A reappraisal of episodic burial metamorphism in the Andes of central Chile

Robinson, D.; Bevins, R. E.; Aguirre, Luis; Vergara, Marcos

doi:10.1007/s00410-003-0516-4

Cited by 20 publications

(43 citation statements)

References 36 publications

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“…Additionally, the presence of zeolites (laumontite) has been recognized towards the upper parts of this formation (Levi, 1970;Levi et al, 1989;Robinson et al, 2004). This, along with the progressive decrease in chlorite layers of the interstratified chlorite-smectite phyllosilicates from the Abanico Formation through the overlying Farellones Formation, has led to the recognition that the metamorphic grade decreases with the stratigraphic height and that the mineral assemblages in the upper portions of the Abanico Formation are representative of the zeolite facies (Levi, 1970;Levi et al, 1989;Robinson et al, 2004). Locally, mineral assemblages containing the zeolites yugawaralite and wairakite record a geothermal field-type metamorphism superimposed on the regional burial metamorphic event, which has been attributed to local hydrothermal systems (Vergara et al, 1993;Fuentes, 2004).…”

Section: Geological Backgroundmentioning

confidence: 92%

“…1). The distribution of the Abanico Formation in two bands has given rise to the informal terminology of the Abanico West and Abanico East formations (e.g., Godoy et al, 1999;Nyström et al, 2003;Robinson et al, 2004;Muñoz et al, 2006). An unconformity and a hiatus of ca.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…3,000 m and the deposition and subsidence of this succession generated very low-grade metamorphic mineral assemblages characteristic of extensional settings in all its rocks (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Levi et al, 1989;Belmar, 2000;Robinson et al, 2004). These mineral assemblages are typical of the prehnite-pumpellyite facies and include prehnite, pumpellyite, epidote and/ or actinolite along with the ubiquitous phases albite, quartz and mixed-layer chlorite-smectite (Levi, 1969(Levi, , 1970Belmar, 2000;Robinson et al, 2004). Additionally, the presence of zeolites (laumontite) has been recognized towards the upper parts of this formation (Levi, 1970;Levi et al, 1989;Robinson et al, 2004).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…These mineral assemblages are typical of the prehnite-pumpellyite facies and include prehnite, pumpellyite, epidote and/ or actinolite along with the ubiquitous phases albite, quartz and mixed-layer chlorite-smectite (Levi, 1969(Levi, , 1970Belmar, 2000;Robinson et al, 2004). Additionally, the presence of zeolites (laumontite) has been recognized towards the upper parts of this formation (Levi, 1970;Levi et al, 1989;Robinson et al, 2004). This, along with the progressive decrease in chlorite layers of the interstratified chlorite-smectite phyllosilicates from the Abanico Formation through the overlying Farellones Formation, has led to the recognition that the metamorphic grade decreases with the stratigraphic height and that the mineral assemblages in the upper portions of the Abanico Formation are representative of the zeolite facies (Levi, 1970;Levi et al, 1989;Robinson et al, 2004).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…12 km thick Meso-Cenozoic succession exposed there (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Levi et al, 1989;Belmar, 2000;Robinson et al, 2004). The early studies were primarily based on petrographic descriptions (Levi, 1969(Levi, , 1970Aguirre et al, 1978Aguirre et al, , 1989Levi et al, 1989), and the incorporation of studies based on mineral chemistry in the last decade has greatly enhance our knowledge and understanding of this process in this area (Aguirre et al, 2000;Belmar, 2000;Robinson et al, 2004;Fuentes, 2004). However, there is still a lack of chemical studies addressing in detail the individual lithostratigraphic formations comprising the Meso-Cenozoic succession, even though some have been carried out at a few localities (Aguirre et al, 2000;Belmar, 2000;Fuentes, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

