OS024-0002
Accessing the Building Blocks of Life: Deepening Hole U1309D, Atlantis Massif, Mid-Atlantic Ridge: IODP Proposal 937.
Thursday, 10 December 2020
Poster
Andrew McCaig1, Donna K Blackman2, Beth Orcutt3, Benedicte Menez4, Marvin D Lilley5, Charles Geoffrey Wheat6, Johan C J Lissenberg7, Benoit Ildefonse8, Frieder Klein9, Susan Q. Lang10, William E Seyfried Jr11, Muriel Andreani12, Barbara E John13, Marguerite Godard14, Antony Morris15, Esther Schwarzenbach16, Christopher J MacLeod7, Ivan P Savov1, Natsue Abe17, Yasuhiko Ohara18 and IODP co-proponents, proposal 937, (1)University of Leeds, Leeds, LS2, United Kingdom, (2)University of California San Diego, La Jolla, CA, United States, (3)Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, United States, (4)University Denis Diderot Paris VII, Paris Cedex 13, France, (5)University of Washington, School of Oceanography, Seattle, WA, United States, (6)NURP/ Univ Alaska, Moss Landing, CA, United States, (7)Cardiff University, Cardiff, United Kingdom, (8)Géosciences Montpellier, Univ Montpellier, CNRS, Univ Antilles, Montpellier, France, (9)Woods Hole Oceanographic Inst., Woods Hole, MA, United States, (10)University of South Carolina, School of the Earth, Ocean, and Environment, Columbia, SC, United States, (11)Univ Minnesota, Minneapolis, MN, United States, (12)University Claude Bernard Lyon 1, Villeurbanne, France, (13)University of Wyoming, Laramie, WY, United States, (14)Géosciences Montpellier, CNRS, Univ. Montpellier, Montpellier, France, (15)Plymouth University, School of Geography, Earth and Environmental Sciences, Plymouth, United Kingdom, (16)Freie Universität Berlin, Institute of Geological Sciences, Berlin, Germany, (17)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Mantle Drilling Promotion Office MarE3, Kanagawa, Japan, (18)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
Abstract:
The Atlantis Massif (AM), on the mid-Atlantic Ridge, is one of the first places where oceanic detachment faults were recognised, bringing ultramafic and gabbroic rocks to the seafloor. It hosts the Lost City Hydrothermal Field (LCHF), which vents highly alkaline fluids rich in H
2 and CH
4. Hydrogen is a by-product of serpentinisation, and many authors have speculated that abiotic production of hydrogen, methane, and more complex organic compounds in such environments was a precursor to the evolution of life on Earth and other worlds. The AM is therefore an ideal natural laboratory for studying active processes of tectonics, magmatism, and interaction between the ocean and lithosphere, and the influence of this on ocean chemistry, subseafloor biosphere, and the generation of hydrogen and organic molecules. These processes link to strategic objectives in the 2050 Science Framework such as Habitability and Life on Earth, The Oceanic Life Cycle of Tectonic Plates, Feedbacks in the Earth System and Global Cycles of Energy and Matter, as well as to the Flagship Initiative “Exploring Life and its Origins”.
In June 2020, proposal 937 was rated “excellent” by the Science Evaluation Panel and forwarded to the Facilities Board for scheduling, signalling a return to the Massif.
IODP Hole U1309D will be deepened to target depths of over 2 kmbsf and expected temperatures of ~ 220 °C. The deep Hole will test the hypothesis that H2 and CH4 in the Lost City fluids are generated at higher depths and temperatures that the current circulation system. Any organic compounds found in the core will be unequivocally abiotic in origin. The Hole will be left open as a legacy for future fluid sampling to study fluid-rock interaction at high temperature in a stable environment.
Two new shallow (<200m) Holes will be drilled in serpentinite close to the LCHF, and in gabbro/diabase at Site U1309. These will address the question of unexpectedly low cell counts in the shallow (<16 mbsf) cores of Expedition 357, by targeting zones of reaction porosity which may have allowed better nutrient access for metabolism, and mafic layers within the serpentinite where pore fluids may be lower in pH. These holes will also sample the detachment fault zone which is marked by talc-tremolite-chlorite schists, and may have been an upflow zone for black smoker fluids.
