Mechanism of formation of Cretaceous to Paleogene cauldron in Chugoku district, Japan

日本西南部内带广泛分布着白垩纪至古近纪的火山岩和花岗质岩基。该项目包括对日本西南部中国地区白垩纪至古近纪火山口的构造地质学、岩石学和地球化学研究。为了模拟大锅的形成过程，我们还进行了缩比模型实验，从这些研究中，我们发现了新的大锅，即，分别位于冈山县新见地区和山口市的新见大锅和山口大锅。这些大锅显示火山-深成复合体。通过离心加速度作用下的缩尺模型试验，推断多边形坩埚的破裂受断裂等先存基底构造的影响。

Cretaceous to Paleogene volcanic rocks and granitic batholiths are extensively distributed in the Inner zone of Southwest Japan. This project includes structural geology, petrology, geochemistry on the Cretaceous to Paleogene cauldrons in the Chugoku district, Southwest Japan. The scale model experiments were also carried out in order to simulate the formation process of the cauldron.From these studies, we found new caulderons, i.e., Niimi caldron and Yamaguchi cauldron in the Niimi area, Okayama Prefecture and Yamaguchi city ; respectively. These cauldrons show volcano-plutonic complexes. From the scale model experiments under centrifuge acceleration, it is inferred that the fracturing of the polygonal cauldron is influenced by the pre-existed basement structures such as faults.