The tholeiitic Kermadec volcanic suite: Additional field and petrological data including iron-enriched plagioclase feldspars

Abstract

New lithological and petrological descriptions are given for a cluster of offshore islands in the Raoul group (Napier, Nugent, North and South Meyer, Dayrell, North and South Chanter) and for L'Esperance Island, along with AFM plots for 40 additional bulk chemical analyses. Petrography and microprobe data for these rocks, and for other islands in the Kermadec chain (Macauley, Curtis, Rumble III), confirm the tholeiitic nature of the volcanic suite which contains olivine, minor orthopyroxene and augitic, subcalcic and pigeonitic clinopyroxene but lacks amphibole. Core-to-rim iron enrichment appears in phenocrystal olivine, orthopyroxene and clinopyroxene, and is most pronounced in fractionated plagioclase feldspar sequences which have Fe: An ratios that are characteristic for each of the main rock groups: basalts, basaltic andesites and andesites|dacite feldspars show progressive Fe depletion.

Keywords:

• Kermadec Ridge
• volcanic rocks
• petrology
• chemical analyses
• microprobe
• tholeiites
• plagioclase
• iron enrichment