Magnetic characterization of a retroarc extensional basin: The Loncopué Trough

Abstract

The Loncopué Trough is a Pliocene to Quaternary extensional basin developed over the hinterland area of the Southern Central Andes. This basin is bounded by two neotectonic extensional fault systems delimiting a narrow topographic low. Previous studies have mostly focused on structural and geochemical aspects of this feature. However, geophysical surveys, aimed to unravel deep structure beneath a thick-younger than 5 My volcanic coverage, are scarce and based their interpretations on low resolution data sets. In this study, we collected new aeromagnetic data with the objective of characterizing the magnetic properties of the crust in the Loncopué Through and nearby zones. Additionally, we analyze the spatial relation between geological structures, volcanic fields and magnetic data. In order to highlight the boundaries of the magnetic sources and calculate the basement depth, we applied derivative techniques and the source parameter imaging. Also, we estimated an effective susceptibility model using the Magnetization Vector Inversion method, which takes into account the combined effects of remanence and induced magnetization. To determine the thermal structure of the area, we calculated the Curie depth points through the spectral analysis technique. From the analysis of magnetic data we were able to characterize the main structures and lineaments associated with this retroarc extensional trough. Notably, only the Loncopué eastern fault system seems to be a crustal-scale tectonic feature, while E-W-, ENE-and ESE-trending lineaments are interpreted as relatively minor structures segmenting the basement. Finally, our susceptibility model, together with the analysis of the Curie point, revealed potential magmatic/hydrothermal reservoirs in the Copahue volcano, and the Codihue and Cajón de Almanza regions that could be connected at depth forming a regional magmatic body.

Tectonic controls on geomorphology and spatial distribution of monogenetic volcanoes in the Central Southern Volcanic Zone of the Andes (Argentina)

“…Geological mapping and fieldwork in the study area also suggest multiple episodes of monogenetic activity in the region (Rojas Vera et al, 2014;Pesce et al, 2019).…”

“…1B). This is a narrow, N-S topographic depression of 200 km in length located between the 36°30' and 39°S and limited by the Agrio fold and thrust belt to the east and the volcanic arc to the west (Folguera et al, 2010;Rojas Vera et al, 2010Folguera et al, 2011;Pesce et al, 2019). The basal volcano-sedimentary infill of the axial part of the depression starts in the early Pliocene (Cola de Zorro Formation), followed by silicic distal pyroclastic sequences associated with the development of a series of calderas in the west during Pleistocene times, and the posterior emplacement of a basaltic cover in the western sector (Rojas Vera et al, 2014;Pesce, et al, 2019).…”

“…2A). In this step, we also rely on the available geological maps that contain the distribution of monogenetic deposits (i.e., lava flows) for some regions in the study area (Kay et al, 2006;Melnick and Echtler, 2006;Cembrano and Lara, 2009;Varekamp et al, 2010;Rojas Vera et al, 2014;Pesce et al, 2019Pesce et al, , 2020. This preliminary dataset was then verified using satellite imagery in ArcMap®.…”

“…Another important feature in the CSVZ is the Loncopué Trough (Rojas Vera et al, 2014;Pesce et al, 2019;. Located between the main volcanic arc and the Agrio Fold and Thrust Belt, this 300 km long extensional structure controls the occurrence of monogenetic volcanism (Rojas Vera et al, 2014; Fig.…”

Tectonic controls on geomorphology and spatial distribution of monogenetic volcanoes in the Central Southern Volcanic Zone of the Andes (Argentina)

“…1B). This is a narrow, N-S topographic depression of 200 km in length located between the 36 • 30 ′ and 39 • S and limited by the Agrio fold and thrust belt to the east and the volcanic arc to the west (Folguera et al, 2010;Rojas Vera et al, 2010Folguera et al, 2011;Pesce et al, 2019). The basal volcanosedimentary infill of the axial part of the depression starts in the early Pliocene (Cola de Zorro Formation), followed by silicic distal pyroclastic sequences associated with the development of a series of calderas in the west during Pleistocene times, and the posterior emplacement of a basaltic cover in the western sector (Rojas Vera et al, 2014;Pesce et al, 2019).…”