Chromium and vanadium impurities in natural green euclase and their relation to the color

Natural specimens of green gemological euclase (chemical formula BeAlSiO₄(OH)) from Brazil were investigated by electron paramagnetic resonance (EPR) and optical absorption. In addition to iron-related EPR spectra, analyzed recently in blue and colorless euclase, chromium and vanadium-related EPR spectra were also detected in green euclase. Their role as color causing centers is discussed. The results indicate that Cr³⁺ ions substitute for Al³⁺ ions in the euclase structure. The EPR rotation patterns of Cr³⁺ with electron spin S = 3/2 were analyzed with monoclinic spin Hamiltonian leading to the parameters of g _xx , g _yy and g _zz equal to 2.018, 2.001 and 1.956 and electronic fine structure parameters of D = −8.27 GHz and E = 1.11 GHz, respectively, with high asymmetry ratio E/D = 0.13. For the vanadium-related EPR spectra the situation is different. It is concluded that vanadium is incorporated as the vanadyl radical VO²⁺ with electron spin S = 1/2 with nearly axial spin Hamiltonian parameters g_zz = 1.9447, g _xx  = 1.9740 g _yy  = 1.9669 and axial hyperfine interactions due to the nuclear spin I = 7/2 of the ⁵¹V isotope leading to A _zz  = 502 MHz, A _xx  = 150 MHz and A _yy  = 163 MHz. The green color of euclase is caused by two strong broad absorption bands centered at 17,185 and 24,345 cm⁻¹ which are attributed to the ⁴A_2g → ⁴T_2g, ⁴T_1g transitions of Cr³⁺, respectively. Vanadyl radicals may introduce some absorption bands centered in the near infrared with tail extending into the visible spectral range.     

Electron paramagnetic resonance studies on clinochlore from Longitudinal Valley area,northeastern Taiwan

A natural sample of clinochlore from the Longitudinal Valley area of northeastern Taiwan has been characterized by using the powder X-ray diffraction (XRD), differential thermal analysis and electron paramagnetic resonance (EPR) spectroscopic techniques. The lattice parameters of the monoclinic (IIb) clinochlore with the composition (Mg_2.988 Al_1.196 Fe_1.6845 Mn_0.026)_5.8945 (Si_2.559 Al_1.441)₄ O₁₀ (OH)₈ have been calculated from the powder XRD data and are found to be a = 5.347 Å, b = 9.223 Å, c = 14.250 Å, β = 97.2° and Z = 2. The thermal behaviour of the sample showed the typical behaviour of clinochlore with a hydroxyl content of 12.5 wt%. The EPR spectrum at room temperature exhibits two resonance signals centred at g ≈ 2.0 and g ≈ 8.0. The signal at g ≈ 2.0 shows a six-line hyperfine structure which is a characteristic of Mn²⁺ ions in octahedral symmetry. The resonance signal at g ≈ 8.0 is a characteristic of Fe³⁺ ions. The EPR spectra have also been recorded at different temperatures (123–295 K). The population of spin levels (N) has been calculated for g ≈ 2.0 and g ≈ 8.0 resonance signals. It is observed that N increases with decreasing temperature. From EPR spectra, the spin-Hamiltonian parameters have been evaluated. The zero-field splitting parameter (D) is found to be temperature dependent. The peak-to-peak width of the g ≈ 8.0 resonance signal is found to increase with decrease in temperature.     

