[1] Sediment gravity cores collected from the Pacific seafloor offshore Central America contain numerous distal ash layers from plinian-type eruptions at the Central American Volcanic Arc dating back to more than 200 ka. In part 1 of this contribution we have correlated many of those ash layers between cores and with 26 tephras on land. The marine ash layers cover areas of up to 10 km in the Pa...

The Central American volcanic arc supplies a significant proportion of the persistent annual global sulphur dioxide emissions from volcanoes. In November/December 2003, we completed a survey of the arc section from Mombacho to San Cristóbal in Nicaragua recording individual mean fluxes of 800, 530 and 220 Mg day 1 in the plumes from San Cristóbal, Telica and Masaya, respectively. An assessment ...

The Nam Pat Group of the Nam Pat Basin, Uttaradit Province, Thailand is situated in the Nan Suture Zone. Two contrasting tectonic framework models of the Nan Suture have previously been proposed: as a main Paleo-Tethyan suture and as a remnant of a closed back-arc basin. The goal of this study is to analyze the tectonic framework of the Nan Suture and reevaluate the existing tectonic models. Th...

Volcanoes find a new carbon platform The geological carbon cycle assumes that carbon is emitted by volcanic eruptions and removed through various forms of burial. Mason et al. found that not all volcanic eruptions have the same source for carbon in their volcanic gas. Arc volcanic activity appears to harvest carbon from old carbonate platforms, which results in a massive difference in the isoto...

19 The Fishguard Volcanic Group represents an excellently preserved example of a volcanic 20 sequence linked to the closure of the Iapetus Ocean. This study re-examines the petrogenesis 21 and proposed tectonic setting for the Llanvirn (467-458 Ma) Fishguard Volcanic Group, 22 South Wales, UK. New major and trace element geochemical data and petrographic 23 observations are used to re-evaluate ...

A remarkable record of early arc volcanism in the Izu–Bonin–Mariana (IBM) arc is exposed in and around the Bonin Islands, an uplifted segment of the IBM forearc. New Ar/Ar dating results imply that the boninitic volcanism on Chichijima Island occurred in a brief period during Eocene time, between 46–48 Ma. A slightly younger volcanic succession is identified along the Bonin Ridge, including 44....

TheOrdovician volcanic and intrusive rocks of the Cadia–Neville region, in the southern Molong Volcanic Belt section of the Macquarie Arc in central-western New South Wales, display a temporal progression from shoshonitic basaltic volcanism (e.g. Mt Pleasant Basalt Member) in the late Darriwilian to Gisbornian (ca 460–453 Ma) to small-volume dacitic medium-K calc-alkaline magmatism (e.g. Copper...

New Zealand’s newest and most active volcano, Mt. Ngauruhoe in the Taupo Volcanic Zone, produced andesite fl ows in 1949 and 1954, and avalanche deposits in 1975. Potassium-argon “dating” of fi ve of these fl ows and deposits yielded K-Ar model “ages” from <0.27 Ma to 3.5±0.2 Ma. “Dates” could not be reproduced, even from splits of the same samples from the same fl ow, the explanation being var...

Evaluation of volcanic and hydrothermal fluxes to the surface environments is important to elucidate the geochemical cycle of sulphur and the evolution of ocean chemistry. This paper presents S/(3)He ratios of vesicles in mid-ocean ridge (MOR) basalt glass together with the ratios of high-temperature hydrothermal fluids to calculate the sulphur flux of 100 Gmol/y at MOR. The S/(3)He ratios of h...

the lower to middle miocene chenar granitoid stock, a part of central iranian volcanic belt, is intruded into eocene volcano-sedimentary complex in northwestern kerman in south central iran. the chenar granitoid stock consists mainly of coarse to medium grain granodiorite and monzogranite with subordinate tonalite and syenogranite. alkali granites as aplitic veins and quartz dioritic dykes freq...