Pb isotopic variability in melt inclusions from oceanic island basalts, polynesia

Area of Science:

• Geochemistry
• Petrology
• Volcanology

Background:

• Trace element variability in basaltic melt inclusions is often attributed to melting processes.
• Ocean island basalts (OIBs) provide insights into mantle heterogeneity and magma evolution.

Purpose of the Study:

• To investigate the origin of trace element and isotopic heterogeneity in olivine-hosted basaltic melt inclusions.
• To determine if melting processes or magma mixing are responsible for observed variability.

Main Methods:

• Analysis of lead (Pb) isotopic compositions in melt inclusions from Mangaia and Tahaa, Cook Islands and Society Islands, respectively.
• Application of two-component mixing models to explain isotopic data.

Main Results:

• Melt inclusions exhibit heterogeneous Pb isotopic compositions, contrasting with homogeneous erupted lavas.
• The range of Pb isotopic compositions within individual melt inclusions is substantial, covering 50% of the global OIB range.
• Data are consistent with two-component mixing models for each island.

Conclusions:

• Magma mixing, rather than solely melting processes, is a significant factor in generating trace element variability in basaltic melt inclusions.
• Isotopically distinct magmas likely coexisted within the volcanic plumbing system prior to or during melt aggregation.