He, Ne and Ar isotopic composition of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nuclide abundances and isotopic ratios can be classified into two types: low He-3/He-4 type and high He-3/He-4 type. The low He-3/He-4 type is characterized by high He-4 abundances of 191x10(-9) cm(3.)STP(.)g(-1) on average, with variable He-4, Ne-20 and Ar-40 abundances in the range (42.8-421)x10(-9) cm(3.)STP(.)g(-1), (5.40-141)x10(-9)cm(3.)STP(.)g(-1), and (773-10976)x10(-9) cm(3.)STP(.)g(-1), respectively. The high He-3/He-4 samples are characterized by low He-4 abundances of 11.7x10(-9) cm(3.)STP(.)g(-1) on average, with He-4, Ne-20 and Ar-40 abundances in the range of (7.57-17.4)x10(-9) cm(3.)STP(.)g(-1), (110.4-25.5)x10(-9) cm(3.)STP(.)g(-1) and (5354-9050)x10(-9) cm(3.)STP(.)g(-1), respectively. The low He-3/He-4 samples have He-3/He-4 ratios (with RIRA ratios of 2.04-2.92) which are lower than those of MORB (R/R-A=8 +/- 1) and Ar-40/Ar-36 ratios (447-543) which are higher than those of air (295.5). The high He-3/He-4 samples have He-3/He-4 ratios (with R/R-A ratios of 10.4-12.0) slightly higher than those of MORB (R/R-A=8 +/- 1) and Ar-40/Ar-36 ratios (293-299) very similar to those of air (295.5). The Ne isotopic ratios (Ne-20/Ne-22 and Ne-21/Ne-22 ratios of 10.3-10.9 and 0.02774-0.03039, respectively) and the Ar-38/Ar-36 ratios (0.1886-0.1963) have narrow ranges which are very similar to those of air (the Ne-20/Ne-22, Ne-21/Ne-22, Ar-38/Ar-36 ratios of 9.80, 0.029 and 0.187, respectively), and cannot be differentiated into different groups. The noble gas nuclide abundances and isotopic ratios, together with their regional variability, suggest that the noble gases in the Fe-Mn crusts originate primarily from the lower mantle. The low He-3/He-4 type and high He-3/He-4 type samples have noble gas characteristics similar to those of HIMU (High U/Pb Mantle)- and EM (Enriched Mantle)-type mantle material, respectively. The low He-3/He-4 type samples with HIMU-type noble gas isotopic ratios occur in the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Seamounts whereas the high He-3/He-4 type samples with EM-type noble gas isotopic ratios occur in the Line Island Chain. This difference in noble gas characteristics of these crust types implies that the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain, and the Mid-Pacific Seamounts originated from HIMU-type lower mantle material whereas the Line Island Chain originated from EM-type lower mantle material. This finding is consistent with variations in the Pb-isotope and trace element signatures in the seamount lavas. Differences in the mantle surce may therefore be responsible for variations in the noble gas abundances and isotopic ratios in the Fe-Mn crusts. Mantle degassing appears to be the principal factor controlling noble gas isotopic abundances in Fe-Mn crusts. Decay of radioactive isotopes has a negligible influence on the nuclide abundances and isotopic ratios of noble gases in these crusts on the timescale of their formation.

Formation of Fe-oxyhydroxides from the East Pacific Rise near latitude 13 degrees N: Evidence from mineralogical and geochemical data

