Metallogenic mechanism of Pingguo bauxite deposit,western Guangxi,China:Constraints from REE geochemistry and multi-fractal characteristics of major elements in bauxite ore

Major and REE geochemistry and multi-fractal analysis of two types of bauxite(primary bauxite and accumulated bauxite) ores were studied in Pingguo bauxite orefield in western Guangxi,China.The results of geochemical data show that the accumulated bauxite has a feature of high Al_2O_3 whereas relative low Fe_2O_3 and SiO_2 contents compared to the primary bauxite.The similar chondrite-normalized rare earth element(REE) patterns illustrate that they have a cognate relationship.However,the negative Ce anomalies of primary bauxite and positive Ce anomalies of accumulated bauxite indicate that the ore-forming system changed from reducing environment to oxidation environment.The results of multi-fractal spectrum and parameters of Al_2O_3,Fe_2O_3 and SiO_2 between primary bauxite and accumulated bauxite show that the distinct multi-fractal spectrum parameters reflect the different grade distribution between accumulated and primary bauxite ores.Metallogenic process from primary bauxite to accumulated bauxite is accompanied by the loss of diffluent elements(e.g.,Si and S) and enrichment of stable elements(e.g.,Al and Fe) in the surface environment.Among the rest,the migration mechanism of iron during the evolutionary process from primary ore to accumulated ore can be described as combined leaching and chemical weathering action with participation of sulfur.

湖南邓阜仙矿田隐爆角砾岩与钨锡成矿关系

湖南邓阜仙矿田是我国华南著名的钨锡多金属矿产地,随着多年的矿山开采,资源已逐渐枯竭,亟需新的找矿突破。近期在矿田西侧发现多处隐爆角砾岩,为钨锡成矿作用和找矿勘查打开了新窗口。本文对该隐爆角砾岩开展了系统地质调查、岩相学、岩石地球化学、锆石年代学与Lu-Hf同位素分析,研究表明:1)隐爆角砾岩筒主要沿茶陵-郴州-临武断裂发育,具有显著分带性,从中心到外围依次为长英质岩脉、隐爆角砾岩带、裂隙带,且存在多期热液活动与矿化;2)长英质岩脉锆石U-Pb加权年龄为(151.9±1.2)Ma,形成时代与矿田成矿高峰期一致;3)岩脉富集Rb、Th和U,亏损Sr、Ba、K和P等元素,具有高的分异指数(DI为94.77~97.11),其锆石ε_(Hf)(t)为-6.8~-0.8(均值为-4.7),TDM2为1253~1638 Ma,与矿田成矿花岗岩具有相似的微量元素和Lu-Hf同位素组成,指示二者应为同一岩浆源区。综合分析认为,矿田隐爆角砾岩与钨锡多金属成矿关系密切,尽管目前已发现的钨锡矿床均集中在矿田东部,但是西部同样有较大的钨锡找矿潜力,尤其是茶陵-郴州-临武断裂附近。隐爆角砾岩是寻找钨锡多金属矿床的有利找矿标志,应给予高度重视。

环保型钢铁钝化耐蚀性及成膜机理

钢铁腐蚀的现象越发普遍,工业上常用磷化作为防止钢铁腐蚀的方法,但磷化对环境污染严重。为了减少磷污染,以Q235钢为基体材料,研发了一种以植酸溶液为基础的环保型钢铁钝化工艺,利用硫酸铜点滴试验和电化学方法测试了环保型钢铁钝化膜的耐蚀性;利用扫描电镜(SEM)观测了钝化膜的成分和微观形貌。结果表明:环保型钢铁钝化后的样品硫酸铜点滴的平均时间达到了107 s,腐蚀电流只有4.3×10^(-3)mA,环保型工艺处理后的钝化膜的阻抗直径和阻抗模量大,其耐腐蚀性能较高。扫描电镜下的环保型钝化膜完整无裂纹,具有良好的耐蚀性能。最后简要分析了环保型钝化膜的成膜机理。