[S-MP43] 変形岩・変成岩とテクトニクス

[SMP43-15] 房総半島嶺岡帯の蛇紋岩化したかんらん岩に残された背弧的特徴とその空間分布

*道林 克禎¹、片貝 寿幸² (1.静岡大学学術院理学領域、2.静岡大学理学部地球科学科)

キーワード：嶺岡帯、かんらん岩、鉱物化学組成、カンラン石の結晶方位

We studied chemical compositions and crystal-preferred orientations of serpentinized peridotites in Mineoka belt, Boso peninsula, Honshu island, Japan. The chemical compositions of both olivine and spinel are in the range of the olivine-spinel mantle array of Arai (1994, Chemical Geology). Spinel Cr# can be divided into two groups: high Cr# (0.5-0.6) and low Cr# (0.3-0.4). Moreover, we found that olivine crystal-fabrics in these peridotites have two types along with the two chemical compositions: A type with the low Cr# to the west and D type with the high Cr# to the east of the Mineoka belt. The chemical compositions are compatible with those of Parece Vela Rift (Ohara et al., 2003, G3). We suggest that the peridotites in the Mineoka belt could be derived from backarc environment and they have not so dismembered at present, since both structural and petrological characteristics are correlated to their spatial distribution in the Mineoka belt.