Dyke swarm history in Belet-ili and Gaia (Gaya) Coronae Region (13°–26°E, 0°–10°N), Central Eistla Regio, Venus

Abstract

Eistla Regio, Venus, is a locus of major plume-generated magmatism and tectonics. We focus on the central portion, termed Central Eistla Regio. More than 19,000 extensional lineaments (grabens, fissures and fractures) were mapped in the area 13°-26°E, 0°-10°N, at 1:500,000 scale using full resolution Magellan SAR (radar) images. These structures are interpreted to represent the surface expression of underlying mafic dykes and have been grouped, on the basis of trend, into radiating, circumferential and linear dyke swarms. Thirty-two swarms are identified and linked to 20 magmatic centres, most of which are located within or near two coronae, Belet-ili and Gaia (Gaya) coronae, while others are linked to magmatic centres outside the study area. These magmatic centres are interpreted to be linked to underlying mantle plumes, and the sizes of the underlying flattened plume heads are estimated from the interpreted dyke swarms: for radiating swarms, the radius of the transition from proximal radiating to more distal linear pattern, and for circumferential dykes, the radial distance to the outer boundary of the circumferential pattern. Plume heads for the largest centres, Belet-ili and Gaia coronae are estimated at about 230 km and 275 km in radius, respectively. These sizes are less than the 1200 km radii predicted for a plume arriving from the deep mantle, and would suggest an origin at a shallower level (likely a mid-mantle boundary, i.e. between upper and lower mantle). The NW alignment of Belet-ili and Gaia corona and other magmatic centres in our study area potentially represents structural control by a rift zone, which can be traced further north to Anala Mons (one of two main plume centres of Central Eistla Regio).