Differential typologic distribution of mafic enclaves and dykes in the Charroux-Civray tonalites (Vienne, France): consequences for the emplacement dynamics of a pluton

The systematic analysis of the spatial distribution and morphology of mafic enclaves and dykes, and of the chemistry and structures of enclosing pluto nic rocks, along a 800 m deep drilling shows that: (i) the pluton is compos ed of several tonalitic injections, each one characterized by a specific ge ochemical evolution and magmatic fabric; (ii) the calc-alkaline mafic magma s are injected synchronously with enclosing melts to form the dark tonalite s; (iii) the sub-alkaline mafic melts are injected slightly later. Thus, an alysis of enclave distribution and morphology, enclave and enclosing rock c hemistry offers a powerful tool to characterize the dynamic of magma emplac ement. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.