U-Pb zircon ages from the Vaggeryd syenite and the adjacent Hagshult granite, southern Sweden

Abstract

South of Lake Vättern a series of syenite bodies have intruded in an elongated area subsequently affected by the Protogine Zone deformation. The by far largest of these bodies, the Vaggeryd syenite, has been dated by the U-Pb zircon method together with the TIB granite immediately to the east of the syenite, in this paper temporarily called the Hagshult granite. The crystallization age of the syenite sample is determined to 1204±6 Ma. The possibility that the Vaggeryd syenite consists of magmas from two separate intrusion events is discussed. Since the Vaggeryd syenite is transected by the ductile deformation of the Protogine Zone, this deformation must be younger than c. 1205 Ma. The result from the Hagshult granite yields an intrusion age of 1673±19 Ma. The granite thus belongs to the youngest group of TIB intrusions.

Keywords:

• Vaggeryd syenite
• TIB
• Protogine Zone
• Hagshult granite
• Vårgårda quartz-monzonite
• U-Pb
• Rb-Sr