祁雨沟金矿自然金的标型特征及其找矿意义

本文以２８００粒自然金的研究为基础，系统讨论了自然金的标型特征。研究指出：本矿床应具较大规模，矿区内除Ｊ＿２、Ｊ＿４角砾岩体外，其余几个角砾岩体也应有一定远景，｛１１１｝、｛１１１｝＋｛１００｝、｛１１０｝的出现可指示富矿地段，自然金晶体形态的空间分带规律可确定（岩）矿体的剥蚀深度及评价外围角砾岩体的含矿性及远景；自然金中Ｂｉ可做为找矿评价的指示元素。     

津巴布韦金刚石中石墨包裹体及金刚石异常双折射特征分析

津巴布韦马朗(Marange)金刚石矿以产出混合习性(八面体与近立方体)金刚石为特征,其石墨包裹体仅存在于近立方体区.石墨包裹体的形态、分布及金刚石的异常双折射与应变特征,能反映其从开始结晶到被搬运至地表过程中经历的地质作用.因此,对津巴布韦混合习性金刚石及石墨包裹体的研究不仅能提供与其他产地金刚石有对比意义的数据,且...     

锆石形态标型特征及标型生长机制探讨

本文在系统总结归纳不同研究者对锆石形态标型特征的研究成果基础上，重点从晶体生长、晶体化学和地球化学理论为重点探讨了锆石形态标型特征的生长机制。研究表明：锆石晶体结构中不同的面网方向，其平面内的原子组成、比例、化学键联结和键力以及面网间距和密度都是有差别的，由此决定了锆石晶体在不同的结晶介质条件下，不同面网的生长速度发生改变，生成相应的晶形。例如，尽管碱性元素并不进入锆石晶格，但它们可以影响Ｚｒ、Ｓｉ、Ｏ离子的扩散速度，但是富钾和富钠的介质对锆石晶形发育的影响是有差别的，表现为：在富钾的介质中，将导致柱面的法向生长速度较锥面快得多，而锥面中，｛１１１｝的法向生长又较｛３１１｝快，由此决定了形成以｛３１１｝锥为主的双锥状晶体；在富钠的介质中，柱面和锥面都有一定程度的发育，但前者弱于后者，而柱面中，｛１００｝的法向生长较｛１１０｝慢，由此决定了形成以｛１００｝柱和｛１１１｝锥为主的短柱锥状晶体。根据类似方法，论证了其它形态标型特征的客观性，从而揭示了标型之间的内在联系和本质，展示了花岗岩研究中锆石形态标型特征应用推广的前景，也可为单颗粒锆石定年研究提供更多的分析应用价值     

黄铁矿加热相变特征的XRD初步研究

<正>黄铁矿,化学成分FeS2,其晶体属等轴晶系的硫化物矿物。常见晶形是立方体、五角十二面体、八面体及它们的聚形。立方体晶面上有与晶棱平行的条纹,各晶面上的条纹相互垂直。     

多形貌纳-微米黄铁矿的TEM观察

黄铁矿是自然界广泛存在的一种硫化物矿物,等轴晶系,常见完好晶形为立方体{100}、五角十二面体{210}、或八面体{111},还可形成它们的聚形。前人研究发现,黄铁矿结晶能力较强,在各种条件下均能自发结晶形成完好的晶形(李     

俄罗斯地台北缘和东北缘的曲面金刚石(英文)

