Quantifying the Plutonic to Volcanic Relationship Along the Puna Plateau: Implications for Cordilleran Plateau Evolution
Abstract
Quantifying well constrained plutonic to volcanic (P:V) ratios is inherently difficult because the tectonic processes that exhume intrusive bodies rarely preserve their extrusive equivalents. Conversely, active magmatic systems that have well-preserved volcanic deposits require sophisticated geophysical or geochemical approaches to estimate their plutonic roots and even when these sophisticated approaches are available, it is not always clear what constitutes a plutonic volume. Further complicating the enigmatic plutonic to volcanic relationship is the highly episodic nature of pluton emplacement where magmatic flare-ups produce several orders of magnitude more magmatism when compared against magmatic lulls. Despite this inherent difficulty, a growing body of independently measured P:V ratios (e.g. seismic tomography, geomorphic modeling, geological mapping/dating, and Zircon age spectra modeling) suggests the contribution of magmatic addition as an uplift mechanism in Cordilleran systems is much larger than is currently accepted. However, it remains unclear if these studies can be generalized to represent type behavior in Cordilleran systems or result from the non-uniform sampling imposed by the ability to measure large P:V ratios in only a few select and potentially anomalous regions of the American Cordillera. To better examine the role of magmatic processes in building Cordilleran high plateaus, we image the crustal seismic shear-wave velocity for an 800 km section (20.5°-28°S) of the active South American Cordillera (Puna Plateau). When placed in the context of existing geological and geophysical datasets, our seismic model reveals numerous mid-crustal low-velocity zones that we unambiguously interpret as the plutonic underpinnings associated with the voluminous silicic volcanics of the Puna Plateau. These larger P:V ratios are consistent with recent thermomechanical modeling of granitic magma intrusions that support the existence of long-lived, partially molten crustal magma reservoirs in continental arcs. It is our contention that integrating advances in crustal-scale seismic imaging with increased geological and geochemical sampling of volcanic deposits can further elucidate the enigmatic plutonic to volcanic relationship.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.V33E3173W
- Keywords:
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- 1211 Non-tectonic deformation;
- GEODESY AND GRAVITYDE: 7280 Volcano seismology;
- SEISMOLOGYDE: 8145 Physics of magma and magma bodies;
- TECTONOPHYSICSDE: 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGY