Boron isotopic composition of olivine-hosted melt inclusions from Gorgona komatiites, Colombia : new evidence supporting wet komatiite origin
MetadataShow full item record
KeywordKomatiites; Gorgona Island; Melt inclusions; Volatile components; Boron isotopes; Ion microprobe
A fundamental question in the genesis of komatiites is whether 30 these rocks originate from partial melting of dry and hot mantle, 400−500°C hotter than typical sources of MORB and OIB magmas, or if they were produced by hydrous melting of the source at much lower temperatures, similar or only moderately higher than those known today. Gorgona Island, Colombia, is a unique place where Phanerozoic komatiites occur and whose origin is directly connected to the formation of the Caribbean Large Igneous Province. The genesis of Gorgona komatiites remains controversial, mostly because of the uncertain origin of volatile components which they appear to contain. These volatiles could equally result from shallow level magma contamination, melting of a “damp” mantle or fluid-induced partial melting of the source due to devolatilization of the ancient subducting plate. We have analyzed boron isotopes of olivine40 hosted melt inclusions from the Gorgona komatiites. These inclusions are characterized by relatively high contents of volatile components and boron (0.2−1.0 wt.% H2O, 0.05−0.08 wt.% S, 0.02−0.03 wt.% Cl, 0.6−2.0 μg/g B), displaying positive anomalies in the overall depleted, primitive mantle (PM) normalized trace element and REE spectra ([La/Sm]n = 0.16−0.35; [H2O/Nb]n = 8−44; [Cl/Nb]n = 27−68; [B/Nb]n = 9-30, assuming 300 μg/g H2O, 8 μg/g Cl and 0.1 μg/g B in PM; Kamenetsky et al., 2010. Composition and temperature of komatiite melts from Gorgona Island constrained from olivine-hosted melt inclusions. Geology 38, 1003–1006). The inclusions range in δ11B values from −11.5 to +15.6 ± 2.2‰ (1 SE), forming two distinct trends in a δ11B vs. B-concentration diagram. Direct assimilation of seawater, seawater-derived components, altered oceanic crust or marine sediments by ascending komatiite magma cannot readily account for the volatile contents and B isotope variations. Alternatively, injection of <3% of a 11B enriched fluid to the mantle source could be a plausible explanation for the δ11B range that also may explain the H2O, Cl and B excess.
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 312 (2011): 201–212, doi:10.1016/j.epsl.2011.09.033.
Suggested CitationPreprint: Gurenko, Andrey A., Kamenetsky, Vadim S., "Boron isotopic composition of olivine-hosted melt inclusions from Gorgona komatiites, Colombia : new evidence supporting wet komatiite origin", 2011-09-11, https://doi.org/10.1016/j.epsl.2011.09.033, https://hdl.handle.net/1912/5018
Showing items related by title, author, creator and subject.
Marschall, Horst R.; Wanless, V. Dorsey; Shimizu, Nobumichi; Pogge von Strandmann, Philip; Elliott, Tim; Monteleone, Brian D. (2017-03-17)A global selection of 56 mid-ocean ridge basalt (MORB) glasses were analysed for Li and B abundances and isotopic compositions. Analytical accuracy and precision of analyses constitute an improvement over previously published ...
Investigating boron isotopes for identifying nitrogen sources supplied by submarine groundwater discharge to coastal waters Tamborski, Joseph; Brown, Caitlin; Bokuniewicz, Henry J.; Cochran, J. Kirk; Rasbury, E. Troy (Frontiers Media, 2020-08-11)Stable isotopes of oxygen, nitrogen, and boron were used to identify the sources of nitrate (NO3–) in submarine groundwater discharge (SGD) into a large tidal estuary (Long Island Sound, NY, United States). Potential ...
Cleaning and pre-treatment procedures for biogenic and synthetic calcium carbonate powders for determination of elemental and boron isotopic compositions Holcomb, Michael; DeCarlo, Thomas M.; Schoepf, Verena; Dissard, Delphine; Tanaka, Kiyoshi; McCulloch, Malcolm (2015-01)In preparing calcium carbonate samples for the measurement of various geochemical proxies, it is often necessary to remove contaminating phases while leaving the phase of interest altered as little as possible. Here we ...