Lithium Abundance and Lithium Isotope Variations in Mantle Sources: Insights from Intraplate Volcanic Rocks from Ross Island and Marie Byrd Land (Antarctica) and other Oceanic Islands

Jeffrey G. Ryan, Philip R. Kyle

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Abstract

<p> <p id="x-x-x-"> The Li abundances and isotopic compositions of lavas from the McMurdo Volcanic Group (MVG) and the Crary Mountains, Antarctica and selected oceanic islands show Li is sensitive to both the mantle sources of basalts, and the open-system processes that occur during magmatic differentiation. Basaltic MVG lavas have uniform Li isotopic signatures, whereas more evolved lavas have variable &delta; <sup> 7 </sup> Li indicating inputs of altered crustal materials. MVG basalts and those of the Crary Mountains have similar &delta; <sup> 7 </sup> Li, and have compositions broadly consistent with mixing between a MORB-source mantle reservoir and a probable HIMU reservoir with elevated &delta; <sup> 7 </sup> Li. <p id="x-x-x-"> &delta; <sup> 7 </sup> Li values in ocean island basalt (OIB) samples examined range from +3&permil; to +7&permil;; only two ocean islands were distinguishable from MORBs. None of our OIB samples showed the anomalously low &delta; <sup> 7 </sup> Li that Nishio et al. (2004) have contended is indicative of the EM1 mantle reservoir. Mixing of plume material with a MORB-like upper mantle can serve to mask extreme Li isotopic signatures to a degree, but it may also be the case that the mantle is heterogeneous in &delta; <sup> 7 </sup> Li on the fine scales represented by xenolith hand samples, but relatively homogeneous on the scales of hotspot melting anomalies. </p> </p></p>
Original languageAmerican English
JournalChemical Geology
Volume212
DOIs
StatePublished - Nov 1 2004

Keywords

  • Lithium abundance
  • Lithium isotope variation
  • Mantle
  • Ross Island
  • Marie Byrd Land

Disciplines

  • Earth Sciences
  • Geology
  • Physical Sciences and Mathematics

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