Disproportionation of Fe<Superscript>2+</Superscript> in Al-free silicate perovskite in the laser heated diamond anvil cell as recorded by electron probe microanalysis of oxygen

Experimental evidence is reported for Fe²⁺ disproportionation in Al-free perovskite (Pv), when submitted to large temperature gradients (i.e., under off-equilibrium conditions) in a laser heated diamond anvil cell (LHDAC). To enable this effect, the experimental procedure was designed to produce large radial and axial temperature gradients. In the Pv and ferropericlase (Fp) assemblage synthesized after dissociation of natural olivine, the three chemical states of iron (i.e., Fe⁰, Fe²⁺ and Fe³⁺) could be evidenced by electron probe microanalysis (EPMA), through variations of oxygen contents attached to the Fe cations. Despite inherent difficulties for determination of O-contents and Fe³⁺/ΣFe ratios using EPMA, we recorded significant changes in iron oxidation state across the laser-heated strip. These changes are correlated with variations in composition for the major elements (Fe, Mg, and Si), which evidences that the Pv/Fp assemblage experienced large segregation under the strong temperature gradients. Grains of metallic iron were detected in parts of the laser-heated strip coexisting with a Pv phase with Fe/(Mg + Fe) = 6 at% and most of its iron as Fe³⁺. This Fe²⁺-disproportionation reaction involves insertion of Fe³⁺-defects in the Pv lattice. This Fe³⁺-bearing Pv phase is presumably unstable and decomposes into a mineral assemblage including magnesioferrite, which is detected at the border of the laser-heated strip.     

内蒙古阿拉善地区绿色戈壁玛瑙的宝石学特征与致色成因研究

内蒙古阿拉善地区经历数亿年的地质活动,产出颜色丰富且结构致密的戈壁玛瑙。通过常规宝石学测试、偏光显微镜及扫描电镜观察、X射线粉晶衍射、电子探针、红外光谱及紫外-可见光-近红外分光光度计等测试分析方法对绿色戈壁玛瑙的宝石矿物学特征及致色成因进行了深入研究。肉眼观察,阿拉善绿色玛瑙呈深绿色至褐绿色,微透明至不透明,相对密度、折射率、摩氏硬度等均符合石英质玉石的特点。偏光显微镜观察,绿鳞石富集于表层,并向内部呈放射状生长;方解石与石英均为隐晶质结构。扫描电镜观察,绿鳞石呈颗粒状分布于石英及方解石之间。X射线衍射分析结果表明,绿色戈壁玛瑙的物相组成主要为石英、方解石和绿鳞石。电子探针分析结果表明绿鳞石的主要化学组成为SiO₂、FeO、Al₂O₃、K₂O和MgO。红外光谱分析也显示存在绿鳞石对应基团的特征峰。表层绿鳞石在紫外-可见光-近红外分光光度计下显示出Fe²⁺与Fe³⁺的特征光谱,Fe²⁺与Fe³⁺之间的电荷转移是其...     

二价铁活化过硫酸盐去除水中苯胺

零价铁和硝基苯反应后生成二价铁和苯胺,而苯胺也是地下水污染物。硫酸根自由基具有强氧化性,可以降解苯胺。而二价铁可以活化过硫酸盐产生硫酸根自由基,进而去除苯胺。本文研究了二价铁浓度、过硫酸盐浓度、苯胺初始浓度、体系初始pH、反应温度等因素对二价铁活化过硫酸盐去除水中苯胺处理效率的影响。结果表明:1)Fe2+活化过硫酸盐生成SO-4·能快速并有效氧化降解苯胺,对于目标浓度为1 000 mg/L的苯胺而言,Fe2+浓度为3.3 mmol/L,Na2S2O8浓度为4.4 mmol/L时,对苯胺有较佳降解效果,苯胺的降解率为86.33%。2体系对较低浓度的苯胺降解效果较好,当污染物初始浓度由1 000 mg/L降低到500 mg/L和100 mg/L时,苯胺降解率由86.33%升高为90.27%和97.16%。3初始pH对苯胺的降解率影响较大,中性条件下(pH=7左右)降解率较好,高初始pH(pH=9,11)和低初始pH条件(pH=3,5)下均低于中性条件下苯胺的降解效率。4体系的温度变化对降解率影响不明显。     

How Cr<Superscript>3+</Superscript> and Fe<Superscript>3+</Superscript> affect Mg–Al order–disorder transformation at high temperature in natural spinels

