Plate tectonics and the origin of the Juan Fernandez Ridge: analysis of bathymetry and magnetic patterns

Abstract

ABSTRACT. Juan Fernández Ridge (JFR) is a ca. 800 km long alignment of seamounts and islands which is thought to be fed by a deep mantle plume. JFR includes the Friday and Domingo seamounts in the western active edge close to the active hotspot, and the O'Higgins Seamount and Guyot at the eastern limit just in front of the Chile-Perú trench. Recent bathymetric (Global Topography) and magnetic (EMAG-2) datasets were interpreted both qualitatively and quantitatively by means of 3D inverse modeling and 2D direct modeling for geometry and susceptibility, together with an interpretation of the synthetic anomalies related to the classical hypothesis of deep seafloor spreading. Topographic and magnetic patterns are used to understand the tectonic evolution and origin of the JFR, especially in the western segment. Results show a continuous corridor with a base at ~3900 m depth formed by four groups of seamounts/islands with a number of summits. The deep ocean floor is ~22 to ~37 Myr old and is younger to the south of the Challenger Fracture Zone that runs in a SW-NE direction. The magnetic pattern of the western JFR segment, which is different than the eastern one, has no correlation with bathymetry and does not present a common polarity nor fit with magnetic models for isolated bodies. This superposition of magnetic patterns indicates a role of the faults/fractures of the Nazca Plate. Geological evidence supports the hypothesis of a fixed mantle plume for the origin of JFR but our data suggest that tectonic processes play a role, thus fueling the global controversy about these competing processes. Keywords: seamounts, hotspots, magnetic anomalies, bathymetry, Juan Fernández Ridge.Tectónica de placas y origen de la dorsal de Juan Fernández: análisis de los patrones batimétricos y magnéticos RESUMEN. El cordón o dorsal de Juan Fernández (JFR) es un alineamiento de montes submarinos e islas supuestamente asociadas a la actividad de una pluma mantélica. Comprende, por el W, desde los montes submarinos Friday y Domingo, cercanos al actual 'hotspot', y por el oeste, el guyot y monte O'Higgins cercanos a la fosa submarina de Chile-Perú, con una extensión total de ca. 800 km y un rumbo de ~N80°E. Compilaciones recientes de datos batimétricos (Global Topography) y magnéticos (EMAG-2), se interpretaron cualitativa y cuantitativamente a través de la generación de modelos de magnetización 3D por modelado inverso, y de geometría y susceptibilidad en una sección 2D por modelado directo, complementado con la interpretación de anomalías sintéticas generadas según la hipótesis clásica de la expansión del piso marino profundo. Se utilizan patrones topográficos y magnéticos para comprender la evolución tectónica y el origen del cordón, particularmente en su segmento occidental. Los resultados muestran que en el área de estudio el cordón genera una alineamiento continuo a ~3900 m de profundidad, conformado por cuatro grupos de montes o islas con varias cumbres individuales. El piso marino profundo tiene una edad que fluctúa de ~22 a ~37 M...

Overview of recent advances in oceanographic, ecological and fisheries research on oceanic islands in the southeastern Pacific Ocean

“…Meanwhile, the Juan Fernández Archipelago (made up of the Robinson Crusoe, Alejandro Selkirk and Santa Clara islands) are 600 km from continental Chile. Chile's oceanic islands are substantially smaller than other Pacific islands (Hawaii: 28,310 (Newman & Foster, 1983;Rodrigo & Lara, 2014). These islands are the visible peaks of a chain of seamounts and volcanoes known as the Easter-Salas y Gómez Seamount Chain (e.g., Kingsley & Schilling, 1998;Simons et al, 2002) and Juan Fernández Ridge (Rodrigo et al, 2014).…”

“…These islands are the visible peaks of a chain of seamounts and volcanoes known as the Easter-Salas y Gómez Seamount Chain (e.g., Kingsley & Schilling, 1998;Simons et al, 2002) and Juan Fernández Ridge (Rodrigo et al, 2014). Rodrigo & Lara (2014) and conducted a qualitative and quantitative morphological analysis of the seamount chains and oceanic islands. They used recent bathymetric compilations that include combined satellite derived and shipboard data ("Global Topography"), multibeam bathymetric data (from NGDC-NOAA), and a magnetic data set, to establish clues about the origin of both seamount chains and their relationships with regional tectonics.…”

“…These hotspots could explain the substantial portion of the Easter Submarine Alignment sea floor occupied by seamounts (27%; Rapopport et al, 1997) in comparison with the Eastern Pacific (6%; Rapopport et al, 1997). Rodrigo & Lara (2014) characterized the bathymetry along the 800 km alignment of the Juan Fernández Ridge, which ranges from the Friday and Domingo seamounts in the west to the O'Higgins seamount in the east. The results show a continuous west-east corridor with a base at ~3900 m depth formed by four groups of seamounts/islands with a total of 22 summits.…”

“…Although geological evidence supports the hypothesis of a fixed mantle plume for the origin of Juan Fernández Ridge. Rodrigo & Lara (2014) suggest that tectonic processes play a role, fueling the global controversy about these competing processes.…”

“…Although the marine environments surrounding the oceanic islands of Chile are characterized by the presence of seamounts Rodrigo & Lara, 2014) and to a lesser extent, of hydrothermal vents, both types of ecosystems have been poorly studied. Only during the last decade were conducted the first explorations to characterize the biodiversity of marine communities associated with seamounts in the Juan Fernández Archipelago (Yañez et al, 2009) and Salas y Gómez Island (Friedlander et al, 2013).…”