TY - JOUR

T1 - Paleobathymetry of Submarine Lavas in the Samail and Troodos Ophiolites

T2 - Insights From Volatiles in Glasses and Implications for Hydrothermal Systems

AU - Belgrano, Thomas M.

AU - Tollan, Peter M.

AU - Marxer, Felix

AU - Diamond, Larryn W.

N1 - Funding Information: We thank Chris Ballhaus and an anonymouns reviewer for their constructive reviews, Ed Spooner and Alastair Robertson for their correspondence on the different lines of ophiolite paleobathymetric evidence, and Dominic Woelki and Maryjo Brounce for the initial conversations that led to this work. Polished sections were prepared with great care by Thomas Aebi (University of Bern). Pierre Lanari (University of Bern) and Julian Allaz (ETH Zürich) are gratefully acknowledged for their assistance with EMPA. The Public Authority for Mining, Sultanate of Oman, are thanked for their permission to undertake fieldwork in Oman, and Robin Wolf and Samuel Weber are thanked for their assistance in the field. This research was supported by Swiss National Science Foundation (SNSF) grant no. P2BEP2‐191795 to T. M. Belgrano and by SNSF grant no. 200020‐169653 to L. W. Diamond.

PY - 2021/7/16

Y1 - 2021/7/16

N2 - Hydrostatic pressure exerted by the ocean water column fundamentally influences magmatic and hydrothermal processes in submarine volcanic settings and is therefore an important parameter to know when investigating such processes. Currently, there are few reliable methods for reconstructing past ocean depths for ancient volcanic terranes. Here, we develop and test an empirically calibrated statistical approach for determining paleodepths of eruption from the concentrations of H 2O and CO 2 dissolved in volcanic glasses, utilizing the well-defined pressure-dependent solubility of these volatiles in silicate melts. By comparing newly determined and published glass compositions from the Samail and Troodos ophiolites with sedimentary and fluid inclusion evidence, we propose that the Samail lavas erupted at ocean depths of ∼3.4 km, and the Troodos lavas at ∼4.1 km. These depths are 1–2 km deeper than those assumed in most previous studies of hydrothermal activity in the two ophiolites. These high depths imply high hydrostatic pressures within the underlying oceanic crust. Such pressures may have allowed convecting hydrothermal fluids to attain significantly higher temperatures (e.g., >450°C) than in typical modern ocean ridge hydrothermal systems during metal leaching in the crust and metal precipitation in seafloor sulfide deposits.

AB - Hydrostatic pressure exerted by the ocean water column fundamentally influences magmatic and hydrothermal processes in submarine volcanic settings and is therefore an important parameter to know when investigating such processes. Currently, there are few reliable methods for reconstructing past ocean depths for ancient volcanic terranes. Here, we develop and test an empirically calibrated statistical approach for determining paleodepths of eruption from the concentrations of H 2O and CO 2 dissolved in volcanic glasses, utilizing the well-defined pressure-dependent solubility of these volatiles in silicate melts. By comparing newly determined and published glass compositions from the Samail and Troodos ophiolites with sedimentary and fluid inclusion evidence, we propose that the Samail lavas erupted at ocean depths of ∼3.4 km, and the Troodos lavas at ∼4.1 km. These depths are 1–2 km deeper than those assumed in most previous studies of hydrothermal activity in the two ophiolites. These high depths imply high hydrostatic pressures within the underlying oceanic crust. Such pressures may have allowed convecting hydrothermal fluids to attain significantly higher temperatures (e.g., >450°C) than in typical modern ocean ridge hydrothermal systems during metal leaching in the crust and metal precipitation in seafloor sulfide deposits.

KW - boninite

KW - ophiolite

KW - Samail

KW - Troodos

KW - volatiles

UR - http://www.scopus.com/inward/record.url?scp=85111485131&partnerID=8YFLogxK

U2 - 10.1029/2021JB021966

DO - 10.1029/2021JB021966

M3 - Article

VL - 126

JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 2169-9313

IS - 7

M1 - e2021JB021966

ER -