摘要
雁荡山破火山口构造以其独特的火山地貌形态，完美的环状断裂和环状圈层分布的岩相，环形展市的航磁异常和地球化学异常，显示出一个地质─地球物理、地球化学、岩相─构造配置较完整的典型破火山口模式，依壳、幔二元混合模拟计算．火山岩和侵入岩源区物质组成为UC56.2DM43．8和UC56．4DM43．6，两者来自相似源区．源区处于地壳下部。
Yandangshan caldera is one of the well developed resurgent caldera tectonics in Moshishan group in eastern Zhejiang provice. Istope geochronological studies on those volcanic rocks show that the age of pre-caldera rhyodacitic ignimbrites in Xishanton formation is 128Ma while that of rhyolites erupeed during the vevivification of the caldera is 121Ma. Large scale eruptions of pyroclastic flow in Xishantou formationn are closely correlated with the subsequent caldera. But during the vevivification, acididic magmas effused and small scale pyroclastic flows erupted. Rb Sr and Sm-Nd istopic constitutions of the rocks indicate that the magmas are derived from partial melting lower crustal materials.
出处
《浙江国土资源》
1997年第1期18-25,共8页
Zhejiang Land & Resources
关键词
破火山口
火山岩相
岩石地球化学
雁荡山
caldera
volcanic lithopacies
petrochemistry and geochemistry
Yandangshan
