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新疆磁海铁矿位于北山构造-成矿带西端,以磁海矿段为主要组成部分,铁矿体主要为透镜状、似层状,围岩以辉绿岩为主,二者接触线截然且平直;另外一种矿体产在基性岩体与地层接触带的石榴子石透辉石矽卡岩岩体内,整个矽卡岩岩体即为铁矿体。通过野外矿床特征与矿相学研究,成矿过程可分为:(1)矿浆期,以磁铁矿+单斜辉石+普通角闪石的近同时产出为特征;(2)矽卡岩期,先期以石榴子石+透辉石+磁铁矿为特征,后期以透闪石/阳起石+石英+磁黄铁矿+黄铜矿+黄铁矿的组合为特征。通过对矿浆期及矽卡岩期典型矿物的地球化学及Fe、S、O同位素结果分析,认为矿浆期铁质具有幔源特征,矽卡岩期成矿流体对矿浆期具有继承性。通过与前人研究结果对比分析,认为磁海成矿可能形成于塔里木地区二叠纪地幔柱背景,含矿母岩浆可能为地幔柱的分支。 相似文献
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Submarine metalliferous sedimentary rocks are chemical precipitates resulted from hydrothermal exhalation near mid‐ocean ridge or faults. They record the submarine hydrothermal activity between lithosphere and hydrosphere and are critical for understanding Fe cycling in marine environment. Fe was expelled from the hydrothermal vent systems and was oxidized and precipitated in the ambient seawater, where the precipitation of hydrothermal Fe is largely controlled by oxidation state of seawater and is potentially revealed by its Fe isotope compositions. This hydrothermal process in modern hydrothermal vent systems have been well observed, but that for the ancient ones are still not well known. Umbers, or ferromanganoan sediments, overlying Troodos ophiolite in Cyprus of Mid‐Cretaceous age thus provides an excellent example for understanding the Fe cycles in ancient submarine hydrothermal process. Samples were collected from Margi village in Troodos and are mostly amorphous Fe‐Mn oxy‐hydroxides with very minor quartz, goethite, smectite and silicates such as clinopyroxene derived from the volcanic rocks. There is no terrestrial, detrital component. Samples were analyzed for their whole‐rock element and Fe isotope compositions. The results show that samples are composed mainly of SiO2 (13～80 wt%), Fe2O3 (9～54 wt%) and MnO (1.5～10.4 wt%), with minor Al2O3 (0.7～4.3 wt%). PAAS‐normalized REE patterns are near flat with significantly negative Ce anomalies (Ce/Ce* is from 0.2 to 0.5) and slightly positive Eu anomalies (Eu/Eu* is around 1.1), indicating a source from the oxidized seawater and the high‐temperature hydrothermal fluids. δ56FeIRMM‐014 values of samples are ‐0.32‰ to ‐0.15‰, with an average of ‐0.20‰, which are consistent with those of the hydrothermal fluids previously reported. The narrow Fe isotope compositions of Cyprus umbers that are close to those of submarine hydrothermal fluids indicates near complete oxidation of hydrothermal Fe2+ during its expulsion from the hydrothermal vent. 相似文献
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This study describes a previously unidentified Neoproterozoic mafic dyke emplaced in the northern flank of the Langshan Tectonic Belt. This dyke intruded into the micaquartz schist of the Zhaertaishan Group, and yielded an age of 908 ± 8 Ma. The youngest U-Pb ages of micaquartz schist from the Zhaertaishan Group in the Langshan area were 1118 ± 33 Ma,1187 ± 3 Ma and 1189 ± 39 Ma,suggesting that the depositional age of the protolith of the schist was between 908 ± 8 Ma and 1118 ± 33 Ma. In addition, 436 U-Pb age data and 155 Lu-Hf isotopic data