Layered Mafic Intrusive Complexes, Possible Terrestrial Analogues of Venusian Coronae

Introduction: Preliminary investigations by these authors concerning the comparison and contrast of characteristics associated with terrestrial layered mafic intrusives (LMI's) and Venusian coronae indicate some similarities in morphology and possibly origin. Our premise is that coronae, and processes related to their formation, may not be unique to Venus and that mantle plumes could have been one of the prevalent forms of heat transfer on Earth during the Archean and Proterozoic Eons. Mantle plumes may have also been instrumental in the initiation of primitive plate tectonic processes during the Archean on Earth. Excellent studies concerning the morphology, structure, distribution, evolution, and origin of coronae based on Magellan data are given in [1,2,3]. Published data and literature on terrestrial LMI's, however, are overwhelmingly dominated by research focused on the origin of compositional layering and origin of economic concentrations of platinum group elements (PGE's), Cu, Cr, V, and Ti, with very little reference to the overall morphology, detailed structure, and ultimate origin. If a correlation between the structures on the two planets is found, then there is potential for huge reserves of PGE's, Cu, Cr, V, Ti, and other metals that may be associated with coronal magmatic deposits. Diapiric Models on Earth and Venus: It is generally accepted that coronae are formed above mantle diapirs. A model for emplacement of these Venusian diapirs is outlined in [3]; however, the mechanism of the diapiric rise of these magma bodies (compositional, thermal, or melt) is currently ambiguous. The process of diapiric rise of mantle plumes on Earth has been more extensively studied. Models for their emplace-ment have been discussed by many authors [4,5]. There are several similarities between diapiric models for Earth and Venus; therefore, it may be reasonable to assume that features and structures formed by similar processes would be evident on both planets. Venusian Coronae: Venusian coronae are interpreted as surface features produced by upwelling diapirs from the Venusian mantle. Coronae can be summarized as circular to elliptical structures with overall diameters between 75 and approximately 2,000 km. Based on Magellan radar imagery, they have an annulus of concentric fractures and exhibit well preserved features, that show minimal affects from weathering and major deformational events. By studying