The mineralogical and geochemical characteristics of Fe-oxyhydroxide samples from one dredge station (long. 103 degrees 54.48'W, lat. 12 degrees 42.30'N, water depth 2655 m) on the East Pacific Rise near lat 13 degrees N were analyzed by XRD, ICP-AES, and ICP-MS. Most Fe-oxyhydroxides are amorphous, with a few sphalerite microlites. In comparison with Fe-oxyhydroxides from other fields, the variable ranges in the chemical composition of Fe-oxyhydroxide samples are very narrow; their Fe, Si, and Mn contents were 39.90%, 8.92%, and 1.59%, respectively; they have high Cu (0.88%-1.85%) and Co (65x10(-6)-704x10(-6)) contents, and contain Co+Cu+Zn+Ni > 1.01%. The trace-element (As, Co, Ni, Cu, Zn, Ba, Sr) and major-element (Fe, Ca, Al, Mg) contents of these samples are in the range of hydrothermal sulfide from the East Pacific Rise near 13 degrees N, reflecting that this type of Fe-oxyhydroxide constitutes a secondary oxidation product of hydrothermal sulfide. The Fe-oxyhydroxide samples from one dredge station on the East Pacific Rise near 13 degrees N are lower in Sigma REE (5.44x10(-6)-17.01x10(-6)), with a distinct negative Ce anomaly (0.12-0.28). The Fe-oxyhydroxide samples have similar chondrite-normalized rare-earth-element (REE) patterns to that of seawater, and they are very different from the REE composition characteristics of hydrothermal plume particles and hydrothermal fluids, showing that the REEs of Fe-oxyhydroxide are a major constituent of seawater and that the Fe-oxyhydroxides can become a sink of REE from seawater. The quick settling of hydrothermal plume particles resulted in the lower REE content and higher Mn content of these Fe-oxyhydroxides, which are captured in part of the V and P from seawater by adsorption. The Fe-oxyhydroxides from one dredge station on the East Pacific Rise near 13 degrees N were formed by secondary oxidation in a low temperature, oxygenated environment. In comparison with the elemental (Zn, Cd, Pb, Fe, Co, Cu) average content of hydrothermal sulfide samples from the East Pacific Rise near 13 degrees N, the Zn, Cd, and Pb contents of the Fe-oxyhydroxides are lower, and their Fe, Co, and Cu contents are higher.

Microstructure and wear properties of laser clad Fe based amorphous composite coatings

A FeNiSiBV amorphous composite coating was developed by laser cladding of metallic powders on AISI 1020 low carbon steel substrate. The coatings were studied using X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The coating reveals different microstructures along the depth of the coating. The transition zone exhibits good metallurgical bonding between the substrate and the coating. The layer consists of amorphous phase in majority and nanocrystalline phase/crystalline phase in minority. Accompanied with the nanocrystalline phase, the amorphous phase is concentrated in the middle of the coating. The crystalline phase in the coating is identified as Fe2B. A gradient distribution of the microhardness ranges from 1208 HV0.2 to 891 HV0.2 in the coating along the depth. The coating shows higher microhardness and better wear property than the substrate.