Three natural Mg(Al_2-yCr_y)O₄ spinels (y 0.07–0.16), highly ordered in terms of Mg–Al, and one Mg(Al_2–yFe³⁺_y)O₄ spinel (y0.08), highly ordered also in terms of Fe³⁺, were studied by means of X-ray single-crystal diffraction. All samples were heated in situ from 25 to 1000 °C in order to follow both thermal expansion and evolution of the structural state of spinel with temperature. Thermal expansion was monitored by means of the variation of cell edge a with temperature, and found to be well represented throughout the temperature range by a regression line a = a₀ (1+T), slightly different at lower and higher temperatures. Thermal expansion coefficient ₁, referring to the lower temperature range (i.e. during pure thermal expansion), was slightly lower than ₂, calculated only over the highest temperatures. The trend showed different slopes for individual crystals. Structural evolution with temperature was studied by means of the variation of oxygen positional parameter u, which is strongly influenced by intersite cation exchange and thus closely correlated with inversion parameter x. In particular, in the three Cr samples, in which Cr resides only in the octahedral site, u parameter variations and hence the order–disorder process, started at about 700 °C. Instead, in the Fe³⁺ sample, this process was triggered at lower temperatures, starting at 550 °C with Fe³⁺–Mg exchange followed at higher temperatures by that of Mg–Al. Cr contents in the Cr samples affected the occupancy of Al in the tetrahedral site at the highest temperatures. In both Mg–Al–Cr and Mg–Al–Fe³⁺ compositions, if CrFe³⁺, parameter u reached the same value only when the Mg–Al exchange was dominant, i.e. at the highest temperatures, but not before. Cation distribution at each temperature was obtained by the bond-length model, applying thermal expansion to pure bond lengths. This method is applied here to complex compositions for the first time.     

The stability of primary alluaudites in granitic pegmatites: an experimental investigation of the Na2(Mn2−2x Fe1+2x )(PO4)3 system

In order to assess the geothermometric potential of the Na₂(Mn_2−2x Fe_1+2x )(PO₄)₃ system (x = 0–1), which represents the compositions of natural weakly oxidized alluaudites, we performed hydrothermal experiments between 400 and 800°C, at 1 kbar, under an oxygen fugacity (f(O₂)) controlled by the Ni–NiO (NNO), Fe₂O₃–Fe₃O₄ (HM), Cu₂O–CuO (CT), and Fe–Fe₃O₄ (MI) buffers. When f(O₂) is controlled by NNO, single-phase alluaudites crystallize at 400 and 500°C, whereas the association alluaudite + marićite appears between 500 and 700°C. The limit between these two fields corresponds to the maximum temperature that can be reached by alluaudites in granitic pegmatites, because marićite has never been observed in these geological environments. Because alluaudites are very sensitive to variations of oxygen fugacity, the field of hagendorfite, Na₂MnFe²⁺Fe³⁺(PO₄)₃, has been positioned in the f(O₂)–T diagram, and provides a tool that can be used to estimate the oxygen fugacity conditions that prevailed in granitic pegmatites during the crystallization of this phosphate.     

泰山玉的矿物岩石学特征

采用电子探针、粉晶X射线衍射、化学分析和傅里叶变换红外光谱等方法对泰山玉进行了测试,系统论述了山东泰山玉的颜色分类、矿物组成、化学成分、微量元素特征、结构和构造类型及物理性质。泰山玉分为3种类型:泰山碧玉、泰山墨玉及泰山花斑玉。泰山玉主要由叶蛇纹石组成,杂质矿物有磁铁矿、碳酸盐、滑石、绿泥石、斜方辉石、云母、黄铁矿、褐铁矿、硫镍矿等。泰山玉中的矿物生成顺序为片状蛇纹石→脉状蛇纹石→滑石→脉状碳酸盐。泰山碧玉和花斑玉由Fe²⁺致色,而泰山墨玉由微粒磁铁矿致色。与辽宁岫玉的区别在于泰山玉中Cr、Ni元素的含量很高。     