曲面金刚石广泛产于金刚石砂矿和含金刚石的金伯利岩管及钾镁煌斑岩中。曲面金刚石是一种特殊的晶体类型 ,它与平坦面金刚石相比 ,不仅晶习不同 ,曲面金刚石常呈四六面体 ,而平坦面金刚石常呈八面体 ,而且它更坚实 ,更具宝石价值。热力学计算和实验表明 ,八面体金刚石比立方八面体和立方体金刚石的形成温度高 ,意味着曲面金刚石形成深度较浅 ,可能在石墨 -金刚石稳定区的边界上。目前对曲面金刚石是生长形还是由平坦面金刚石熔蚀而成尚有不同见解。文章对俄罗斯地台北缘和东北缘的曲面金刚石进行了综合研究。经切割抛光 ,用 X射线形貌法、阴极发光法和普通光学法进行了结构研究 ,还对金刚石进行了光学荧光、 X射线荧光 ( T=77～ 2 90 K)、ESR电子自旋共振、可见光区的吸收谱等研究。用光学测角仪和扫描电镜查明 ,研究区的金刚石中四六面体单形占 60 %～ 80 %、 { 0 65} +{ 365} +{ 1 1 1 }聚形占 8%～35%、平坦面八面体占 0～ 8%且无菱形十二面体。研究发现金刚石表面覆有成分不同的薄膜 ,厚约 0 .1～ 1 μm,其成分有 2 9种之多。表明天然金刚石是在多种金属和碳的熔体中结晶的 ,乌拉尔 -巴西型金刚石的曲面晶为生长晶而非熔蚀晶。在罗蒙诺索夫金伯利岩管中获取的金刚石表面附有超基性岩的原生矿物组合?     

乌达奇内金伯利岩筒橄榄石中硫化物包裹体的混入元素

在亚库梯亚和南非的金刚石中广泛发育Ｆｅ－Ｎｉ－Ｃｕ硫化物的原生包裹体,对超基性岩和榴辉岩中金刚石的Ｆｅ－Ｎｉ－Ｃｕ－Ｓ系列包裹体进行了对比研究,结果表明,二者中的原始硫化物熔融体成分有明显差异,对金刚石及其共生矿物中硫化物包裹体的化学成分的研究相当全面,而对微量元素成分的研究还刚刚起步,对亚库梯亚金刚石（包括乌达奇内金伯利岩筒中的金刚石）的硫化物包裹体中混入元素成分进行了研究。其结果表明,超基性岩     

湖南铲子坪金矿的矿物标型及其地质意义

矿床位于白马山花岗岩外接触带附近，成矿阶段单一，矿物组份较复杂．金矿物颗粒细小，杂质少，成色高，硬度较高，与硫化物密切共生．石英以充填于构造空间的乳白色石英和交代构造岩的烟灰色、灰白色石英两种形式产出．二者同期共生，普遍发生塑性变形，含大量气液包裹体，气相成分以Ｈ２Ｏ和ＣＯ２为主，Ｈ２Ｏ＞＞ＣＯ２，贫Ｎ２，包裹体水的δ１８ＯＨ２ｏ比白马山花岗岩稍低．黄铁矿重结晶和动力变质现象普遍．五角十二面体、八面体黄铁矿的含金性好，立方体的含金性则较差．向深部，立方体黄铁矿减少，五角十二面体及其与立方体的聚形增多．黄铁矿的化学成分复杂，Ｓ／Ｆｅ＝１．９２—２．０２，亏硫；Ｃｏ／Ｎｉ平均为１．１７；Ｓｅ／Ｔｅ＝１２．４；Ｓ／Ｓｅ＝７．８×１０４；δ３４Ｓ分布于＋０．３２‰－７．５８‰的狭窄范围内．其晶胞参数（ａ０）与Ｃｏ、Ｎｉ、Ａｓ、Ｈｇ、Ｓｎ等质元素的含量相关．本矿床与胶东夏甸金矿类似，具有中－浅成中－低温岩浆热浪成因特点．成矿热浪来自白马山花岗岩，矿液由北向南，自西向东迁移．具大型矿床规模．矿床西部和Ⅰ矿脉带的深部有较好的找矿前景．     

山东郯城砂矿金刚石特征及包裹体研究

通过对115粒山东郯城砂矿金刚石样品进行矿物学和光谱学特征研究,结果显示郯城金刚石的粒径集中在1. 0~4. 0mm之间,晶体形态以菱形十二面体为主,其次八面体与菱形十二面体聚形,八面体较少;晶面形貌除倒三角凹坑、塑性变形滑移线、熔蚀沟、生长丘、生长阶梯、叠瓦状蚀象、滴状丘、晕线等原生形貌发育外,小部分发育有次生形貌 绿色色斑,且大多数金刚石的边棱清晰,磨圆程度不高。研究首次测得了郯城金刚石的拉曼特征峰的半高宽数据和金刚石包裹体拉曼谱图,显示郯城砂矿金刚石结晶程度差异较大,暗示其形成的金刚石地质生长条件和环境的复杂性;金刚石包裹体有橄榄石、黄铜矿、针铁矿、石墨矿物,其中橄榄石包裹体占比较高,表明郯城金刚石包裹体类型以橄榄岩型为主,测试结果与华北东部古老克拉通之下的岩石圈地幔大部分由橄榄岩组成的结论一致。对比郯城金刚石与蒙阴金刚石特征的异同,初步探讨了金刚石砂矿的物质来源,为揭示郯城砂矿金刚石的形成及演化提供了金刚石及其包裹体的新的证据。     

