Whole rock major and trace elements of andesites and basaltic inclusion from Narewa Andesitic plug, Rakiraki, Fiji
Abstract:
The Narewa sub-volcanic plug (Rakiraki, Viti Levu, Fiji) consists of andesites containing the phenocryst assemblage: plagioclase > amphibole > pyroxene, which were investigated to establish their petrogenesis. The andesites host enclaves of amphibole-gabbro and sporadic centimeter-scale, quenched basaltic inclusions with an ultra-depleted REE composition (LaN/YbN ~0.20) similar to other regional volcanic rocks. Chemical compositional mapping reveals complex zoning in hornblende and larger, corroded plagioclase phenocrysts, which contrasts with normally-zoned smaller plagioclase. These zoning patterns suggest the system experienced periodic magma replenishment by depleted basaltic magma. The replenishment is further supported by a lack of correlation between Cr/Al and Ti/Al in pyroxene, as well as Sr isotopic disequilibrium in plagioclase. Specifically, the 87Sr/86Sr (0.6979 to 0.7149) in plagioclase lack correlation with the An-content (63.3 to 97.6) confirming crystallization from isotopically distinct melts. The less radiogenic 87Sr/86Sr of the smaller, normal-zoned phenocrysts and the outer rims of the larger grains indicates they crystallized from a more mafic melt that was injected into the system. Trace element similarities suggest a genetic relationship between basalts and andesites where the basalts differentiated to form the andesites. The ultra-depleted rare earth elements (REE) of basalts and mid-ocean ridge basalt (MORB)-like signatures of the andesites indicate that the Narewa andesites originated from supra-subduction melting of a depleted mantle source, differentiating in a magma chamber that was periodically replenished by influx of depleted basaltic magma before eruption.
How to cite this dataset:
Regmi, K. R., Imayama, T., Shrestha, S., Button, M., Cottle, J. M., 2028. Whole rock major and trace elements of andesites and basaltic inclusion from Narewa Andesitic plug, Rakiraki, Fiji, Version 1.0. Interdisciplinary Earth Data Alliance (IEDA).
https://doi.org/10.60520/IEDA/114482. Accessed 2026-05-25.
DOI Creation Date:
2026-05-21
License:
Creative Commons Attribution 4.0 International [CC-BY-4.0]
Funding source(s):
Social Policy Grant, Nazarbayev University
Keyword(s):
Coverage Scope: Global
Geographic Location: Narewa Andesitic Plug, Rakiraki, Viti Levu, Fiji
User Contributed Keyword(s):
Narewa Andesite petrogenesis; magma replenishment; plagioclase Sr isotopes; supra-subduction depleted magmatism; MORB-like signatures of andesite; Rakiraki Fiji Geology.
Data Available On:
2028-04-18