SOUTHERN APHRODITE FRACTURE ZONE, VENUS: SUBSURFACE TO SURFACE VOLCANO-TECTONIC CONNECTIONS, AND A NEW MECHANISM FOR HEAT TRANSFER

We are conducting 1:10M geologic mapping of the Aphrodite 1:10M map sheet (0-57S/60-180E, I-2476), Venus in order to establish the geologic history and discover implications for the geodynamic evolution of Earth’s sister planet. The map area includes four spatially overlapping geologic domains: [1] highland crustal plateaus (Ovda and Thetis regiones) and lowland ribbon-tessera terrain; [2] Artemis (chasma, interior, 12000 km-diameter radial dike swarm, 13000 km-diameter concentric wrinkle ridge suite); [3] coronae chain of large coronae across a narrowly defined (~1500 km) region east of Atla Regio, that widened into 500-km wide splays to the west with smaller coronae; and [4] an extensive fracture zone that overlaps with the focused coronae chain to the east, and splits into regional splays to the west, cutting crustal plateaus in the highlands to the NW along a NW-trend and mesoland/lowland regions along W, WSW and SW trends. We focus here on domains 4, which is likely genetically related, in part, to domain 3, and a new type of hybrid structure expressed therein.

The hybrid structures, the epitome of tectono-volcanic features, change along strike from zones of en echelon fractures, fractures, pit-chains, graben, leaky dikes, and canali. Widths range from 1 to >5 km; lengths exceed several 100 km; structure spacing ranges from 10’s of km to lineament overlapping, intersecting, or coalescing. Hybrid structures can from along trends, or result from reactivation of parts of different fracture suites, resulting in a stepped or even sinuous surface pattern, ultimately even forming canali. Although hybrid structures locally source flows, their more note worthy role is in transferring material to depth, as evidenced by widespread development of pit-chains, and topographic troughs across much of domain 4. Transfer of material to the subsurface leaves a record of earlier tectonic and volcanic events; hybrid structures both predate and postdate various flows, providing evidence of their dynamic role in the extensive volcano-magmatic province of southern Aphrodite Terra. The fracture zone domain is the youngest regional domain in Aphrodite Terra, which extends ~2000 km in width and over 6000 km in length. The hybrid structures likely play a significant role in cooling, and may record a contemporary mechanism/process.