Local relaxation around [6]Cr 3+ in synthetic pyrope–knorringite garnets, [8]Mg 3 [6](Al 1-X Cr X 3+) 2 [4]Si 3O 12, from electronic absorption spectra

Pyrope-knorringite garnets, Mg₃(Al_1-X Cr³⁺_X)₂Si₃O₁₂ with X=0.25, 0.50, and 1.00, were synthesized between 9 and 16 GPa and 1300 and 1600 °C, using multianvil high-pressure techniques. The garnets with X=0.25 and 0.50 are fine-grained, pink and violet in color. The end-member knorringites with X=1.00 are black when compact and gray when coarse-grained. The fine powder is greenish gray in natural light and pale pink under a tungsten lamp. Powder remission spectra in the wavenumber range 30 000–10 000 cm^–1 on finely powdered crystals were measured by two different methods: (I.) by the use of a small integrating sphere for small samples or (II.) microscope-spectrometric measurement using diffusely reflected radiation from a 45° illuminated microsample. Both methods yielded similar diffuse reflectance spectra. The following crystal-field parameters of ^[6]Cr³⁺ were determined for garnets with X=0.25, 0.50, 1.00: 10 Dq=17 856, 17 596, 17 286 cm^–1; and B=654, 677, 706 cm^–1; nephelauxetic ratio =(B_field/B_free)= 0.71, 0.74, 0.77. The -values indicate decreasing covalency of the Cr–O bond with increasing Cr content. The 10 Dq value for together with the mean Cr–O distance in end-member knorringite, 1.96 Å (Novak and Gibbs 1971), were used to calculate from the spectral data, local mean Cr–O distances (Langer 2001a) as a function of composition. The results indicate relatively strong local site relaxation with a value of =0.77.     

Energy transfer among Pb, Ce and Mn in fluorescent calcite from Kuerle, Xinjiang, China

Natural calcite from Kuerle, Xinjiang, China, shows orange-red fluorescence when exposed to short-wave ultraviolet (UV) light (Hg 253.7 nm). Photoluminescence (PL) emission and excitation spectra of the calcite are observed at room temperature in detail. The PL emission spectrum under 208 nm excitation consists of three bands: two UV bands at 325 and 355 nm and an orange-red band at 620 nm. The three bands are ascribed to Pb²⁺, Ce³⁺ and Mn²⁺, respectively, as activators. The Pb²⁺ excitation band is observed at 243 nm, and the Ce³⁺ excitation band at 295 nm. The Pb²⁺ excitation band is also observed by monitoring the Ce³⁺ fluorescence, and the Pb²⁺ and Ce³⁺ excitation bands, in addition to six Mn²⁺ excitation bands, are also observed by monitoring the Mn²⁺ fluorescence. These indicate that four types of the energy transfer can occur in calcite through the following processes: (1) Pb²⁺ → Ce³⁺, (2) Pb²⁺ → Mn²⁺, (3) Ce³⁺ → Mn²⁺ and (4) Pb²⁺ → Ce³⁺ → Mn²⁺.     

电感耦合等离子体质谱法测定含气天然矿泉水中的铬

含气天然矿泉水含有高浓度的HCO;和CO2,其中元素Cr的浓度在电感耦合等离子体光谱(ICP-AES)的检出限附近甚至更低,应用电感耦合等离子体质谱(ICP-MS)测定又容易形成多原子离子40 Ar12C,对52 Cr的测定形成干扰,致使ICP-MS不能直接准确测定含气天然矿泉水中的Cr元素.本文对水样进行前处理,加热煮沸2 min后放置至室温,加入硝酸调节水样酸度为5％,促进HCO3-与H+反应生成大量的CO2迅速释放出来,消除了40Ar12C对52Cr产生的质谱干扰,实现了ICP-MS能够直接准确分析Cr的含量,方法检出限为0.23 ng/mL,加标回收率为92.3％～93.7％,相对标准偏差(RSD)小于10％.此方法简单实用,精确度和准确度能够满足天然矿泉水分析测试的要求,还可同时测定此批前处理水样中的锌铜砷镉铅等痕量元素.     

