Structural and tectonic evolution of orogenic belts, with an emphasis on kinematics of shear zones, Archean tectonics and implications for mineralization

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My long term objective of research is a better understanding of structural and tectonic evolution of mountain belts of various ages, evolution of tectonic processes through time and structural and tectonic control on mineralization. The proposed study will focus on three ancient mountain belts, the Archean Superior craton in Canada, the Proterozoic to Mesozoic South China Block and the Paleozoic Central Asian Orogenic Belt (CAOB) in China. My extensive experience with the Canadian Appalachians in the last two decades, one of the best studied orogens in the world, has proved to be very beneficial to our work in the Superior craton, the South China Block and the CAOB. A fundamental debate concerning Archean tectonic processes is that of vertical vs. horizontal tectonism. There is a tendency for advocates of plate tectonics (horizontal tectonism) in the Archean to downplay the significance, if not deny the presence, of vertical tectonism, and vice versa. Our work in the Superior craton has led to the recognition of evidence for both vertical and horizontal tectonism, and more importantly for their synchronous operation. We have proposed that synchronous vertical and horizontal tectonism was an important process in the Neoarchean and represented a transition from dominant vertical tectonism in the Meso-(and Paleo-?) Archean to dominant horizontal tectonism in Proterozoic and Phanerozoic. Such a conclusion makes it necessary that both processes (as opposed to either one or the other) and their potential interactions are considered in interpretations of Archean terrains. As importantly, we have suggested that such a process in the period of transition was important for gold mineralization, and the Hemlo deposit, a world-class deposit with >650 tons of gold, formed during the process. These interpretations were mostly based on data from the western, in particular the northwestern Superior craton. Here we propose to test these interpretations and their general applicability, not only through continuing work in the western Superior craton, but more importantly through additional work in the southeastern Superior craton, in particular in the Abitibi greenstone belt. The Abitibi belt is arguably the best studied and most prolific greenstone belt in the world, containing numerous world-class gold deposits. Vast amount of data is available concerning the belt and the deposits. In addition, the PI is familiar with the geology of the belt. These form a very good basis for the proposed study. As importantly, essentially all major gold deposits in the belt are spatially associated with two major shear zones in the area (the Desptor-Porcupine and Larder Lake-Cadillac faults) and the two shear zones spatially coincide with what appear to be synclinal keels between granitoid domes, as predicted by our model. This area thus provides an ideal opportunity to test the model. In addition, we will investigate the relative significance of vertical and horizontal tectonism and its variation with time and space (if any). We suspect that there exists a feedback relationship between the two processes and will explore the possible mechanisms for this. The results will have significant implications for Archean geological evolution in general and for Archean gold mineralization. The latter will help exploration targeting in Archean terranes worldwide. Our work in the South China Block and the CAOB will focus on the geometry, kinematics, and temporal evolution of major shear zones. The results will shed significant light on the tectonic evolution of these two accretionary orogens, in particular on the potential role of large-scale orogen-parallel motion along terrane-bounding shear zones in the amalgamation of the terranes.