VI Simpósio de Vulcanismo e Ambientes Associados

DATA: 2 a 5 de agosto de 2015 - LOCAL: USP - Cidade Universitária - São Paulo - SP

Palestrantes Confirmados

Donald Bruce Dingwell
Department for Earth and Enviromental Sciences | Ludwig Maximilians University, Alemanha
web page
Experiments with magmas and volcanoes
Abstract


Jeroen Ritsema
Department of Earth and Environmental Sciences | University of Michigan, EUA
web page
Ten questions for a tomographer
Abstract


José Madeira
Faculdade de Ciências da Universidade de Lisboa, Portugal
web page
The 2014-2015 eruption and the post-settlement eruptive activity in the Island of Fogo, Cape Verde
Abstract


Michele Lustrino
Dipartimento di Scienze della Terra | Università degli Studi di Roma La Sapienza, Italia
web page
The role of geology in determining the age, location and composition of igneous rocks within and around the Mediterranean area
Abstract


Umberto Cordani
Instituto de Geociências – Universidade de São Paulo
web page
A história geológica de Fernando de Noronha


Experiments with magmas and volcanoes

Abstract

The rise of experimental volcanology provides a valuable third approach (after observational and simulation studies) for advancing the understanding of igneous processes. Our understanding of the processes of explosive volcanism has profited greatly from this development. The experimental approach can validate mechanisms of magmatic processes, provide tests for hypotheses of volcanic scenarios, and quantify the materials response of the magmas, with significant implications for the interpretation of igneous rocks and the monitoring of active volcanoes.

Ten questions for a tomographer

Abstract

Seismic tomography is a key technique for illuminating the thermal and compositional structure of the mantle. Quantitative resolution analysis and full 3D wave simulations must accompany the seismic modeling. Using examples from upwelling regions, I will demonstrate that incomplete data sampling leads to heterogeneous image distortion and that wave diffraction inhibits the resolution of small-scale structures (e.g., mantle plumes).

The 2014-2015 eruption and the post-settlement eruptive activity in the Island of Fogo, Cape Verde

Abstract

An eruption started on November 23rd, 2014 in the Island of Fogo and is still on-going as this abstract is being written (end of January 2015). The most significant aspects of this eruption and a comparison with previous events will be presented, together with the geological setting of the archipelago and structure of the island.

The Island of Fogo, the only volcano in Cape Verde archipelago with reported historical activity, is one of the most active oceanic volcanoes in the world and the only one where the volcanically active area is inhabited. Including the present event, there are 29 accounts to eruptions in Fogo since its discovery in 1460, 12 of which (including the latest three that were studied by geoscientists) are sufficiently detailed to allow for the reconstruction of the eruptive centres and correlative lava flows.

Fogo is a central polygenetic stratovolcano, about 25 km in diameter at sea-level, located in the south-western part of the Archipelago. Its morphology is characterized by an 8 km-wide summit depression open to the East and partially delimited by an almost vertical wall (Bordeira) rising 1000m from Chã das Caldeiras, a flat area at an average altitude of 1600-1700m. Inside this depression an 1100m-high cinder cone (Pico do Fogo) grew up to the maximum altitude of the island (2.829m). Most of the area inside the summit depression and down the east flank is floored by historical lava flow fields.

The role of geology in determining the age, location and composition of igneous rocks within and around the Mediterranean area

Abstract

Igneous activity in tectonically complex areas can be interpreted in many different ways, producing completely different petrogenetic models. Processes such as oceanic and continental subduction, lithospheric delamination, changes in subduction polarity, slab break-off and mantle plumes have all been advocated as causes for changes in plate boundaries and magma production, including rate and temporal distribution, in the circum-Mediterranean area. This region thus provides a natural laboratory to investigate a range of geodynamic and magmatic processes. Although many petrologic and tectonic models have been proposed, a number of highly controversial questions still remain. No consensus has yet been reached about the capacity of plate-tectonic processes to explain the origin and style of the magmatism. Similarly, there is still not consensus on the ability of geochemical and petrological arguments to reveal the geodynamic evolution of the area. The wide ranges of chemical and mineralogical magma compositions produced within and around the Mediterranean complicate models and usually require a large number of unconstrained assumptions.

Can the calcalkaline-sodic alkaline transition be related to any common petrogenetic point? Is igneous activity plate-tectonic- (top-down) or deep-mantle-controlled (bottom-up)? Do the rare carbonatites and carbonate-rich igneous rocks derive from the deep mantle or a normal, CO2-bearing upper mantle? Do ultrapotassic compositions require continental subduction?

Understanding chemically complex magmas emplaced in tectonically complex areas require open minds, and avoiding dogma and assumptions. Studying the geology and shallow dynamics, not speculating about the deep lower mantle, is the key to understanding the igneous activity.

 

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