华北克拉通新生代玄武岩携带的地幔橄榄岩Fe同位素地球化学及含金云母地幔岩岩石学研究

In recent years, thanks to the improvement of analytical methods and the use of MC-ICP-MS, Fe isotope can be measured precisely. Fe isotope shows considerable variation both in biological and inorganic processes (from low T to high T) in nature, Therefore, Fe isotope has become one of the exciting frontier sciences and has favorable prospects of the application to the geosciences and life sciences. Based on a comprehensive review of available references in the related field, this study focuses on the development of techniques for high-precision measurement of iron isotope using MC-ICP-MS, and application of the techniques developed to study the Fe isotopes as well as major and trace element compositions of minerals (Ol, Opx, Cpx and Sp) from spinel peridotitic xenoliths from Cenozoic alkaline basalts to investigate Fe isotopic features of the lithospheric mantle beneath the North China Craton. The minerals from these xenoliths are similar to those off-cratonic peridotites world-wide, but are remarkably different from those on-cratonic peridotites and clinopyroxenes from these spinel lherzolites exhibit two types of chondrite-normalized REE patterns i.e. LREE-depleted and flat or spoon-shaped. It is noted that total abundances of REE in clinopyroxenes from these peridotites show a broad negative correlation with Cr# numbers of Cpx and Sp. The Fe isotope results show that the spinel peridotitic xenoliths have small but distinguishable Fe isotopic variations in minerals (generally Ol < Opx < Cpx) and samples, and the isotopic range in spinel is relatively large. Positive linear relationship with the ε57Fecpx/ε57Feopx ratio close to one unit has been observed between Fe isotopes of coexistent Opx and Cpx, indicating that the Cpx and Opx have generally reached Fe isotopic equilibrium. However, Fe isotopes between the Ol and Sp show apparent disequilibrium. The broadly negative correlation between mineral Fe isotopes and oxygen fugacity (fo2), metasomatic indexes such as spinel Cr#, (La/Yb) N and (La/Sm) N ratios of clinopyroxenes suggest that Fe isotopic variations in different minerals and peridotites were probably produced by melt-peridotite interaction. This study further confirms the previous observation that the lithospheric mantle has distinguishable and heterogeneous Fe isotopic variations at a scale of xenoliths. Mantle metasomatism that induces the interaction of the lithospheric mantle peridotite with metasomatic agent is a most potential mechanism for the Fe isotope fractionation in mantle peridotites. Therefore, Fe isotope could be a new and powerful tool to probe the evolution of the lithospheric mantle. We also report mineral compositions, clinopyroxene trace element concentrations and Sr-Nd isotopes for newly-discovered phlogopite-bearing spinel lherzolite and olivine clinopyroxenite xenoliths from three different localities （Hannuoba, Hebei Province; Jining Sangyitang, Inner Mongolia; Hebi, Henan Province）of the North China Craton. Systematic comparisons with phlogopite-free spinel lherzolite xenolith from the same locality reveals that the phlogopite-bearing peridotitic xenoliths have relatively higher Al2O3, CaO, Na2O, K2O, TiO2 contents and lower MgO contents than those phogopite-free counterparts. The former also has higher LREE concentrations, but relatively less radiogenic Sr-Nd isotopic ratios. This demonstrates that mantle metasomatism can not only enrich the basaltic components and trace element concentrations, but also make a decrease in Mg# of the peridotites and olivines and a relative depletion in Sr-Nd isotopes. 87Rb/86Sr-87Sr/86Sr isochrons of the phlogopite-bearing xenoliths indicate that mantle metasomatism happened in the Mesozoic and/or Cenozoic time. The metasomatic agent was derived from the asthenosphere. The result also manifests that the widespread similarity of the geochemical features such as major and trace elements and isotopic compositions in the Cenozoic lithospheric mantle beneath the North China Craton to those “oceanic” lithospheric mantle could be as a result of the ubiquitous presence of the interaction between the old refractory peridotites and the infiltrated asthenospheric melt, rather than the actually newly-accreted lithospheric mantle.

