Cenozoic volcanic and tectonic history of the northeast Japan.

本文对日本东北部新生代火山和沉积层序的地层学、火山地质学、沉积学、岩石学、磁地层学和K-Ardating定年进行了研究，以期了解本州弧东北部的火山和构造演化。根据火山作用类型、沉积作用类型和构造应力状态的变化，将日本东北部近25年来的构造演化划分为4个阶段。1)裂谷期（RS）（约25Na ~ 16na）。2)弧后盆地开启阶段（BBOS）（16 ~ 12Ma）。3)过渡阶段（TS）（12 ~ 3 Ma）。4)缩短变形阶段（SDS）（3 Ma后）。通过对RS和BBOS早期形成的火山层序的产状模式描述和相分析，揭示了该层序的喷发和侵位环境。生物地层学的发展有助于中新世下至中中新世的精确对比和年龄确定，从而使古气候和古生物地理的时间变化更加清晰。钙质纳米化石生物地层学表明，早中新世Martini带n4带第一次海洋环境侵入日本海沿岸地区。白垩纪至近代火山岩的石油化学结果阐明了岩石和地幔化学成分的时空变化，以及火山作用与构造作用的关系。晚白垩世至早中新世晚期，K20含量的横向变化与近代相似，从海沟侧向弧后侧增加。而在17 ~ 14 Ma期间，日本海东部边缘出现了低碱含量带。在此之后，该带的轴向部分向东迁移，在8 Ma左右位于近代火山锋附近。

The stratigraphy, volcanic geology, sedimentology, petrology, magnetostratigraphy and K-Ardating dating of the Cenozoic volcanic and sedimentary sequences in the northeast Japan have been studied in order to know volcanic and tectonic evolution of the northeast Honshu arc.Tectonic evolution of the northeast Japan in the past 25 m.y. is divided into four stages from the type of volcanism, sedimentation and variation of the tectonic stress regime.1)Rifting Stage (RS) (around 25Na to 16 Na).2)Back-arc Basin Opening Stage (BBOS)(16 Ma to 12Ma).3)Transitional Stage (TS)(12 to 3 Ma).4)Shortening Deformation Stage (SDS)(after 3 Ma).Description of the mode of occurrence and facies analysis of the volcanic sequences formed in the RS and the early BBOS revealed eruption and emplacement environment of the sequences.Development of the biostratigraphy contributed to the precise correlation and age determination of the Lower to Middle Miocene, and so temporal changes of the paleoclimate and paleobiogeography became clear in detail. The calcareous nannofossil biostratigraphy showed that the first marine environment invaded the area along the Japan Sea in the Early Miocene NN 4 Zone of Martini's zonation.Petrochemical result on the Cretaceous to the Recent volcanic rocks clarified the variation of the chemical composition of the rocks and mantle in time and space, AND relationships between volcanism and tectonics. During from the Late Cretaceous to the Early Miocene late, the lateral variation of K20 content is similar to the Recent, the content increase toward back-arc side from the trench side. However, in the period between 17-14 Ma, a low alkali content zone appeared in the eastern margin of the Japan Sea. After the period, axial part of the zone migrated toward east and situated near the recent volcanic front at around 8 Ma.