Geometry of granite emplacement in the upper crust: contributions of analogue modelling
Published:January 01, 1999
Teresa Román-Berdiel, 1999. "Geometry of granite emplacement in the upper crust: contributions of analogue modelling", Understanding Granites: Integrating New and Classical Techniques, Antonio Castro, Carlos Fernández, Jean Louis Vigneresse
Download citation file:
Granite emplacement in the brittle crust can be modelled by means of the injection of a Newtonian fluid (low-viscosity silicone putty) into sandpacks. This paper describes dynamically scaled analogue models of granite intrusions in the upper crust under different tectonic regimes. Experiments analyse three boundary conditions: (1) static conditions, with different rheological profiles (single sand-layer system, two-layer silicone-sand system, three-layer sand-silicone-sand system and five-layer sand-silicone-sand-silicone-sand system), (2) extensional regime, including gravitational sliding and divergent basal plate, with both mobile and fixed velocity discontinuities and (3) strike-slip regime, induced by two mobile basal plates. The results obtained indicate that: (1) a soft level between two competent units is necessary for laccolith formation—the critical thickness of the soft layer necessary for laccolith formation decreases with increasing depth, (2) when there are two soft layers in the brittle crust, laccolith emplacement occurs in the deeper soft level, even when this is thin and the overburden does reach its critical thickness, (3) in extensional regimes the geometry of intrusions is mainly controlled by normal faults and at the same time intrusions determine the location of faults within the cover and (4) in strike-slip zones intrusions are elongate and their long axis tends to track the principal stretching direction associated with the strike-slip regime. Some natural examples of granitic bodies were considered to test the applicability of experimental results.
Figures & Tables
Understanding Granites: Integrating New and Classical Techniques
Granite magmatism represents a major contribution to crustal growth and recycling and, consequently, is one of the most important mechanisms to have contributed to the geochemical differentiation of the Earth’s crust since Archaean time. Granites are also often associated with ore bodies, and their study therefore has direct commercial relevance.
The modern view of the granite problems requires the application of many different theoretical, experimental and empirical resources provided by geophysics, geochemistry, experimental petrology, structural geology, scale modelling and field geology. Because of the complexity of the granite problem, it is necessary to integrate a variety of techniques and corroborate the findings with field observations.This is the philosophy of this book.
Many chapters are review papers dealing with the development and achievements of a particular technique, whilst other chapters deal with the application of a number of techniques to a specific problem. This volume brings together papers that would otherwise be dispersed in different publications.
The book will be of interest to igneous petrologists, geophysicists, structural geologists and geochemists.