Staged storage and magma convection at Ambrym Volcano, Vanuatu

New mineral-melt thermobarometry and mineral chemistry data are presented for basaltic scoriae erupted from the Mbwelesu crater of Ambrym volcano, Vanuatu, during persistent lava lake activity in 2005 and 2007. These data reveal crystallisation conditions and enable the first detailed attempt at reconstruction of the central magma plumbing system of Ambrym volcano. Pressures and temperatures of magma crystallisation at Ambrym are poorly constrained. This study focuses on characterising the magma conditions underlying the quasipermanent lava lakes at the basaltic central vents, and examines petrological evidence for magma circulation. Mineral-melt equilibria for clinopyroxene, olivine and plagioclase allow estimation of pressures and temperatures of crystallisation, and reveal two major regions of crystallisation, at 24–29 km and 11–18 km depth, in agreement with indications from earthquake data of crustal storage levels at c.25–29 km and 12–21 km depth. Temperature estimates are ~1150–1170 ºC for the deeper region, and ~1110 1140 ºC in the midcrustal region, with lower temperatures of ~1090–1100 ºC for late-stage crystallisation. More primitive plagioclase antecrysts are thought to sample a slightly more mafic melt at sub-Moho depths. Resorption textures combined with effectively constant mafic mineral compositions suggest phenocryst convection in a storage region of consistent magma composition. In addition, basalt erupted at Ambrym has predominantly maintained a constant composition throughout the volcanic succession. This, coupled with recurrent periods of elevated central vent activity on the scale of months, suggest frequent magmatic recharge via steady-state melt generation at Ambrym

National population and housing census : 2009

Vol. 1. Basic tables report -- v. 2. Analytical report

Vanuatu demographic and health survey : MICS 2013

xxvi, 395 pages : illustrations ; 31 cmThis report summarises the findings of the Vanuatu Demographic and Health Survey – Multiple Indicator Cluster Survey (DHS–MICS) 2013 implemented by the Vanuatu National Statistics Office in coordination with the Ministry of Health. The Secretariat of the Pacific Community (SPC) was the executing agency for the project. The Government of Vanuatu provided financial assistance in terms of in-kind contribution of government staff time, office space, and logistical support. The project was funded jointly by the Asian Development Bank, the United Nations Children’s Fund, the United Nations Population Fund and the Australian Agency for International Development. SPC was responsible for the overall coordination of the demographic and health survey operations, as well as the sample design, survey planning and budgeting, providing data processing support to the implementing agency, and coordinating the report. SPC had also provided technical assistance in the areas of survey design, questionnaires, manual adaptations, conduct of pretesting and main training, fieldwork monitoring, systems development, data processing and tabulation programmes as part of its contract with the Asian Development Bank. The opinions expressed in this report are those of the authors and do not necessarily reflect the views of the donor organisations