seg student chapter uns...copahue volcano. unfortunately, there was a huge ash column that made it...
TRANSCRIPT
SEG STUDENT CHAPTER UNS
Departamento de Geología
Universidad Nacional del Sur
“Copahue geothermal field. Renewable alternative energy resource and actual
hydrothermal system”
Field Trip
February 2016
FIELD TRIP LEADER: Dr. Luis Carlos Mas
PARTICIPANTS.
1. Abelaira, Alan
2. Angeletti, Melisa
3. Bauer, Emiliano
4. de Azevedo, Natalia
5. Di Lorenzo, Mercedes
6. Galina, Matias *
7. Jara, Evelin
8. Jovic, Sebastián *
9. Luna, Geraldine
10. Maydagán, Laura
11. Meschini, Carolina
12. Miraglio, Verónica
13. Paez, Gerardo *
14. Palma, Diego *
15. Perez, Silvina
*Universidad Nacional de La Plata
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Introduction.
The five-day field trip to Copahue, Neuquen province was part of the “Copahue
geothermal field” course. Renewable alternative energy resource and actual
hydrothermal system” that was held between February 1st-5th, 2016. The field
trip was organizated by members of the SEG Student Chapter UNS and was
guided by Dr. Luis Carlos Mas (Universidad Nacional del Comahue, Neuquen,
Argentina). A group of 16 people participated in this field trip, 11 members of
our Student Chapter, 4 members of the Student Chapter of Universidad
Nacional de La Plata and 1 driver. During the trip we visited the Copahue
geothermal field.
Copahue is a little touristic center next to Caviahue town. It’s located in the
west-north of Neuquen province, Argentina (Fig. 1).
Fig. 1: Location map of the trip.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
First Day
We left Bahia Blanca at 7am and we spent about 8 hours driving. The first stop
in Neuquen city was around 535km (332 miles) from Bahia Blanca. We used a
van from the Geology Department of the Universidad Nacional del Sur. Once
in town, we headed to the Universidad Nacional del Comahue to attend a class
with basic concepts on geothermics and the Copahue geothermal field, that was
held by Dr. Luis Carlos Mas. (Fig. 2)
Finally, we spent the night in the Cipolletti city, 8km of Neuquen.
Fig. 2. Theoretical class in the Universidad Nacional del Comahue
Second Day
We left Cipolletti towards Caviahue-Copahue around 7am. We drove
approximately 344km. In the middle of the trip, we made some geological stops
to recognize the geology of the area.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
The first stop was in the Huarenchenque zone, where we observed a profile
corresponding to pyroclastic flows, and we compared them with the Mesozoic
sediments outcropping on the left bank of the Agrio river corresponding to the
Neuquen basin fold-and-thrust belt (Fig. 3). Then in the volcanic soil of
Copahue, Loncopué town, can be recognized some of the major eruptive
centers, such as the Copahue and Sierras Bayas (Fig. 4). Near Caviahue-
Copahue, the Hualcupen Fm. or Precaldera units can be observed,
corresponding to the first stage of the eruptive system (4.3 ± 0.2Ma).
Fig. 3. Rock profile corresponding to pyroclastic flows
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 4. Volcanic soil of Copahue, Loncopué town. Major eruptive centers, such as the
Copahue and Sierras Bayas
Since the volcano is active, the amount of ash issued at the time did not allow
us to continue the schedule, so we took some pictures of the place.(Fig 5 and 6)
Fig. 5. Copahue Volcano.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 6. All together with the volano background.
Aproximately at 7pm we arrived to Caviahue town. We stayed in the city school
164 of Caviahue who gave us their facilities and we gave some donation, mainly
bookstore articles (Fig. 7).
.
Fig. 7. City school 164 of Caviahue were we stayed.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Third Day
In the morning of the third day, we went to “Cascada del Basalto”. The river
has water falls and cascades related with columnar disjunction of lavas (Fig. 8).
Here, the professor measured the pH and temperature of the water of the Agrio
River, pH between 2 and 4 and a temperature of 11.4°C. The next stop was
“Cascada Escondida” (Fig. 9). This area presents outcrops of sedimentary rocks
of possible glaciar origin. The pH of the water was 5, and the temperature of
15.7°C.
Fig.8. Left: Columnar disjunction. Right: The top of the hexagonal columnar disjunction.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 9. Dr. Luis Mas measuring the pH and water temperature
In the afternoon, we went to “Las máquinas”. That constitutes the second largest
thermal area. Within the region there is a depression in which a warm lagoon is
formed because of the damming spring water, very murky water because the
presence of colloidal sulphur (Fig. 10). Well crystalized and relatively pure
alunite occurs, accompanied by clays and siliceous minerals (Fig.11). The
presence of alunite indicates low pH of the fluids, the pH is between 2 and 5
with a temperatures between 49°C and 95°C (Fig. 12). In the margins of Las
Maquinas, we recognized an increase in kaolinite and quartz. These minerals
are covered by iron oxides, forming gossan.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 10. Alteration zone in Las Maquinas.
