Textures, Structures and Processes of Volcanic Successions

Textures, Structures and Processes of Volcanic Successions
Author: Beatriz L.L. Coira
Publisher: Springer Nature
Total Pages: 173
Release: 2020-09-18
Genre: Nature
ISBN: 3030520102

This book provides a complete study of the Central Andean volcanism and its most distinctive features, from the lower Paleozoic to the Cenozoic times in the framework of its processes, eruptive mechanisms and geodynamic conditions. It helps readers understand the nature of the volcanic geology and the volcaniclastic related deposits linked to the evolution of the Andean continental margin. Special attention is paid to the analysis of the ancient volcanic successions and the difficulties in recognition of the original rock type caused by the effects of deformation, metamorphism and alteration. The authors use distinctive cases to describe how to apply different tools in analysis and interpretation. The selected representative, well exposed and preserved volcanic records of the Southern Central Andes analyzed in this book open new perspectives in the understanding of the volcanic processes linked to active continental margins as the Central Andes. This book will be of special interest to volcanologists and specialists in the earth sciences and appeal to both undergraduate and graduate students in geology.

Volcanoes of the Central Andes

Volcanoes of the Central Andes
Author: Shanaka L. DeSilva
Publisher: Springer
Total Pages: 216
Release: 1991-07-22
Genre: Science
ISBN: 9783540537069

With sharp satellite images, detailed figures and a highly competent description of each registered volcano, this catalog is invaluable for all earth scientists working in the Andes. Detailed descriptions of 44 major, potentially active volcanoes form the core of the book. A compendium of geographical and morphological data is followed by a summary of the structural and volcanological evolution

Quantifying the Properties of Magmatic Intrusions in the Central Andes with Geodesy

Quantifying the Properties of Magmatic Intrusions in the Central Andes with Geodesy
Author: Scott Thomas Henderson
Publisher:
Total Pages: 199
Release: 2015
Genre:
ISBN:

Volcanism in convergent arcs is the end result of magma ascending to the Earth's surface. However, many of the details of the ascent process are still debated. In particular, how long does magma persist in reservoirs at particular depths? What is the timescale and physical mechanism of ascent between reservoirs? To address these questions this thesis investigates volcanic deformation in the Central Andes Volcanic Zone of South America (CVZ, 15-28? S). The CVZ is one of three distinct volcanic arc segments in the Andes that results from the subduction of the Nazca Plate beneath the South America Plate. To begin, I compile available information for Holocene eruptions to show that despite containing the largest number of 'active volcanoes' (70), the CVZ has only 12% of recorded eruptions in the Andes. I then demonstrate through a synoptic survey with Interferometric Synthetic Aperture Radar (InSAR) that 40% of volcanic deformation events in the Andes over the last two decades occur in the CVZ. Next, I attempt to constrain the physical properties of two active intrusions in the CVZ that are unique in terms of their large size (>50km diameter) and persistent maximum rates of uplift (>1 cm/yr for>10yrs). First, I focus on Uturuncu Volcano, where I analyze InSAR and GPS data to constrain the spatial and temporal deformation pattern between 1992 and 2014. I propose a 'dipole' model of magma transport between vertically-aligned reservoirs in the lower crust and middle crust to explain the observation of uplift and peripheral subsidence at Uturuncu. The ratio of vertical to radial surface displacements for single inflation source is increased by adding a dipole reservoir, but decreased to a greater degree by crustal heterogeneity known from seismic tomography. Additionally, volume discrepancies of 1-10x between source and sink reservoirs are expected given known ranges of lower crustal material properties in the Central Andes. Finally, I present current InSAR and GPS observations at Lazufre Volcanic Complex through 10/2014 that show maintained spatial and temporal patterns of uplift compared to the previous two decades. Using a finite element model for an opening sill I demonstrate the role of layering and 3D heterogeneous structure based on newly-available seismic tomography. The proposed heterogeneous structure increases the surface displacements for homogeneous crust by less than 7% within a 10km radius of the center of uplift.

