Change in catastrophic eruptions the volcanic processes from the continental margin to the island arc

欧亚大陆边缘沿着白垩纪-早第三纪的岩浆活动以灾难性的火山喷发为特征，并伴随有釜式建造。这项研究的重点是在中国中部地区的大锅，其中只有不充分的数据是已知的。(1)二神山大锅。火山口充填的安山质胶结物：83± 13 Ma（Rb-Sr等时线），花岗闪长斑岩：72.8± 1.8Ma（角闪石K-Ar），石英闪长岩：66.6± 2.4Ma（角闪石K-Ar），角闪-黑云母花岗岩（基底岩石）：85.2±1.9Ma（角闪石K-Ar）。这些年龄表明，二神山火山口的火山活动发生在85 - 73 Ma之间。(2)比木原坩埚。釜状充填体的流纹质熔结凝灰岩为73.2±2.5Ma（FT），石英斑岩为69.0±2.2Ma（FT），黑云母花岗岩为63.1±2.3Ma（Rb-Sr等时线）。这些年龄表明，该火山口的火山活动发生在75 - 60 Ma之间。(3)作户大锅。火山口充填的流纹岩熔岩为77.3±4.3Ma（Rb-Sr等时线），石英闪长岩为71.3±3.7Ma（角闪石K-Ar）。这些年龄表明，Sakuto火山口的火山活动发生在80 - 70 Ma。(4)柳原大锅。石英年龄：79.8±1.8Ma（角闪石K-Ar）。这表明，火山活动的大锅发生在约。因此，这些数据表明，在80 - 70 Ma期间，与坩埚有关的灾难性喷发集中在中国中部地区。古近纪（44 - 30 Ma）弧火山作用取代了热点火山作用，火山前缘明显。

The igneous activity along the Eurasian continental margin in Cretaceous to Paleogene is characterized by catastrophic eruptions associated with cauldron formations. This study focuses on the dating of the cauldrons in the central Chugoku district, where insufficient data are only known.(1) Futakamiyama cauldron. Andesitic agglutinate of the cauldron infill: 83±13Ma (Rb-Sr isochlon); granodiorite porphyry: 72.8±1.8 Ma (hornblende K-Ar); quartz diorite: 66.6±2.4 Ma (hornblende K-Ar); hornblende-biotite granite (the basement rock): 85.2±1.9Ma (hornblende K-Ar). These ages suggest that the volcanic activity of the Futakamiyama cauldron occurred during 85 - 73Ma.(2) Hikihara cauldron. Rhyolitic welded tuff of the cauldron infill: 73.2±2.5Ma (FT); quartz porphyry: 69.0±2.2Ma (FT); biotite granite: 63.1±2.3Ma (Rb-Sr isochlon). These ages suggest that the volcanic activity of the Hikihara cauldron occurred during 75 - 60Ma.(3) Sakuto cauldron. Rhyolite lava of the cauldron infill: 77.3±4.3Ma (Rb-Sr isochlon); quartz diorite: 71.3±3.7Ma (hornblend K-Ar). These ages suggest that the volcanic activity of the Sakuto cauldron occurred during 80 - 70Ma.(4) Yanahara cauldron. Quartz diorite: 79.8±1.8Ma (hornblend K-Ar). This suggests that the volcanic activity of a cauldron occurred in ca. 80Ma.Accordingly, these data show that the catastrophic eruptions associated with cauldrons concentrated in the central Chugoku district during 80 - 70Ma. This hotspot-like volcanism was replaced by the Paleogene (44 - 30Ma) arc volcanism with a clear volcanic front.