福建紫金山矿田黄铁矿标型特征研究

通过手标本及显微镜下矿相学观察,结合电子探针成分及X射线粉晶衍射分析,总结紫金山矿田各矿床的黄铁矿形态标型、结构标型及成分标型特征,发现紫金山矿田黄铁矿主要晶形为八面体、立方体、五角十二面体及其聚形,晶胞参数值的变化范围为a0=0.541 12~0.541 97nm,平均0.541 58nm。自形-半自形八面体和立方体晶形,粒度粗,淡黄色黄铁矿晶胞参数接近于正常值,其含矿性小;而他形-半自形,八面体,五角十二面体及其聚形黄铁矿,粒度细小,晶胞参数偏大,一般表现为浅铜黄色,含矿性高。w(S)、w(S)/w(Fe)、w(Co)/w(Ni)比值指示了紫金山矿田的成矿热液来源及成矿温度的变化,并对具环带结构黄铁矿的不同环带进行了电子探针成分分析。     

金刚石中微量元素的同步辐射X射线荧光分析

利用同步辐射X射线荧光技术,对人工合成金刚石以及产自山东、辽宁、湖南的天然金刚石进行了微量元素的测试分析。结果表明,在合成金刚石中,检测到了第四周期的元素(除As、Ge、Kr和Br外)和Pb;其中Fe、Co、Ni相对含量高,可能是合成时触媒的混入引起的。天然金刚石中检测到的微量元素有Ca、Ti、Cr、Mn、Fe、Co、Ni、Cu、Zn、W、Au和Pb,但相对含量比合成金刚石中相应的微量元素相对含量低。不同产地的天然金刚石中的微量元素种类及含量存在差异,反映了金刚石地幔生长环境的不同及岩浆对金刚石生长过程的影响。     

The Mg-carbonate-Fe interaction:Implication for the fate of subducted carbonates and formation of diamond in the lower mantle

The fate of subducted carbonates in the lower mantle and at the core-mantle boundary was modelled via experiments in the MgCO3-Fe^0 system at 70-150 GPa and 800-2600 Kin a laser-heated diamond anvil cell.Using in situ synchrotro n X-ray diffraction and ex situ transmission electron microscopy we show that the reduction of Mg-carbonate can be exemplified by:6 MgCO3+19 Fe=8 FeO+10(Mg0.6Fe^0.4)O+Fe7 C3+3 C.The presented results suggest that the interaction of carbonates with Fe^0 or Fe^0-bearing rocks can produce Fe-carbide and diamond,which can accumulate in the D"region,depending on its carbon to Fe ratio.Due to the sluggish kinetics of the transformation,diamond can remain metastable at the core-mantle boundary(CMB)unless it is in a direct contact with Fe-metal.In addition,it can be remobilized by redox melting accompanying the generation of mantle plumes.     

Experimental and thermodynamic study of the crystallization of diamond and silicates in a metal-silicate-carbon system

Silicate inclusions are widespread in natural diamonds, which also may contain rare inclusions of native iron. This suggests that some natural diamonds crystallized in metal-silicate-carbon systems. We experimentally studied the crystallization of diamond and silicate phases from the starting composition Fe_0.36Ni_0.64 + silicate glass + graphite and calculated the Fe mole fractions of the silicate phases crystallizing under these conditions. The silicates synthesized together with diamond had low Fe mole fractions [Fe/(Fe + Mg + Ca)] in spite of strong Fe predominance in the system. The Fe mole fractions of the silicates decreased in the sequence garnet-pyroxene-olivine, which is consistent with the results of our thermodynamic calculations. The Fe mole fraction of silicates under various redox conditions under which metal-carbon melts are stable drastically decreases with decreasing fo₂. The low Fe mole fractions of silicate inclusions in diamond from the Earth’s mantle can be explained by the highly reducing crystallization conditions, under which Fe was concentrated as a metallic phase of the magmatic melts and could be only insignificantly incorporated in the structures of silicates.     

