El Basamento ígneo-metamórfico

CINGOLANI, CARLOS ALBERTO; ZANETTINI, JUAN C.M:; LEANZA, HÉCTOR ARMANDO

Relatorio de la Geología y Recursos Naturales de la Provincia de Neuquén

XVIII Congreso Geológico Argentino

Lugar: Neuquén; Año: 2011;

RESUMEN Las exposiciones más septentrionales del basamento ígneo metamórfico de la provincia del Neuquén se desarrollan en la comarca de Varvarco, pero los afloramientos mayores que se reconocen entre la latitud del paso de Pino Hachado y el límite con la provincia de Río Negro. El ‘basamento’ ha recibido diversas denominaciones como Fm. Colohuincul, Fm. (Ectinita) Piedra Santa y Ectinita Guaraco Norte, para las rocas metamórficas y Fm. Mamil Choique para las rocas ígneas intrusivas. La Fm. Colohuincul reúne a las metamorfitas expuestas en afloramientos dispersos en la Cordillera Neuquina. De acuerdo a las evidencias isotópicas modernas las edades se agrupan en su mayoría dentro del Devónico. La Fm. Mamil Choique que se desarrolla en el sudeste del territorio provincial (zona de Piedra del Águila) se interpreta como un complejo plutónico-metamórfico del Neopaleozoico (ca. 300 Ma). Por su parte, el Granito Yuncón es un cuerpo de dimensiones batolíticas aflorante en la misma zona que fuera reconocido en los mapeos regionales como parte del Basamento Cristalino. Su posible edad varía entre el Neopaleozoico y Triásico. La Ectinita Guaraco Norte está compuesta por pizarras y esquistos que se exponen en la región de Varvarco y sería correlacionable con otra unidad considerada dentro del ‘basamento» del Neuquén conocida como Ectinita Piedra Santa. Esta última se desarrolla en la comarca delimitada por los parajes de Pino Hachado, Sainuco y Primeros Pinos y su principal afloramiento es en el cordón de la Piedra Santa, donde se encuentra su localidad tipo. El aporte de nuevos datos petrológicos y geocronológicos con metodologías de alta resolución, ha permitido por un lado descartar la presencia del Neoproterozoico dentro del basamento del Neuquén y ajustar su evolución tecto-magmática principal dentro del Devónico y destacar la superposición de actividad magmática durante el Neopaleozoico y Triásico. Los mapeos regionales más recientes han permitido ampliar los conocimientos con nuevos afloramientos y mejorar las interpretaciones evolutivas y posibles correlaciones con áreas vecinas. Se destaca El basamento neuquino se destaca por registrar una historia geológica clave vinculada a la posibilidad de acreción de terrenos como Chilenia y Patagonia, en el margen convergente de Gondwana durante el Meso y Neopaleozoico respectivamente. Por su parte, el Granito Yuncón es un cuerpo de dimensiones batolíticas aflorante en la misma zona que fuera reconocido en los mapeos regionales como parte del Basamento Cristalino. Su posible edad varía entre el Neopaleozoico y Triásico. La Ectinita Guaraco Norte está compuesta por pizarras y esquistos que se exponen en la región de Varvarco y sería correlacionable con otra unidad considerada dentro del ‘basamento» del Neuquén conocida como Ectinita Piedra Santa. Esta última se desarrolla en la comarca delimitada por los parajes de Pino Hachado, Sainuco y Primeros Pinos y su principal afloramiento es en el cordón de la Piedra Santa, donde se encuentra su localidad tipo. El aporte de nuevos datos petrológicos y geocronológicos con metodologías de alta resolución, ha permitido por un lado descartar la presencia del Neoproterozoico dentro del basamento del Neuquén y ajustar su evolución tecto-magmática principal dentro del Devónico y destacar la superposición de actividad magmática durante el Neopaleozoico y Triásico. Los mapeos regionales más recientes han permitido ampliar los conocimientos con nuevos afloramientos y mejorar las interpretaciones evolutivas y posibles correlaciones con áreas vecinas. Se destaca El basamento neuquino se destaca por registrar una historia geológica clave vinculada a la posibilidad de acreción de terrenos como Chilenia y Patagonia, en el margen convergente de Gondwana durante el Meso y Neopaleozoico respectivamente. ca. 300 Ma).  