Experiments on granite intrusion in transtension
T. Román-Berdiel, A. Aranguren, J. Cuevas, J. M. Tubía, D. Gapais, J.-P. Brun, 1999. "Experiments on granite intrusion in transtension", Salt, Shale and Igneous Diapirs in and around Europe, Bruno C. Vendeville, Yossi Mart, Jean-Louis Vigneresse
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Granite intrusion in transtensional regime is modelled by injecting a Newtonian fluid into a sand pack containing a ductile layer. The transtensional regime is obtained using two plastic sheets sliding along two rigid horizontal plates, and diverging from two narrow spaces (two fixed velocity discontinuities). The injection tube is located in a central space between these plates. Both symmetric experiments (when the two sheets were displaced with equal and opposite velocity vectors) and asymmetric experiments (in which only one sheet was displaced) were performed. Transtension was applied with a systematic variation (every 15°) of the divergence angle (α), between 15° and 90°. Experiments showed that: intrusions localize strain from the first stages of deformation; intrusions result in partially conformable laccoliths with bowler-hat geometry in cross-section; intrusions show an important offset towards the mobile basal plate for asymmetric transtensional regime, and are more symmetric and centred on the injection point for symmetric transtensional regime; the geometry of intrusions is controlled by the faults developed in the overburden. The significance of this control depends upon the angle of divergence α. Examples of the Hombreiro and Los Pedroches granites of the Variscan belt of Spain have been addressed to test the applicability of these experimental results.
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Salt, Shale and Igneous Diapirs in and around Europe
The ten articles in this book describe the mode of emplacement of various types of intrusions (salt diapirs, mud volcanoes and magmatic bodies) by means of theoretical reasoning, analogue and analytical modelling, interpretation of seismic and field data, and geodetic surveying. All the articles emphasize the role of regional tectonics in driving or controlling the emplacement of the intrusions. The selection of articles includes examples from Spain, Romania, onshore and offshore Italy, the Eastern Mediterranean, Israel and iran.
Better understanding of the mode of emplacement of these intrusions has applications in hydrocarbon exploration (e.g., where salt structures or mud diapirs are present) and in the mining industry (where mineralization is related to the emplacement of batholiths).