Balancing crustal thickening in arcs by tectonic vs. magmatic means

Haschke, Michael; Günther, Andreas

doi:10.1130/g19945.1

Cited by 100 publications

(99 citation statements)

References 20 publications

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“…Shape and location of this fan match the Eocene transpressional structure responsible for the proto-Precordillera as found further south (22°-23°S) [Maksaev and Zentilli, 1999;Haschke and Günther, 2003]. Here it was shown to form a classical positive flower structure.…”

Section: Resultssupporting

confidence: 66%

“…An average sedimentation rate of 0.008 cm/yr calculated for APF 3 yields an estimate of $27-29 Ma for the base of the APF. This value correlates with the reported age of $29 Ma of the widespread unconformity at the base of the ''Gravas de Atacama'' that overlies the same type of basement further south [Haschke and Günther, 2003]. The entire age data set from the APF and the overlying formations therefore embraces the time from the middle Oligocene to the late Pleistocene, i.e., the time of uplift of the Altiplano plateau (Figure 3).…”

Section: Altos De Pica Formationsupporting

confidence: 78%

“…For the latter, the elevation estimate for the Oligocene makes use of results by Haschke and Günther [2003] at 20°-22°S on Eocene crustal shortening of the CretaceousPaleogene arc constituting the Precordillera, as well as of fission track data [Maksaev and Zentilli, 1999]. Initial crustal thickness prior to the Eocene is estimated to some 37 km based on sedimentation above sea level (continental red beds of Cretaceous/Paleocene age grading into shallow water carbonates in the back arc to the east) and geochemical data [Haschke and Günther, 2003]. Observed Eocene shortening (9 km) added a minimum of 5.4 km to crustal thickness.…”

Section: Restoration Proceduresmentioning

confidence: 99%

“…A maximum addition of 8 km (equivalent to nearly doubling the observed shortening) is estimated from the maximum crustal thickness of 45 km allowed by geochemical data. Minimum average erosion in the Eocene/Oligocene of 1.2 ± 0.3 km was derived from the volume of eroded hanging walls of Eocene thrusts (based on the above results from Haschke and Günther [2003]). The maximum erosion estimate is some 4 -5 km from apatite fission track data.…”

Section: Restoration Proceduresmentioning

confidence: 99%

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Uplift of the western Altiplano plateau: Evidence from the Precordillera between 20° and 21°S (northern Chile)

2004

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We present a quantitative reconstruction of uplift of the western flank of the Altiplano plateau (central Andes), one of the largest monoclines on the Earth, on the basis of an analysis of tectonic structures, syntectonic deposits, and geophysical data. Uplift occurred on a west vergent, slowly propagating system of high‐angle reverse faults merging into a joint detachment that ramps down to midcrustal levels below the plateau edge. The upper ramps determine local fold geometries while the lower ramp controls large‐scale surface tilting and uplift. At 20°S, this fault system was active between ∼30 Ma and 5–10 Ma, with maximum shortening rates of 0.22 mm/yr between 17 and 10 Ma. It generated some 2600 m of surface uplift with only minor shortening of ∼3000 m. Its activity was largely synchronous to eruption of large‐volume ignimbrites from a midcrustal source. Geophysical data indicate that the fault system localized deformation at the boundary between a cool, strong forearc crust and a presumably fluid‐rich and/or partially molten zone underneath the plateau area. The systematic relation between crustal melting and shortening with uplift at the western plateau margin can be traced along most of the plateau flank, with a stepwise decrease in age of deformation and magmatism toward the south indicating discontinuous addition of plateau segments. Crustal thickening to as much as 70 km from westward underthrusting in the back arc parts of the plateau isostatically compensated the tectonic surface uplift and monocline formation with respect to a stable forearc, which only reacted with minor tilting.

