Activity of proto-Pacific superplume from the viewpoint of Paleozoic ophiolites in Southwest Japan.

1.大江山蛇绿岩：阿什达奇杂岩的Sm-Nd同位素年龄显示，粗粒辉长岩为560 Ma，细粒辉长岩为350 ~ 450 Ma.矢久野蛇绿岩：片麻状变辉长岩的Sm-Nd同位素年龄为340 ~ 380 Ma。对朝后町地区两个英云闪长岩样品的锆石U-Pb年龄分别为282和285 Ma。辉长岩混合岩是在浅子町地区的下辉长岩段发现的，在那里，未成熟岛弧的底部部分熔融过程被很好地记录下来。侏罗系增生杂岩中的绿岩：增田地区绿岩的Sm-Nd同位素年龄为约1000 nm。在望月濑町地区的绿岩中发现了340 Ma碱性玄武岩，如铁闪石，显示出非常高的Nb/Zr比值，与HIMU玄武岩相似.其他地区的海泡石：对萨哈林岛北方施密特半岛蛇绿岩进行了Sm-Nd、Rb-Sr等时线法年龄测定和SHRIMP锆石U-Pb年龄测定。获得了125 Ma。对马里亚纳弧前蛇绿岩进行了变质相和地球化学分析，发现其与矢久野蛇绿岩有相似之处.地球化学数据库的建设：数据库系统采用“filemaker Pro ver. 3.O”组成了一个地球化学关系数据库。总结：侵入Ce-yama蛇绿岩、秋吉地体的海山群、Yakuno蛇绿岩的片麻状变质辉长岩、侏罗纪增生杂岩中的绿岩等古生代蛇绿岩在350 ~ 400 Ma期间的同时代活动在日本西南部较为突出。在泥盆纪至早石炭世的古太平洋地区，可能发生了同步活动，使超地幔柱得以延续。

1. Oe-yama ophiolite : Ashidachi complex shows the Sm-Nd isotopic ages of 560 Ma for coarse-grained gabbro, and 350 to 450Ma for the fine-grained gabbro.2. Yakuno ophiolite : Gneissose metagabbro shows the Sm-Nd isotopic ages from 340 to 38OMa. U-Pb dating for the zircon from two samples of tonarite in the Asago-cho area yield ages of 282 and 285Ma respectively. Gabbro migmatite was discovered from the Lower gabbro member in the Asago-cho area, at where the partial melting process was well documented at the base of immature island arc.3. Greenstones in the Jurassic accretionary complex : Greenstone of Masuda area shows the Sm-Nd isotopic ages of ca. 340Ma Alkaline basalt such as ankaramite was found from the greenstones in Mochigase-cho area, which shows very high Nb/Zr ratio that it was similar to HIMU basalt.4. Cphiolite of other areas : Age determinations using Sm-Nd, Rb-Sr isochron methodand the U-Pb for zircon by SHRIMP were carried out about the Schmidt Peninsula ophiolite of the northern Sakhalin, and the ages ca. 125Ma were obtained. Metamorphic facies and geochemical analysis were enforced about the Mariana forearc ophiolite, and a resemblance with the Yakuno ophiolite was found.5. construction of the geochemical data base : Data base system using "filemaker Pro ver. 3.O" was composed as a relational database for geochemistry.6. Summary : A coeval activities from 350 to 400Ma among Paleozoic ophiolitic rocks such as fine-grained gabbro and diabase intruded in the Ce-yama ophiolite, the sea mount group of the Akiyoshi terrane, the gneissose metagabbro of the Yakuno ophiolite, greenstones in the Jurassic accretionary complex are prominent in Southwest Japan. The simultaneous activities might be occurred to make superplume lasted from Devonian to early Carboniferous time in the proto-Pacific region.