摘要
The Monte Santo Alkaline Intrusive Suite (MSAIS) is an association syenite foid, nepheline syenite and syenite, which are intruded in metapelites of the Rio do Coco meta-volcanic-sedimentary Sequence, presenting abundant pegmathoid veins cutting all of them. The ages obtained by Shrimp (1051 ± 22 Ma, 1048 ± 11 Ma) are very close those younger age obtained by U-Pb laser ablation (1056 ± 21), beeing interpreted as crystallization age. These dating reveal also that MSAIS rocks were affected by common succession of younger events below 550 Ma ago, responsible by the later rocky bodies of varying composition occurring in the region, including the alkaline pegmatites hosted in the nepheline syenite of the MSAIS.
The Monte Santo Alkaline Intrusive Suite (MSAIS) is an association syenite foid, nepheline syenite and syenite, which are intruded in metapelites of the Rio do Coco meta-volcanic-sedimentary Sequence, presenting abundant pegmathoid veins cutting all of them. The ages obtained by Shrimp (1051 ± 22 Ma, 1048 ± 11 Ma) are very close those younger age obtained by U-Pb laser ablation (1056 ± 21), beeing interpreted as crystallization age. These dating reveal also that MSAIS rocks were affected by common succession of younger events below 550 Ma ago, responsible by the later rocky bodies of varying composition occurring in the region, including the alkaline pegmatites hosted in the nepheline syenite of the MSAIS.