内蒙古白云鄂博地区元古宙构造-岩浆演化史与超大型REE-Nb-Fe矿床成因

Bayan Obo giant REE-Nb-Fe deposit in the northen margin of the North China Craton (NCC) is well known in the world for its abundant rare earth element resources. There is nearly one hundred year of studying history in substance component, chronology and geochemistry of the ore deposit, since the main ore body was found in 1927. However, there still exist remarkable divergences in genesis, mineralized age and material origin. Especially the REE enrichment mechanism leaves us a secret. Recent research shows that the Bayan Obo ore deposit likely resulted from the carbonatite magma activity, which is a favorable factor for REE accumulation. Based on the analysis of tectonic evolution history of north margin of NCC this thesis mainly discussed the formation background of cratonic margined rifts in Bayan Obo, and presented the analytical results of formation environment, intrusion age and deep origin of Proterozoic carbonatite magma. These research results can provide evidence for ore genesis. LA ICP-MS U-Pb dating on zircon shows that the Neoarchean basement was mainly composed of calc-alkaline TTG gneisses (2588±16Ma). The collision orogeny movement of the northen margin of the NCC between 2.0 Ga to 1.9 Ga brought the swarm of diorite-granodiotite magma (2023±16Ma) and intense regional metamorphism event (1906.3±7.7 Ma to 1892.7±6.7 Ma). In the sequent super continent break up background, intense metamorphic and deformed basement complex was uplifted to the surface suffered denudation, forming Mesoproterozoic Bayan Obo group in the contemporary continental margin rifts. The uplift of basement complex and formation of continental rifts were likely related with mantle plume activity. Evidence from petrological and geochemical data suggests that abundant alkaline-basic magma resulted from enhancement of continental breakup activity, that separated into carbonatite veins and mafic dykes by melt immiscibility mechanism, intruded in Bayan Obo margin rifts at the late stage of extension movement. Carbonatite veins can be divided into three main types by mineral composition: dolomite carbonatite, dolomite-calcite coexistent carbonatite and calcite carbonatite. Intrusion relationship between different types of carbonatite veins show that the calcite carbonatite veins were formed latter than the dolomite type as well as the coexistent type. Moreover, geochemical data also reveals successive and evolutive character between them. The content of REE increases together with the calcite minerals component. That is to say that REE gradually accumulated as the evolution of carbonatite magma. High precision Sm-Nd isochron data shows that the intrusion age of carbonatite veins was at 1319±48Ma. Moreover, the REE mineralization age in calcite carbonatite veins was around 1275±87Ma that is consistent with the intrusion age in error range. According to these data the abundant REE already existed in the carbonatite magma before intrusion and result in the earlier ore mineralization. The average age of mineralized dolomite was at 1353±100Ma, and the mineralization age of apatite in coarse grain dolomite was around 1329±150Ma. These data is consistent with carbonatite. Considering the coincident rare, trace element and isochron composition between them, it is presumed that mineralized dolomite was also the carbonatite intrusion and was the mainly factor for huge REE enrichment.

内蒙古白云鄂博超大型REE-Nb-Fe矿床脉状矿化时代与成矿流体特征

Bayan Obo REE-Nb-Fe ore deposit is the largest REE deposit in the world. Owing to its unique type and tremendous economic value, this deposit has widely attracted interests from geological researchers and vast amount of scientific data have been accumulated. However, its genesis, especially ore-forming age and REE sources, have been under dispute for a long time. On the basis of previous research works, this paper mainly conducts studies on the Early Paleozoic ore-forming event in the Bayan Obo deposit. The following results and conclusions can be suggested: Sm-Nd isotopic analytical results of bastnaesite, beloeilite, albite and fluorite samples from a coarse-crystalline ore lode present an isochron age of 436±35Ma. Besides, Rb-Sr isotope dating of the coarse-crystalline biotite lode that intruded into banded ores gives an isochron age of 459±39Ma. The two ages verify the exist of Early Paleozoic ore-forming event at Bayan Obo, which characterized by extensive netted mineralization of REE fluorocarbonates, aeschynite and monazite, accompanied by widely fluorite-riebeckite-aegirine-apatite alteration. Sr-Nd isotope composition of vein minerals is located between EMI and ancient lower crust component in the ISr(t)-εNd(t) correlation diagram, indicating that there is a crustal contamination during veined mineralization. A large area late Paleozoic granitoids are distributed in the southeast region of east open pit of the mine. The granitoids intruded directly into the ore-bearing dolomite, and produced intense skarnization. Moreover, at 650-660m of the drill core on 22 line and 1598m level flat in the south of East Open Pit, we firstly found skarnization rocks. Single grain and low background Rb-Sr isochrone dating on phlogopite in skarn gives 309±12Ma. Considering the intruded contacting relationship, the late Paleozoic granitoids, already extended to the under part of REE ore bodies, must be posterior to the latest intense REE mineralization, and is only a destructive tectonic and magmatic activity. Fluid inclusion types of fluorite in the Bayan Obo deposit consist of multiphase daughter mineral-bearing inclusion, two or three phase CO2-bearing inclusion and two phase aqueous inclusion. Petrography, laser Raman analysis and microthermometry study indicate that the fluids involving in REE-Nb-Fe mineralization at Bayan Obo might be mainly of H2O-CO2-NaCl-(F-REE) system. The presence of REE-carbonate as a daughter mineral in fluid inclusions shows that the original ore-forming fluids are rich in REE elements.

