Magmatic rocks are widely distributed in the Yanshanian north Huaiyang fault basin． The Upper Jurassic volcanic rocks consist mainly of andesitic and trachytic pyroclastic rocks， and their source magma shows an evolution trend from intermediate to alkaline． The south and north belts may be distinguished： the south belt is dominated by intermediate rocks， while trachytic pyroclastic rocks increase in the north belt． The intrusion， which is regarded as having been derived from a common parent magma with the volcanic rocks， consists of gabbro diorite granite alkali granite， and obviously has the characteristics of I-type granite． The Yanshanian north Huaiyang magmatic belt resulted from large-scale intracontinental subduction of the Yangtze and Huaibei massifs．%北淮阳燕山期断陷盆地中岩浆岩广泛分布。晚侏罗世火山岩以安山岩、粗面质火山碎屑岩为主，岩浆由中性向碱性方向演化。可划分出南北2个火山岩带，南带以中性岩为主，北带粗面质火山岩增多。与火山岩同源的侵入体由辉长岩—闪长岩—花岗岩—碱性花岗岩组成，带有明显的I型花岗岩特征。北淮阳燕山期岩浆岩带是扬子地块与华北地块大规模陆内俯冲的产物。
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