from six samples in the Langshan Tectonic Belt and one Permian greywacke from the Wuhai area show distinct differences between the northern and southern flanks of the Main Langshan area. The U-Pb ages of the northern flank are primarily Meso-Neoproterozoic; similar ages have not been identified in the southern flank to date.Moreover, two-stage Hf model ages of the northern flank feature three age peaks at ～900 Ma,～1700 Ma and ～2600 Ma; this differs from Hf model ages of the southern flank, which feature one strong age peak at ～2700 Ma. These results suggest that the northern and southern flanks of the Main Langshan area have different geochronologic characteristics and should be divided further. Based on the U-Pb ages and Hf model ages, the northern and southern flanks of the Main Langshan area are named the North and South Langshan Tectonic Belts. Comparison of the U-Pb age and two-stage Hf model age distributions from the North Langshan Tectonic Belt, South Langshan Tectonic Belt, Alxa Block and the North China Craton(NCC) reveal that the North Langshan Tectonic Belt is similar to the Alxa Block and that the South Langshan Tectonic Belt is similar to the NCC. In addition, the zircon U-Pb age of 860 ±7 Ma commonly observed in the Alxa Block was detected in the Permian greywacke from the Wuhai area of the NCC, which suggests that the amalgamation of the North and South Langshan Tectonic belts(i.e.,the amalgamation of the Alxa Block and the NCC), occurred between Devonian and late Permian. 相似文献
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内蒙古劳家沟上打井斑岩型钼矿床是近年来在西拉木伦钼矿带新发现的一个矿床,其绿泥石化蚀变与钼矿化关系具有密切的时空关系。因此,对绿泥石化学成分的分析,有助于查明该矿床成矿过程的物化条件。本文采集矿区典型绿泥石样品,通过岩矿鉴定,结合绿泥石的电子探针化学成分分析,研究其特征。分析结果显示,该矿床绿泥石以富铁种属铁镁绿泥石为主,个别为铁绿泥石,揭示其形成于还原环境;绿泥石结构的离子置换主要体现为Fe、Mg间的置换;由绿泥石温度计估算得到绿泥石的形成温度为270～344℃,平均312℃;绿泥石形成机制：一为先溶蚀,后结晶,二为先溶蚀,后迁移,最后结晶。 相似文献
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峡东地区埃迪卡拉系黑色页岩的微量元素和Fe同位素特征及其古环境意义 总被引：2，自引：0，他引：2
通过分析宜昌峡东地区九龙湾剖面埃迪卡拉系陡山沱组黑色页岩的微量元素和Fe同位素组成,对埃迪卡拉纪海洋的氧化还原状态进行了制约。黑色页岩氧化还原敏感元素的富集系数以及U/Th、V/(V+Ni)、V/Cr值等在陡山沱期存在着明显的演化趋势。这些趋势显示陡山沱组二段下部水体处于氧化的状态,陡山沱组二段上部水体处于还原状态,陡山沱组四段黑色页岩发育在氧化环境中。同时,陡山沱组二段下部黑色页岩富集重的Fe同位素,表明黑色页岩来自于海水的铁主要是以Fe3+的氧化物或氢氧化物形式沉淀的,进一步说明这个时期的水体处于氧化状态。综合黑色页岩微量元素和Fe同位素信息,显示在埃迪卡拉纪陡山沱早期海水经历了先氧化后还原的过程,陡山沱晚期海水变得氧化了。这种特征与埃迪卡拉纪陡山沱期生物群的出现和演化相对应,说明海洋的氧化为埃迪卡拉纪生物的出现和演化提供了前提条件。 相似文献
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A novel way to absorb industrial tail gas vinyl chloride by room temperature ionic liquids (RTILs) is presented. The absorption amount and rate of vinyl chloride in these RTILs at 288.15, 298.15 and 323.15 K was determined. Results suggested that RTILs can be used as alternative green solvents for vinyl chloride absorption and desorption. 1H‐NMR experiments showed that a chemical bond was not formed between the RTILs and vinyl chloride, which means this was a physical absorption process. Experimental results also indicated that the vinyl chloride can be easily desorbed at higher temperatures and/or under vacuum. This makes RTILs reusable. 相似文献
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