[HCG34-P03] Identification of historical building stones and their distribution on the basis of magnetic susceptibility of granites
Keywords:granite, historical stone materials, magnetic susceptibility, granitic stones
Determination of quarrying area of historical stone materials is effective for researches on social condition, culture and so on. In particular, granite stones are widely distributed in various historical times. However, observation of stone materials tends to be qualitative and subjective, because of necessity of nondestructive inspection. Accordingly, I applied measurement of magnetic susceptibility and color index of granitic stone materials and their out crop in some quarries for the quantitative determination. Islands and coastal area of Seto Inland Sea are major production area of granitic stones. They are composed of ilmenite-series granites with low magnetic susceptibility but ranges of magnetic susceptibility of each intrusive mass are slightly different. Magnetic susceptibility reflects iron contents and oxygen fugacity of granite magma. Magma compositions of granites are reflected in contents of mafic minerals. Diagram of magnetic susceptibility and color index is more effective to identification of granitic stones and their product area.
Identification of product area of granite stones revealed following change history of their quarrying and distributions.
(1) Surrounding area of Rokko Mountains is main producing area of granitic stones at 14th to 16th century. They have been used mainly tomb stones and memorial towers of influential persons.
(2) Quarrying sites were extended to entire area of Seto Inland Sea after construction of Osaka Castle at 17th century.
(3) Large amount of granitic stone materials transferred from Seto Inland Sea area to shrines and temples in Sea of Japan area by cargo ships (Kitamae-bune) at 17th to 19th century.
(4) Especially, Onomichi area was raised major production area and quarrying in Rokko Mountains was declined at 19th century.
Identification of product area of granite stones revealed following change history of their quarrying and distributions.
(1) Surrounding area of Rokko Mountains is main producing area of granitic stones at 14th to 16th century. They have been used mainly tomb stones and memorial towers of influential persons.
(2) Quarrying sites were extended to entire area of Seto Inland Sea after construction of Osaka Castle at 17th century.
(3) Large amount of granitic stone materials transferred from Seto Inland Sea area to shrines and temples in Sea of Japan area by cargo ships (Kitamae-bune) at 17th to 19th century.
(4) Especially, Onomichi area was raised major production area and quarrying in Rokko Mountains was declined at 19th century.