【摘要】 <正> 矿物是在一定的物理化学条件下形成的,物化条件的改变它可能发生相变、脱溶、阳离子有序化,溶解、熔蚀、氧化等诸多复杂的现象,这些都是成因矿物学所要研究的重要内容。历来受到结晶学家,矿物学家的重视。本文试图以穆斯堡尔谱为主、结合红外、差热、X射线等方法开展蓝铁矿氧化机理的研究,并提出B型氧化的概念。更多还原

【Abstract】 Vivianite and its oxidized products at different temperatures are studied by means of Mossbauer spectroscopy, infrared spectroscopy, differential thermal analysis, microscope heating-stage, decrepitation temperature measuring, X-ray diffraction and chemical analysis. The results show that oxidation process of vivianite coincides with the A-type oxidation mechanism reported by Catherine.Our study reveals another oxidation mechanism of vivianite, that is B-type oxidation. When samples of fresh vivianite fragments were cooled after heating in a muffle furnace to 350℃ for forty five minutes, its colour does not keep blue-dark but change to orange. The data of Mossbauer spectroscopy reveal that Fe（2+） ion of such samples had been completely oxidized to Fe（3+） . The oxidation of vivianite has a sudden change point. Observation on heating-stage reveals that the mineral suddenly changes from colourless to translucent orange while the samples are heated to 150℃ （for 10℃/minute） , which is confirmed by the results of other methods. Fitted data of Mossbauer spectroscopy show that Fe_A²⁺ and Fe_B²⁺ ions completely and simultaneously oxidized to Fe（3+） in three sites, resulting in forming an orthophosphate compound containing H2O.In A-type oxidation, if one Fel_B²⁺ ion in a double octahedron is oxidized to Fe（3+） ion, the second Fe_B²⁺ would be relatively immune to oxidation and make Fe_A²⁺ ion to oxide. While in B-type oxidation, two Fe（2+） ions in double octahedron and one in isolated octahedron are oxidized to Fe（3+） ion in all three sites at the same time. This is the main distinction between two types of oxidation A and B.By study on oxidation mechanism of several minerals, it is confirmed that Fe（2+） are not of the same immunity to oxidation when Fe（2+） ion occupy in two kinds and/or more positions. The oxidation usually begins with Fe（2+） ion in one of the sites and as soon as the oxidation of Fe（2+） in other sites takes place, the mineral crystal lattice will collapse completely and form its equivalent products. It is reasonable to conclude that the oxidizing vivianite can be regarded as a variety of vivianites.The weakest hydrogen bonding is the only force in connecting the lattice in the crystal structure of vivianite.It is seldom that the bondingin in crystals is the same as that between crystal and absorbed water. The dta shows endothermic valley（at 225℃）with smaller gradient on the lower temperature side and with great gradient on the other. The endothermic valleys reflected by absorbed water is coincide with that of crystalline water. That means when vivianite exposed to the air, it will be oxidized rapidly and the form of oxidation changes sensitively with varieties of conditions.The visible distinction between the two types of oxidation is their colour: A-type with black blue-green colour and B-type with orange.更多还原