冀西北张纪煤矿东部酸性火成岩体特征及其找煤意义

Acidic Igneous Rock Mass Characteristics and Its Coal Prospecting Significance in Eastern Part of Zhangji Coalmine, Northwestern Hebei

河北省西北部张纪煤矿东部地表出露有大面积酸性火成岩,以往地质资料将其划归张家口组,近期地质工作证实该火成岩地表部分岩性为流纹斑岩,向深部相变为花岗斑岩,前者属于后者的边缘相,岩体厚度大于2 000 m,产状应为岩株。该岩体范围内原有的下花园组已被吞蚀殆尽,失去找煤意义。

Large area of acidic igneous rock has outcropped in eastern part of Zhangji coalmine, northwestern Hebei. In the past geological information had put them into Zhangjiakou Formation. But recent geological works have confirmed that the surface part of the igneous rock is rhyolite porphyry, to deep part lithofacies changing into granite-porphyry, the former is the border facies of the later, thickness of the rock mass larger than 2 000 m, occurrence as stock. Within the rock mass extension, the original Xiahuayuan Formation already had been eroded all, thus has no longer any coal prospecting significance.