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- Title
浙东长屿破火山的典型识别特征.
- Authors
贺振宇; 颜丽丽; 褚平利; 张进
- Abstract
Calderas are widely distributed in the Cretaceous giant siliceous volcano-intrusion complex belts along the southeast coast of China. Their genesis and related volcanic activity processes are important scientific issues for understanding tectonic-magmatic and mineralization in southeastern China. Calderas are nearly circular volcanic depressions whose formation is associated with the collapse of the magma roof slab accompanied by explosive pyroclastic flow eruptions of massive magma ejections. For the ancient caldera that has undergone denudation, the internal rocks are younger than the surrounding rocks, and they are juxtaposed with the surrounding rocks and have a clear boundary, which is an important basis for identifying the caldera. Caldera generally undergoes multi-stage volcanic activity processes, including pre-collapse eruption, caldera formation eruption, caldera formation eruption, and caldera reactivation, etc. Identifying these different stages of volcanic eruption and magma activity is the key to understanding the formation and evolution of caldera. The key issue. The Late Cretaceous Changyu Volcano in eastern Zhejiang has typical caldera identification features: (1) The volcanic rocks are distributed in a circle with a diameter of about 12 km, and lacustrine deposits in the caldera are locally developed; (2) The first-stage rhyolite in the south of the caldera The brecciated fused tuff is spatially juxtaposed with the older crystal-rich volcanic rocks of the Jiuliping Formation, bounded by normal fault zones, and the Jiuliping Formation volcanic rocks constitute the surrounding rocks and possible basement of the Changyu caldera; (3) The volcanic rocks of the three phases of Changyu are mainly distributed in the caldera, and have the petrographic characteristics of typical pyroclastic flow facies. They are stacked in sequence in the vertical direction, reflecting that the first stage of volcanic activity led to the formation of collapsed caldera., the second and third stages are eruptions after the formation of the caldera, and the eruption products further fill the caldera; (4) The rhyolite domes developed in many places in the caldera represent multiple magma channels inside the caldera.
- Publication
East China Geology / Huadong dizhi, 2022, Vol 43, Issue 4, p448
- ISSN
2096-1871
- Publication type
Article
- DOI
10.16788/j.hddz.32-1865/P.2022.04.005