Por su parte, el Granito Yuncón es un cuerpo de dimensiones batolíticas aflorante en la misma zona que fuera reconocido en los mapeos regionales como parte del Basamento Cristalino. Su posible edad varía entre el Neopaleozoico y Triásico. La Ectinita Guaraco Norte está compuesta por pizarras y esquistos que se exponen en la región de Varvarco y sería correlacionable con otra unidad considerada dentro del ‘basamento» del Neuquén conocida como Ectinita Piedra Santa. Esta última se desarrolla en la comarca delimitada por los parajes de Pino Hachado, Sainuco y Primeros Pinos y su principal afloramiento es en el cordón de la Piedra Santa, donde se encuentra su localidad tipo. El aporte de nuevos datos petrológicos y geocronológicos con metodologías de alta resolución, ha permitido por un lado descartar la presencia del Neoproterozoico dentro del basamento del Neuquén y ajustar su evolución tecto-magmática principal dentro del Devónico y destacar la superposición de actividad magmática durante el Neopaleozoico y Triásico. Los mapeos regionales más recientes han permitido ampliar los conocimientos con nuevos afloramientos y mejorar las interpretaciones evolutivas y posibles correlaciones con áreas vecinas. Se destaca El basamento neuquino se destaca por registrar una historia geológica clave vinculada a la posibilidad de acreción de terrenos como Chilenia y Patagonia, en el margen convergente de Gondwana durante el Meso y Neopaleozoico respectivamente. Palabras clave: Basamento, rocas metamórficas, complejos plutónicos, evolución paleozoica. Basamento, rocas metamórficas, complejos plutónicos, evolución paleozoica. ABSTRACTBasamento, rocas metamórficas, complejos plutónicos, evolución paleozoica. ABSTRACT The igneous-metamorphic basement.- The most northern outcrops of the igneous-metamorphic basement of the Neuquén province are located in the Varvarco area, but widespread outcrops occur between the latitudes of Pino Hachado and at the boundary with the Río Negro Province. This basement has received several nominations like Colohuincul Fm. and Piedra Santa and Guaraco Norte Ectinites, for the metamorphic rocks. The intrusive igneous rocks are included within the Mamil Choique Fm. The Colohuincul Fm comprises the isolated metamorphic rocks exposed in the Cordillera of Neuquén. In the type locality, three main lithologies are described: schist, phyllite and quartzite rocks, and they are also intruded by magmatic arc granitoids. The isotopic data shows that the ages are grouped mostly within the Devonian. The Mamil Choique Fm is exposed in the southwestern border of the Province, in the Piedra del Águila area and it is interpreted as an igneous-metamorphic complex of Neopaleozoic age (c. 300 Ma). On the other hand, the Yuncón Granite is a pluton cropping out in the same area and was recognized in regional maps as part of the crystalline basement. Its crystallization age was assigned tentatively to the Neopaleozoic and cooling-age during the Triassic. The Guaraco Norte Ectinite is composed by slates and schists exposed in the Varvarco area. This unit can be correlated with the Piedra Santa Ectinite that is exposed in the localities of Pino Hachado, Sainuco and Primeros Pinos and the main outcrops are restricted within the type locality of the Piedra Santa Range. New petrologic and geochronologic data provided by high resolution methodologies and published during recent years, allowed us to discard the presence of Neoproterozoic rocks within the Neuquén Basement and adjust its evolution to the main tecto-magmatic event that took place during the Devonian, with latter magmatic activity during the Neopaleozoic and the Triassic. The last regional mapping projects have provided new insights on the geological evolution and were discovered new outcrops that enhanced the regional correlations with neighboring areas. It is underlined that the Neuquén Basement has a key role in the interpretation of accreted terranes (Chilenia and Patagonia) in the convergent margin of Gondwana during the Meso and Neo-Paleozoic times. are located in the Varvarco area, but widespread outcrops occur between the latitudes of Pino Hachado and at the boundary with the Río Negro Province. This basement has received several nominations like Colohuincul Fm. and Piedra Santa and Guaraco Norte Ectinites, for the metamorphic rocks. The intrusive igneous rocks are included within the Mamil Choique Fm. The Colohuincul Fm comprises the