Fig. 11. Fine material extracted from around the altered areas. Doughy rock of fine material
with alunite, kaolinite and pyrite.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig.12. Measurement of pH and temperature of the lagoon in Las Maquinas.
Towards the northeast of the Copahue volcano, there are thermal manifestations
known as “Las Mellizas” (Fig. 13). They present low temperatures of fluids and
intermediate alteration, that evidence a retrograding thermal evolution.
The “Vertiente del Agrio” is a manifestation that appears directly Copahue
volcano rocks. The pH of the water is 0.75 and it directly associated with the
crater lagoon. It corresponds to the center of the last volcanic emission of
Copahue volcano. Unfortunately, there was a huge ash column that made it
imposible to reach the top.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 13. Las Mellizas lagoon. It presents a low temperature and intermediate alteration.
Fourth Day
In the morning we went to “Termas de Copahue”. It’s located in the urbanized
areas of Copahue town and constitutes one of the major zones of geothermal
alteration in the field. Thermal manifestation in this section forms lagoons of
murky and cloudy appearance, due to the presence of emanations of colloidal
sulphur and gas, which are used as theraphy centers (Fig. 14). The area of
“Aguas del Limon” is a zone with fumaroles with alunite and kaolinite minerals.
On the upwelling centers cristobalite, alunite and fine crystals of sulphur are
developed.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
The geomorphic and mineralogical changes are developed in short periods of
time (only in years) and manifested in the way of cavities with almost vertical
walls which contain greyish “mud spot” thermal fluids (Fig.15), with
temperatures that exceed 90°C (Fig. 16) and pH lower 4. Regarding mineralogy,
they are constituted by sulphur and kaolinite which cause the fluid to acquire
the characteristic color observed and acidity.
Fig. 14. Thermal manifestation which are used as balneotheraphy centers. It has a
temperature of 40°C and a pH 5.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 15. Left: alteration zone. Right: mud spot developed in the cavities.
Fig. 16. Shows the temperatures reached in the cavities and the constant bubbling.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
“El Anfiteatro” thermal manifestation located in the west of Copahue town,
present various liquid and gaseous manifestation. In each of these upwellings,
native sulphur precipitates surrounded by a halo of pyrite and sulphur (Fig. 17).
The rock surrounding the manifestations have alteration and silicification with
quartz, tridymite, and cristobalite.
Fig. 17. Mud spot and native sulphur precipitation.
In the afternoon, we went to the thermal manifestation “Las Maquinitas”
(Fig.18). It is the smallest thermal manifestation and consists of two
depressions, upper and lower along a fault N 55° E. Currently, the lower
depression is the most
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
active with a 95°C and a pH 5. Alteration minerals present are amorphous silica,
kaolinite and alunite.
Fig.18. Thermal manifestation “Las Maquinitas”.
After that, we visited the edge of the Rio Agrio, we measure the pH of the river
water (pH = 3) (Fig. 19). In the afternoon, we gave to each participant the
corresponding course certificate. (Fig.20).
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fig. 19. Agrio River. The high acidity of the water gives the orange hue to water
Fig. 20. Left to right. Dr. Luis Carlos Mas, Geraldine Luna and Emiliano Bauer.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
Fifth Day
Finally we left Caviahue-Copahue early in the morning and we spent all the day
driving from Caviahue to Bahia Blanca where we arrived in the afternoon
(Fig.21).
Fig 21. All together driving from Caviahue to Bahia Blanca.
It was very satisfying and interesting to see alteration processes directly and
how these are linked to volcanic processes in this active geothermal field. At
the same time it was compared with oldest alteration hydrothermal deposits.
SEG-STUDENT CHAPTER UNS Universidad Nacional del Sur, Bahía Blanca, Argentina
General expenditures during the Field Trip
Field Trip expenses
Details Amount (AR$)
Driver Food
Fuel
Acomodations Car Washing
4000 3400
4600
2500 500
Total 15000
Field Trip Sponsor: SEG U$S 1500.
Acknowledgements
All the members of the Student Chapter UNS would like to thank to the Society
of the Economic Geologists for the financial support and for giving us the
possibility to organize events like this course and field-trip.
We would like also to thank to the Universidad Nacional del Sur for the great
support and for providing us the van we used for this field-trip.
We want to thank also to Leandro Campo, the driver that he always ready to
join us in the trip.
Finally, we want to thank Luis Carlos Mas who transmitted us his experience
and accept our invitation to give his course and be the leader of this field trip.
STUDENT CHAPTER UNIVERSIDAD NACIONAL DEL SUR