![]() ![]() ![]() Compositionally intermediate magmas were erupted during the Rotoma and Whakatane episodes are likely to be hybrids. The least evolved (SiO2=72.8–74.1 wt%, Sr=132–134 ppm) magma was erupted from the northeastern (Pararoa) vent and is characterised by an orthopyroxene+ hornblende-dominant mineralogy, temperature of 764☑8☌, and fO2 of NNO+0.40☐.13. The most evolved (SiO2=73.3–76.2 wt%, Sr=88–100 ppm) Whakatane magma erupted from the southwestern (Makatiti) vent and is cummingtonite-dominant, cool (745☑1☌), and reduced (NNO+0.34☐.08). The ~11 km3 Whakatane episode occurred at 5.6 ka and also erupted three magmas, each from a separate vent. The least evolved (SiO2=75.0–76.4 wt%, Sr=128–138 ppm, orthopyroxene+ hornblende-dominant) Rotoma magma erupted from several vents, and was hotter (764☑8☌) and more reduced (NNO+0.40☐.13). The most evolved Rotoma magma (SiO2=76.5–77.9 wt%, Sr=96–112 ppm) erupted from a southeastern vent, and is characterised by a cummingtonite-dominant mineralogy, a temperature of 739☑4☌, and fO2 of NNO+0.52☐.11. Three magmas totalling ~8 km3 were erupted during the 9.5 ka Rotoma episode. Two of the three eruption episodes have tapped multiple compositionally distinct homogeneous magma batches. Post-10 ka rhyolitic eruptions from the Haroharo linear vent zone, Okataina Volcanic Centre, have occurred from several simultaneously active vents spread over 12 km. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |