牟定安益地区超贫磁铁矿产出特征

牟定安益地区元古界龙川群变质岩地层及侵位于其中的基性超基性岩体出露较广, 近期工作发现了产于路古模组第三段绿片岩中的超贫磁铁矿及产于基性超基性岩体中的含铂钯超贫磁铁矿两种铁矿化类型, 该区具有找超贫磁铁矿的前景。     

阶段磨选工艺在白云鄂博磁铁矿选矿中的应用

白云鄂博磁铁矿是由沉积变质并经多期热液叠加形成,矿石矿物间嵌布关系复杂,嵌布粒度细.为进一步提高白云鄂博磁铁矿选矿铁精矿品位,降低有害杂质含量,采用阶段磨选工艺流程后的铁精矿品位达到66.91％,回收率为73.12％,与原连续磨矿分级—弱磁选—反浮选工艺流程相比,精矿品位和回收率同时提高,选别指标有了明显改善.     

高精度磁法测量在龙岩马坑铁矿中的应用

根据高精度磁法测量在龙岩马坑铁矿磁异常的分布情况,圈定测区东南段为规模较大的正负伴生异常,大致以官寮坑—太保林为界,东南为正异常,西北为负异常.走向北东,西南向未闭合.△T磁异常长度大于3 200 m,宽度800～2 300m.通过磁异常反演情况推测地下磁性体呈板状体,埋深在标高-200～-400 m,磁性体厚度约30 m,倾角约30°.经钻孔验证,磁铁矿体出现在标高-200～-400m,视厚度30.68 m.根据地质验证结果,工作区东南部的△T磁异常证实是由地下磁铁矿体所致,从而证实了高精度磁法在寻找磁铁矿床具有较高的应用效果.     

X射线荧光光谱法测定钒钛磁铁矿石中的主次量组分

采用熔融玻璃片制样,选用ZSX Primus Ⅱ X射线荧光光谱仪对钒钛磁铁矿样品中的V₂O₅、TiO₂、TFe、CaO、MgO、Al₂O₃、SiO₂、P₂O₅、MnO等组分进行测定,分析结果与标准值和及化学值相吻合,10次测定的相对标准偏差小于10%。     

矿业活动固体废弃物中重金属元素释放机理 的浸出实验

矿业活动中产生的固体废弃物包括废石、尾矿和冶炼废渣。这些固体废弃物堆放于露天环境,经过长期的自然风化作用,会对周围环境产生重要的影响。以攀枝花钒钛磁铁矿矿业活动为例,采集了废石、尾矿和冶炼废渣3种类型的固体废弃物,通过浸出实验,研究了不同粒度、不同pH值条件下这些废弃物中重金属元素的释放机理及其对环境产生的影响。结果表明,大多数元素在pH值条件偏小的环境中浸出率更大,在碱性环境中浸出率更小,但废石中的V、Cr和废渣中的Ti在碱性条件下浸出率更高;细粒样品在相同pH值条件下浸出率较粗粒大,但在pH=12的条件下Ti 、V、Ni、Cr和pH=1条件下Ti、Cr的浸出量出现反常,即在粗粒样品中高于细粒样品。固体废弃物释放的重金属元素会对周围环境产生一定的影响,需要加强监测。     

AMT在印尼某铁矿区勘查中的应用

以印尼某铁矿区为例,说明AMT法寻找隐伏铁矿的有效性。配合磁法,利用AMT法的低阻体圈定隐伏磁铁矿,为钻孔设计及矿山开发提供了物探依据,在国际化的商业勘查中取得了良好的勘探效果。     

Magnetic Susceptibility Screening of Anthropogenic Impact on the Danube River Sediments in Northwestern Bulgaria - Preliminary Results

Several events of anthropogenic impacts on the floodplain river sediments of the Danube along a section near the town of Oryakhovo (NW Bulgaria) have been detected using magnetic technique. In the field, magnetic susceptibility was measured using three susceptibility meters – MS2D, KT-5 and SM30. The differences in the surface susceptibility values measured with the different instruments are ascribed to the various penetration depths which depend on several parameters like sensor diameter, frequency and field strength. This is supported by the detailed laboratory study on penetration depth and sensitivity of the new SM30 susceptibility meter and the comparison with the already existing data for the other two sensors. Boundaries between different flooding events are clearly linked with significant variability of the measured susceptibility values corresponding to one and the same level. Sediment cores, taken at different distances from the water level, show the history of depositional events and corresponding degree of anthropogenic pollution. Identification of the magnetic phases responsible for the signal was carried out by means of thermomagnetic (T) curves. The main carrier is magnetite with Tc of 580°C or oxidized magnetite with Tc of 600°C. A second kink at about 300°C is better expressed for samples with lower susceptibilities. It may correspond to several minerals, e.g. maghemite, pyrrothite, titanomagnetite, as well as different mineral transformations of paramagnetic minerals (decomposition, dehydroxilation, etc. for example siderite, lepidocrocite). The samples showing strong magnetic enhancement are characterized by the predominance of magnetite. Optical microscopy on magnetic extracts shows the presence of small spherical particles, typical for the anthropogenic magnetic phases from high-temperature technological processes. Well expressed susceptibility variations along the cores suggest the presence of several stages of different degree of pollution, covering an estimated period of about 30 years.     

Oxygen isotope ratios in magnetite core-and-mantle structures

In a polymetamorphic, felsic, biotite-bearing gneiss, biotite has reacted to form magnetite and microcline. The resulting structure is a magnetite core surrounded by a mantle of feldspar and quartz normally not exceeding 20mm in diameter. Measurements of oxygen isotope ratios disclose disequilibrium between mantle microcline and mantle quartz and also between mantle and matrix minerals of the same species. A clustering of temperature estimates from the oxygen isotope distribution between magnetite and quartz and between magnetite and microcline in the interval 550 to 600°C suggests an approach to oxygen isotope equilibrium. No signs of a re-equilibriation of the reacting biotite can be found.     

Changes in Magnetic Parameters After Sequential Iron Phase Extraction of Eastern Mediterranean Sapropel S1 Sediments

Iron is distributed over different minerals (i.e. silicates, pyrite, detrital oxides) that are present in a sediment sequence that formed under anoxic conditions. After post-depositional re-oxidation of the sediments pyrite is no longer present and diagenetic iron phases constitute an important portion of the iron in the oxidised part of the sapropel. They are very fine-grained making them amenable to analysis by means of sequential extraction and mineral-magnetic methods. The sequential extraction shows that besides iron in silicates, iron mainly occurs in amorphous oxides in the oxidised part of the S1 sapropel. Pyrite constitutes an important fraction in the still reduced part of the S1 sapropel. Some silicon is dissolved during the extraction for the amorphous oxides, suggesting that amorphous iron also occurs as ferro-silicate coatings. Mineral-magnetic analysis involved component analysis of the isothermal remanent magnetisation (IRM) and hysteresis loop measurements. Three coercivity phases could be identified in the IRM component analysis; these were interpreted as detrital magnetite, hematite, and biogenic magnetite. The diagenetically formed iron phases influence the parameters of the IRM components. Hysteresis measurements together with the IRM component analysis, indicate the importance of bacterial magnetite in the oxidised sapropel, particularly in the lower part of the active oxidation zone.