海南岛高通岭钼矿床赋矿岩体LA-ICP-MS锆石U-Pb年龄、Hf同位素和Ce4+/Ce3+特征

高通岭钼矿床位于海南岛中部的早白垩世—晚白垩世高通岭岩体中,是一个小型热液脉型钼矿床。作者对赋矿围岩黑云母钾长花岗岩进行了岩相学观察、LA-ICP-MS锆石U-Pb定年、锆石Lu-Hf同位素测试和锆石微量元素分析。结果显示:赋矿围岩矿物组合为钾长石(45%~60%)、石英(20%~30%)、斜长石(10%~20%)及黑云母(10%~15%);矿石矿物以辉钼矿为主,矿石类型主要为石英脉型,次为蚀变黑云母钾长花岗岩型和碎裂岩型;高通岭岩体中的锆石,具有清晰的振荡环带,显示其岩浆成因;锆石U-Pb年代学研究获得206U/238Pb加权平均年龄为(102.5±1.8)Ma,锆石的~(176)Hf/~(177)Hf比值为0.282 349~0.282 663,εHf(t)为-12.8~-1.7,二阶段地壳模式年龄(TCDM)为1976~1271 Ma,峰值为1450~1400 Ma,锆石稀土元素配分模式显示高通岭岩体的陆壳源区属性。地表取样的黑云母钾长花岗岩(GTL-03和GTL-04)具有较低Ce~(4+)/Ce~(3+)比值(160左右),反映了较低氧逸度,钻孔取样的黑云母钾长花岗岩具有较高Ce~(4+)/Ce~(3+)比值(平均值377)。高通岭岩体总体上氧逸度较低,暗示其大规模成矿潜力较低。     

北大别北东地区榴辉岩温度条件分析

北大别榴辉岩温度条件的精确评价直接涉及到北大别变质单元性质的判定.由于榴辉岩温度分类方案的不同,以及温度估算时温度计选择和绿辉石Fe2+校正方法不同的影响,导致北大别榴辉岩温度评价和分类归属具有较大的不确定性.为此,本研究应用5个不同的温度计和4种不同的绿辉石Fe2+校正方法,评价了北大别北东地区榴辉岩的温度条件.研究显示,当应用Kogh (2000)的Grt-Cpx Fe-Mg温度计和设定绿辉石的铁为Fe3+/Fe2+=1∶1时,温度计算较为合理:P标定=3.5 GPa,温度范围为600～740℃或P标定=5.0GPa,温度范围为670～ 810℃.参照Carswell (1990)的温度分类,北大别榴辉岩应属于中温类型.但结合此次榴辉岩的地质特征、岩相学和矿物成分分析,以及前人的研究资料,北大别榴辉岩与中大别和南大别榴辉岩有明显的差异,其可能是在相对高温的条件下形成的.     

溶出珊瑚砂中Ca~(2+)、Mg~(2+)的动力学实验研究及其影响因素

通过改变固液比、摇床转速、珊瑚砂粒径、温度、溶液pH值及溶液含盐量等参数,对珊瑚砂在水溶液中溶出Ca~(2+)、Mg~(2+)进行了实验,以探讨溶出过程中的动力学规律和影响因素。实验结果表明,珊瑚砂中Ca~(2+)、Mg~(2+)溶出量随反应时间逐渐增大;摇床转速越快、固液比越大、温度越高、溶液pH值越低,Ca~(2+)、Mg~(2+)溶出量越大;当珊瑚砂粒径为2.36~4.75 mm、溶液含盐量为100 mg/L时,Ca~(2+)、Mg~(2+)溶出量最大。统计分析表明,摇床转速、温度及溶液p H值均对珊瑚砂溶出有显著影响,但溶液p H值影响最大。珊瑚砂在水中的溶出过程符合收缩核内扩散模型,表明控制整个溶出过程反应速率的决定因素是内扩散速率;在15~40℃时,珊瑚砂在纯水中溶出Ca~(2+)、Mg~(2+)的活化能分别为78.07和74.91 k J/mol。     