Muñoz

Aguirre

Vergara

et al. 2010

AndGeo

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ABSTRACT. In the El Volcán and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33º50'S), an Upper Oligocene-Lower Miocene volcanic series belonging to the Abanico Formation (Late Eocene-Early Miocene) is exposed. The rock successions outcropping in both areas, ca. 3,300 m total thickness, have been affected by very low-grade, non-deformative metamorphism in the prehnite-pumpellyite facies. This is represented by the widespread development of secondary mineral assemblages composed of epidote, mixed-layer chlorite-smectite, albite, quartz, white mica, and titanite. These mineral assemblages also contain pumpellyite, prehnite or prehnite+actinolite in a few samples. Chemical characteristics, such as low compositional variability of mixed-layer chlorite-smectite and actinolite independent from the metadomain where these phases are hosted, along with a high proportion of chlorite layers in the former, suggest that these phases closely represent the whole rock effective bulk composition. On the contrary, pumpellyite compositions show a higher variability and a strong metadomain control evidencing its lower equilibration kinetics and leaving only those that grow in the rock matrix as the more closely representative of a whole rock effective bulk compositional control. Mineral assemblages from both areas show evidence of having been formed during the same metamorphic event where reactions have ocurred equivalently between them. However, local differences in chemical variables controlling this process are recognizable. A higher CO 2 concentration in the fluids during the metamorphism in the El Volcán area than in the Rodeo de los Bueyes area is suggested by the scarce development of prehnite and the ubiquitous presence of calcite in the metamorphic assemblages of the former. Pressure and temperature of this metamorphic event have been roughly estimated to be lower than 2-3 kbar and 320ºC, respectively. Esto está representado en el desarrollo extensivo de arreglos de minerales secundarios formados por epidota, interestratificados de clorita-esmectita, albita, cuarzo, mica blanca, y titanita. Estos arreglos minerales contienen además pumpellyita, prehnita o prehnita+actinolita en algunas muestras. Las características químicas tales como una baja variabilidad composicional de los interestratificados de clorita-esmectita y actinolita independientemente del dominio donde se hospedan estas fases, junto con una alta proporción de capas de clorita en las primeras, sugieren que estas fases representan cercanamente la composición efectiva de la roca total. Por el contrario, la composición de las pumpellyitas muestra una mayor variabilidad y un fuerte control del metadominio donde éstas se desarrollan evidenciando una baja cinética de equilibrio y dejando sólo a aquellas desarrolladas en la matriz como formadas bajo un control composicional efectivo de la roca total. Los arreglos minerales de ambas áreas muestran evidencias de haberse formado bajo un mismo evento metamórfico bajo el cual las reacciones se ...

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Section: Geological Backgroundmentioning

confidence: 92%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

Muñoz

Aguirre

Vergara

et al. 2010

AndGeo

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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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Revisiting the Crustal Structure and Kinematics of the Central Andes at 33.5°S: Implications for the Mechanics of Andean Mountain Building

et al. 2018

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The Andean belt is the only present‐day active case example of a subduction‐type orogeny. However, an existing controversy opposes classical views of Andean growth as an east verging retro wedge, against a recently proposed bivergent model involving a primary west vergent crustal‐scale thrust synthetic to the subduction. We examine these diverging views by quantitatively reevaluating the orogen structural geometry and kinematics at the latitude of 33.5°S. We first provide a 3‐D geological map and build an updated section of the east vergent Aconcagua fold‐and‐thrust belt (Aconcagua FTB), which appears as a critical structural unit in this controversy. We combine these data with geological constraints on nearby structures to derive a complete and larger‐scale section of the Principal Cordillera (PC) within the fore‐arc region. We restore our section and integrate published chronological constraints to build an evolutionary model showing the evolving shortening of this fore‐arc part of the Andes. The proposed kinematics implies uplift of the Frontal Cordillera basement since ~20–25 Ma, supported by westward thrusting over a crustal ramp that transfers shortening further west across the PC. The Aconcagua FTB is evidenced as a secondary east verging roof thrust atop the large‐scale basement antiform culmination of the Frontal Cordillera. We estimate a shortening of ~27–42 km across the PC, of which only ~30% is absorbed by the Aconcagua FTB. Finally, we combine these findings with published geological data on the structure of the eastern back‐arc Andean mountain front and build a crustal‐scale cross section of the entire Andes at 33.5°S. We estimate a total orogenic shortening of ~31–55 km, mainly absorbed by crustal west vergent structures synthetic to the subduction. Our results provide quantitative key geological inferences to revisit this subduction‐type orogeny and compare it to collisional alpine‐type orogenic belts.

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A reappraisal of episodic burial metamorphism in the Andes of central Chile

Cited by 20 publications

References 36 publications

Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

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

Revisiting the Crustal Structure and Kinematics of the Central Andes at 33.5°S: Implications for the Mechanics of Andean Mountain Building

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