Structure and development of the Andean system between 36° and 39°S

Vera, Emilio A. Rojas; Folguera, Andrés; Valcarce, Gonzalo Zamora; Bottesi, Germán; Ramos, Víctor A.

doi:10.1016/j.jog.2013.09.001

Cited by 43 publications

(38 citation statements)

References 55 publications

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“…At these latitudes, the Nazca Plate subducts with a 30°E angle beneath the South American Plate, at a velocity of 79 mm yr −1 . The development of the Andean fold and thrust belts between 33–39° S have shortened the upper crust decreasingly from north to south along strike, from 55 km (39%) to 11 km (4.78%) (Giambiagi et al ., ; Rojas Vera et al ., ).…”

Section: Tectonic and Geological Settingmentioning

confidence: 97%

Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 30′–37° S)

et al. 2015

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The Neuquén Group is an Upper Cretaceous continental sedimentary unit exhumed during the latest Miocene contractional phase occurred in the southern Central Andes, allowing a direct field observation and study of the depositional geometries. The identification of growth strata on these units surrounding the structures of the frontal parts of the Andes, sedimentological analyses and U–Pb dating of detrital components, allowed the definition of a synorogenic unit that coexisted with the uplift of the early Andean orogen since ca. 100 Ma, maximum age obtained in this work, compatible with previous assignments and constrained in the top by the deposition of the Malargüe Group, in the Maastrichtian (ca. 72 Ma). The definition of a wedge top area in this foreland basin system, where growth strata were described, permitted to identify a Late Cretaceous orogenic front and foredeep area, whose location and amplitude contrast with previous hypotheses. This wedge top area was mostly fed from the paleo‐Andes with small populations coming from sources in the cratonic area that are interpreted as a recycling in Jurassic and Lower Cretaceous sections, which contrasts with other analyses performed at the foredeep zone that have mixed sources. In particular, Permian sources are interpreted as coming directly from the cores of the basement structures, where Neopaleozoic sections are exposed, next to the synorogenic sedimentation, implying a strong incision in Late Cretaceous times with an exhumation structural level similar to the present. The maximum recognised advance for this Late Cretaceous deformation in the study area is approximately 500 km east of the Pacific trench, which constitutes an anomaly compared with neighbour segments where Late Cretaceous deformations were found considerably retracted. The geodynamic context of the sedimentation of this unit is interpreted as produced under the westward fast moving of South America, colliding with two consecutive mid‐ocean ridges during a period of important plate reorganisation. The subduction of young, anhydrous, buoyant lithosphere would have produced changes in the subduction geometry, reflected first by an arc waning/gap and subsequently by an arc migration that coexisted with synorogenic sedimentation. These magmatic and deformational processes would be the product of a shallow subduction regime, following previous proposals, which occurred in Late Cretaceous times, synchronous to the sedimentation of the Neuquén Group.

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Section: Tectonic and Geological Settingmentioning

confidence: 97%

Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 30′–37° S)

et al. 2015

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“…In this portion of the magmatic arc, oblique (~78°) plate convergence at rates of ~8 cm/yr has resulted in EW to ENE‐directed crustal shortening since the middle Miocene (Angermann et al, ; Marrett & Strecker, ; Pardo‐Casas & Molnar, ). The Miocene crustal shortening is recorded by NS to NNW‐striking, reverse faults and folds tens of km long, located immediately west of the volcanic chain (Astaburuaga, ; Piquer et al, ; Rojas Vera et al, ; Figure b). Present crustal shortening at rates of 10 −7 yr −1 is recorded by interseismic ENE‐oriented Global Positioning System (GPS) velocities that decrease in magnitude away from the trench toward the magmatic arc (Ruegg et al, ).…”

