Download Detailed Mapping in the Alpha Regio (V

Detailed Mapping in the Alpha Regio (V-32) Quadrangle, Venus, and Testing a New Model
for Coronae
Erin M. Bethell
Department of Earth Sciences, Carleton University, Ottawa, Canada
Detailed geological mapping of the Alpha Regio (V-32) quadrangle on Venus (0° to -25° N, 0° to 30° E)
is being conducted as part of my PhD program, co-supervised by Drs. Ernst and Samson. Of particular
interest to this project are the six densely clustered coronae contained in the Alpha Regio quadrangle,
which include Kuan-Yin, Atargatis, Thouris, Cybele and Fatua coronae, as well as an unnamed coronalike structure (~60 km northwest of the annulus of Cybele corona). The quadrangle also contains
structures attributed to Heng-o and Thermuthis coronae. Each corona in the quadrangle possesses a welldefined circumferential graben-fissure system. Fatua corona, in particular, also possesses a prominent
radiating graben-fissure system that extends northwest and ~1500 km south into the Brynhild fossae in
the Kaiwan Fluctus (V-44) quadrangle. The graben-fissure systems associated with coronae in the Alpha
Regio quadrangle are being explored, through detailed structural mapping, as analogues to giant dyke
swarms on Earth. In particular, giant circumferential dyke swarms are a newly discovered class of dyke
swarm that are increasingly being recognized on Earth in association with large igneous provinces. They
typically span 50°-180° in arc, are hundreds to thousands of kilometers in diameter, are interpreted to
circumscribe mantle plume centers at the time of formation, and are sometimes associated with roughly
coeval giant radiating dyke swarms. Modelling and multiple lines of evidence have demonstrated that
radiating graben-fissure systems associated with coronae and volcanic centers on Venus can be underlain
by laterally propagating, radiating dykes. We propose that circumferential graben-fissure systems
associated with the annuli of Venusian coronae may also be underlain by dykes that are morphologically
similar to giant terrestrial circumferential dyke swarms. The presence of circumferential dykes underlying
the annuli of coronae would have significant implications for the underlying magmatic plumbing system.