江苏某些花岗岩类岩石中的自碎包体

江苏省东海、宁镇和苏州地区分布有若干分属于两类不同成因类型的花岗岩类岩体。在这些岩体的边部和顶部分布着许多形态极不规则、大小各异的暗色包体,它们的矿物组合、岩石化学和地球化学特征与主体岩石相似,为同源产物。包体中矿物的结晶粒度明显细于主体岩石,并含有大量因骤冷而晶出的针状磷灰石,且见不同程度的重熔现象。故它们是由于岩浆脉动上侵、挤碎并重熔的早期形成的岩体边缘相岩石,而不是早期火成岩和围岩捕虏体,也不是岩浆析离体和深源包体。

The Autoclastic Inclusions in Some Granitoid Masses in Jiangsu

There are several granitic bodies of two defferent genetic types occurreo in Donghai, Nanjing-Zhenjiang as well as Suzhou areas, Jiangsu Province. At the marginal and topmost parts of these bodies there are plenty of greyish black to dark green inclusions with very irregular shapes and disparate sizes throughout the whole rock mass. Inasmuch as they contain more mafic minerals than the relevant host rocks, they usually show darker. But the mineral assemblage, petrochemical and geochemical characteristics of them are very close to these of the hosts, thus they were considered as comagmatic derivatives. The mineral grain sizes in the inclusions are usually much smaller than those in the hosts. They also carry numerous acicular crystals of apatites(L/W>20) which were thought to be the precipetates under the quenching condition. Bes ides these, they also show some corrosion phenomena. Based upon the facts me ntioned above, these kinds of inclusion could attributes neither to xenoliths of early formed magmatic rocks or sedimentary rocks, nor to sehlireus or deep mantle source inclusions. This is possible of ascribing them to autoclastic inclu sions formed originally as a marginal facies enriched mafite and later on frag- mented and corroded by the successive magmatic pulsation.