溶液介质条件对Fe^3＋共沉淀去除Cu^2＋的影响

采用室内试验方法，研究了溶液介质条件对Fe^3+共沉淀去除Cu^2+的影响。试验结果表明，pH是影响Fe^3+共沉淀去除Cu^2+的主要因素之一，其去除率随pH的增加而增加，并且其固液分配系数Kd的对数值与pH之间显示出较好的线性关系；天然水体中溶解的电解质离子及无机和有机配位体对Cu^2+的去除均产生很大影响，Cu^2+的去除率随加入的NaCl和NaClO4浓度的增加而降低，而随Ca(NO3)2和Mg(NO3)2浓度的增加而增加，除磷酸盐的增强作用外，硫酸钠、碳酸氢钠、甘氨酸、草酸钠、柠檬酸钠以及十二烷基苯磺酸钠的加入则不同程度地减弱了Cu^2+的去除；与Cu^2+共存的等量竞争阳离子Pb^2+、Zn^2+和Cd^2+也同样减弱了Fe^3+对Cu^2+的去除。

高效液相色谱法分离测定Fe(Ⅱ)和络合物Fe(Ⅱ)-PDT的两种几何异构体

铁在自然界中广泛分布，其环境和生态效应主要取决于它们的理化性质、形态、溶解性以及与溶解有机质的结合程度。氧化还原性敏感元素铁在自然界主要以Fe(Ⅱ) 和Fe(Ⅲ)两种价态存在。铁在水环境中的地球化学循环作用主要通过其自身的各种价态之间转化以及与周围其他物质(微量元素,营养盐,有机质)之间的相互作用来实现的。不同形态的铁具有不同的理化性质，其环境效应和生物有效性都是不同，不同形态的铁还可对其他重金属在水体中的循环迁移、赋存形态和生物有效性等均产生不同程度的一定的影响。因此，为铁的环境地球化学行为提供更为准确的信息，就必须进行铁的形态分析，由于Fe(Ⅱ)的氧化还原敏感性，故对铁进行形态分析的前提就是准确测定Fe(Ⅱ)的含量，用普通分光光度法测定Fe(Ⅱ)特别是低含量的Fe(Ⅱ)时，结果的不准确性以及高检出限等缺点都严重制约了准确测定环境中Fe(Ⅱ)的含量。为克服用普通分光光度法测定Fe(Ⅱ)时易受样品溶液其他组分的基体干扰以及灵敏度低等缺点，我们采用了用3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪（PDT）作为柱前衍生试剂，反相离子对高效液相色谱法来测定Fe(Ⅱ)。由于络合物Fe(II)-PDT存在两种几何异构体，故在建立反相离子对高效液相色谱法来测定Fe(Ⅱ)的同时，我们进一步研究了PDT及Fe(II)-PDT的两种几何异构体色谱分离与测定的实验研究，取得了如下进展： 1．研究了有机萃取分光光度法测定Fe(Ⅱ)，实验中发现加入离子对试剂四溴酚酞乙酯钾(TPBE-K)，由于TPBE和Fe(Ⅱ)-PDT络合物生成三元离子缔合物，导致最大特征吸收波长红移，由555nm增加至610nm，三元离子缔合物[Fe(PDT)3] [TBPE]2的摩尔吸收系数由2.4×104 l•mol-1•cm-1增加至1.9×105 l•mol-1•cm-1，显著改善了方法的灵敏度，降低了检出限，在Fe(Ⅱ)含量为0~0.3μg/ml范围内，方法的线性关系良好，线性方程为y＝0.3582x＋0.01，R2＝0.9974，检出限为0.96ng/ml(S/N＝3)，达到ng/ml水平，成功应用于测定泉水及表层湖水的Fe(Ⅱ)及总铁含量。 2．将3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪(PDT)作为衍生显色络合试剂应用于分光光度法来测定Fe(Ⅱ)已得到较为充分的报道。在上述研究基础上，首次研究了将PDT作为柱前衍生络合试剂，应用于反相离子对高效液相色谱法来测定Fe(Ⅱ)，不仅克服了常规络合衍生分光光度法过量络合剂干扰试验结果的缺点，而且进一步优化选择了检测波长，由于HPLC的应用，突破了在分光光度法中只能在可见波长范围内选择检测波长为555nm，将检测波长选择在Fe(Ⅱ)-PDT吸收更强烈的紫外区295nm处，使得灵敏度得到了显著提高。在Fe(Ⅱ)浓度为0～3.5×10-6mol/l时，峰面积A和峰高H均和标准溶液的浓度C(×10-7mol/l)的线性关系良好,线性回归方程分别为：A=7.4951x-0.0785(R2=0.9999) 和H=0.5126x- 0.0915(R2=0.9997)，方法的检测限为0.35ng/ml (S/N＝3)。