Hébert, Rejean; Adamson, Andrew C; Komor, Stephen C (1990): Chemistry of serpentinized peridotites from ODP Hole 109-670A. PANGAEA, https://doi.org/10.1594/PANGAEA.745321, Supplement to: Hébert, R et al. (1990): Metamorphic petrology of ODP Leg 109, Hole 670A serpentinized peridotites: serpentinization processes at a slow spreading ridge environment. In: Detrick, R; Honnorez, J; Bryan, WB; Juteau, T; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 106/109, 103-115, https://doi.org/10.2973/odp.proc.sr.106109.129.1990
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In this paper we describe textural relationships in hydrated upper mantle peridotites emplaced at a nonconstructive ridge segment. Development of serpentinites and partially serpentinized peridotites takes place in four main stages: (1) pervasive serpentinization forming mainly lizardite, (2) a tensional stage forming chrysotile + talc + chlorite, (3) a deformational stage forming antigorite + tremolite, and (4) a late local tensional stage forming another generation of chrysotile veinlets. Mineral chemistry of serpentine pseudomorphs reflects in part primary mineral compositions. Olivine pseudomorphs are typically nickeliferous and depleted in aluminum and chromium. Orthopyroxene pseudomorphs have lower nickel contents and relatively high iron, aluminum, and chromium contents. Clinopyroxene pseudomorphs have very low nickel contents and relatively high aluminum and chromium contents. These chemical patterns in the serpentinites can be used to help discriminate between harzburgitic and lherzolitic protoliths. Oxygen isotopes and mineral parageneses suggest serpentine is derived from circulation of hydrothermal (200 infinity C) fluids through the peridotite body. Crystallization of tremolite, talc, and chlorite may have occurred at temperatures up to 525 infinity C if C02/H20 ratios were less than 0.25. Open fissures developing in aging upper mantle provide paths for important seawater circulation through a thin basaltic carapace down to shallow mantle rocks.
Latitude: 23.166600 * Longitude: -45.032200
Date/Time Start: 1986-06-12T01:30:00 * Date/Time End: 1986-06-16T16:15:00
109-670A * Latitude: 23.166600 * Longitude: -45.032200 * Date/Time Start: 1986-06-12T01:30:00 * Date/Time End: 1986-06-16T16:15:00 * Elevation: -3625.0 m * Penetration: 92.5 m * Recovery: 4.58 m * Location: North Atlantic Ocean * Campaign: Leg109 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 7 cores; 76.6 m cored; 0 m drilled; 6 % recovery
Datasets listed in this publication series
- Hébert, R; Adamson, AC; Komor, SC (1990): (Table 1) Primary and secondary mineral analyses of serpentinized peridotites from ODP Hole 109-670A. https://doi.org/10.1594/PANGAEA.745319
- Hébert, R; Adamson, AC; Komor, SC (1990): (Table 2) Whole-rock oxygen isotope geochemistry of serpentinized peridotites from ODP Hole 109-670A. https://doi.org/10.1594/PANGAEA.745320