| 英文摘要: | Earthquakes and their after shocks generate energy in the form of seismic waves, heat, strain, fractured rock and chemical reactions producing hydrogen gas. Can the repeated energy pulses from seismic activity stimulate subsurface life that generates methane and acetic acid? Does this microbial activity impact the frequency and distribution of after shocks? In 2017 the International Continental Drilling Program (ICDP) supported DSeis (Drilling into Seismogenic Zones) project will examine a previously unknown fault zone responsible for the 2014 5.5-magnitude Orkney earthquake, South Africa's largest earthquake in over 50 years. At a depth of 3 km in the bottom of Moab Khotsong gold mine, geophysicists and geomicrobiologists will join forces to drill down an additional 600 meters into this still-active fault zone, analyze core samples, install seismic instruments and deploy a Kinetically Activated Subsurface Microbial Sampler (KASMS). KASMS is a novel, portable, autonomous fluid sampling and preservation device that will be triggered by seismic events along the fault zone. The data from this study will significantly advance our understanding of the type of earthquakes that are associated with ultra-deep mining, hydrofracking and fracking brine injections and thus better inform safety and environmental regulations. The high-resolution temporal data will provide the first picture of how subsurface microbial communities respond to environmental stimuli, such as hydrogen gas pulses. If a substantial biomass enhancement is found within the fault zone, then similar ancient fault zones exposed on the surface of Mars may be selected for the Mars 2020 rover mission, the first step in the Mars Sample Return mission series. With the involvement of geophysics, geology, rock mechanics, and geomicrobiology students from Japan, South Africa, Switzerland, Israel, Germany, India, Australia and the United States, DSeis and this project will stimulate cross-disciplinary international STEM education. Through videos of the coring and sampling activity and of the installation and operation of KASMS, and downhole videos of the borehole, DSeis and this project will relate to the public how science is conducted in one of the most extreme environments on the planet and what subsurface life says about the origin and evolution of life on Earth and possibly other planets.
This two-year project will design, construct and deploy KASMS, the first fully automated sampling device for geochemical and microbiological studies. KASMS is comprised of a borehole-deployed U-tube fluid sampling system and a discrete sensor array for monitoring the wellbore environment. KASMS will also contain two osmo-samplers combined with mineral coupons to collect biofilms within the fault zone. Unique to the KASMS system is the capability to autonomously respond to seismic events and capture a time progression of fluid samples. These samples will be analyzed for aqueous geochemistry, dissolved gas concentrations and isotopic values, and they will be subsampled using two types of filters with preservatives, one for SEM/TEM microscopy and the other for metagenomic/metatranscriptomic/metaproteomic analyses. During the year that KASMS is deployed at Moab Khotsong gold mine, experiments will be performed with positive and negative controls: samples collected before and after small magnitude seismic events within the fault zone, before, during and after mine detonations, during mining holidays when the mine is inactive and before, during and after the injection of hydrogen and methane gas. After one year KASMS will be retrieved and returned to Princeton University, where it will be available for deployment to other subsurface microbiology sites. |