本方法测定Fe(Ⅱ)时，不需复杂的前处理步骤，如固相萃取、有机溶液萃取等，直接柱前衍生HPLC方法测定，方便、快速且灵敏度高，低于众多分光光度报道的检出限水准7～170ng/ml范围。 3．由于络合物Fe(II)-PDT存在面式和经式两种几何异构体，故在建立起反相离子对高效液相色谱法来测定Fe(Ⅱ)新方法的同时，进一步研究了PDT及Fe(II)-PDT的两种几何异构体色谱分离及测定实验研究，关于这方面的试验研究，目前来说还没有相关的研究报道，所以将反相离子对高效液相色谱法应用到分离及测定PDT及Fe(II)-PDT的两种几何异构体中，这也是本论文的第二个创新之处。在本实验中，所用的色谱固定相为普通的反相键合C8柱，但由于优化选择了最佳流动相条件，使得PDT及Fe(II)-PDT的两种几何异构体直接在C8柱上得到完全的基线分离。讨论了流动相中有机改性剂乙腈不同比例、不同种类的离子对试剂(高氯酸钠和十二烷基硫酸钠)及不同浓度对PDT和Fe(II)-PDT两种几何异构体的色谱行为的影响。根据不同试验条件下，对所获得的色谱参数(容量因子、分离度、选择性因子、保留时间等)进行了较为深入的分析，据此探讨了色谱分离异构体过程的机理。 4．在上述实验的基础之上，引入更能灵活的调节洗脱强度和被分离物质分离度的三元流动相(乙腈/甲醇/水=20/50/30)，优化选择了三元流动相中有机改性剂的比例以及离子对试剂的种类及浓度，使得异构体的分离度和选择性因子均得到满意结果。对一系列不同浓度的Fe(II)-PDT异构体分离，面式和经式异构体的面积和浓度之间的线性关系在4~25×10-7mol/l范围内良好，线性关系分别为：y = 3.6333x - 2.3378(R2 = 0.9957，经式异构体)，y = 1.8219x - 1.0783(R2 = 0.9964, 面式异构体)。面式和经式异构体的检测限分别为4.28ng/ml和3.44ng/ml (S/N＝3)。 5．进一步研究发现Fe(II)-PDT的两种几何异构体之间存在相互转化的动态平衡，故根据异构体含量随时间的变化就可以探讨在转变过程中的动力学和热力学参数。用高效液相色谱法研究了异构体转变过程中色谱峰高和面积随时间的变化，并依此首次得出了两种几何异构体相互转化可逆过程中的热力学和动力学参数，如熵变、焓变、自由能变化、反应速率常数等，对两种几何异构体之间的动力学转变平衡机理进行合理的解释提供了有益的参考。各不同温度下(30℃，35℃，40℃，45℃)，反应时间在3倍半衰期以内，两种几何异构体之间的相互转变平衡均符合动力学一级反应。各不同温度下Xeln[(Xe-X0)/Xe-X)]随时间变化的线性关系良好，分别为：y=0.0821x+0.7288(R2=0.9911,T=45℃)；y = 0.0486x + 0.598(R2 = 0.9987, T=40℃); y = 0.0216x + 0.5861(R2 = 0.9987, T=35℃)；y = 0.0124x + 0.591(R2 = 0.9988, T=30℃)。 首次将PDT作为柱前衍生络合试剂，应用于反相离子对高效液相色谱法来测定环境中的Fe(Ⅱ)，且无需复杂的样品前处理过程(固相萃取，有机溶液萃取等浓缩富积过程)，克服了普通分光光度法检测限高、易受样品基体效应的干扰等缺点；在建立起的高效液相色谱法测定Fe(Ⅱ)的基础上，进一步对络合物Fe(II)-PDT的两种几何异构体色谱分离及动力学转变实验研究，则是对建立起的反相离子对高效液相色谱法测定Fe(Ⅱ)试验研究基础上的进一步延伸和扩展，是对测定Fe(Ⅱ)的高效液相色谱法的机理的进一步认识和探讨。PDT作为柱前衍生络合试剂首次应用于高效液相色谱测定Fe(Ⅱ)为铁的环境地球化学工作者提供了一种灵敏度高的测定Fe(Ⅱ) 的新途径，为环境样品中Fe(Ⅱ)含量的准确测定提供保证，对铁的环境地球化学研究，如铁形态分析、铁的水-沉积物界面行为等提供更翔实可靠的信息。

