Tertiary volcanism during extension in the Andean foothills of central Chile (33°15′–33°45′S)

Nyström, Jan Olov; Vergara, Marcos; Morata, Diego; Levi, Beatriz

doi:10.1130/b25099.1

Cited by 73 publications

(80 citation statements)

References 43 publications

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“…In the initial 143 Nd/ 144 Nd versus Th/La diagram, the data (Fig. 10c) (Lucassen et al, 2004), central Chilean Coastal Batholith rocks (Parada et al, 1999), Pacific pelagic sediments (Othmann et al, 1989), Teniente Volcanic Complex (Kay et al, 2005), Río Blanco-Los Bronces porphyries (Stern and Skewes, 1995), Farellones and Abanico formations (Nyström et al, 2003), southernmost Southern Volcanic Zone (SSVZ) (Kilian and Behrmann, 2003) and DM (Michard et al, 1985;McCulloch and Black, 1984).…”

Section: Isotopic Characteristicsmentioning

confidence: 99%

“…The southern intrusives (Cerro Mesón Alto and La Gloria pluton) are slightly more radiogenic in their 87 Sr/ 86 Sr i ratio than the northern group (San Francisco Batholith and Yerba Loca stock) at equivalent 143 Nd/ 144 Nd i values. As a result of this characteristic the southern group plots inside many fields: the Chilean Coastal Batholith of central Chile (31°-34°S) (Parada et al, 1999), where its depleted portion overlaps with the SSVZ volcanic field (Kilian and Behrmann, 2003), Teniente Volcanic Complex (Kay et al, 2005) and in parts with the Farellones and Abanico formations (Nyström et al, 2003). Río Blanco-Los Bronces porphyry (Stern and Skewes, 1995) 87 Sr/ 86 Sr i ratios are similar with the SSVZ volcanic field but 143 Nd/ 144 Nd i values are less depleted compared to the rest of the rock groups of the depleted quadrant.…”

Section: Isotopic Characteristicsmentioning

confidence: 99%

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Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

Deckart

Godoy²,

Bertens

et al. 2010

AndGeo

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ABSTRACT. Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were undertaken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32° and 34°S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Mesón Alto massif), 10.3±0.2 Ma (La Gloria pluton), 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock) and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith). Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32°S, slightly younger mineralized porphyries at Río Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758-0.512882), plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf-data variation for the younger age group (10-12 Ma; 7.04-9.54) and show a more scattered range for the older one (14-15 Ma; 8.50-15.34); both sets plot between the DM and CHUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Río Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening across the NE-SW-trending Yeso Valley transfer fault, assumed as coeval, which also explains the local lack of easterly magmatic arc front migration. Francisco). Elementos mayores y trazas excluyen una característica adakítica, como ha sido sugerido para los intrusivos porfídicos a los 32°S, los pórfidos mineralizados ligeramente más jóvenes de Río Blanco-Los Bronces y otras adakitas del Cenozoico. Las rocas volcánicas de caja son menos fraccionadas que las unidades de rocas intrusivas. La misma conclusión se obtiene con relación a los plutones de la zona norte comparados a los del sur. Valores isotópico iniciales Sr-Nd muestran una variación insignificante (0,703761-0,704118 y 0,512758-0,512882) en el campo del manto. El enriquecimiento de elementos traza puede ser explicado a través de una adición de fluidos de la placa subducida y/o por sedimentos terrígenos transportados hacia la cuña de manto y/o por un leve aporte cortical durante el ascenso del magma. Granos de circón separados de los intrusivos estériles del grupo más joven (10-12 Ma; 7,04-9,54) comparten valores i...

