The relationship between mineralization and tectonics at the Kainantu gold–copper deposit, Papua New Guinea
Tom Blenkinsop, Gerard Tripp, Dave Gillen, 2018. "The relationship between mineralization and tectonics at the Kainantu gold–copper deposit, Papua New Guinea", Characterization of Ore-Forming Systems from Geological, Geochemical and Geophysical Studies, K. Gessner, T.G. Blenkinsop, P. Sorjonen-Ward
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Epithermal veins and breccias at the Kainantu gold–copper deposit in Papua New Guinea, host gold mineralization in NW–SE steeply dipping lodes. The lodes are parallel to a pre-mineralization dextral strike-slip shear-zone network, which is itself parallel in places to an early greenschist-facies cleavage in basement schists. The cleavage, shear zone and veins are all cut by dextral strike-slip faults. High Au grades correlate with areas of obliquity between the shear-zone fabrics and the cleavage, and plunge at approximately 40° SE in the plane of the lodes – coincident with minor fold axes related to a crenulation cleavage in the basement rocks. This clear structural history shows that gold mineralization was confined to a particular late structural event, but lode geometry was influenced by all previous structures, as well as being displaced by post-mineralization faulting. The north–south shortening recorded through most of the tectonic history can be related to Tertiary convergence along the major plate boundary located approximately 15 km north of the mine. However, mineralization occurred under a different tectonic regime from the current north–south convergence, when there was a change of tectonics between 9 and 6 Ma, possibly related to delamination.
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Economically viable concentrations of mineral resources are uncommon in Earth’s crust. Most ore deposits that were mined in the past or are currently being extracted were found at or near Earth’s surface, often serendipitously. To meet the future demand for mineral resources, exploration success hinges on identifying targets at depth. Achieving this requires accurate and informed models of the Earth’s crust that are consistent with all available geological, geochemical and geophysical information, paired with an understanding of how ore-forming systems relate to Earth’s evolving structure. Contributions to this volume address the future resources challenge by (i) applying advanced microscale geochemical detection and characterization methods, (ii) introducing more rigorous 3D Earth models, (iii) exploring critical behaviour and coupled processes, (iv) evaluating the role of geodynamic and tectonic setting and (v) applying 3D structural models to characterize specific ore-forming systems.