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本破火山口为一塌陷式成因的火山盆地。它是一个以酸性岩浆岩为主构成的复杂地质体,具有独特的地质特征(图1)。从平面上看它大致呈椭圆形,现代地貌是正地形,中间高,四周低。盆地基底为震旦系变质岩和一部分石炭系下统和三迭系上统的沉积地层。塌陷盆地由上侏罗系酸性火山熔岩、火山碎屑岩以及沉积岩夹层构成,其中以厚层熔岩出露面积最大,为盆地的主体岩性,直接复盖于晶屑玻屑凝灰岩(J_3e~1)之上。正因为这次大体积喷
This caldera is a collapsed volcano basin. It is a complex geological body mainly composed of acidic magmatic rocks, with unique geological features (Figure 1). From the plane it is generally oval, modern landscape is a positive terrain, the middle of the high, low around. The basement of the basin is Sinian metamorphic rocks and a part of Carboniferous and Triassic sedimentary strata. The collapse basins are composed of the Upper Jurassic acidic volcanic lava, volcaniclastic rocks and sedimentary interlayer. Among them, the area exposed by thick lava is the largest and is the main lithology of the basin, directly covering the crystal vitreous tuff (J_3e ~ 1 ) Above. Because of this large volume spray