Composed of a series of circular to elliptical bowl-shaped depressions, pit crater chains are common on the surface of many of our solar system’s terrestrial planets and moons. Using Magellan synthetic aperture radar (SAR) images, four areas of Venus are examined in which a total of 354 pit crater chains are found: Ganiki Planitia (180°E–210°E, 25°N–50°N), Ulfrun Regio (200°E–240°E, 0°N–25°N), Themis Regio (270°E–300°E, 25°S–40°S), and Idunn Mons (205°E–225°E, 35°S–55°S). A study of the distribution of these pit crater chains at regional and local scales reveals hierarchical clustering. On a regional scale, pit crater chain clusters are associated with graben–fissure systems that are radiating (associated with volcano-tectonic features), circumferential (associated with coronae), and linear (with uncertain volcano-tectonic genesis). At a local scale, pit crater chains are found with marked restriction to particular portions of graben–fissure systems. We conclude that this hierarchical clustering is an indication that both an extensional process and a lithological control contribute to the formation of pit crater chains. Specifically, we propose that pit crater chain formation on Venus occurs in poorly welded volcaniclastic material (e.g., shield plains material unit) that has been crosscut by graben–fissure system(s). Only portions of the shield plains material unit may have sufficient thickness of volcaniclastic material, thus explaining the lack of a co-extensive relationship. Additionally, pit crater chains in other map units may be explained by shallow burial of the volcaniclastic material.

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This report summarizes mineralization associated with the Nipissing Diabase sills in the broader Sudbury area and evaluates the geochemical link between these sills and potential feeder dykes that are part of the broader ca. 2.2 Ga Ungava large igneous province. New whole-rock major and trace element data are presented for the Nipissing sills and these are combined with previously published data. Sm-Nd isotope data are presented for the Maguire, Senneterre and Klotz dykes, and the Triangle Mountain sill, providing key constraints on their magmatic sources and history of crustal assimilation. To help constrain the temporal evolution of the magmatic system, a new U-Pb baddeleyite age has been determined for the Triangle Mountain sill at 2216.5 ± 2.1 Ma. We also report a previously obtained, precise, U-Pb zircon age for the Ni-Cu-PGE mineralized Shakespeare intrusion at 2217.0 +1.7/-1.5 Ma. Together, whole-rock major and trace elements, Sm-Nd isotopes, and U-Pb geochronology are used to gain a more complete picture of how the mineralized components of the ca. 2.2 Ga Ungava large igneous province were generated.

This study has mapped two types of extensional tectono-magmatic structures including radiating graben-fissure systems (RGFS) in the Idunn Mons and Mielikki Mons study areas, and pit crater chains in Idunn Mons, Themis Regio, Ulfrun Regio, and Ganiki Planitia on Venus. The areas selected to map RGFS host high emissivity anomalies focused on a single volcano and are proposed to reflect younger lava flows which might have occurred as recently as 250 ka. A relative chronology of RGFS is determined using cross-cutting relationships between interacting systems and surface geology. The Idunn Mons high emissivity anomaly is host to the youngest magmatic and volcanic activity, while the Mielikki Mons high emissivity anomaly is not the youngest.Hierarchical clusters of pit crater chains are predominantly focused on RGFS and coronae. It is hypothesized that hierarchical clustering is due to a lithology related variable as lithology may dictate how tensile stress is expressed.ii supervisor, for his support, wisdom and encouragement. He provided me the opportunity to pursue a Masters degree at Carleton University and for that I am truly grateful. I woul like to thank my second co-supervisor, Dr. Claire Samson, for her patience, carefulness, knowledge and endless number of funny stories -all of which are applicable to the world of graduate studies.