Understanding the fracture-volcanism pattern: gravity and magnetic characterization of the Early Jurassic pull-apart structure in the Western Northpatagonian Region, Argentina

Abstract

The Early Jurassic outcrops of the Río Negro Province provide a remarkable opportunity to evaluate the genetic significance of the potential anomalies related to the syn-rift structures. The Cañadón Chileno Complex pull-apart structure consists of two different areas, northern and southern, infilled with sedimentary and volcanic deposits. The residual gravity data indicate that the thicknesses vary significantly. The north area reaches 700 m, while the south has 500 m, which agrees with the on-site thicknesses. In addition, the 2D model indicates that the thicker sequence has a subcircular morphology coinciding with the ancient crater or diatreme structure location.

The gravity and magnetic data reveal an array of positive and negative anomalies, providing comprehensive insights into the intricate configuration of the pull-apart structures. A remarkable attribute of the gravimetric and magnetic methods is their ability to identify volcanic structure's position linked to the pull-apart extension. In this sense, we can confidently assert that these volcanic structures form at the intersection of the complex's internal faults (in horsetail faults) and the eastern boundary of the pull-apart (sinistral strike-slip fault). The results show that the combined gravity and magnetic methods offer a workflow useable for understanding the behavior of sedimentary and volcanic interaction inside the pull-apart structures.