Abstract:
Chile is an active seismic and volcanic country due to its location on an
Active Continental Margin, where an oceanic plate subducts under a
continental plate. Chilean Quaternary volcanism is part of the Andean
Quaternary volcanism situated along the western margin of South America,
which is segmented into four zones: the Northern Volcanic Zone (NVZ; 6°N-
2°S), Central Volcanic Zone (CVZ; 14°S - 27°S), South Volcanic Zone (SVZ;
33° - 46° and focus of this presentation) and Austral Volcanic Zone (AVZ;
49° 55°S) separated by three segments that lack of Quaternary volcanoes.
The first three volcanic zones are the product of the subduction of the
oceanic Nazca plate under the continental South American plate while the
AVZ is a consequence of the subduction of the oceanic Antarctic plate
under the continental plate. The northern limit of the SVZ coincides with
the impingement of the Juan Fernàndez asismic ridge on the Chile trench
(27°-33°; Pampean flat slab segment), and its southern limit is marked by
the intersection of the active Chile Ridge with the Chile trench
(46°-49°S; Patagonian Volcanic Gap). Petrologically, the SVZ has been
subdivided in four provinces: Northern (NSVZ; 33° – 34.5°S), Transitional
(TSVZ; 34.5° – 37°S), Central (CSVZ; 37° – 41.5°S) and Southern (SSVZ;
41.5° – 46°S). The continental crust decreases in thickness from the NSVZ
(> 50 km) to the south, reaching a thickness of about 30-35 km along the
CSVZ and SSVZ. The subduction angle is relatively steep along the SVZ (>
25° at depths > 90 km). The geohemical characteristics of the SVZ
magmatism are controlled by a combination of processes occurring in the
subducted oceanic crust, the overlying mantle and the continental crust.
In the NSVZ, the effect of the continental crust is significant but is
insignificant south of 37°S. Magmatism is initiated by variable fluxing
from the subducted slab which interact with the overlying mantle wedge. In
the NSVZ, continental crust is incorporated into magmas by a combination
of both subduction of the crust into the subarc mantle and/or assimilation
of the crust by mantle-derived magmas. In their ascent to the surface, the
magmas evolve mainly by low-pressure crystallization, especially in the
CSVZ and SSVZ. Other processes such as magma mixing are also important in
some cases. Lava, pyroclastic and debris flows, tephra falls and lahars
are all hazards associated with SVZ volcanoes. Nonetheless, geothermal
waters are also associated with these active volcanoes. Actually, the same
faults that control volcanism also control the source of these thermal
waters. In the SVZ of the Andes the main sources of geothermal waters are
controlled by the Pocuro fault in the north (33°-34.5°S) and the
Liquiñe-Ofqui fault zone in the south (38°-45°S). The enthalpy of the
northern sources is relatively low since the temperature of the waters is
less than 40°C, but the enthalpy of the southern sources, where most
active volcanoes are found, is higher where some reach up to 95°C. The
chemical composition of the geothermal waters depends upon a series of
factors including the temperature vs. solubility and meteoric components
vs magmatic components ratios. Most of the low enthalpy waters are used in
resorts spas. The few high enthalpy cases are currently being explored as
sources of geothermal energy.
Brief
Biography of the Speaker:
1.- PERSONNEL ANTECEDENTS
Name: Leopoldo
López-Escobar
Born: August 05, 1940
Nacionality: Chilean
Hierarchy: Full Professor
Working Unit: Instituto de Geología Económica Aplicada (GEA), Unversidad
de Concepción. Chile
2.- ACADEMIC
DEGREES:
2.1 Bachelor in
Biology and Chemistry. Universidad Católica de Chile. February, 1963
2.2 Master of
Science in Chemistry. Massachusetts Institute of Technology (MIT),
Cambridge, Massachusetts, USA. June, 1972. Thesis: Determination of trace
mercury in organic matrices by flameless atomic absorption.
2.3 Master of
Science in Earth and Planetary Sciences. Massachusetts Institute of
Technology (MIT), Cambridge, Massachusetts, USA. June, 1972. Thesis:
Appalachian rhyolites: Geochemical data concerning their origin.
2.4 Doctor of
Philosophy (Ph.D) in Earth and Planetary Sciences. Massachusetts Institute
of Technology (MIT), Cambridge, Massachusetts, USA. February, 1975.
Thesis: Plutonic and volcanic rocks from central Chile (33° - 42°S):
Geochemical evidences regarding their petrogenesis.
2.5 Science
Doctor in Geology, July, 1976. Ratified by the Universidad de Chile,
Santiago, Chile.
3. TEACHING
ACTIVITIES AT THE UNIVERSIDAD DE CHILE AND UNIVERSIDAD DE CONCEPCION:
Thermodynamic
for Geologists.
Geochemistry.
Volcanology.
Volcanic Petrology.
Doctoral and Magister thesis advisor.
4.- RESEARCH
EXPERIENCE (PROJECTS):
National
Science Foundation.
Japan Ministry of Education.
ECOS – Chilean National Foundation (CONICYT).
Chilean National Foundation (FONDECYT).
Volkswagen Foundation.
University of Chile.
Andean Foundation.
5. NEAR 60
PUBLICATIONS IN BOOKS AND JOURNALS SUCH AS:
Analytical
Letters.
Bulletin of Volcanology.
Compte Rendus de la Académie des Sciences, Paris.
Contributions to Mineralogy and Petrology.
Earth and Planetary Sciences Letters.
Geochimical Journal.
Geological Society of America Special Papers.
Geology.
Journal of Volcanology and Geothermal Research.
Journal of Chemical Technology and Biotechnology.
Journal of Geophysical Research.
Journal of Mineralogy, Petrology and Economic Geology.
Journal of Petrology.
Journal of South American Earth Sciences.
Journal of Volcanology and Geothermal Research.
Mineralium Deposita.
Pacific Geology.
Revista Geológica de Chile.
Zentralblatt für Geologie und Paläontologi.
6. HE HAS
BEEN INVITED SPEAKER IN DIFFERENT INSTITUTIONS, SUCH AS:
MIT, USA.
Southern Methodist University, USA.
Tübingen Universität, Germany.
Heilderberg Universität, Germany.
Ibaraki University, Japan.
American Geophysical Union.
Universidad de Chile.
Universidad Católica de Chile.
Universidad de Concepción, Chile.
Universidad Católica del Norte, Chile.
Universidad Austral de Chile.
Comisión Chilena de Energía Nuclear, Chile.
Comisión Chilena del Cobre (CODELCO), Chile.
Servicio Nacional de Geología y Minería, Chile.
7. HE HAS
BEEN MEMBER OF DIFFERENT SCIENTIFIC SOCIETIES, SUCH AS:
International
Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI).
Sociedad Geológica de Chile.
The American Association for the Advancement of Sciences.
The Geological Society of America.
The New York Academy of Sciences.
The Scientific Research Society of North-America (Sigma-Xi).
