Regional structural controls on hydrothermal fluid flow in the North Fiji Basin
Katherine Power, Mark Hannington
Department of Earth and Environmental Sciences, University of Ottawa
Katherine Power, Mark Hannington
Department of Earth and Environmental Sciences, University of Ottawa
The North Fiji Basin is the largest area of active back-arc spreading in the southwest Pacific, continuously opening since the Miocene. Previous studies have suggested a complicated history of microplate interactions, rotation and reorganization, with crustal-scale structures having a strong influence on magmatic and hydrothermal activity. The objective of this study is to better understand the link between crustal-scale features, hydrothermal pathways and the evolution of the NFB. To identify crustal-scale features two datasets were used; satellite-derived Vertical Gravity Gradient (VGG), and a global compilation of magnetic data. VGG enhances short wavelength variations in the gravity field, which highlights fine-scale structures in oceanic crust. Magnetic anomalies are local variations in the Earth’s magnetic field caused by the chemical or magnetic properties of the rocks, and are used to identify the age and spreading history of oceanic crust.
Crustal-scale features were mapped as lineaments at 1:500,000 scale. Over 1385 lineaments were digitized from the VGG dataset and 224 for the magnetic anomalies dataset. The average length for the VGG lineaments is 20 km and 60 km for the magnetic anomalies. Regions with similarly oriented lineaments were grouped into tectonic domains, to construct the history of the NFB. Based on the density of the lineaments constructed and the amount of domains identified, VGG records the history of the basin in more detail. The majority of the large-scale structures are formed during accretion at spreading centers. However, in several areas, crosscutting structures can be observed that indicate a more complex evolution of these areas, particularly adjacent to plate boundaries. The structures in present-day microplate mosaics provide a useful framework for understanding how and where crustal-scale faults and hydrothermal pathways form in analogous terranes on land.
Crustal-scale features were mapped as lineaments at 1:500,000 scale. Over 1385 lineaments were digitized from the VGG dataset and 224 for the magnetic anomalies dataset. The average length for the VGG lineaments is 20 km and 60 km for the magnetic anomalies. Regions with similarly oriented lineaments were grouped into tectonic domains, to construct the history of the NFB. Based on the density of the lineaments constructed and the amount of domains identified, VGG records the history of the basin in more detail. The majority of the large-scale structures are formed during accretion at spreading centers. However, in several areas, crosscutting structures can be observed that indicate a more complex evolution of these areas, particularly adjacent to plate boundaries. The structures in present-day microplate mosaics provide a useful framework for understanding how and where crustal-scale faults and hydrothermal pathways form in analogous terranes on land.