岩浆作用与煤变质——煤的岩浆热液接触变质作用

MAGMATISM AND COAL METAMORPHISM:MAGMATIC-THERMAL CONTACT-METAMORPHISM OF COAL

煤的岩浆热接触变质作用分直接接触和间接接触两亚类。规模小、定位浅的岩体多与煤层直接接触,换热过程中热系统相对开放,传导换热快,形成窄的煤变质带。最高变质产物为天然焦。规模大、定位深的岩体多与煤层间接接触,热系统相对封闭,传导换热慢,形成宽的煤变质带。煤的次生显微组分具区域性分布特征,最高变质产物为石墨。这两亚类变质作用形成的煤,在煤岩学、煤化学和变质带的空间变化上存在较大的差异。岩体、围岩、煤层和构造条件控制着煤变质带的分布。

Magmatic-thermal contact-metamorphism of coal may be divided intotwo subtypes: direct and indirect. Small-scale epimagmatic intrusions aremostly in a direct contact with coal layers, in which the thermal systemis relatively open and thermal conduction is quick during heat transforma-tion, resulting in narrow aureols and peak metamorphosed coal-naturalcoke. Large-scale plutonic intrusions are in an indirect contact with coal la-yers, in which the thermal system is relatively closed and thermal conduc-tion is slow, resulting in wide aureols, regional secondary macerals and peakmetamorphosed coal-graphite. For the coal metamorphosed by the twosubtypes, there are considerable differences in coal petrology, coal chemis-try and space distribution of aureols. The distribution of coal aureols maybe controlled by intrusions, wall rocks, coal layers and tectonic conditions.