193 resultados para ddc: 510
Resumo:
Through field outcrop dolomite observation, laboratory petrography (macroscopy, microscopy, cathodeluminescence and scan electronic microscopy), geochemistry (carbon-oxygen-strontium isotopes and trace elements) and fluid inclusion microthermometry study in Keping-Bachu area of Tarim Basin, it can be inferred that there are existing eight dolomite texture types within four evolution phases in Keping-Bachu area of Tarim Basin. The paragenesis of different dolomite texture types and associated minerals in Keping-Bachu area has been established. The carbon and oxygen isotopes of saddle dolomites and matrix dolomites overlap greatly. The Strontium isotopes results of Keping-Bachu outcrop area show that the strontium isotopes differentiation of the matrix and saddle dolomites is not obvious, the reason of which is that there is thousands of Cambrian-Ordovician dolomite strata below the stratum bearing the saddle dolomite. In the process of the heat flow upward migration, the isotopes of the heat interacts with the host rock, which leads to the similarity betwwen the strontium of the saddle dolomite and matrix dolomite. The strontium isotope of the saddle dolomite is not very radiogenic. the six types samples within four phases in the study area show Eu negatively. Comparing to the other types of samples, the δEu of saddle dolomite is relatively high falling into the range of 0.510-0.874, which shows that the saddle dolomite forms in the hydrothermal setting and is affected by the hydrothermal activity to some extend.The Lan/Ybn of saddle dolomite is high up to 15.726, which means that the HREE is very rich. It belongs to the typical hydrothermal genesis model. The δCe of saddle dolomite is positive anomaly, which is the result of high effect from the land source debris. The homogeneous temperature of the saddle dolomite falls into two ranges 110-120℃ and 125-160℃, after pressure correction, they are 141-152℃,157.5-196℃, the salinity of the saddle dolomite can reach to 20-25%. With the comparing with the burial history, the Th of the saddle dolomite is high than the ambient strata temperature, these data show that the saddle dolomite is of hydrothermal origin. The evolution trend of different dolomite and associated minerals is from matrix dolomite, dolomite cementation, saddle dolomite, quartz to calcite. Alonging with this evolution trend, the temperature of the diagenetic flow initiated from 80-100℃, after rising to 135-160℃, then gradually declined. Finally, a structurally-controlled dolomitization model is established in Keping-Bachu area of Tarim Basin.
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Chinese eolian deposits are especially suitable for the studies of paleoclimatic changes, environmental magnetism and remanence acquisition mechanisms. In the past two decades, many studies have documented their magnetic properties. However, some important problems, such as the origin of magnetic minerals, the mechanisms for enhancing magnetic susceptibility and the lock-in effect, remain debatable. Therefore, it is essential to detail the rock-magnetic properties of the eolian deposits. This study shows thermomagnetic analyses, petrographic measurements and soil chemistry methods can be combined to obtain a better understanding of the sequence of magnetic mineral alterations during thermal treatment and of the pedogenic mechanism responsible for the susceptibility enhancement. This helps to further develop the interpretation of paleoclimate records in the Holocene eolian deposits along a NW-SE transect of the loess plateau. A partial heating/cooling method and X-ray diffraction (XRD) analysis were performed on representative samples of the present-day loess, in order to investigate mineralogical changes during thermal treatment. The temperature-dependent susceptibility (TDS) and XRD results show complex alteration of magnetic phases during heating and cooling. The 300 ℃ susceptibility hump in heating curves might be due to the production of maghemite from less magnetic lepidocrocite during heating. Goethite is transformed into hematite when heating to above 300 ℃. The susceptibility decrease from 300 ℃ to 450 ℃ can be interpreted as the conversion of maghemite to hematite. This thermal instability makes it possible to quantatively estimate the maghemite contribution to the pedogenically-enhanced susceptibility in loess or paleosols. Minor occurrence of thermally-stable maghemite in the present-day loess is possible; nevertheless, the TDS measurements show that the degree of the thermally-induced alteration is closely related to pedogenesis. The TDS measurement and XRD analysis results demonstrate that although magnetite and hematite both exist in the Holocene loess eolian deposits and their modern source area, magnetite is the predominant contributor to magnetic susceptibility. Both magnetite and hematite are the primary carriers of the remanent magnetization. Fine-grained maghemite, mainly produced by pedogenesis, is significantly responsible for enhancement of the magnetic susceptibility in the Chinese loess and paleosols. Since the degree of oxidation of magnetite grains depends on climate, the presence of maghemite has paleoclimatic significance, and variations in climate could be reflected as variations in the amount of low-temperature oxidation. If that is the case, the TDS curves can be used to compare the effects of climate at different sampling sites. The TDS results along the studied NW-SE transect suggest that stronger pedogenesis results in higher content of maghemite and greater susceptibility decrease during thermal treatment. This behavior seems to indicate that the final product of pedogenic magnetite in Chinese loess and paleosols is maghemite, which makes significant contributions to the enhanced magnetic susceptibility of Chinese eolian deposits. It is interesting to note that the 510 ℃ Hopkinson/alteration peak is larger in the present-day loess than in the black loam for each section. Obiviously, the Hopkinson/alteration peak of the Holocene eolian deposits is closely related to the degree of pedogenesis, which is a function of climate, and thus the peak itself could be a useful climate indicator. There are three effects that may be important in producing this trend. First, low-temperature oxidation preferentially affects the finer single-domain magnetites responsible for the Hopkinson peak, which is therefore suppressed in the more oxidized loams. Second, the possible production of uniaxial magnetite with shape anisotropy can also lead to a relatively muted Hopkinson peak. There is, additionally, a third alternative, and the one preferred here, that the natural alteration processes involved in pedogenic susceptibility enhancement have probably depleted the supply of iron-bearing precursor phases, so that less new magnetite is formed on heating. In summary, the TDS method is very reliable and highly sensitive in detecting magnetic phase changes in eolian deposits during thermal treatment, which are closely related to pedogenic processes. Thus, the studied NW-SE transect clearly exhibits paleoclimatically-induced mineral- and rock-magnetic variations. It is suggested that TDS can be used as a new method for the analysis of pedogenesis and climatic change.
