河南小秦岭大湖金－钼矿床地球化学及其矿床成因

秦岭造山带是华北与扬子两大古板块的接合带，在空间上，自北而南，秦岭造山带可分为华北板块南缘（华熊地块）、北秦岭造山带、南秦岭造山带和扬子板块北缘等4个构造单元。小秦岭金矿田位于华熊地块北缘，是国内外学者共识的造山型金矿田，河南灵宝大湖金－钼矿床位于小秦岭金矿田，属断控脉状矿床。大湖金－钼矿床最先正是以金矿床进行勘查的，其黄金储量28t，平均品位8.7g/t。随着开采深度的加大，部分含金石英脉向深部转变为辉钼矿－石英脉，目前探明钼资源量已达中型规模。 本论文主要从区域地质背景、矿床地质特征、元素地球化学、同位素地球化学、流体包裹体地球化学、矿床年代学及成矿机理等角度对大湖金－钼矿床进行了较为系统的研究，主要获得如下认识： 成矿过程经历3个阶段：早阶段为黄铁矿-石英脉，遭受变形、破碎，应形成于挤压或压剪过程；中阶段为细粒的辉钼矿-黄铁矿-石英网脉，贯入到早阶段黄铁矿或石英矿物的裂隙（可呈共轭状），应形成于剪切环境；晚阶段石英-碳酸盐细脉具梳状构造，充填于张性或张扭性裂隙。 大湖金-钼矿床的金属硫化物ISr=0.70470-0.71312，平均0.70854；(143Nd/144Nd)i=0.51143-0.51215，平均0.51162；(206Pb/204Pb)i=17.033-17.285，(207Pb/204Pb)i=15.358-15.438，(208Pb/204Pb)i = 37.307-37.582。其围岩太华群样品平均值ISr＝0.72294，(143Nd/144Nd)i=0.51107，(206Pb/204Pb)i=17.127-18.392，(207Pb/204Pb)i =15.416-15.604，(208Pb/204Pb)i=37.498-37.814，它们的平均值分别是17.547，15.470，37.616。通过金属硫化物及围岩太华群的对比，可以看出，成矿物质具有太华群和深部地幔混合的特征。 通过对不同阶段的含矿石英脉中的流体包裹体特征研究表明，早阶段只发育CO2-H2O型流体包裹体；中阶段流体包裹体类型复杂，有纯CO2型、CO2-H2O型、H2O-NaCl型和含子晶包裹体，指示流体沸腾作用强烈；而晚阶段只发育水溶液包裹体。早、中、晚3个阶段的流体包裹体均一温度分别集中在400-500℃、290-470℃、220-260℃；估计的早、中阶段流体的最低捕获压力分别为138-331MPa和78-237MPa，对应于成矿深度分别为13.8-11.0km和7.8-8.0km。早、中阶段的压力反应出静岩压力到静水压力的转变。成矿温度和压力明显高于浅部含金石英脉的成矿温度120-310℃，成矿压力100-150MPa。与野外观察到的“上金下钼”的空间关系一致。 大湖金－钼矿床辉钼矿－石英脉Re-Os同位素模式年龄较集中，介于215.4±5.4－255.6±9.6Ma，Re-0s等时线年龄为218±41Ma(MSWD=38，2σ误差)，表明大湖金－钼矿的辉矿化形成于印支期。 三叠纪末，随着古秦岭洋的逐渐封闭，处在弧后转换带的深部岩石在挤压作用下发生变质脱水而形成初始成矿流体，成矿流体沿断裂带（韧性剪切带）向上迁移而引起大湖钼矿床成矿系统的发育。随着区域构造环境由挤压转为伸展，区域的变质脱水更强，形成大量成矿流体，变质流体上侵为浅层流体循环提供了的热能，而浅层构造也因减压扩容而为流体循环提供了通道，这无疑有利于浅层流体循环和混入成矿系统。同时，增温和减压也有利于成矿流体发生沸腾。因此，充足的流体、热以及强烈的流体沸腾等，势必导致发生最为强烈的成矿物质快速沉淀作用。随着挤压作用的减弱，伸展作用的增强，区域热异常消失，地壳深部组分发生亏损，流体以浅源大气降水占主导，成矿作用迅速衰竭，形成石英-碳酸盐网脉，对成矿作用贡献减弱。总之，通过对大湖金钼矿床研究表明，大湖金钼矿床形成于由挤压转向伸展的构造背景，这与矿床地质的特征一致。

Capillary electrochromatography using a strong cation-exchange column with a dynamically modified cationic surfactant

A novel mode of capillary electrochromatography (CEC), called dynamically modified strong cation-exchange CEC (DMSCX-CEC), is described in this paper. A column packed with a strong cation-exchange (SCX) packing material was dynamically modified with a long-chain quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), which was added to the mobile phase. CTAB ions were adsorbed onto the surface of the SCX packing material, and the resulting hydrophobic layer on this packing was used as the stationary phase. Using the dynamically modified SCX column, neutral solutes were separated with the CEC mode. The highest number of theoretical plates obtained was about 190 000/m, and the relative standard deviations (RSD's) for migration times and capacity factors of alkylbenzenes were less than 1.0% and 2.0% for five consecutive runs, respectively. The effects of CTAB and methanol concentrations and the pH value of the mobile phase on the electroosmotic flow and the separation mechanism were investigated. Excellent simultaneous separation of the basic and neutral solutes in DMSCX-CEC with a high-pH mobile phase was obtained, A mixture containing the acidic, basic, and neutral compounds was well separated in this mode with a low-pH mobile phase; however, peak tailing for basic compounds was observed in this mobile phase.