Variations in the Composition of MORB Chilled Glasses from the Mid-Atlantic Ridge, 12°–31° N: Reflection of Compositional Evolution of Parental Melts and the Influence of a Hydrothermal Component

• Published in: Petrology 2023-10, Vol.31 (5), p.475-491
• Main Authors: Silantyev, S. A., Buikin, A. I., Tshovrebova, A. R., Shabykova, V. V., Bel’tenev, V. E.
• Format: Article
• Language: English
• Subjects: Basalt; Composition; Contamination; Cooling; Earth and Environmental Science; Earth Sciences; Fluids; Geochemistry; Hydrothermal systems; Lithosphere; Melts; Mid-ocean ridges; Mineralogy; Oceanic crust; Outcrops; Segments; Serpentinite
• ISSN: 0869-5911; 1556-2085
• DOI: 10.1134/S0869591123050053

The geochemical peculiarities of sample collection of MORB chilled glasses obtained in six areas of the axial zone of the Mid-Atlantic Ridge (MAR), 12°–31° N have been studied. The results of this study provided information on the composition of the parental melts for these glasses and made it possible to assess the probable geochemical effects reflecting the interaction of magmatic melts with hydrothermal systems of the MAR axial zone or with altered oceanic crust (AOC). It is shown that basalts of the E-MORB family which includes most samples are localized mainly in the “cold” segments of the MAR, in the crustal section dominated by serpentinites. On the other hand, samples with depleted signatures (N-MORB) belong to MAR segments where serpentinite outcrops either are absent or play a subordinate role. The E-MORB chilled glasses from “cold” segments of the MAR show signs of contamination of basaltic melts with components assimilated either from the host serpentinites or from aqueous–saline fluids circulating in hydrothermal systems located in serpentinites (“serpentinite hosted”). Judging by the data obtained on the nature of Cl, U, and Sr variations in the studied chilled glasses ascribed to the N-MORB family, there are no signs of intracrustal contamination. It is assumed that relics of the ancient continental lithosphere preserved under axial zone of the MAR and involved in the partial melting of the shallow mantle took part in the formation of E-MORB parental melts in some MAR segments.