河南舞阳和冀东地区前寒武系几种含铁母岩溶蚀实验

为配合在华北地区寻找风化淋滤型富铁矿,作者对采自河南舞阳二铁矿区太华群和冀东桑干群马兰峪组六块含铁变质岩进行了硅、铁差异性溶蚀实验。含铁母岩的矿物和化学组成见表1。

RESOLUTION EXPERIMENTS OF SEVERAL KINDS OF THE PRE-CAMBRIAN IRON-BEARING ROCKS FROM THE EASTERN HEBEI PROVINCE AND THE COUNTY WU YANG,HENAN PROVINCE

In order to provide the scientific basis for exploring rich iron deposits formed by weathering and leaching,the present authors have carried out the experiments in resolution of the silica and iron from the hornblende magnetite-quartzite,magnetite-bis-tagite and magnetite pyroxenolite.The rock samples were collected from the Eastern Hebei and Wu Yang,Henan. By mixing the distilled,meteoric and sea water with the sodium bicarbonate,potassium carbonate,oxatic acid,acetic acid and the buffer solution of potassium biphthalate,respectively,we prepared the solution of different pH values.The samples were ground into five grades (1.0-0.5mm,0.5-0.154mm,0.154-0.09mm,0.09-0.06mm,<0.06mm).The weight of samples used for experiments was 3-5 g.The time for resolution lasted twenty-six months (Eastern Hebei) and twenty months (Wu Yang,Henan),respectively.The results obtained are given as follows.1.In alkaline solution the amounts of SiO₂ resolved from the hornblende magnetite-quartzite from Wu Yang is about 3-6 times as great as that from the magnetite quart-zite from Eastern Hebei.The amount of SiO₂ resolved from the magnetite quartzite from Eastern Hebei is very low (from 2.55-2.73 mg/l in the neutral water to 2.76-3.33 mg/l in the solution with pH 8.5-11),whereas that from hornblende magnetite-quar-tzite from Wu Yang is 7.62 mg/l (in the neutral water) and 21.74-22.59 mg/l (in the solulion with pH 8.5-10.5).2.The dark minerals (hornblende separated from the hornblende magnetite-quar-tzite in Wu Yang and chlorite separated from the magnetite-quartzite in the Eastern Hebei) as well as quartz from quartzite in both areas were also used in the resolution experiments.The results show that the amount of SiO₂ resolved from the hornblende from Wu Yang is more greater than that from the chlorite from the Eastern Hebei.However,the amount of SiO₂ resolved from the quartzite from both areas is very similar.It seems to us that the high amount of resolved SiO₂ in the alkaline solution from the hornblende magnetite-quartzite from Wu Yang results from relatively high content of the minerals in this kind of rock.3.Iron can only exist in the solution when its pH is constantly kept up above 7,in such a case the amount of SiO₂ can not exist.Apparently,it is difficult for iron to be transported in the form of true solution in nature.4.The amount of SiO₂ resolved from rocks increases with the decreasing grain size of the samples,but the influence of grain size on the amount of SiO₂ is relatively smaller than that of the types of the rocks.The results obtained are helpful to explaining why the ancient weathering crust on the Pre-cambrian iron-bearing rocks from Wu Yang is so thick (more than two hundreds metres),and why there absents any evidence on the ancient weathering crust on the Pre-cambrian iron-bearing rocks from the Eastern Hebei.