Mineral chemistry and water-rock interaction in exhumed mantle rocks at the Atlantis Massif: Insights from the newly drilled (April-June 2023) IODP Exp. 399
- 1Institute of Geodynamics and Tectonics, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
- 2Istituto di Geoscienze e Georisorse - Consiglio Nazionale delle Ricerche, Pisa, Italy
- *A full list of authors appears at the end of the abstract
Hydrothermal circulation at slow-ultraslow spreading ridges represents the primary means by which seawater can penetrate the oceanic crust. This process redistributes volatile elements that can be sequestered in hydrous alteration minerals and later remobilised during plate subduction. Accordingly, the hydration state of the oceanic crust fundamentally influences a variety of fluid-mediated processes across subduction zones.
Numerous drill cores penetrate the upper oceanic crust and provide relatively robust constraints on the volatile content of sedimentary and volcanic crustal components. However, very few drill cores sample the lower gabbroic and lithospheric mantle crustal domains, which are rich in hydrous minerals (serpentine, brucite, amphibole, chlorite, talc, zeolites, etc.). This has led to considerable uncertainty regarding the volatile makeup of the crust entering subduction zones, and the behaviour of fluid tracers such as boron and its isotopes.
Lower crustal units are exposed by domal detachment faulting at the Atlantis Massif (30°N; Mid-Atlantic Ridge). We will present preliminary data from IODP Expedition 399, which recovered 1268m of serpentinized mantle peridotite and subordinate gabbroic rocks from the southern wall of the massif, proximal to the famous Lost City Hydrothermal Field. This is by far the longest core ever drilled in situ in serpentinized oceanic peridotite. We will report whole-rock and mineral (serpentine, amphibole, chlorite, prehnite, talc, Cr-spinel, oxide) chemistry in order to investigate the down-hole style of alteration. This will include whole-rock 11/10 B and 87/86 Sr isotope ratios to assess the role of seawater vs. possible ongoing metamorphic alteration at depth. These data represent an important step towards quantifying the fluid mobile element budgets and specifically the boron and 11/10 B content of the lower oceanic crust.
Andrew McCaig(1). Susan Q. Lang; Department of Geology and Geophysics, Woods Hole Oceanographic Institution, USA. Peter Blum; International Ocean Discovery Program, Texas A&M University, USA. Natsue Abe; Agency for Marine-Earth Science and Technology, Japan. William Brazelton; School of Biological Sciences, University of Utah, USA. Rémi Coltat; Geosciences Department, Ecole Normale Supérieure, Paris, France and Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Spain. Jeremy R. Deans; School of Biological, Environmental, and Earth Sciences, University of Southern Mississippi, USA. Kristin L. Dickerson; Department of Earth and Planetary Sciences, University of California, Santa Cruz, USA. Marguerite Godard; Department of Geosciences, University of Montpellier, France. Barbara E. John; Department of Geology and Geophysics, University of Wyoming, USA. Frieder Klein; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, USA. Rebecca Kuehn; Institute of Geosciences and Geography, Martin-Luther-University Halle-Wittenberg, Germany. Kuan-Yu Lin; Department of Earth Sciences, University of Delaware, USA. C. Johan Lissenberg; School of Earth and Environmental Sciences, Cardiff University, United Kingdom. Haiyang Liu; Institute of Oceanology, Chinese Academy of Sciences, China. Ethan L. Lopes; Department of Geophysics, Stanford University, USA. Toshio Nozaka; Department of Earth Sciences, Okayama University, Japan. Andrew J. Parsons; School of Geography, Earth, and Environmental Sciences, University of Plymouth, United Kingdom. Vamdev Pathak; Department of Geology, Central University of Punjab, India. Mark K. Reagan; Department of Earth and Environmental Sciences, University of Iowa, USA. Jordyn A. Robare; School of Molecular Sciences, Arizona State University, USA. Ivan Savov(1). Esther Schwarzenbach; University of Fribourg, Switzerland. Olivier J. Sissmann; 1 et 4 avenue de Bois-Preau 75005 Paris, France. Gordon Southam; Earth and Environmental Sciences, The University of Queensland, Australia. Fengping Wang; International Center for Deep Life Investigation (IC-DLI), Shanghai, Jiao Tong University, China. C. Geoffrey Wheat; College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, USA. Lesley Anderson; United States Antarctic Program, USA. Sarah N.R. Treadwell; Department of Communication, University of North Dakota and Blue Marble Space Institute, USA.
How to cite: Osborne, W., Savov, I., Agostini, S., McCaig, A., and Baker, E. and the International Ocean Discovery Program Expedition 399 Sci Party: Mineral chemistry and water-rock interaction in exhumed mantle rocks at the Atlantis Massif: Insights from the newly drilled (April-June 2023) IODP Exp. 399, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20498, https://doi.org/10.5194/egusphere-egu24-20498, 2024.
