Silicate-Carbonate Liquid Immiscibility: Insights from the Crevier Alkaline Intrusion (Quebec)

摘要: This contribution explores the petrogenetic relationships between silicate and carbonatitic rocks in Crevier Alkaline Intrusion (CAI, Quebec, Canada). The CAI is located Proterozoic Grenville Province composed of a suite undersaturated peralkaline from ijolite to nepheline syenite carbonatites. Petrogenetic different alkaline igneous rocks, carbonate-bearing carbonate-free carbonatites observed suggest that (i) are comagmatic with carbonatite, (ii) both liquids fractionated an ijolitic parental magma has undergone liquid immiscibility. One facies characterized by spectacular ocelli matrix carbonatite. younger can be divided into two groups based on presence or absence magmatic carbonates. Both pyrochlore-group minerals carry Nb-Ta mineralization. We specifically use accessory such as zircon, pyrochlore apatite constrain temporal physicochemical parameters immiscibility process. By coupling mineral textures, trace elements, (iii) Ti-in-zircon thermometry, (iv) oxygen isotope compositions, we have traced crystallization zircon before, during after results allowed us minimum temperature this process at ∼815-865 °C. In addition, populations identified through their petrographic geochemical characteristics within facies. Pyrochlore earlier follow differentiation trend, whereas more classical Nb-Ti trend. Following complete liquids, fractionation Nb Ta stopped while new generation Nb-rich grew, displaying trend constant Nb/Ta ratio syenite.