Heterogeneous Fossil Réunion Plume Component in the Source Region of Enriched MORB Along the Central Indian Ridge Between 12° and 17°S. Issue 12 (12th December 2022)

• Record Type: Journal Article
• Authors: Vincent, Clément; Park, Jung‐Woo; Lee, Sang‐Mook; Kim, Jonguk; Lee, Mi‐Jung; Révillon, Sidonie
• Is Part Of: Journal of geophysical research. Volume 127:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-12
• Subjects: Central Indian Ridge -- E‐MORB -- mantle heterogeneity -- Réunion plume; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2022JB025379
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: Mid‐ocean ridge basalts (MORB) from the Central Indian Ridge (CIR) between 12° and 17°S show a wide range of geochemical and isotopic variations. Particularly, MORB from a segment between 14° and 15°S are more enriched in incompatible trace elements with more radiogenic Sr and Pb isotope and unradiogenic Nd isotope values than the lavas between 15° and 16°S with geochemical features of normal MORB. However, the causes for the enrichment between 14° and 15°S are poorly constrained. In this study, we re‐examined the CIR MORB from 12° to 17°S with new geochemical data obtained based on high spatial resolution sampling to better understand the nature of the enriched mantle source. Our new geochemical data show that the MORB between 14° and 15°S, with maximum values for (La/Sm)N = 1.95, 87 Sr/ 86 Sr = 0.703526 and 206 Pb/ 204 Pb = 18.7558, are more enriched than those from the southern segments (16° to 20°S) known to be influenced by the Réunion mantle component. The new trace element and isotopic compositions of MORB suggest that three mantle end‐members are required to explain the geochemical variations shown between 14° and 16°S: the depleted Indian‐type MORB mantle, Réunion Plume (RP), and Seychelles/Madagascar‐like continental crust components. Moreover, our mixing model suggests that the differences in enriched MORB signature from 14° to 20°S are due to variable proportions of continental material previously mixed with the RP. Our study implies that a continental component interacted with the plume into the asthenosphere, possibly beneath Madagascar or below Mauritius Island and the Mascarene plateau. Plain Language Summary: The basaltic lavas erupting on the mid‐ocean ridges are considered a window to understand the geochemical features of the upper mantle because they are produced by partial melting of the underlying mantle. The mid‐ocean ridge basalts (MORB) from the Central Indian Ridge (CIR) between 12° and 17°S show a wide range of geochemical and isotopic variations. Particularly, the MORB from the segment between 14° and 15°S have higher trace element contents with more radiogenic Sr and Pb isotopes and unradiogenic Nd isotopes than those from the neighboring ridges. We investigated the mantle source of the E‐MORB using our new geochemical data of basaltic lava samples collected with high spatial resolution along the ridge between 12° and 17°S and showed that the enriched lavas between 14° and 15°S are not only linked to the Réunion mantle plume, but also to a continental crust component that contaminated the Réunion mantle plume. Moreover, our new results enlarge the isotopic range of the Réunion mantle plume and show the complexity and heterogeneity of the upper mantle underlying the CIR. Key Points: Source of enriched MORB (E‐MORB) from the Central Indian Ridge (12°–17°S) is constrained by Sr‐Nd‐Pb isotope and trace element geochemistry The E‐MORB source between 14° and 16°S is related to three components: a depleted mantle, Réunion Plume (RP), and continental components Variable proportions of continental components mixed with the RP may account for the MORB geochemistry between 14° and 20°S