Section: Geologic Settingmentioning

confidence: 99%

Interpreting Granitic Fabrics in Terms of Rhyolitic Melt Segregation, Accumulation, and Escape Via Tectonic Filter Pressing in the Huemul Pluton, Chile

et al. 2018

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The physical process of rhyolite segregation from crystal mushes remains elusive as microstructural evidence of conventional segregation mechanisms is not available. This study provides direct fabric evidence for deformation‐assisted segregation of eruptible rhyolite in the Chilean Andean arc. The shallow (<7 km), 6.4–6.2 Ma Huemul pluton comprises domains of quartz monzonite, granite, and high‐silica granite. Compositional modeling shows that rhyolitic melt (high‐silica granite) was extracted from a granitic parent, leaving behind silicic cumulates (quartz monzonite). To understand mechanisms of rhyolite segregation, we investigate magmatic fabrics in the pluton. Anisotropy of Magnetic Susceptibility analyses reveal oblate magnetic fabrics and NNW‐striking, subvertical magnetic foliations throughout Huemul. Within the high‐silica granite, magnetic lineations are subvertical and parallel to elongate miarolitic cavities. Magnetic lineations in the quartz monzonite plunge moderately to the NNW, away from the high‐silica granite. In the quartz monzonite, the Shape‐Preferred Orientation of early feldspars is parallel to the magnetic lineation and developed while suspended in melt. Estimations of early feldspar clustering and crystallinity yield ~38% of interstitial volume loss in the quartz monzonite and no volume loss in the granite. These fabric data suggest ENE tectonic shortening coeval with rhyolite extraction. We explain these observations with a model of tectonic filter pressing in which shortening is accommodated by interstitial melt flow at slow (10−5 km3/yr) rates, segregating moderate volumes of rhyolite in Myr time scales. These interactions link plutonism, tectonic deformation, and upward mobility of eruptible rhyolite in tectonically active margins.

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“…• Malargüe fold-and-thrust belt: [252][253][254][255][256][257][258] • Chos Malal fold-and-thrust belt: [259,260] • Agrio fold-and-thrust belt: [257,261] For this paper the Malargüe fold-and-thrust belt was chosen because it clearly shows the interaction between basin inversion and the involvement of the crystalline basement in compression. The structure of the entire Andean chain along latitude 31 • S is discussed in Section 2.4 (see Figure 12).…”

Section: Malargüe Fold-and-thrust Belt In the Andesmentioning

confidence: 99%

Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

Pfiffner

2017

Geosciences

119

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This paper gives an overview of the large-scale tectonic styles encountered in orogens worldwide. Thin-skinned and thick-skinned tectonics represent two end member styles recognized in mountain ranges. Both styles are encountered in former passive margins of continental plates. Thick-skinned style including the entire crust and possibly the lithospheric mantle are associated with intracontinental contraction. Delamination of subducting continental crust and horizontal protrusion of upper plate crust into the opening gap occurs in the terminal stage of continent-continent collision. Continental crust thinned prior to contraction is likely to develop relatively thin thrust sheets of crystalline basement. A true thin-skinned type requires a detachment layer of sufficient thickness. Thickness of the décollement layer as well as the mechanical contrast between décollement layer and detached cover control the style of folding and thrusting within the detached cover units. In subduction-related orogens, thin-and thick-skinned deformation may occur several hundreds of kilometers from the plate contact zone. Basin inversion resulting from horizontal contraction may lead to the formation of basement uplifts by the combined reactivation of pre-existing normal faults and initiation of new reverse faults. In most orogens thick-skinned and thin-skinned structures both occur and evolve with a pattern where nappe stacking propagates outward and downward.

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Structure and development of the Andean system between 36° and 39°S

Cited by 43 publications

References 55 publications

Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 30′–37° S)

Cretaceous deformation of the southern Central Andes: synorogenic growth strata in the Neuquén Group (35° 30′–37° S)

Interpreting Granitic Fabrics in Terms of Rhyolitic Melt Segregation, Accumulation, and Escape Via Tectonic Filter Pressing in the Huemul Pluton, Chile

Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

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