Effect of sulfur concentration on diamond crystallization in the Fe–C–S system at 5.3–5.5 GPa and 1300–1370°C

The paper presents results of experiments aimed at diamond synthesis in the Fe–C–S system at 5.3–5.5 GPa and temperatures of 1300–1370°C and detailed data on the microtextures of the experimental samples and the composition of the accompanying phases (Fe₃C and Fe₇C₃ carbides, graphite, and FeS). It is demonstrated that diamond can be synthesized after temperatures at which carbides are formed are overcome and can crystallize within the temperature range of 1300°C (temperature of the peritectic reaction melt + diamond = Fe₇C₃) to 1370°C (of thermodynamically stable graphite) under the appearance experimental pressure. The possible involvement of natural metal- and sulfur-bearing compounds in the origin of natural diamond is discussed.     

金刚石中氢的研究及其意义

含氢对于天然与高温高压合成金刚石体内而言是固有的，但是对CVD金刚石来说并非固有。氢可以稳定存在于晶格位、键心、反键心及四面体空隙等金刚石的结构属性中，也可以存在于显微流体包裹体中。即便是在 1473K下淬火，氢在金刚石中也并不发生迁移或扩散，表明氢在金刚石结构中是自陷的。金刚石中的氢的研究对于地幔矿物学及材料科学等均有重要理论意义和实际意义。     

Comparison of enigmatic diamonds from the Tolbachik arc volcano (Kamchatka) and Tibetan ophiolites: Assessing the role of contamination by synthetic materials

The enigmatic appearance of cuboctahedral diamonds in ophiolitic and arc volcanic rocks with morphology and infrared characteristics similar to synthetic diamonds that were grown from metal solvent requires a critical reappraisal. We have studied 15 diamond crystals and fragments from Tolbachik volcano lava flows, using Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), synchrotron X-ray fluorescence (SRXRF) and laser ablation inductively coupled plasma mass-spectrometry (LA-ICP-MS). FTIR spectra of Tolbachik diamonds correspond to typical type Ib patterns of synthetic diamonds. In TEM films prepared using focused ion beam technique, we find Mn-Ni and Mn-Si inclusions in Tolbachik diamonds. SRXRF spectra indicate the presence of Fe-Ni and Fe-Ni-Mn inclusions with Cr, Ti, Cu, and Zn impurities. LA-ICP-MS data show variable but significantly elevated concentrations of Mn, Fe, Ni, and Cu reaching up to 70 ppm. These transition metal concentration levels are comparable with those determined by LA-ICP-MS for similar diamonds from Tibetan ophiolites. Mn-Ni (+Fe) solvent was widely used to produce industrial synthetic diamonds in the former USSR and Russia with very similar proportions of these metals. Hence, it appears highly probable that the cuboctahedral diamonds recovered from Kamchatka arc volcanic rocks represent contamination and are likely derived from drilling tools or other hard instruments. Kinetic data on diamond dissolution in basaltic magma or in fluid phase demonstrate that diamond does not form under the pressures and temperature conditions prevalent within the magmatic system beneath the modern-day Klyuchevskoy group of arc volcanoes. We also considered reference data for inclusions in ophiolitic diamonds and compared them with the composition of solvent used in industrial diamond synthesis in China. The similar inclusion chemistry close to Ni₇₀Mn₂₅Co₅ for ophiolitic and synthetic Chinese diamonds scrutinized here suggests that most diamonds recovered from Tibetan and other ophiolites are not natural but instead have a synthetic origin. In order to mitigate further dubious reports of diamonds from unconventional tectonic settings and source rocks, we propose a set of discrimination criteria to better distinguish natural cuboctahedral diamonds from those produced synthetically in industrial environments and found as contaminants in mantle- and crust-derived rocks.     

