Seeing past the effects of re-equilibration to reconstruct magmatic gradients in plutons: La Gloria Pluton, central Chilean Andes

Cornejo, Paula; Mahood, Gail A.

doi:10.1007/s004100050273

Cited by 41 publications

(42 citation statements)

References 11 publications

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“…4e). Similar compositional variations (from granodioritic to quartzmonzodioritic; LGP*) for the La Gloria Pluton have been already described by Cornejo and Mahood (1997). Furthermore, MADSB samples GD-13 and GD-19 plot in the granodioritic field, whereas MADSB (GD-20) classifies as quartzdiorite.…”

Section: Petrographysupporting

confidence: 74%

“…1, Table 1). Where possible, we include geochemical data and petrographic information of La Gloria Pluton samples (LGP*) from Cornejo and Mahood (1997) to increase the data set. The goal of this comparison is to determine which plutonic unit mainly provided the blocks of this unconsolidated deposit.…”

Section: Petrographic and Geochemical Datamentioning

confidence: 99%

“…The third LGP and CMA samples (Deckart et al, 2010) as well as MADSB samples GD-13, GD-16 and GD-21 are represented in the granitic field. LGP* samples from Cornejo and Mahood (1997) occupy the same fields as LGP samples taken from Deckart et al (2010), i.e., quartzmonzonitic to granitic. The CAI sample plots at the limit of the quartzmonzonite and quartz syenite fields, separated from the rest.…”

Section: Geochemistrymentioning

confidence: 99%

“…Oligo-Miocene rocks (Abanico and Farellones Formations); 3. plutonic rocks; 4. Mesón Alto deposit; 5. alluvial deposits; 6. water bodies; 7. faults; 8. landslide scarp; CMA=Cerro Mesón Alto Massif, LGP=La Gloria Pluton, LGP*=La Gloria Pluton (Cornejo and Mahood, 1997), CAI=Cerro Aparejo Intrusion.…”

Section: Introductionmentioning

confidence: 99%

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Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Deckart

Pinochet

Sepúlveda

et al. 2014

Andgeo

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ABSTRACT. The Mesón Alto chaotic deposit, located in the Main Cordillera at about 33°40'S, is an important landform with a volume of ca. 4.5 km 3 unconsolidated material deposited downstream of the Yeso Dam in the Yeso Valley, Río Maipo drainage basin. Historical work related this large deposit to a glacial origin whereas later on, it was assigned to a megalandslide that originated in the Cerro Mesón Alto Massif. First results of integrated fieldwork along with petrographic and geochemical laboratory work on granitoid blocks from five different portions of the deposit, compared with the major outcropping intrusive units in the neighbourhood (La Gloria Pluton, Cerro Mesón Alto Massif and Cerro Aparejo Intrusion) point to a landslide origin of the surface blocks. The results suggest that granitoid fragments of the deposit most likely belong to the Cerro Mesón Alto Massif, the proposed source of the rock avalanche. However, morphometric parameters and field observations support the idea of a rock avalanche deposited on top of glacial material. Therefore, the Mesón Alto deposit should be assigned to a composite origin. Confirmation of a post-glacial, large volume rock avalanche in a strategic area for existent infrastructure for Santiago water supply and ongoing energy projects is fundamental for a correct hazard and risk assessment of the region. Keywords: Mesón Alto deposit, Landslide, Glacial material, Granitoids, Yeso Valley, Geological hazard. RESUMEN. Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa? El depósito caótico de Mesón Alto, localizado en la cordillera Principal a los aproximadamente 33°40'S, es un rasgo morfológico con un volumen de 4,5 km 3 de material no consolidado depositado aguas abajo del embalse El Yeso, en el valle del río Yeso, cuenca del río Maipo. Históricamente, este enorme depósito se relacionó con un origen glacial, mientras que más tarde fue asignado a un megadeslizamiento proveniente del macizo Cerro Mesón Alto. Los primeros resultados de un trabajo integrado de campo, análisis petrológico y geoquímico de bloques de granitoides de diferentes sectores del depósito, comparados con datos de las mayores unidades intrusivas de la zona (el plutón La Gloria, el macizo Cerro Mesón Alto y el intrusivo Cerro Aparejo) apuntan a un depósito compuesto por bloques superficiales de procedencia de remoción en masa. Los resultados sugieren que los granitoides del depósito provienen del sector Cerro Mesón Alto. Sin embargo, observaciones de campo y parámetros morfométricos soportan la idea de una avalancha de rocas emplazada sobre material glacial. En consecuencia, se asignaría un origen compuesto al depósito del Mesón Alto. La confirmación de una remoción en masa postglacial de gran volumen en un área con infraestructura crítica para suministro de agua de Santiago y donde se emplazan proyectos energéticos en desarrollo es clave para realizar correctas evaluaciones del peligro y riesgo geol...

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Section: Petrographysupporting

confidence: 74%

Section: Petrographic and Geochemical Datamentioning

confidence: 99%

Section: Geochemistrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Deckart

Pinochet

Sepúlveda

et al. 2014

Andgeo

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“…A single K-Ar age on biotite of 9.8 Ma (R.E. Drake, unpublished) has been presented for the La Gloria pluton by Cornejo and Mahood (1997) and interpreted as a cooling age, possibly close to its crystallization age. The Cerro Mesón Alto granitoid, which represents the intrusive lower unit of the andesitic mountain peak, was dated by Kurtz et al (1997), who named it after its outcrop south of 'Lago Yeso' rather than after its outcrop as a part of the Cerro Mesón Alto, and assigned it to the Teniente Plutonic Complex on the basis of a hornblende 40 Ar/ 39 Ar age of 12.4±2.5 Ma.…”

Section: Plutonism At 33°-34°s: Current Interpretationmentioning

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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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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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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Seeing past the effects of re-equilibration to reconstruct magmatic gradients in plutons: La Gloria Pluton, central Chilean Andes

Cited by 41 publications

References 11 publications

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

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

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

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