Resumo:
重庆城口地区从震旦统到下寒武统发育有丰富的黑色岩系,20世纪末期在该地区黑色岩系中开展了大量的铂族元素(PGE)的找矿工作,但是由于种种原因,关于该地区是否存在PGE矿化异常,还没有得到最终的结论。本次研究在PGE分析方法论证的基础上,进行了大量样品的PGE分析和微量元素分析。主要结论如下:①区域上上震旦统槽区和断块区两套黑色岩系在原始的沉积环境和物源供给上有较大的差异,虽然槽区上震旦统的黑色岩系具有和下寒武统黑色岩系相似但强度较低的V-Cu-Y-Mo—U异常,但基本上不具有明显的PGE-Au-Ag异常。②断块区水井沱组黑色岩系:和平剖面西段新发现的U-V-Mo-PGE异常可能是今后工作的重点,Pt+Pd最高达248.9×10^-9,局部U-V都达到了工业品位。③槽区巴山组硅质岩:四个剖面都揭示了在硅质岩中广泛存在连续的PGE异常,87个碳质硅质岩平均含Pt+Pd 57.2×10^-9,有10个样品Pt+Pd〉100×10^-9,最高达196.5×10^-9;大部分碳质硅质岩都具有不同程度的V-Cu-Y-Mo-Tl-U组合异常,V都达到了独立矿床的品位要求,其中猪草河、燕子河等剖面还存在厚度较大的富矿地段,特别是燕子河剖面,局部还存在REE+Y的高异常,值得深入研究。④城巴地区下寒武统黑色岩系存在广泛的PGE异常,但没有达到PGE的矿化要求,建议加强该地区的钒矿和铀矿勘探研究,PGE可以综合评价。
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对岩背火山-斑岩型锡矿含黄玉黑云母花岗岩和含黄玉花岗斑岩中黑云母矿物化学研究表明,含黄玉黑云母花岗岩中的黑云母属于富铁黑云母,含黄玉花岗斑岩中的黑云母属于铁叶云母。含黄玉花岗斑岩的成岩温度为720℃-730℃,logfO2为-15.5- -15.7;含黄玉黑云母花岗岩的成岩温度为510℃-550℃,logfO2为-19.2- -18.7。含黄玉花岗斑岩成岩温度、氧逸度高于含黄玉黑云母花岗岩成岩温度和氧逸度。与含黄玉花岗斑共存热液流体log(fH2O/fHCl)^fluid值为4.29-4.99,与含黄玉黑云母花岗岩共存热液流体log(fH2O/fHCl)^fluid值为3.15-3.67。因此,相对于含黄玉黑云母花岗岩,含黄玉花岗斑岩岩浆演化过程中分异出的流体富F和Sn,即岩背含黄玉花岗斑岩岩浆演化过程分异出的原始流体以富F和Sn为特征,结合有关岩背Sn矿成矿流体的研究结果,进一步揭示出岩背Sn矿成矿流体为岩背含黄玉花岗斑岩岩浆演化过程分异出的岩浆热液,相对于含黄玉黑云母花岗岩,含黄玉花岗斑岩与锡成矿关系更密切。
Resumo:
云南会泽铅锌矿床位于扬子板块西缘川-黔-滇铅锌银多金属成矿域的中南部,严格受断裂带的控制.长期以来,对于该矿的成矿流体来源存在着较大的争论.研究表明,矿石中脉石矿物方解石的C、O同位素组成相对均一,其δ^13C(PDB)为-2.1×10^-3~-3.5×10^-3极差-1.4×10^-3、均值-2.8×10^-3,δ^18O(SMOW)为16.7×10^-3~18.6×10^-3、极差1.9×10^-3、均值17.7×10^-3,不同矿体(不同标高)、不同产状以及相同矿体不同产状方解石的C、O同位素组成不具明显差别;除了纯液相包裹体(L)和富液相的气液两相包裹体(L+V)外,还存在含子晶的三相包裹体(S+L+V)和不混溶的CO2三相包裹体(VCO2+LCO2+LH2O),流体包裹体均一温度介于110~400℃之间,具有双峰现象;矿床的(^87Sr/^86Sr)0(0.713676-0.717012)不仅明显高于地幔(0.704±0.002)和峨嵋山玄武岩(0.703932~0.707818;85件样品)的(^87Sr/^86Sr)0,也相对高于矿区赋矿地层(C16)的(^87Sr/^86Sr)。(0.70868~0.70931;3件样品),但明显低于基底岩石的(^87sr/^86Sr)。(0.7243~0.7288;5件样品),且成矿过程中流体基本没有发生Sr同位素分馏现象.因此,成矿流体为均一流体,是不同性质流体的混合产物,具有多源性.而从气液两相包裹体盐度-均一温度图解可以看出,在300-400℃区间,包裹体盐度基本被孤立为两群:一群为5%~6%(w(NaCl)),另一群为12%~16%(w(NaCl)).而在100300℃特别是150-250℃区间,包裹体盐度则基本均匀分布在7%~23%(w(NaCl))之间.断裂带形成压力为(50~320)×10^5Pa,矿体上覆岩石压力为(574-640)×10%5Pa,矿床成矿压力为(145-754)×10^5Pa.流体在上升到断裂带后压力的剧降,导致了沸腾作用的发生.在混合作用和沸腾作用的双重影响下,受狭窄断裂带控制的成矿流体高度浓缩,金属矿物得以大规模地从流体中沉淀出来,形成品位极高的铅锌矿石.
Resumo:
位于贵州织金县的新华磷矿是一个超大型磷、稀土综合矿床。已探明磷矿石储量13.148亿吨,稀土氧化物储量144.16万吨。至今稀土元素未找到一条效益理想的综合利用途径.
Resumo:
通过力学性能试验、金相、扫描电镜及透射电镜等方法和手段对MB26(Mg—Zn—Zr—RE)合金在不同热加工工艺条件下的样品进行了分析和研究。研究结果表明:MB26镁合金在挤压、淬火及淬火时效3种热加工工艺条件下,以挤压状态下所获得的力学性能为最佳,其σb值可达370MPa以上。510℃/2h的淬火工艺使挤压态下的力学性能大为下降。微观原因为:加热破坏了挤压态下均匀的板条组织及合金元素的均匀分布,并产生严重的过烧组织。170℃/10h时效工艺可使淬火态下微观范围内的淬火空位得到填补,但不能改善较为宏观的孔洞的存在及组织疏松的状况,并产生再结晶等轴晶粒及晶界,因而也不能明显地改善其力学性能。MB26镁合金以挤压态为最佳使用状态。
