Gravimetric structure for the abyssal mantle massif of Saint Peter and Saint Paul peridotite ridge, Equatorial Atlantic Ocean, and its relation to active uplift

KENJI F. MOTOKI,AKIHISA MOTOKI,SUSANNA E. SICHEL

doi:10.1590/0001-37652014117712

Abstract

This paper presents gravimetric and morphologic analyses based on the satellite-derived data set of EGM2008 and TOPEX for the area of the oceanic mantle massif of the Saint Peter and Saint Paul peridotite ridge, Equatorial Atlantic Ocean. The free-air anomaly indicates that the present plate boundary is not situated along the longitudinal graben which cuts peridotite ridge, but about 20 km to the north of it. The high Bouguer anomaly of the peridotite ridge suggests that it is constituted mainly by unserpentinised ultramafic rocks. The absence of isostatic compensation and low-degree serpentinisation of the ultramafic rocks indicate that the peridotite ridge is sustained mainly by active tectonic uplift. The unparallel relation between the transform fault and the relative plate motion generates near north-south compression and the consequent tectonic uplift. In this sense, the peridotite massif is a pressure ridge due to the strike-slip displacement of the Saint Paul Transform Fault.

Highlights

Satellite-derived gravimetry is an efficient instrument for geotectonic and structural studies of oceanic regions
The present paper introduces two highlighted research method: 1) Satellite-derived bathymetry and gravimetry; 2) Macro Concavity Index
The Satellite-derived gravimetry and geomorpho logic analyses for the studied area have led the authors to the following conclusions

Summary

Introduction

Satellite-derived gravimetry is an efficient instrument for geotectonic and structural studies of oceanic regions. The mantle rocks crop out at the top surface of a large and steep submarine hill, called Saint Peter and Saint Paul peridotite ridge (Figure 2, cadeia peridotítica de São Pedro e São Paulo). The authors have performed gravimetric and morphologic analyses for the northwest corner of the Saint Paul Transform Fault Zone based on the satellite-derived data sets of EGM2008 and TOPEX.

Results

Conclusion