Textures, Structures and Processes of Volcanic Successions

Textures, Structures and Processes of Volcanic Successions
Author: Beatriz L.L. Coira
Publisher:
Total Pages: 0
Release: 2021
Genre:
ISBN: 9783030520113

This book provides a complete study of the Central Andean volcanism and its most distinctive features, from the lower Paleozoic to the Cenozoic times in the framework of its processes, eruptive mechanisms and geodynamic conditions. It helps readers understand the nature of the volcanic geology and the volcaniclastic related deposits linked to the evolution of the Andean continental margin. Special attention is paid to the analysis of the ancient volcanic successions and the difficulties in recognition of the original rock type caused by the effects of deformation, metamorphism and alteration. The authors use distinctive cases to describe how to apply different tools in analysis and interpretation. The selected representative, well exposed and preserved volcanic records of the Southern Central Andes analyzed in this book open new perspectives in the understanding of the volcanic processes linked to active continental margins as the Central Andes. This book will be of special interest to volcanologists and specialists in the earth sciences and appeal to both undergraduate and graduate students in geology.

Unraveling the Magmatic and Geomorphic Processes Recorded in the Topography of the Central Andes

Unraveling the Magmatic and Geomorphic Processes Recorded in the Topography of the Central Andes
Author:
Publisher:
Total Pages: 115
Release: 2015
Genre:
ISBN: 9781339401881

The topography of volcanic arcs reflects a combination of magmatic ascent processes that deform the overlying crust, volcanic eruptions that blanket the surface in lava and ash, and geomorphic processes that shape these deposits into the observable landscape and consequently record an erosional archive of surface deformation. A central goal of geomorphology is to utilize the form of landscapes to infer the processes that shape them, yet comparatively little work has been done to quantitatively understand the geomorphology of volcanic landscapes. The Central Volcanic Zone of the South American Andes (CVZ, 15-28°S) represents an ideal location for understanding the processes that shape the surface of volcanic arcs; the arid climate and well-constrained geochronology of volcanic deposits provide a geomorphic archive going back 11 Myrs, and the wealth of available geophysical imaging data provides a high-resolution glimpse into the subsurface. In this thesis I utilize geormophic and geophysical data to explore fundamental questions in volcanic landscape evolution at varying spatial scales. To begin, I examine the isostatic uplift response to crustal intrusion of mantle-derived melt, resulting in growth of the largest known active magma reservoir on Earth (the Altiplano-Puna Magma Body). From topography I show that it is possible to calculate the contribution of mantle-derived melt to crustal thickening, and I compare these results to independent seismic estimates that agree well with our data. I then use the record of volcanic deposits from the Altiplano-Puna Magma Body to estimate the flux of mantle melt into the crust, and show that predicted uplift rates are comparable to the surface uplift associated with convective lithospheric removal. Next, I explore how the topography of individual volcanic systems can help discern the style of melt ascent from deeper crustal magma reservoirs to shallow ones. Using two actively deforming volcanoes in the CVZ, Uturuncu volcano and the Lazufre volcanic complex, I use river profiles, lake shorelines, and lava flow deflections to infer each volcano's surface deformation record into the geomorphic past. Uturuncu volcano shows little signs of permanent paleo-deformation, suggesting transient ascent of magma over millenial timescales, while Lazufre's long wavelength deformation suggests continued accumulation of magma since > 0.3 Ma. Finally, I utilize the unique topography of a windswept ignimbrite erupted from the Altiplano-Puna Magma body to better understand how wind abrasion can incise bedrock canyons, a fundamental geomorphic process in arid landscapes on both Earth and Mars. Using a natural experiment within the 4 Ma Puripicar ignimbrite on the western slope of the Central Andes, we quantify the relative contribution of wind and water erosion in propagating bedrock canyons and show that wind can incise canyons an order of magnitude faster than rivers, streamlining their profiles in the process. Thus, in these chapters I illustrate how geomorphology can be a useful tool for quantifying subsurface magmatic processes, while volcanic landscapes themselves can also provide unique opportunities for understanding fundamental planetary geomorphic processes not often observed elsewhere on Earth.

