铜官山铁铜矿床中显微球粒磁铁矿的发现及其成因意义

THE DISCOVERY OF MICROSPHERULITIC MAGNETITE IN THE TONGGUANSHAN IRON-COPPER DEPOSIT AND ITS GENETIC SIGNIFICANCE

借助电子显微镜首次在铜官山铁铜矿床中发现显微球粒磁铁矿。显微球粒磁铁矿主要呈连球状(或葡萄状),少数为单球状,粒径0.7—1.8μm。这种与地层整合产出的显微球粒磁铁矿在产状、物性、波谱、微量元素、稀土元素及铅同位素诸方面均明显不同于接触交代(矽卡岩)型磁铁矿,但与沉积成岩黄铁矿有相似之处。故认为这类磁铁矿可能为黄铁矿热变质产物。

By means of electron microscopy, microspherulitic magnetites were discovered for the first time in the Tongguanshan copper and iron deposit in 1987. 0.7-1.8(?)m in dimension, they generally assume clustered bead form or botryoidal form with a few appealing as single spherulites. The magnetite orebodies are obviously hosted by Middle Carboniferous strata.The microspherulite magnetite(L-2-18) is different evidently from that of the skarn type(X-I-2)in such aspects as mode of occurrence, physical properties, wave spectra, minor elements, REE and lead isotopes. Nevertheless, it is similar to the pyrite formed at the sedimentary-diagenetic stage. This sort of magnetite is therefore considered to be the product of thermal metamorphism of sedimentary-diagenetic pyrite.