Upper and Middle Crustal Velocity Structure of the Colombian Andes From Ambient Noise Tomography: Investigating Subduction‐Related Magmatism in the Overriding Plate

Abstract

New maps of S velocity variation for the upper and middle crust making up the northwestern most corner of South America have been developed from cross correlation of ambient seismic noise at 52 broadband stations in the region. Over 1,300 empirical Green's functions, reconstructing the Rayleigh wave portion of the seismic wavefield, were obtained after time and frequency‐domain normalization of the ambient noise recordings and stacking of 48 months of normalized data. Interstation phase and group velocity curves were then measured in the 6–38 s period range and tomographically inverted to produce maps of phase and group velocity variation in a 0.5° × 0.5° grid. Velocity‐depth profiles were developed for each node after simultaneously inverting phase and group velocity curves and combined to produce 3‐D maps of S velocity variation for the region. The S velocity models reveal a ~7 km thick sedimentary cover in the Caribbean region, the Magdalena Valley, and the Cordillera Oriental, as well as crustal thicknesses in the Pacific and Caribbean region under ~35 km, consistent with previous studies. They also display zones of slow velocity at 25–35 km depth under regions of both active and inactive volcanism, suggesting the presence of melts that carry the signature of segmented subduction into the overriding plate. A low‐velocity zone in the same depth range is imaged under the Lower Magdalena Basin in the Caribbean region, which may represent either sublithospheric melts ponding at midcrustal levels after breaching through a fractured Caribbean flat slab or fluid migration through major faults within the Caribbean crust.

Constraints on the Cenozoic Deformation of the Northern Eastern Cordillera, Colombia

“…This magmatic phase has been related to slab shallowing (Wagner et al, ). Furthermore, shear‐wave models reveal the presence of a low‐velocity domain below the EC, related to the presence of fluids and magma below the belt (Poveda et al, ). This anomaly is especially clear beneath the Paipa‐Iza volcanic area and below the Cocuy Sierra at depths shallower than 35 km (Poveda et al, ).…”

The role of subducted sediments in the formation of intermediate mantle-derived magmas from the Northern Colombian Andes

“…Volcanoes of the NVP are emplaced on top of a ~42-52 km thick continental crust that becomes slightly thicker southwards (up to 52) (Poveda et al, 2015;Poveda et al, 2018;Yarce et al, 2014), following a tectonic lineament defined by the right-lateral Palestina fault system (Borrero et al, 2009). Magmas of the NVP intrude and rest on top of Paleozoic metapelites metamorphosed at green-schist and amphibolite facies of the Cajamarca Complex, which comprises the metamorphic core of the Colombian Central Cordillera (Villagómez et al, 2011).…”

Joint Inversion of Receiver Functions and Surface‐Wave Dispersion in the Pantanal Wetlands: Implications for Basin Formation

“…Indeed, if the TBL were projected in the SW direction under the Pantanal basin, stations MURT and ANTJ would lie close to the lineament as well (see Figure ). The presence of this layer under stations PTET and SALV would be harder to explain, but we note that similar lateral offsets in present‐day arc magmatism do exist on continents (e.g., Poveda et al, ). Thus, if our interpretation were correct, this crustal type would be around 55 km thick and include a 10–15 km thick layer of mafic cumulates at its base.…”