Convergent Margin Magmatism in the Central Andes and Its Near Antipodes in Western Indonesia

Convergent Margin Magmatism in the Central Andes and Its Near Antipodes in Western Indonesia
Author: Morgan J. Salisbury
Publisher:
Total Pages: 131
Release: 2011
Genre:
ISBN:

This dissertation combines volcanological research of three convergent continental margins. Chapters 1 and 5 are general introductions and conclusions, respectively. Chapter 2 examines the spatiotemporal development of the Altiplano-Puna volcanic complex in the Lipez region of southwest Bolivia, a locus of a major Neogene ignimbrite flare- up, yet the least studied portion of the Altiplano-Puna volcanic complex of the Central Andes. New mapping and laser-fusion 40Ar/39Ar dating of sanidine and biotite from 56 locations, coupled with paleomagnetic data, refine the timing and volumes of ignimbrite emplacement in Bolivia and northern Chile to reveal that monotonous intermediate volcanism was prodigious and episodic throughout the complex. 40Ar/39Ar age determinations of 13 ignimbrites from northern Chile previously dated by the K-Ar method improve the overall temporal resolution of Altiplano-Puna volcanic complex development. Together with new and updated volume estimates, the new age determinations demonstrate a distinct onset of Altiplano-Puna volcanic complex ignimbrite volcanism with modest output rates beginning ~11 Ma, an episodic middle phase with the highest eruption rates between 8 and 3 Ma, followed by a general decline in volcanic output. The cyclic nature of individual caldera complexes and the spatiotemporal pattern of the volcanic field as a whole are consistent with both incremental construction of plutons as well as a composite Cordilleran batholith. Chapter 3 examines the spatiotemporal development of marine tephra deposits in deep sea sediment cores from the Sunda trench near Sumatra, which reveal evidence for seven large (minimum volume 0.6 - 6.3 km3), previously undocumented, explosive eruptions in this region over the last ~110,000 years, presumably sourced from mainland Sumatra. Sediment cores were collected within and adjacent to the Sunda trench from 3.3°N to 4.6°S at water depths between 1.8 and 5.5 km and distances of ~200 to 310 km from the active Sumatran volcanic arc. Glass shards within the tephra horizons were analyzed via the electron microprobe and laser ablation ICP-MS and define three compositional groups. Minimum volume estimates for the seven unique units are consistent with volcanic explosivity index (VEI; Newhall and Self, 1982) values of 4 - 5. The most frequent, widespread, and youngest deposits were found in the central region of the study area suggesting the central Sumatran arc as at the highest risk for large explosive eruptions. The first detailed chronological and geochemical data are presented for Tunupa volcano and nearby Huayrana lavas in chapter 4. New 40Ar/39Ar age determinations reveal edifice construction at ~1.5 Ma, a duration of ~90-240 k.y., and extrusion rates of 0.43 to 0.93 km3/k.y. Mineralogical compositional and textural data are consistent with shallow crustal storage (~7-18 km) and magma mixing. Volcano morphology, extrusion rates, mineralogy and textures are all similar to the Pleistocene to recent composite cones of the arc front, although new and available age data from the literature indicate that Western Cordilleran volcanism was concomitant with extrusion of both Huayrana (~11 Ma) and Tunupa (~1.5 Ma) lavas in the behind arc region. Arc-related volcanism was either widespread during these eruptive periods, or an additional melting mechanism was involved. Geochemical data, such as lower Ba/Nb ratios and enriched high field strength elemental concentrations, compared to volcanoes of the modern arc front suggest that Huayrana and Tunupa lavas were derived from a different source than the modern arc front. Geophysical and geochemical research in the central Andes indicate local variations in crustal and lithospheric thicknesses and compositions consistent with a dynamic continental lithosphere that has foundered in piecemeal fashion into the underlying asthenosphere throughout the mid to late Cenozoic. The data presented in this chapter for Tunupa and Huayrana indicate a complex petrogenetic origin and more research is necessary to determine the relative roles of arc and non-arc volcanism beneath the central Altiplano.