Resumo:
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。
Resumo:
A method for the screening and analysis of biologically active compounds in traditional Chinese medicine is proposed. Affinity chromatography using a human serum albumin (HSA) stationary phase was applied to separate and analyze the bioactive compounds from Artemisia capillaris Thunb. Five major peaks and several minor peaks were resolved based on their affinity to HSA, two of them were identified as scoparone (SCO, 6,7-dimethoxycoumarin) and capillarisin (CAP). CAP shows a much higher affinity to HSA than SCO. The effects of acetonitrile concentration, eluent pH, phosphate concentration and temperature on the retention behaviors of several major active components were also investigated, and it was found that hydrophobicity and eluent pH play major roles in changing retention values. The results demonstrate that the affinity chromatography with a HSA stationary phase is an effective way for analyzing and screening biologically active compounds in traditional Chinese medicine. (C) 2000 Elsevier Science B.V. All rights reserved.
Resumo:
A series of aluminosilicate zeolites are characterized by UV Raman spectroscopy for the first time, and UV Raman spectra of various zeolites give strong and clear bands with high resolution, while conventional Raman spectra of these zeolites are difficult to obtain because of a strong background fluorescence. Additionally, these zeolites show several new bands in UV Raman spectroscopy. A summary of these UV Raman spectra over various zeolites suggests that the bands at 470-530, 370-430, 290-410, and 220-280 cm(-1) can be assigned to the bending modes of 4-, 5-, 6-, and 8-membered rings of aluminosilicate zeolites, respectively. Furthermore, it is found that the band intensity of zeolites in UV Raman spectroscopy is dependent on the Si/Al ratio. Moreover, the UV Raman spectra of crystallization, for zeolite X at various times show that, in the initial stage of crystallization, the 4-membered rings (510 cm(-1)) interconnect each other to form beta -cages with 6-membered rings (390 cm(-1)), which further crystallize to zeolite X. (C) 2001 Elsevier Science B.V. All rights reserved.