安徽省姑山铁矿床中赤铁矿微晶的聚合

安徽省姑山铁矿床的矿石产在中生代辉长闪长岩与以三叠纪页岩，粉砂岩和砂岩为主的围岩的接触带上，矿石成分主要是微晶赤铁矿，其粒径为０．０１－０．０５ｍｍ，并与玉髓和细粒石英相交生，粒径达１－２ｍｍ的赤铁矿斑晶呈板状自形晶浸染于块状矿石中，显微镜观察表明，赤铁矿自形斑晶是在成矿期后由赤铁矿微晶聚合而成的。整个聚合过程包括微晶颗粒的相互靠近，颗粒旋转，结晶方位的定向以及最终的焊结，从而形成光性均一的变斑晶

COALESCENCE OF HEMATITE MICROCRYSTALLITES IN THE GUSHAN IRON DEPOSIT,ANHUI,PROVINCE

Iron ores in the Gushan deposit, Anhui Province, occur in a contact tone between Mesozoic gabbro diorite and its country rocks dominated by Triassic shale, siltstone and sandstone. They are composed principally of hematite microcrystallites, mostly 0. 01 - 0. 05 mm in size, inter-grown with chalcedony and fine-grained quartz. Hematite phenocrysts, up to 1 - 2 mm in size, can be seen to occur as euhedral laths disseminated in massive ores.Microscopic observations have revealed that euhedral phenocrysts of hematite were formed by post-mineralization coalescence of hematite microcrystallites. It is suggested that the whole process involves mutual approaching, grain rotation, crystallographical orientation and eventual welding of the microcrystallites. The resultant porphyroblasts show optical uniformity. A series of microphotographs are given to illustrate each stage of the process.