Gravity Anomalies and Implications for Shallow Mantle Processes of the Western Cocos-Nazca Spreading Center

This study analyzes up-to-date gravity data in the Galapagos triple junction region to understand crustal structure and melt distribution beneath the propagating Cocos-Nazca spreading center (CNSC). Application of a standard thermal model to the mantle Bouguer gravity anomaly (MBA) does not appear to result in a realistic crustal thickness in this region. The cross-CNSC MBA profiles flatten and axial values increase from east toward the western end of the CNSC. A simple smoothing filter applied to the standard thermal model with different filter widths can explain the progressive flattening of the MBA and is interpreted as different distribution widths (concentrations) of partial melt in the mantle. The east-west residual MBA gradient along the CNSC is similar to the east flank of the East Pacific Rise (EPR), suggesting that the along-CNSC gradient could partly reflect the shallow mantle properties associated with the EPR.

Automated summary

This study uses gravity data to analyze the crustal structure and melt distribution beneath the propagating Cocos-Nazca spreading center in the Galapagos triple junction region. The standard thermal model applied to the mantle Bouguer gravity anomaly does not accurately determine crustal thickness. A smoothing filter applied to the model with different widths explains the flattening of the gravity anomaly and suggests different concentrations of partial melt in the mantle. The residual gravity gradient along the spreading center is similar to that of the East Pacific Rise, indicating similar shallow mantle properties.