© ICDP, the International Continental Scientific Drilling Program, 1996-2022

www.icdp-online.org

Scientific Drilling in the Samail Ophiolite, Sultanate of Oman

Asia, Oman

revised full-proposal: ICDP-2014/03
for the funding-period starting 2014-01-15
by Peter B. Kelemen, Jürg Michael Matter, Damon A.H. Teagle, Raeid M.M. Abed, Judith (Jude) Ann Coggon, Wolfgang Bach, Keir Becker, Francoise Irène Boudier, Georges Ceuleneer, Laurence A. Coogan, Steven L. Goldstein, Philippe Gouze, Greg Hirth, Albrecht Werner Hofmann, Benoit Ildefonse, Bjorn Jamtveit, Frieder Klein, Jürgen Koepke, Charles H. Langmuir, Christopher John MacLeod, Craig E. Manning, Katsuyoshi Michibayashi, D. Jay Miller, Sumio Miyashita, Adolphe Nicolas, Matthew O. Schrenk, Barbara Sherwood Lollar, Robert A. Sohn, Martin Stute, Eiichi Takazawa, Alexis S. Templeton, Susumu Umino, Jessica M. Warren, Gretchen Lieuana Bernasconi-Green, Dieter Garbe-Schönberg, David S. Goldberg
Abstract
The Samail ophiolite in Oman and the United Arab Emirates (UAE) is the world’s largest, best-exposed, and most-studied subaerial block of oceanic crust and upper mantle. In an ongoing dialogue between geological studies of the ophiolite and seagoing investigations along modern oceanic ridges, observations from Oman and the UAE are central to scientific understanding of oceanic plates formed at spreading centers. Observations of mantle peridotites overlying the subduction zone thrust, which carried the ophiolite onto the Arabian continental margin, reveals an unexpected reservoir of carbon, derived from subducted sediments and precipitated as carbonate minerals in the mantle wedge. This could form an important, hitherto unrecognized part of the global carbon cycle. And, following on ground-breaking work in the 1980’s, there has been a recent surge of interest in the Samail ophiolite as the ideal site for studies of weathering in mantle peridotite, together with the subsurface biosphere fueled by microbial catalysis of low temperature alteration reactions. Such studies will contribute to understanding of microbial ecosystems in extreme environments and the origin of life. Following a successful workshop in September 2012, our international team of 38 investigators proposes a comprehensive drilling program in the Samail ophiolite in the Sultanate of Oman. Via observations on core, geophysical logging, fluid sampling, hydrological measurements, and microbiological sampling in a series of diamond- and rotary-drilled boreholes, we will address long-standing, unresolved questions regarding melt and solid transport in the mantle beneath oceanic spreading ridges, mass transfer between the oceans and the crust via hydrothermal alteration, and recycling of volatile components in subduction zones. We will undertake frontier exploration of subsurface weathering processes in mantle peridotite, natural mechanisms of carbon dioxide uptake from surface waters and the atmosphere via alteration and weathering, and the nature of the subsurface biosphere in peridotite undergoing alteration and weathering. Societally relevant aspects of our project include the involvement and training of university students in earth science research, including numerous students from Sultan Qaboos University in Oman. Studies of the natural system of mineral carbonation in peridotite will contribute to design of engineered systems for geological carbon dioxide capture and solid storage. More generally, our studies of alteration will contribute to fundamental understanding of the mechanisms of reaction-driven cracking: chemical reactions that cause subsurface cracking, enhancing permeability and reactive surface area, in a positive feedback mechanism. The results of these studies could enhance geothermal power generation and extraction of unconventional hydrocarbon resources.
Scientific Objectives
  • (1) Quantify the nature and timing of solid upwelling beneath a spreading ridge using crystal shape and lattice preferred orientation data systematically collected on core from the periphery of a mantle diapir.
  • (2) Quantify the nature and structural relationships of melt transport features in the shallow mantle, to evaluate mechanisms that focus transport from a melting region 100’s of kilometers wide into a zone 2 kilometers wide where igneous oceanic crust is formed.
  • (3) Quantify chemical variability deformation structures in the crust-mantle transition zone and plutonic lower crust, to determine the depth of crystallization, the nature of ductile flow, and mechanisms of melt transport.
  • (4) Quantify hydrothermal alteration and cooling of the plutonic lower crust using mineral compositions, diffusion profiles, and stable isotopes to determine the importance of hydrothermal convection in heat and mass transfer.
  • (5) Investigate processes in the critical “dike-gabbro transition” via study of cross-cutting igneous relationships, metamorphic mineral assemblages, and geochemical alteration.
  • (6) Quantify mass transfer from subducted sediments into overlying peridotite at the “leading edge of the mantle wedge” via petrologic and geochemical studies, with special focus on carbon cycling.
  • (7) Systematic and detailed study of ongoing, subsurface alteration of mantle peridotite, including fluid compositions, flow rates and hydrology, characterization of fracture and vein spacing, studies of mineral assemblages formed by carbonation, hydration (serpentinization) and oxidation and resulting mass transfer, and characterization of the subsurface microbial biosphere that derives energy from catalysis of low temperature alteration in this unique and fundamentally important environment.
Keywords
Asia, Carbon capture, Crust, Hydrothermal alteration, ICDP-2014/03, Mantle, OMAN
Location
Asia, Oman: 22.5, 58.515

© ICDP, the International Continental Scientific Drilling Program, 1996-2022

www.icdp-online.org