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The nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge 33–35°N: A Sr-Nd-Hf isotopic perspective.
- Source :
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Geochimica et Cosmochimica Acta . Aug2021, Vol. 307, p72-85. 14p. - Publication Year :
- 2021
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Abstract
- • New Sr-Nd-Hf isotopic data on MORB lavas from OH-1 and OH-3 segments at the Mid-Atlantic Ridge 33–35°N. • Three mantle components are identified in the mantle source of these MAR lavas. • A Sr-Nd-Hf isotopic view on the origin of geological differences in OH-1 and OH-3 segments. We present new Sr-Nd-Hf isotopic data on mid-ocean ridge basalts from two ridge segments (OH-1, OH-3) between the Oceanographer and Hayes fracture zones at the Mid-Atlantic Ridge 33–35°N to constrain the nature and origin of upper mantle heterogeneity beneath the Mid-Atlantic Ridge. Together with the major and trace elements data (Niu et al., 2001), the new Sr-Nd-Hf isotopic data illustrate that the mantle sources of these lavas comprise three components, i.e., a depleted mantle with high radiogenic Hf isotopic compositions (ADM), an incompatible elemental enriched component with radiogenic Sr and un-radiogenic Nd-Hf isotopic compositions (E-type I), and an incompatible element depleted component with variably enriched Sr-Nd-Hf isotope compositions (i.e., E-type II). The ADM and E-type I components may be understood as representing ancient mantle melting residues and metasomatic veins developed at the base of the thickening oceanic lithosphere, respectively. The unique E-type II component is best explained as recent mantle melting residues of a geochemically enriched mantle, probably associated with the Azores mantle plume to the north. Taking together, we interpret the E-MORB dominated OH-1 lavas as resulting from a relatively higher degree melting of a mantle source composed of ADM matrix and E-type I material, whereas the N-MORB dominated OH-3 lavas resulting from lower degree melting of the mantle source primarily comprising ADM and E-type II components. Such a petrological and geochemical understanding explains the contrast in crustal thickness, ridge morphology and tomography, and mantle Bouguer anomalies between the two ridge segments. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00167037
- Volume :
- 307
- Database :
- Academic Search Index
- Journal :
- Geochimica et Cosmochimica Acta
- Publication Type :
- Academic Journal
- Accession number :
- 151290187
- Full Text :
- https://doi.org/10.1016/j.gca.2021.05.033