Composition and density model of the continental crust at an active continental margin—the Central Andes between 21° and 27°S

Lucassen, Friedrich; Becchio, Raúl; Harmon, Russell S.; Kasemann, Simone A.; Franz, Gerhard; Trumbull, Robert B.; Wilke, Hans-Gerhard; Romer, Rolf L.; Dulski, Peter

doi:10.1016/s0040-1951(01)00188-3

Cited by 151 publications

(111 citation statements)

References 73 publications

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“…The fit represents a reasonable approximation to the findings by Lucassen et al (2001) and Kösters (1999) as well as the 1s upper bound of the data from Equation 3.…”

Section: Crustsupporting

confidence: 80%

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Thermomechanical modeling of the Altiplano-Puna deformation anomaly: Multiparameter insights into magma mush reorganization

et al. 2017

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A 150-km-wide ground deformation anomaly in the Altiplano-Puna volcanic complex (APVC) of the Central Andes, with uplift centered on Uturuncu volcano and peripheral subsidence, alludes to complex subsurface stress changes. In particular, the role of a large, geophysically anomalous and partially molten reservoir (the Altiplano-Puna magma body, APMB), located ~20 km beneath the deforming surface, is still poorly understood. To explain the observed spatiotemporal ground deformation pattern, we integrate geophysical and petrological data and develop a numerical model that accounts for a mechanically heterogeneous and viscoelastic crust. Best-fit models imply subsurface stress changes due to the episodic reorganization of an interconnected vertically extended mid-crustal plumbing system composed of the APMB and a domed bulge and column structure. Measured gravity-height gradient data point toward low-density fluid migration as the dominant process behind these stress changes. We calculate a mean annual flux of ~2 × 10 7 m 3 of water-rich andesitic melt and/or magmatic water from the APMB into the bulge and column structure accompanied by modest pressure changes of <0.006 MPa/yr. Two configurations of the column fit the observations equally well: (1) a magmatic (igneous mush) column that extends to a depth of 6 km below sea level and contains trapped volatiles, or (2) a volatile-bearing hybrid column composed of an igneous mush below a solidified and permeable body that extends to sea level. Volatile loss from the bulge and column structure reverses the deformation, and explains the absence of broad (tens of kilometers) and long-term (>100 yr) residual deformation at Uturuncu. Episodic mush reorganization may be a ubiquitous characteristic of the magmatic evolution of the APVC.

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“…The fit represents a reasonable approximation to the findings by Lucassen et al (2001) and Kösters (1999) as well as the 1s upper bound of the data from Equation 3.…”

Section: Crustsupporting

confidence: 80%

“…In order to convert the 3D mechanical data for parameterization of the solid mechanics to the 2D axisymmetric models, we use a third-order polynomial fit to the density data calculated in Equation 3, the mineralogically derived densities presented in Lucassen et al (2001), and the density model reported in Kösters (1999). The resultant fit (Fig.…”

Section: Crustmentioning

confidence: 99%

Thermomechanical modeling of the Altiplano-Puna deformation anomaly: Multiparameter insights into magma mush reorganization

et al. 2017

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“…The upper crust is constructed of Mesozoic igneous and marine sedimentary rocks, Cretaceous continental volcaniclastic rocks and Miocene-to-Holocene volcanic rocks (Lucassen et al 2001). Feeley and Hacker (1995) have suggested that the upper 20 km of crust are dominated by granitoid plutons that intrude Mesozoic sedimentary rocks and that these plutons are likely to be comagmatic with the recent volcanism in the CVZ.…”

Section: Central Volcanic Zonementioning

confidence: 99%

Volcanic evolution of Volcán Aucanquilcha: a long-lived dacite volcano in the Central Andes of northern Chile