isolated metamorphic rocks exposed in the Cordillera of Neuquén. In the type locality, three main lithologies are described: schist, phyllite and quartzite rocks, and they are also intruded by magmatic arc granitoids. The isotopic data shows that the ages are grouped mostly within the Devonian. The Mamil Choique Fm is exposed in the southwestern border of the Province, in the Piedra del Águila area and it is interpreted as an igneous-metamorphic complex of Neopaleozoic age (c. 300 Ma). On the other hand, the Yuncón Granite is a pluton cropping out in the same area and was recognized in regional maps as part of the crystalline basement. Its crystallization age was assigned tentatively to the Neopaleozoic and cooling-age during the Triassic. The Guaraco Norte Ectinite is composed by slates and schists exposed in the Varvarco area. This unit can be correlated with the Piedra Santa Ectinite that is exposed in the localities of Pino Hachado, Sainuco and Primeros Pinos and the main outcrops are restricted within the type locality of the Piedra Santa Range. New petrologic and geochronologic data provided by high resolution methodologies and published during recent years, allowed us to discard the presence of Neoproterozoic rocks within the Neuquén Basement and adjust its evolution to the main tecto-magmatic event that took place during the Devonian, with latter magmatic activity during the Neopaleozoic and the Triassic. The last regional mapping projects have provided new insights on the geological evolution and were discovered new outcrops that enhanced the regional correlations with neighboring areas. It is underlined that the Neuquén Basement has a key role in the interpretation of accreted terranes (Chilenia and Patagonia) in the convergent margin of Gondwana during the Meso and Neo-Paleozoic times. The most northern outcrops of the igneous-metamorphic basement of the Neuquén province are located in the Varvarco area, but widespread outcrops occur between the latitudes of Pino Hachado and at the boundary with the Río Negro Province. This basement has received several nominations like Colohuincul Fm. and Piedra Santa and Guaraco Norte Ectinites, for the metamorphic rocks. The intrusive igneous rocks are included within the Mamil Choique Fm. The Colohuincul Fm comprises the isolated metamorphic rocks exposed in the Cordillera of Neuquén. In the type locality, three main lithologies are described: schist, phyllite and quartzite rocks, and they are also intruded by magmatic arc granitoids. The isotopic data shows that the ages are grouped mostly within the Devonian. The Mamil Choique Fm is exposed in the southwestern border of the Province, in the Piedra del Águila area and it is interpreted as an igneous-metamorphic complex of Neopaleozoic age (c. 300 Ma). On the other hand, the Yuncón Granite is a pluton cropping out in the same area and was recognized in regional maps as part of the crystalline basement. Its crystallization age was assigned tentatively to the Neopaleozoic and cooling-age during the Triassic. The Guaraco Norte Ectinite is composed by slates and schists exposed in the Varvarco area. This unit can be correlated with the Piedra Santa Ectinite that is exposed in the localities of Pino Hachado, Sainuco and Primeros Pinos and the main outcrops are restricted within the type locality of the Piedra Santa Range. New petrologic and geochronologic data provided by high resolution methodologies and published during recent years, allowed us to discard the presence of Neoproterozoic rocks within the Neuquén Basement and adjust its evolution to the main tecto-magmatic event that took place during the Devonian, with latter magmatic activity during the Neopaleozoic and the Triassic. The last regional mapping projects have provided new insights on the geological evolution and were discovered new outcrops that enhanced the regional correlations with neighboring areas. It is underlined that the Neuquén Basement has a key role in the interpretation of accreted terranes (Chilenia and Patagonia) in the convergent margin of Gondwana during the Meso and Neo-Paleozoic times. Key words: Basement, metamorphic rocks, plutonic complexes, Paleozoic evolutionBasement, metamorphic rocks, plutonic complexes, Paleozoic evolution