The origin of ferro-manganese oxide coated pumice from the Central Indian Ocean Basin

Abstract

Pumice clasts, partially and fully coated with ferro-manganese oxide from the Central Indian Ocean Basin (CIOB) were analysed for major, trace and rare earth elements; and glass and mineral grain chemistry to assess their possible source. These pumice clasts have similar to 95% glassy matrix with similar to 5% of plagioclase, ortho-pyroxene, amphibole, and spinel mineral grains. Pumice is rhyolitic, with high content of silica and total alkalis and show strong light rare earth element enrichment, with La 100 times enriched compared to chondritic abundance and exhibits a pronounced negative Eu-anomaly. Both the partially and fully coated pumice clasts have a similar composition, but this, and their, glass and mineral (orthopyroxene) chemistry differs from all tuffs known to have erupted from the Toba Caldera Complex. The partial to complete Fe-Mn oxide coating suggests the pumice probably predates activity from the Toba caldera. Their general composition is consistent with a volcanic arc origin, and show similarities to rhyolitic eruptives from Sumatra. The distribution of partially and fully coated pumice in the CIOB overlaps with that of uncoated pumice from the voluminous YTT eruption, suggesting that other large rhyolitic calderas active in Sumatra/Indonesia. Similarities in composition to ash layers from the CIOB suggest a possible Late Miocene - Late Pleistocene age for these pumices. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.Peer reviewe

Reworked volcaniclastic deposits from the Usumacinta river, Mexico: A serendipitous source of volcanic glass in Maya ceramics

“…Pattan et al. () described pumice with Fe–Mn coatings in the Central Indian Ocean Basin (CIOB). Many of these pumice fragments have partial Fe–Mn oxide deposition along their rim with spots and patches of oxide surrounding uncoated areas.…”

“…Fisher and Schmincke (1984) comment that the occurrence of accretionary lapilli is due to contemporary rains in the basin during pyroclastic ash-fall events; in distal volcaniclastic environments, this feature is only preserved in the subaerial floodplain due to the destruction of nonwelded ash-aggregated particles by water (Cas & Wright, 1987). Pattan et al (2013) described pumice with Fe-Mn coatings in the Central Indian Ocean Basin (CIOB). Many of these pumice fragments have partial Fe-Mn oxide deposition along their rim with spots and patches of oxide surrounding uncoated areas.…”

Composition and genesis of ferromanganese deposits from the northern South China Sea

“…nodules reported to occur in the Pacific (Hein et al, 2012) and Indian Ocean basins (Pattan and Parthiban, 2011;Pattan et al, 2013). The scattered Fe-Mn crusts are mostly distributed around Zhongsha and Xisha carbonate platforms.…”

Nature and composition of interbedded marine basaltic pumice in the ∼52–50 Ma Vastan lignite sequence, western India: Implication for Early Eocene MORB volcanism offshore Arabian Sea

“…The Arabian Sea region has several prominent fea tures, such as several deep ocean basins by submarine plateaus, aseismic Laxmi and Chagos-Laccadive Ridges, seismically active Carlsberg and Sheba Ridges, the regionally extending Owen fracture zone, and the cental Indian Ocean basin (figure 1). Pumice rafts in the central Indian Ocean may not represent our samples, because they are largely high silicic compositions (rhyolite to dacite) believed to have sourced from large rhyolitic calderas active in Sumatra/Indonesia (Kalangutkar et al 2011;Pattan et al 2013).…”