3-D Mohr circle analysis of vein opening,Indarama lode-gold deposit,Zimbabwe: implications for exploration |
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| Institution: | 1. Department of Geological Sciences, University of Oregon, 1272 University of Oregon, Eugene, OR 97403-1272, USA;2. School of Earth Sciences and Environmental Sustainability, Northern Arizona University, 625 South Knoles Drive, Flagstaff, AZ 86011-4099, USA;3. Department of Earth and Planetary Sciences, University of California–Davis, 2119 Earth and Physical Sciences, One Shields Avenue, Davis, California 95616, USA;4. Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, C.P. 76230 Juriquilla, Querétaro, Mexico.;5. The University of Texas at Austin, Jackson School of Geosciences, 2305 Speedway, Stop C1160, Austin, TX 78712, USA;1. School of Geosciences, University of Sydney, NSW 2006, Australia;2. Bare Rock Geological Services Pty Ltd, Fremantle, WA 6160, Australia;3. School of Earth Sciences, University of Western Australia, Crawley, WA 6009, Australia;4. Geology Department, Lakehead University, 955 Oliver Rd, Thunder Bay, Ontario, P7B 5E1, Canada |
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| Abstract: | The Indarama lode gold deposit is hosted by vertically-dipping basalt in the Late Archaean Midlands Greenstone Belt of Zimbabwe. Major deformation events at 2.68 and 2.58 Ga established a complex array of fractures. A limited range of orientations of this fracture network opened towards the end of the younger deformation event, creating a lode pattern where 92% of mineralised veins dip at less than 50°, mainly to the E and W, and most strike directions are represented. A clustered distribution of poles to the quartz–carbonate veins indicates a constrictional stress field at the time of vein opening where σ1 and σ2 were near horizontal, (directed NNW–SSE and ENE–WSW, respectively), and σ3 was near vertical. 3-D Mohr circle analysis demonstrates that σ2 was approximately 67% of σ1 (the stress ratio) and that the driving pressure ratio (R′) was approximately 0.4, reflecting the role of fluid pressure, mean stress, and the maximum shear stress in controlling conditions of fracture opening. |
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