Abstract
The role of magmatic processes as a significant mechanism for the generation of voluminous silicic crust and the development of Cordilleran plateaus remains a lingering question in part because of the inherent difficulty in quantifying plutonic volumes. Despite this difficulty, a growing body of independently measured plutonic-to-volcanic ratios suggests the volume of plutonic material in the crust related to Cordilleran magmatic systems is much larger than is previously expected. To better examine the role of crustal magmatic processes and its relationship to erupted material in Cordilleran systems, we present a continuous high-resolution crustal seismic velocity model for an ~800 km section of the active South American Cordillera (Puna Plateau). Although the plutonic-to-volcanic ratios we estimate vary along the length of the Puna Plateau, all ratios are larger than those previously reported (~30:1 compared to 5:1) implying that a significant volume of intermediate to silicic plutonic material is generated in the crust of the central South American Cordillera. Furthermore, as Cordilleran-type margins have been common since the onset of modern plate tectonics, our findings suggest that similar processes may have played a significant role in generating and/or modifying large volumes of continental crust, as observed in the continents today.
Highlights
Continental crust covers ~40% of the Earth’s surface, comprises ~70% of the total volume of crust, and is intermediate in composition[1, 2]
We use a recently developed multi-dataset inversion to examine the role of magmatic processes in the evolution and development of an ~800 km section (20.5°–28°S) of the active South American Cordilleran crust
Located along the active South American Cordillera, the Central Andean Plateau (CAP) is the largest orogenic plateau on Earth associated with long-lived subduction[10]
Summary
Located along the active South American Cordillera, the Central Andean Plateau (CAP) is the largest orogenic plateau on Earth associated with long-lived subduction[10]. Smaller in erupted volume (~3,100 km3), the ignimbrites of the southern Puna (24°–28°S) resemble the spatial distribution mapped over the first-half of the APVC flare-up with distinct arc and backarc locations[11]. Magma mixing models constrain the crustal melt contribution of ignimbrites erupting through the thick crust (~70 km) of the Puna Plateau[19] to range between 22–68% with a large amount of the Puna ignimbrites exhibiting a roughly 1:1 crust to mantle melt provenance[11, 19] Despite this wide spatial distribution, plateau ignimbrites display trace element ratios that indicate a clear arc affinity[11, 19] and are dominantly calc-alkaline in composition, with some of the older eastern (backarc) deposits exhibiting mild to strongly peraluminous compositions indicating a greater crustal melt contribution[20,21,22]. Five prominent low-velocity zones are highlighted in west-east cross-sections (Fig. 2) with correlations between Holocene volcanoes, known ignimbrite source calderas, and INSAR measured vertical surface deformation centers[28] further supporting a magmatic/ plutonic interpretation
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