Uptake of Cu2+ by the calcium carbonates vaterite and calcite as studied by continuous wave (cw) and pulse electron paramagnetic resonance

The investigation of the Cu²⁺ uptake by the calcium carbonate minerals vaterite and calcite with continuous wave and pulse electron paramagnetic resonance (EPR) yields information on a molecular scale about the relevant complexation reactions at the mineral–water interface. The structural assignment is based on changes in the coordination geometry of the copper complexes. Magnetic interactions of the unpaired Cu²⁺ electron with nuclei of ¹³C-labeled carbonate ligands and protons from water or hydroxyl ligands in the first and second coordination spheres of the cation are detected by pulse EPR techniques. Our results show that the Cu²⁺ ions are rapidly dehydrated upon adsorption on the mineral surface. The strong surface binding is due to monodentate coordination to three or four carbonate surface ions, comparable to chelate complexation in solution. The formation of square-planar or square-pyramidal copper complexes at exposed surface sites like kinks and steps yields a convincing explanation for the inhibition of calcium carbonate growth and dissolution. Upon recrystallization the Cu²⁺ ions are integrated into the calcite lattice where they exhibit a dynamic Jahn–Teller effect. The resulting local lattice distortions are expected to destabilize the Cu_xCa_(1−x)CO₃(s) solid solution. Our results support the concept of a dynamic calcium carbonate surface, covered by a thin, structured surface layer. The detailed structural information obtained for Cu²⁺ provides a better understanding of the interaction of other metal ions with calcium carbonate minerals.     

皖南晚中生代花岗闪长岩地球化学:成岩成矿制约

皖南地区是铜、钼、金多金属成矿区,成矿与晚中生代花岗闪长岩类关系密切。近十年来,皖南花岗闪长岩的成因仍然存在分歧。本次报道了皖南花岗闪长岩全岩主、微量元素和锆石原位元素数据。皖南花岗闪长岩(Si O2=64.3%~70.8%)为高钾钙碱性、过铝质岩石,具有相似的埃达克岩特征:高Si O2、Sr/Y(17.1)和(La/Yb)N(14.9)比值,低Yb(1.72×10-6)和Y(18.4×10-6)含量。它们也具有较低Al2O3和Cr(3.40×10-6~10.0×10-6)含量、低Mg#(0.34~0.42)和Nb/Ta(9.6~13.3)值,高K2O和Ba(404×10-6)含量,高K2O/Na2O(0.89~1.55)、Th/La(0.27~0.51)和Th/U(2.79~7.49)比值。锆石原位地球化学特征显示其岩浆源区为低温(锆石Ti-in-zircon温度均值674℃)和高氧逸度(lgfO2集中在-21.4~-9.18,均值-16.4;锆石Ce4+/Ce3+平均值276)的陆壳。这些特征说明皖南花岗闪长岩可能起源于较年轻的加厚下地壳的部分熔融,并经历了斜长石、钾长石和铁镁矿物等结晶分异作用。它们可能形成于与古太平洋板块俯冲密切相关的大陆活动边缘弧至弧后拉张构造转换背景。本区大规模Cu、Mo、Au成矿作用与岩浆的高氧逸度密切相关,而锆石Ce4+/Ce3+可作为矿床勘探一个有效的指标。     

The Speciation of (CH3)2Sn2+ in Electrolyte Solution Containing the Major Components of Natural Waters