云贵高原湖泊近代沉积作用的Fe、Mn、S指示

铁、锰、硫具有强烈的氧化还原敏感性，在湖泊沉积地球化学过程中扮演着重要的角色。铁、锰、硫控制了沉积物中的氧化还原分带，对磷及其它一些微量金属元素的形态和分布具有重要影响。因此本文中我们选择铁、锰、硫来指示湖泊沉积作用中氧化还原过程的变化，为进一步高精度提取环境信息奠定基础。本文对比阿哈湖、洱海和阳宗海，通过铁、锰、硫在湖水、孔隙水和沉积物体系内的垂直剖面特征分析，阐述了三湖沉积物中氧化还原过程的区别、氧化还原边界层对铁锰循环的控制作用以及铁-锰-硫对重金属的控制作用，深入探讨了铁、锰、硫及微量元素记录的早期成岩改造特征及其对湖泊沉积作用的指示意义，进一步阐明了沉积物中的有机质降解规律及早期成岩机制，获得了如下结论：1．阿哈湖水中铁、锰出现季节性释放，锰的季节性释放强度比铁大；在冬季和夏季，阿哈湖沉积物界面铁、锰均出现富集。冬季的富集程度强于夏季，锰的富集程度远远强于铁。沉积物表层由冬季的黄褐色转变为夏季的黑色，表示铁、锰氧化物层转变为FeS层。2．洱海沉积物中，铁、锰均在沉积物一水界面出现富集，界面以下，铁、锰的含量逐渐递降。铁、锰在孔隙水中产生扩散迁移，而在沉积物表层形成富集，说明洱海沉积物表层处于较好的含氧状况，氧化还原边界层处于沉积物中；阳宗海沉积物孔隙水中铁锰峰值均位于界面2cm处，而沉积物中铁在表层出现亏损，表明夏季阳宗海表层处于缺氧状态，氧化还原边界层位于湖水中。3．铁、锰的界面扩散和沉降通量在不同湖间差异较大。但锰的扩散通量占沉降通量的比例高于铁，锰在界面的沉积后再迁移程度和沉积记录的改造程度比铁显著。湖泊中铁、锰在有机质降解过程的驱动下，围绕沉积物一水界面形成氧化还原循环。其中锰的循环相当激烈，铁则较为缓和。铁、锰界面循环受氧化还原边界层和沉积物—水界面的双重控制。4．三湖沉积物界面处均存在硫酸盐的还原作用。洱海硫酸盐由于其含量较低以及表层良好的含氧状况因此不可能成为有机质降解的主要氧化剂，而阳宗海和阿哈湖则情况相反。阿哈湖沉积物柱芯好氧菌和SRB的分布进一步证实了表层处硫酸盐在SRB的参与下强烈的还原作用，同时说明有机质的好氧和厌氧降解并不是完全对立的；水体向沉积物内部扩散是高硫酸盐浓度湖泊的主要清除作用，而对于低硫酸盐含量湖泊而言，水体浮游生物如藻类吸收和同化作用应是水体硫酸盐的主要清除机制。5．三湖沉积物硫主要都以黄铁矿存在。阳宗海的AVS含量较高，AVS和FeS_2在界面的富集进一步证实了在阳宗海沉积物界面存在着强烈的硫酸盐还原作用；阿哈湖沉积物中硫酸盐的还原与季节无太大联系。