|Authors||A. Lavecchia, S. Clark, F. Beekman, S. A. P. L. Cloetingh and E. Burov|
|Title||Thermal perturbation, mineral assemblages and rheology variations induced by dyke emplacement in the crust|
|Project(s)||No Simula project|
|Publication Type||Journal Article|
|Year of Publication||2016|
We constructed a thermo-mechanical model to examine the rheology variations in a two-layered crustal section, resulting from the intrusion of a sequence of basaltic dykes. The mineralogical assemblage can change in space and time as the result of temperature-induced metamorphism. We adopted typical intracontinental lithologies, with a temperature and melt dependent rheology, and paid particular attention to determine how different mineral assemblages and reaction kinetics during metamorphism may influence the thermo-mechanical behavior of the crust, in terms of differential stress values. We have investigated: 1) a quartz-feldspathic crust (QF), 2) a crust whose mineralogical assemblage approximates estimations of average chemical composition occurring in literature (CC), and 3) a micaschists crust (MS).
Our model shows that temperature profiles are weakly influenced by metamorphism, with negligible variations in the T-t paths. The results indicate that the intrusion-induced changes in the crustal rheology are strongly dependent on mineralogical assemblage variation. The strength of a dyke aureole in the upper crust increases during dyke emplacement; this may cause migration of later dykes and influence the dyke spacing. In contrast, the strength of a dyke aureole in the lower crust decreases during dyke emplacement. Fast kinetics results in a ductile lower crust in proximity of the dykes, whereas slower kinetics leads to the formation of partial melts and subsequent switch from ductile to brittle behavior. Lithology exerts a dominant role on the quantity of melt produced, with higher volume percentages occurring in the MS case study. Produced melts may migrate and support acidic volcanic activity.