福岡県篠栗町の三郡変成岩中の“角閃岩”

抄録

Amphibolite in the Sangun metamorphic rocks of Sasaguri district was studied from petrological and petrochemical point of view. The Sasaguri metamorphic rocks, which are mainly composed of greenschist and blackschist, were found to be the products of the glaucopbanitic metamorphism. Closely accompanied with these rocks, serpentinite and amphibolite occur in the southeastern part of this district.
In the northeastern part of the area the Sangun metamorphic rocks suffered contact metamorphism by the later intrusion of the Hagio granodiorite. The contact aureole around it can be divided into two zones, of which zone I belongs to the albite epidote hornfels facies, and zone II to the hornblende hornfels facies. However, among the Sangun metamorphic terrane, high grade metamorphic rocks corresponding to the amphibolite facies have never been found. So far amphibolite of this district has ever been considered to be the product of contact metamorphism of the Sangun metamorphic rocks by the Hagio granodiorite.
But the present study clarified that amphibolite occurs beyond the contact aureole of granodiorite mass. This fact indicates the possibility that amphibolite may be formed by the pre-Sangun metamorphism. The recent finding that K-Ar ages of hornblende from this amphibolite are 295±20 and 383±14 m. y. may support this aspect.