Evidence of subduction and crust–mantle mixing from a single diamond

Cathodoluminescence (CL) imaging of polished sections of a diamond from the Guaniamo region of Venezuela suggests a history of the diamond involving two periods of growth separated by a period of resorption and possibly brittle deformation. In situ electron probe analysis of multiple eclogitic garnet inclusions reveals a correlation between garnet composition and location in the stone. An early-formed garnet in the diamond core has higher Ca/(Ca+Mg) and lower Mg/(Mg+Fe) values than later garnets associated with the second period of diamond growth. This variation conforms to an extensive trend of variation in the suite of eclogitic garnets extracted from Venezuelan diamonds. The diamond is zoned in carbon isotope composition (in situ secondary ion mass spectrometry, SIMS, data). The core compositions (δ¹³C PDB), corresponding to the first stage of growth, average −17.7‰. The second period of growth is apparently in two sub-sets of CL zones with mean values of −13.0‰ and −7.9‰. Nitrogen contents of diamond are low (30–300 atomic ppm) and do not correlate with carbon isotope composition. Oxygen isotope ratios of the garnet inclusions are elevated substantially above those expected for “common mantle”; δ¹⁸O VSMOW of early garnet is approximately +10.5‰ and two late garnets average +8.8‰. The evolutionary trend of magnesium enrichment in garnet is unlikely to represent igneous fractionation. The stable isotope data are consistent with diamond formation in subducted meta-basic rocks that had interacted with sea water at low temperatures at or near the sea floor and contained a substantial biogenic carbon component. During or following subduction, diamonds continued to form in an evolving system that was progressively modified by interaction with mantle material.     

Local environment and valence state of iron in microinclusions in fibrous diamonds: X-ray absorption and Mössbauer data

Iron valence state and local environment in a set of fibrous diamonds from Brazilian and Congolese placers were investigated using X-ray absorption and Mössbauer spectroscopies. It is shown that the diamonds could be divided into two main groups differing in the type of dominant Fe-bearing inclusions. In the first group Fe is mostly trivalent and is present in octahedral coordination; diamonds from the second group contain a mixture of Fe²⁺ and Fe³⁺, most likely with Fe²⁺ in dodecahedral coordination. A few other diamonds contain iron in a more reduced state: The presence of metallic Fe and Fe₃O₄ is inferred from XAS measurements. Spatially resolved XANES and Mössbauer measurements on polished diamond plates show that in some cases the Fe valence state may change considerably between the core and rim, whereas in other cases Fe speciation and valence remain constant. It is shown that Fe valence does not correlate with water and/or carbonate content or ratio, suggesting that iron is a minor element in the growth medium of fibrous diamonds and plays a passive role. This study suggests that, when present, evolution of the C isotopic composition with diamond growth is largely due to changes in chemistry of the growth medium and not due to variations of f_O2.     

Formation of epigenetic graphite inclusions in diamond crystals: experimental data

To elucidate the conditions of formation of epigenetic graphite inclusions in natural diamond, we carried out experiments on high-temperature treatment of natural and synthetic diamond crystals containing microinclusions. The crystal annealing was performed in the CO–CO₂ atmosphere at 700–1100 °C and ambient pressure for 15 min to 4 h. The starting and annealed diamond crystals were examined by optical microscopy and Raman spectroscopy. It has been established that the microinclusions begin to change at 900 °C. A temperature increase to 1000 °C induces microcracks around the microinclusions and strong stress in the diamond matrix. The microinclusions turn black and opaque as a result of the formation of amorphous carbon at the diamond–inclusion interface. At 1100 °C, ordered graphite in the form of hexagonal and rounded plates is produced in the microcracks. A hypothesis is put forward that graphitization in natural diamond proceeds by the catalytic mechanism, whereas in synthetic diamond it is the result of pyrolysis of microinclusion hydrocarbons. The obtained data on the genesis of graphite microinclusions in diamond are used to evaluate the temperature of kimberlitic melt at the final stage of formation of diamond deposits.     

以碳酸盐为碳源生成金刚石的实验研究

本世纪五十年代初,在金属触媒物质的参与下,由石墨得到金刚石的成功,标志着人工合成超硬材料及高温高压技术两方面的巨大突破。三十年来的科学研究和生产实践推动着这一领域不断地向纵深发展,并提出了建立在不同理论基础上的金刚石生成方法,如爆破法、晶种法、气相生长法、常压高温法、薄膜推移法等等。