(Table 2, page 1208) Average of 8 partial chemical analyses of opaque mineral grains bordering aragonite veins crossing serpentinized peridotite rocks from the Romanche Fracture Zone, Atlantic Ocean, supplement to: Bonatti, Enrico; Lawrence, James R; Hamlyn, P R; Breger, Dee (1980): Aragonite from deep sea ultramafic rocks. Geochimica et Cosmochimica Acta, 44(8), 1207-1214


Aragonite mineralization was observed in serpentinized peridotites from the Romanche and Vema Fracture Zones in the Atlantic and the Owen Fracture Zone in the Indian Ocean, either in veins or as radial aggregates in cavities within the serpentinites. Evidence of incipient dissolution of the aragonite crystals was observed in one case. The aragonites tend to have lower Mg content ( 0.95%) relative to other marine aragonites. Their 18O16O, 13C12C and 87Sr86Sr isotopic ratios suggest the aragonite was deposited at ocean floor temperatures from solutions derived from sea water circulating in fissures and fractures within the ultramafic rocks. The 18O16O ratios of the serpentines indicate serpentinization occurred at higher temperatures, probably deeper in the crust. Low-T reactions between circulating seawater and Mg-silicates (primarily serpentine and pyroxenes) caused high pH and enrichment of Mg and Ca in the solution, conditions favoring carbonate precipitation. Aragonite was formed rather than calcite presumably because the high Mg2+ concentration in the solution inhibited calcite precipitation. The high Sr content of the aragonites is probably related, at least in part, to their low temperature of formation. Opaque mineral grains containing over 8% NiO and over 40% MnO were observed concentrated along the margins of some of the aragonite veins, suggesting that Ni is one of the elements mobilized during reactions between ultramafic rocks and circulating seawater.

DOI https://doi.org/10.1594/PANGAEA.873506
Related Identifier https://doi.org/10.1016/0016-7037(80)90074-5
Related Identifier https://doi.org/10.7289/V52Z13FT
Related Identifier https://doi.org/10.7289/V53X84KN
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.873506
Creator Bonatti, Enrico; Lawrence, James R; Hamlyn, P R; Breger, Dee
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 1980
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 14 data points
Discipline Earth System Research
Spatial Coverage (-18.562 LON, -0.337 LAT); Romanche Fracture Zone, Atlantic Ocean