Crystallization conditions and magmatic–hydrothermal evolution of syenite dykes spatially associated with gold mineralization: the example of the Dolodau syenite–carbonatite complex, Abitibi greenstone belt

The Dolodau syenite–carbonatite complex is one of several syntectonic intrusions of the Abitibi greenstone belt, Superior craton, Canada. It formed during the syntectonic period, which is the main deformation stage leading to craton stabilization. Such magma can be involved in intrusion-related gold systems (IRGS) and be overprinted by orogenic gold systems (OGS), with IRGS and OGS being the main gold mineralizing systems of the syntectonic period. Determining whether magmas of the syntectonic period can transport enough gold to fertilize the upper crust requires insights into the crystallizing conditions and the volatile content of these magmas. Retrieving such data from the altered rocks generally encountered in mineralized areas is best accomplished by accumulating case studies. This study focuses on the Au–W–Ag mineralization spatially associated with the Dolodau intrusive complex to evaluate its fertility for Au. Using field relationships, petrographic observations, whole rock geochemical analyses, and mineral chemistry (titanite, apatite), we show that Dolodau is a carbonatite–syenite–granodiorite intrusive suite that crystallized rapidly at shallow depth in an active fault zone. The magma was S- and Cl-poor according to apatite chemistry, and it was likely incapable of transporting a significant amount of gold through the crust. It is concluded that the Dolodau Au–W–Ag mineralization is an OGS related to a major northeast–southwest-oriented fault.