Granitoids with 300 Ma in the Joban coastal region, east of Abukuma Plateau, northeast Japan

作者：Tsutsumi Yukiyasu^*; Ohtomo Yukiko; Horie Kenji; Nakamura Ko ichi; Yokoyama Kazumi

来源：Journal of Mineralogical and Petrological Sciences, 2010, 105(6): 320-327.

DOI：10.2465/jmps.091204

• SHRIMP
• U-Pb age
• Zircon
• Paleozoic granitoid
• Northeast Japan
• GSJ B326

The GSJ B326 borehole was drilled in the joban coastal region, east of the Abukuma Plateau, reached a depth of similar to 1005 m. Although most of the sequence is composed of Tertiary sediments, plutonic rocks occur from 815.1 m to 1005 in in depth. The lithology of the plutonic rocks is tonalite and subordinate aplite veins. Radiometric ages of zircons in three granitoids were obtained from the U-238/Pb-206 ratio and isotopic compositions of Pb using a Sensitive High Resolution Ion MicroProbe (SHRIMP II). The weighted mean of the zircon ages of a sample from the shallower part of the borehole is 293 +/- 1.8 Ma, whereas that for two samples from the deeper part of the borehole is 300.3 +/- 1.5 Ma and 304.3 +/- 1.7 Ma. The previously reported U-Th-Pb chemical age of uraninite from the deeper part of the borehole is 285 +/- 4 Ma. These data indicate that a melt intruded into the similar to 300 Ma rock body at similar to 290 Ma. Granitoid with 300 Ma are scarce in the Japanese Islands, and this is the first report of such granitoids in northeast Japan.

• 出版日期2010-12
• 单位中国极地研究中心