Hydrolysis constants of dimethyltin(IV) cation, in different salt solutions (CaCl₂: 0.15 I 0.90; MgCl₂: 0.30 I 0.60; NaCl-–NaClO₄, NaCl-–NaNO₃ mixtures: I = 3; NaCl-–Na₂SO₄ mixtures: I = 1 mol dm^-3) were determined by potentiometric ([H⁺]-glass electrode) measurements. These data, together with previous data (De Stefano et al., 1996b) were interpreted in terms of DHT (Debye–Hückel type) and Pitzer equations. The mixed electrolyte solution results also allowed us to obtain and parameters for the Pitzer equation. Calorimetric measurements were made at different ionic strengths in order to find the temperature dependence of hydrolysis constants and of the relative interaction parameters. The body of results allows us to determine the speciation of natural waters in a wide range of ionic strengths and temperatures.     

Detection of tannins in modern and fossil barks and in plant residues by high-resolution solid-state C nuclear magnetic resonance

Bark samples isolated from brown coal deposits in Victoria, Australia, and buried wood from Rhizophora mangle have been studies by high-resolution solid-state nuclear magnetic resonance (NMR) techniques. Dipolar dephasing ¹³C NMR appears to be a useful method of detecting the presence of tannins in geochemical samples including barks, buried woods, peats and leaf litter. It is shown that tannins are selectively preserved in bark during coalification to the brown coal stage.     

湖南宝山-大坊矿区成矿花岗闪长斑岩的锆石U-Pb年龄、Hf同位素及微量元素组成对区域成矿作用的指示

钦-杭成矿带是华南地区新近识别出的一条重要的中生代斑岩-矽卡岩型铜多金属成矿带。宝山矿床处于铜山岭-宝山-水口山矿区的中部,是湘南地区最大的铜多金属矿床,而大坊金矿床与宝山Cu-Mo-Pb-Zn矿相邻,在空间上亦与花岗闪长斑岩密切相关。矿区内岩浆活动复杂,矿化类型齐全,成矿元素多样。我们对宝山成矿花岗闪长斑岩、花岗闪长质隐爆角砾岩和大坊成矿花岗闪长斑岩进行了LA-MC-ICP-MS锆石U-Pb测年,结果表明宝山花岗闪长斑岩、花岗闪长质隐爆角砾岩和大坊花岗闪长斑岩的侵位年龄分别为156. 3±0. 9Ma、157. 1±1. 8Ma和154. 5±1. 0Ma,三者在误差范围内一致,均为晚侏罗世岩浆活动的产物;锆石Hf同位素研究表明,宝山和大坊矿床的成矿岩体均主要为古元古代地壳物质部分熔融的产物,并有幔源组分的加入;锆石微量元素分析结果显示,上述三类岩石的锆石具有相似的稀土元素配分模式,显示它们可能是同一期岩浆作用的产物。宝山矿区花岗闪长斑岩中锆石的Ce~(4+)/Ce~(3+)比值平均为355,与全球典型的含铜斑岩的Ce~(4+)/Ce~(3+)比值( 300)相似。而大坊矿区花岗闪长斑岩中锆石的δEu平均为0. 48,与宝山岩体δEu平均值(0. 42)相近,指示二者具有相对较高的氧逸度,均为与铜金多金属矿化有关的斑岩体。锆石U-Pb年龄、Hf同位素及微量元素特征表明,大坊金矿和宝山铜多金属矿床均与矿区花岗闪长斑岩具有时空及成因联系,共同构成钦杭成矿带中段一套与花岗闪长斑岩有关的Cu(Mo)-Pb-Zn-Au-Ag成矿系统。     

多硅白云母中Fe2+的高压有序效应

21个多硅白云母来自4个低温高压变质带。用电子探针、X射线粉末衍射及穆斯堡尔谱测定其化学成分、b0值及Fe²⁺占位。建立Fe²⁺(M1)/Fe²⁺(M2)对b0值相关图,发现Fe²⁺在八面体晶位有序化并解释其有序机理。