在夏季和冬季，沉积物表层均表现出明显的SO_4~(2-)还原作用。只不过随着氧化还原边界层的迁移，SO_4~(2-)还原作用的范围也随之发生迁移。铁氧化物作为电子受体参与有机质分解的过程中，水铁矿和纤铁矿等Feo首先被还原而溶解出来。同时，Feo和Fec是可以互相转化的，针铁矿和赤铁矿等晶体铁氧化物可以向水铁矿和纤铁矿转化。6．三湖中Corg都表示出明显的降解趋势，证明了沉积物表层存在的早期成岩作用。洱海表现出“沉降一降解一堆积”三阶段分布特征，而阳宗海和阿哈湖沉积物中Corg表现出“降解一堆积”二阶段分布特征；洱海沉积物中有机质的选择性分解不明显，C／N指示沉积物有机质主要来自无纤维束的陆源植物；阿哈湖沉积物中C／N很高，均>20，且随深度增加呈现上升的趋势，说明阿哈湖沉积物中有机质含易降解的低N和难降解的高C，有机质主要来源于陆源输入。7．洱海和阳宗海沉积物中均存在明显的重金属再迁移现象。洱海沉积物中铁、锰循环对Pb、Cu的迁移影响很大；颗粒物的吸附一解析作用是影响Cd迁移的主要因素；洱海沉积物中可迁移释放的Ni含量并不高。8．阳宗海沉积物孔隙水中Ni、Cu、Cd均与铁、锰表现出良好的相关性，铁、锰氧化物的还原是造成它们在孔隙水表层富集的主要控制因素。而Pb与铁、锰呈现微弱的正相关。Pb、Cd相对于Cu、Ni的释放趋势较强，再迁移作用较剧烈。Pb、Cd在表层孔隙水中与一些有机、无机化合物络合，由于沉积物的吸附作用而再次沉降到沉积物表层形成富集。沉积物中重金属的再迁移主要受有机质降解、铁锰氧化物还原和硫化物沉积控制，但是不同的湖泊控制因索各不相同。

白云鄂博超大型Fe-Nb-REE矿床碳酸盐脉状体的包裹体研究

白云鄂博矿床是世界上最大的Fe-Nb-REE矿床,其矿床成因一直是中外地质学家争论的焦点.而矿床附近的碳酸盐脉状体则成为赋矿白云岩岩浆成因的直接因素,该文拟从包裹体的角度对矿区碳酸盐脉状体进行研究,对其成因进行探讨,并对其与赋矿白云岩的关系作初步的讨论.通过对碳酸盐脉状体包裹体在包裹体类型,组合,均一温度,盐度,成分等方面的研究,发现不同区域,不同产状的碳酸盐脉状体包裹体特征存在较大的差异,这反映了其在岩石成因方面的差异:(1)都拉哈拉和尖山附近:为典型的岩浆成因;(2)宽沟背斜核部:可能是富碳酸盐盐熔体侵入构造裂隙形成的;(3)白云镇东北部(CV31,CV32)可能为侵入到混合岩中的热液脉;(4)东介勒格勒以南:具有明显的沉积特征.