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Section: Resultssupporting

confidence: 66%

Section: Altos De Pica Formationsupporting

confidence: 78%

Section: Restoration Proceduresmentioning

confidence: 99%

Section: Restoration Proceduresmentioning

confidence: 99%

See 2 more Smart Citations

Uplift of the western Altiplano plateau: Evidence from the Precordillera between 20° and 21°S (northern Chile)

2004

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“…deeper than those associated with the EPRIM samples (e.g., Haschke et al, 2002;Haschke and Günther, 2003;Chung et al, 2009). The magma source depths of MPST is probably related with the underplated mafic magmas and increasing crustal thickness during Eocene and Oligocene (e.g., Chung et al, 2009).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Geochemical differences between subduction- and collision-related copper-bearing porphyries and implications for metallogenesis

Chen

Wang

et al. 2015

Ore Geology Reviews

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Porphyry Cu (-Mo-Au) deposits occur not only in continental margin-arc settings (subduction-related porphyry Cu deposits, such as those along the eastern Pacific Rim (EPRIM)), but also in continent-continent collisional orogenic belts (collision-related porphyry Cu deposits, such as those in southern Tibet). These Cu-mineralized porphyries, which develop in contrasting tectonic settings, are characterized by some different trace element (e.g., Th, and Y) concentrations and their ratios (e.g., Sr/Y, and La/Yb), suggesting that their source magmas probably developed by different processes. Subduction-related porphyry Cu mineralization on the EPRIM is associated with intermediate to felsic calc-alkaline magmas derived from primitive basaltic magmas that pooled beneath the lower crust and underwent melting, assimilation, storage, and homogenization (MASH), whereas K-enriched collision-related porphyry Cu mineralization was associated with underplating of subduction-modified basaltic materials beneath the lower crust (with subsequent transformation into amphibolites and eclogite amphibolites), and resulted from partial melting of the newly formed thickened lower crust. These different processes led to the collision-related porphyry Cu deposits associated with adakitic magmas enriched by the addition of melts, and the subduction-related porphyry Cu deposits associated with magmas comprising all compositions between normal arc rocks and adakitic rocks, all of which were associated with fluid-dominated enrichment process.In subduction-related Cu porphyry magmas, the oxidation state (fO 2 ), the concentrations of chalcophile metals, and other volatiles (e.g., S and Cl), and the abundance of water were directly controlled by the composition of the primary arc basaltic magma. In contrast, the high Cu concentrations and fO 2 values of collision-related Cu porphyry magmas were indirectly derived from subduction modified magmas, and the large amount of water and other volatiles in these magmas were controlled in part by partial melting of amphibolite derived from arc basalts that were underplated beneath the lower crust, and in part by the contribution from the rising potassic and ultrapotassic magmas. Both subduction-and collision-related porphyries are enriched in potassium, and were associated with crustal thickening. Their high K 2 O contents were primarily as a result of the inheritance of enriched mantle components and/or mixing with contemporaneous ultrapotassic magmas.

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A mass balance and isostasy model: Exploring the interplay between magmatism, deformation and surface erosion in continental arcs using central Sierra Nevada as a case study

Cao¹,

Paterson

2016

Geochem Geophys Geosyst

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A one-dimensional mass balance and isostasy model is used to explore the feedbacks between magmatism, deformation and surface erosion and how they together affect crustal thickness, elevation, and exhumation in a continental arc. The model is applied to central Sierra Nevada in California by parameterizing magma volume and deformational strain. The simulations capture the first-order MesozoicCenozoic histories of crustal thickness, elevation and erosion including moderate Triassic crustal thickening and Jurassic crustal thinning followed by a strong Cretaceous crustal thickening, the latter resulting in a 60-70 km-thick crust plus a 20 km-thick arc eclogitic root, and a $5 km elevation in the Late Cretaceous. The contribution of contractional deformation to the crustal thickening is twice that of the magmatism. The contribution to elevation from magmatism is dampened by the formation of an eclogitic root. Erosion rate increases with the magnitude of crustal thickening (by magmatism and deformation) but its peak rate always lags behind the peak rate of thickening. We propose that thickened crust initially promotes magma generation by downward transport of materials to the magma source region, which may eventually jam the mantle wedge affecting the retro-arc underthrusting process and reducing arc magmatism.

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Balancing crustal thickening in arcs by tectonic vs. magmatic means

Cited by 100 publications

References 20 publications

Uplift of the western Altiplano plateau: Evidence from the Precordillera between 20° and 21°S (northern Chile)

Uplift of the western Altiplano plateau: Evidence from the Precordillera between 20° and 21°S (northern Chile)

Geochemical differences between subduction- and collision-related copper-bearing porphyries and implications for metallogenesis

A mass balance and isostasy model: Exploring the interplay between magmatism, deformation and surface erosion in continental arcs using central Sierra Nevada as a case study

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