by Yasuo Yabe, Musa S.D. Manzi, Alba Gomez-Arias, Devan M. Nisson

The 2014 Orkney earthquake (M5.5) ruptured an ultramafic lamprophyre dike at 3.5-7 km depths in the West Rand Group (WRG) beneath Moab Khotsong mine. Deep development of the mine enables PROTEA to drilli from a site at 3 km depth to the nucleation zone, ultimately the hypocenter, of the Orkney earthquake to elucidate spatial variations of frictional properties, stress state, pore pressure, and lithology along the source fault for better understanding of nucleation, propagation and termination of an earthquake. The lamprophyre dike is altered and rich in potassium and intersects felsic rocks, basaltic andesite, and dolerite sills intruded into the WRG. Each intersection with different formations has different rheology associated with talc and biotite abundances, suggesting different metamorphism and alteration of the intersection under the pressure and temperature (P-T) conditions from greenschist to amphibolite facies. PROTEA will drill though a substantial thickness of the WRG to systematically investigate the variation of host rock lithology associated with the dike-sill complex and its impact on the alteration of the lamprophyre dike. PROTEA will also conduct a pre-drilling seismic site survey and post-drilling seismic monitoring using up-to-date techniques. The finer structure of the dike-sill complex will elucidate its role in an extensional tectonic event such as supercontinent breakup. Extreme environmental conditions, i.e. high salinity (23 wt% Ca-Na-Cl), high T (54?) and long isolation (1.2 Ga groundwater age) in a mafic dike adjacent and subparallel to the aftershock plane mimic expected Martian underground environments. The microbial ecosystem in these extreme conditions expands understanding of the limits of life and informs the search for extraterrestrial life. The temporal distribution and abundances of carbon, nitrogen, and sulfur species will be quantified in the brine to elucidate water-rock reactions that enable long-term microbial persistence in the hypersaline oligotrophic closed ecosystem. The long-isolated brine also offers an excellent opportunity to test the novel hypothesis that seismic events stimulate microbial activity by facilitating the release of water-rock-generated redox species. PROTEA drilling/coring will adhere to strict contamination control procedures. The PROTEA workshop will explore scientific opportunities of the above-mentioned topics and formulate feasible drilling strategies that maximize their scientific productivity. Contributions to the education in earth science to the local people and outreach to the mining industry will also be planned.

• Main scientific objectives/questions of PROTEA are: Q1. How do variations in the mechanical properties and conditions along the fault affect the nucleation, propagation and termination of an earthquake? Q2. How do the interactions between continental and mantle rocks and fluids under the P-T condition at the bottom or below the natural seismogenic zones generate diversity of rheology? Q3. How great is the diversity of microbial ecosystems in an environment that mimics the expected Martian underground environment? In addition to the main scientific objectives/questions, PROTEA will investigate the following questions through pre-drilling survey and post-drilling monitoring. Q4. Do seismic events stimulate microbial activity? Q5. What is the detailed structure of the source fault? Q6. How do water-rock reactions enable long-term microbial persistence in the hypersaline oligotrophic closed ecosystem?

Deep Biosphere, Earthquake Rupture, Greenschist Metamorphism, In-Situ Stress

Latitude: -26.41611, Longitude: 27.42722