was possible because the support of academic organizations as the Society
of Economic Geologist SEG (http://www.segweb.org/) through the Funding Program, Data
Metallogenica DM (http://www.dmgeode.com/) through AMIRA P1040 project,
Corpogemmas (Corporación para el avance de la geología, geotécnia y minería en
armonía con el medio ambiente y la sociedad; Corporation for the advances of geology,
geotechnics and mining in armony with environmental and society http://www.corpogemmas.com/),
Sociedad
Colombiana
de
Geología
SCG
(http://www.sociedadcolombianadegeologia.org/) and some national mining industries of
medium scale.
‘The information contained in the report is for information purposes only. The information
contained within the report may be changed or updated from time to time without notice.
The authors of this report have taken all reasonable care in producing and publishing
information contained in this report. Material in this report may contain technical or other
inaccuracies, omissions, or typographical errors, for which the Society of Economic
Geology assumes no responsibility. In consideration for using this material, the reader
agrees to hold the Society and its affiliates harmless against any claims for damages or
costs or any loss of any kind arising out of the access to or use of this report or any
information contained in or obtained through this report. Technical information contained in
this report is for personal use only. Any reliance on the information contained in these
reports by any third party shall be entirely at their own risk.’
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