SEG STUDENT CHAPTER UNS...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,

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.


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.


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


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.


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.


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.


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.


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.


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.


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.


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.


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.


“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


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).


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.


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.


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

Documents

SEG STUDENT CHAPTER UNS...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,