内蒙古迪彦钦阿木超大型钼矿床成矿流体特征及成矿机制

迪彦钦阿木钼矿是近年来发现的一个超大型斑岩钼矿床,位于大兴安岭中段二连浩特-东乌旗多金属成矿带。本文主要对迪彦钦阿木钼矿床的流体包裹体及硫同位素进行了系统研究。迪彦钦阿木钼矿发育有四个成矿阶段:石英-钾长石阶段、石英-辉钼矿阶段、石英-多金属硫化物阶段及石英-萤石-碳酸盐阶段。矿床不同阶段的流体包裹体中,富气相(V类)、富液相(L类)和含子晶(S类)包裹体大量共存。显微测温结果显示,第一阶段包裹体均一温度为492～> 600℃,盐度分为两部分:5. 36%NaCleqv(L类)和32. 39%～64. 90%NaCleqv(S类);第二阶段包裹体均一温度为292～510℃,盐度为4. 49%～19. 92%NaCleqv(L类)和28. 43%～70. 21%NaCleqv (S类);第三阶段包裹体均一温度为206～388℃,盐度为2. 24%～22. 71%NaCleqv(L类)和28. 62%～54. 64%NaCleqv(S类);第四阶段包裹体均一温度、盐度最低,均一温度为133～288℃,盐度为0. 88%～7. 86%NaCleqv。流体具有从高温、高盐度向低温低盐度演化趋势。前三个成矿阶段L类、V类和S类包裹体大量共存,端元包裹体均一温度相近,盐度相差很大,表明发生了强烈的流体沸腾作用。多期次的流体沸腾作用是迪彦钦阿木矿床的主要成矿机制。硫同位素研究显示,δ^(34)S值的变化范围是1. 78‰～10. 41‰,暗示着迪彦钦阿木钼矿成矿物质主要来自于岩浆。

Relative paleointensity of the geomagnetic field during the past 0.8 Ma from Nihewan Basin, Hebei Province, China

We conducted a detailed rock magnetic study on upper 80 m of Jing抏rwa core from the Nihewan basin. The results indicate that the sediments from Jing抏rwa core are suitable for relative paleointensity study, and anhyster-etic remanent magnetization (ARM) can be used as the nor-malization parameter of the natural remanent magnetization (NRM). Our relative paleointensity data of upper 80 m of Jing抏rwa core provide a continuous record of the intensity variation during the last 0.8 Ma, which correlates well with the results from marine sediments cores in the Pacific Ocean. This means that the sediments records are reliable for rela-tive paleointensity of Earth抯 magnetic field, and suggests that these sediments have recorded the real changes of geo-magnetic field, which would provide a new method for re-gional stratigraphic correlation.