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Section: Isotopic Characteristicsmentioning

confidence: 99%

Section: Isotopic Characteristicsmentioning

confidence: 99%

Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

Deckart

Godoy²,

Bertens

et al. 2010

AndGeo

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“…9) (Parada et al, 1999), where its depleted portion overlaps with the SSVZ volcanic field (Kilian and Behrmann, 2003), Teniente Volcanic Complex (Kay et al, 2005) and in parts with the Farellones and Abanico formations (Nyström et al, 2003). Río Blanco-Los Bronces porphyry (Stern and Skewes, 1995) 87 Sr/ 86 Sr i ratios are similar with the SSVZ volcanic field but 143 Nd/ 144 Nd i values are less depleted compared to the rest of the rock groups of the depleted quadrant.…”

Section: Isotopic Characteristicsmentioning

confidence: 87%

Section: Isotopic Characteristicsmentioning

confidence: 99%

“…Geochemical data of four Coya Machalí (CM) and three Farellones Formation (FF) volcanic rocks from Kay et al (2005) were included since it has been suggested that coeval igneous rocks originated from the same magma source (e.g., López-Escobar et al, 1979;Nyström et al, 2003). A sample from the La Obra Plutonic Complex (LO; ca.…”

Section: Major and Trace Element Characteristicsmentioning

confidence: 99%

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Granitoides esteriles del Mioceno en la franja metalogenica de los Andes Centrales, Chile: geoquimica e isotopia de Nd-Hf y U-Pb.

Deckart¹,

Godoy²,

Bertens³

et al. 2010

Andgeo

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ABSTRACT. Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were undertaken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32° and 34°S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Mesón Alto massif), 10.3±0.2 Ma (La Gloria pluton), 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock) and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith). Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32°S, slightly younger mineralized porphyries at Río Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758-0.512882), plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf-data variation for the younger age group (10-12 Ma; 7.04-9.54) and show a more scattered range for the older one (14-15 Ma; 8.50-15.34); both sets plot between the DM and CHUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Río Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening across the NE-SW-trending Yeso Valley transfer fault, assumed as coeval, which also explains the local lack of easterly magmatic arc front migration. RESUMEN. Granitoides estériles delMioceno en la franja metalogénica de los Andes Centrales, Chile: geoquímica e isotopía de Nd-Hf y U-Pb. Cuatro complejos plutónicos del Mioceno Temprano a Medio que se encuentran ubicados entre los depósitos de pórfidos gigantes de cobre de los Andes chileno centrales fueron seleccionados para un estudio de geocronología U-Pb por LA-ICPMS y de isótopos de Hf en granos individuales de circón. Estudios geoquímicos de elementos mayores y trazas y los isótopos de Sr-Nd-Hf en roca permiten compararlos con rocas intrusivas ligeramente más jóvenes o coetáneas estériles y fértiles entre 32° y 34°S. Los granitoides estudiados muestran edades de cristalización de 11,3±0,1 Ma (masivo Cerro Mesón Alto), 10,3±0,2 Ma (plutón La Gloria), 14,9±0,2 Ma/14,9±0,1 Ma (Yerba Loca stock) y 11,2±0,1 Ma/14,7±0,1 Ma (Batolito San Francisco). Elementos mayores y trazas excluyen una característica adakítica, como ha si...

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Kinematics of the active West Andean fold-and-thrust belt (central Chile): Structure and long-term shortening rate

et al. 2017

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West verging thrusts, synthetic with the Nazca‐South America subduction interface, have been recently discovered at the western front of the Andes. At ~33°30′S, the active San Ramón fault stands as the most frontal of these west verging structures and represents a major earthquake threat for Santiago, capital city of Chile. Here we elaborate a detailed 3‐D structural map and a precise cross section of the West Andean fold‐and‐thrust belt based on field observations, satellite imagery, and previous structural data, together with digital topography. We then reconstruct the evolution of this frontal belt using a trishear kinematic approach. Our reconstruction implies westward propagation of deformation with a total shortening of 9–15 km accumulated over the last 25 Myr. An overall long‐term shortening rate of 0.1–0.5 mm/yr is deduced. The maximum value of this shortening rate compares well with the rate that may be inferred from recent trench data across the San Ramón fault and the slip associated with the past two Mw > 7 earthquakes. This suggests that the San Ramón fault is most probably the only presently active fault of the West Andean fold‐and‐thrust‐belt and that most—if not all—the deformation is to be released seismically.

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Tertiary volcanism during extension in the Andean foothills of central Chile (33°15′–33°45′S)

Cited by 73 publications

References 43 publications

Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

Granitoides esteriles del Mioceno en la franja metalogenica de los Andes Centrales, Chile: geoquimica e isotopia de Nd-Hf y U-Pb.

Kinematics of the active West Andean fold-and-thrust belt (central Chile): Structure and long-term shortening rate

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