Klemetti

Grunder

2007

Bull Volcanol

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Volcán Aucanquilcha, northern Chile, has produced ∼37 km 3 of dacite (63-66 wt% silica), mainly as lavas with ubiquitous magmatic inclusions (59-62 wt% silica) over the last ∼1 million years. A pyroclastic flow deposit related to dome collapse occurs on the western side of the edifice and a debris avalanche deposit occurs on the eastern side. The >6,000-m high edifice defines a 9-km E-W ridge and lies at the center of a cluster of more than 15 volcanoes, the Aucanquilcha Volcanic Cluster, that has been active for at least the past 11 million years. The E-W alignment of vents is nearly orthogonal to the arc axis. A majority of Volcán Aucanquilcha was constructed during the first 200,000 years of eruption, whereas the last 800,000 years have added little additional volume. The peak eruptive rate during the edifice-building phases was ∼0.16 km 3 /ka and the later eruptive rate was ∼0.02 km 3 /ka. Comparable dacite volcanoes elsewhere show a similar pattern of high volcanic productivity during the early stages and punctuated rather than continuous activity. Volcán Aucanquilcha lavas are dominated by phenocrysts of plagioclase, accompanied by two populations of amphibole, biotite, clinopyroxene, Fe-Ti oxides and (or) orthopyroxene. Accessory phases include zircon, apatite and rare quartz and sanidine. One amphibole population is pargasite and the other is hornblende. The homogeneity of dacite lava from Volcán Aucanquilcha contrasts with the heterogeneity (52-66 wt% silica) at nearby Volcán Ollagüe, which has been active over roughly the same period of time. We attribute this homogeneity at Aucanquilcha to the thermal development of the crust underneath the volcano resulting from protracted magmatism there, whereas Volcán Ollagüe lacks this magmatic legacy.

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“…7(d). Although the differences range from −32 m to +52 m, larger differences occur only in isolated locations (maximum values in the Andes region), which is also documented by the rather low RMS-fit of ±3.6 m. The reason for the regional geoid anomaly in the Andes can be explained by sudden geoid height changes due to the presence of three different mass layers at three different depth levels that combine to produce the total regional geoid anomaly (Bowin, 2000;Lucassen et al, 2001;Tassara et al, 2006). Based on the constant density assumption for this particular layer, it was not possible to model this geoid anomaly properly, although the modelled mass elements reach the maximum user-defined thickness of 100 kilometres in this area.…”

Section: The Optimised Segmmentioning

confidence: 94%

Development of a Synthetic Earth Gravity Model by 3D mass optimisation based on forward modelling

2012

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Several previous Synthetic Earth Gravity Model (SEGM) simulations are based on existing information about the Earth's internal mass distribution. However, currently available information is insufficient to model the Earth's anomalous gravity field on a global scale. The low-frequency information is missing when modelling only topography, bathymetry and crust (including the Mohorovičić discontinuity), but the inclusion of information on the mantle and core does not seem to significantly improve this situation. This paper presents a method to determine a more realistic SEGM by considering simulated 3D mass distributions within the upper mantle as a proxy for all unmodelled masses within the Earth. The aim is to improve an initial SEGM based on forward gravity modelling of the topography, bathymetry and crust such that the missing low-frequency information is now included. The simulated 3D mass distribution has been derived through an interactive and iterative mass model optimisation algorithm, which minimises geoid height differences with respect to a degree-360 spherical harmonic expansion of the EGM2008 global external gravity field model. We present the developed optimisation algorithm by applying it to the development of a global SEGM that gives a reasonably close fit to EGM2008, and certainly closer than a SEGM based only on the topography, bathymetry and crust.

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Composition and density model of the continental crust at an active continental margin—the Central Andes between 21° and 27°S

Cited by 151 publications

References 73 publications

Thermomechanical modeling of the Altiplano-Puna deformation anomaly: Multiparameter insights into magma mush reorganization

Thermomechanical modeling of the Altiplano-Puna deformation anomaly: Multiparameter insights into magma mush reorganization

Volcanic evolution of Volcán Aucanquilcha: a long-lived dacite volcano in the Central Andes of northern Chile

Development of a Synthetic Earth Gravity Model by 3D mass optimisation based on forward modelling

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