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1.
纳米比亚金刚石资源丰富且品质优良,矿床类型以次生砂矿为主。文章对前人的大量研究成果进行分析总结,概述了纳米比亚金刚石矿床的区域地质背景,分析了金刚石矿床的地质特征及矿床成因。对纳米比亚金刚石包裹体氩-氩法定年分析发现,80%的包裹体熔蚀年龄<300Ma,表明大部分纳米比亚碎屑金刚石源自Dwyka期(<300Ma)以后的金伯利岩;纳米比亚金刚石以橄榄岩型(占比46%)和榴辉岩型(占比41%)为主,其余为二辉岩型或介于橄榄岩型-二辉岩型之间;纳米比亚橄榄岩型金刚石包裹体中石榴石-橄榄石平衡矿物的温度为961~1223℃,平均(1107±98)℃;石榴石-斜方辉石的平衡压力多为4.5~6.0GPa。纳米比亚金刚石的找矿有利地区主要为奥兰治河沿线及Oranjemund、卢得立次海岸地区,以次生金刚石砂矿为主。 相似文献
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对山东郯城砂矿中的金刚石开展了傅里叶红外光谱和显微激光拉曼光谱的测试,结果显示,红外光谱均可见C—C的本征峰;绝大多数可见氮的吸收峰:双氮的吸收峰、聚合氮的吸收峰和氮片晶的吸收峰;部分可见氢的吸收峰:C—H的吸收峰、C—N的吸收峰和H2O的吸收峰.郯城金刚石以Ⅰa型金刚石为主,有ⅠaA、ⅠaB、ⅠaAB型,而Ⅱa型仅1粒;氮类型包括双氮(A心)、聚合氮(B心)及氮片晶(B'心),说明金刚石中的孤氮(C心)已经转化为双原子氮,但部分双原子氮未完成进一步的聚形.金刚石拉曼峰值集中在1131 cm–1,拉曼位移漂移程度较小,说明金刚石内部应力发生小幅的变化.在郯城金刚石中首次发现柯石英包裹体,出现139 cm–1、152 cm–1、212 cm–1、272 cm–1、328 cm–1、356 cm–1、428 cm–1和529 cm–1左右的拉曼峰值.在1粒金刚石中柯石英包裹体数量多达十余个,直径几μm至几十μm,呈针状、哑铃状、浑圆状和短柱状等多种形态.郯城金刚石中柯石英包裹体的出现,可作为郯城地区存在榴辉岩型金刚石的可靠标志,也佐证了该地部分金刚石的来源可能和洋壳循环或者俯冲过程有关.镁橄榄石包裹体上覆分散的黑色石墨斑点,与山东蒙阴、辽宁和湖南金刚石中的镁橄榄石等不同种类包裹体具有相似特征,推测这些石墨斑点是晶体包裹体形成后,由于外部环境温压条件的变化产生. 相似文献
3.
苏北古沂沭河流域,通过近二十多年的工作,已发现100多颗金刚石。这些金刚石的特征及其地质意义引起了地质学家的关注。一、苏北金刚石特征到目前为止,苏北古沂沭河流域已发现了100多颗金刚石。最大者52.714克拉,最小者仅几毫克。笔者通过对其中的83颗金刚石镜下详细观察与统计,发现有如下特征:1.金刚石的结晶习性苏北发现的金刚石中见有八面体,菱形十二面体,八面体与菱形十二面体聚形晶体及上述晶体的双晶,连生体。八面体金刚石:本区规则八面体金刚石少见,一般都以不同程度的歪晶出现,或呈沿三次对称轴压平之八面体尖晶石律双晶(图4),或构成平行连生体和不规则连生体。 相似文献
4.
湖南砂矿金刚石包裹体原位测试:对金刚石成因来源的启示 总被引：2，自引：0，他引：2
包裹体是探究矿物结晶生长过程及其地球化学环境的重要探针,是反演寄主矿物形成机制及形成环境的有效工具。本文采用显微激光拉曼光谱、电子探针和LA-ICP-MS技术对来自湖南沅水流域的24颗宝石级金刚石的包裹体进行了原位分析。结果显示,湖南砂矿金刚石中橄榄岩型和榴辉岩型包裹体比例接近,橄榄岩型和榴辉岩型包裹体可在同一颗金刚石中"共存";湖南金刚石形成时地幔的温度和压力分别为1109~1237℃和4.05~5.83 GPa,相应的形成深度大致为133~192 km;包裹体成分及组合特征显示,扬子克拉通金刚石的形成环境与华北克拉通金刚石有显著差异,前者的形成与榴辉岩的关系更为密切,暗示有古老的地壳物质参与了金刚石的形成过程。 相似文献
5.
俄罗斯地台北缘和东北缘的曲面金刚石(英文) 总被引：8，自引：0，他引：8
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? 相似文献
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7.
胶东玲珑金矿田的东山矿区-620~-670m标高和西山矿区-50m标高均发现与金矿脉时空关系密切的煌斑岩脉中存在具有深源特征的地幔橄榄岩解体矿物——橄榄石捕掳晶,且广泛发育蛇纹石和滑石蚀变,其中东山矿区以蛇纹石化为主,兼有少量滑石化,西山矿区以滑石化为主。蚀变热力学计算表明,东山橄榄石蚀变温度为282℃以上,西山橄榄石蚀变温度为243℃以下。流体包裹体的数据显示:东山和西山橄榄石蚀变的温度分别为282~300℃和200~243℃。上述研究为该区提供了新的找矿信息。 相似文献
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9.
宝石级合成金刚石中的包裹体研究 总被引：2，自引：1，他引：1
金刚石的包裹体作为研究金刚石生成时的温度、压力、成矿流体的化学组分等性质的重要窗口,长久以来倍受人们的关注,在天然金刚石包裹体的研究上,前人已作了大量的工作［１］,而合成金刚石的包裹体的研究的却少有报道。最近,我们对俄罗斯合成金刚石的包裹体进行了研究,取得一定的进展。今年投入市场的俄罗斯合成无色宝石级金刚石一般为０－２０～０－７０ｃｔ。晶体常生成八面体｛１１１｝、立方体｛１００｝或立方体｛１００｝和八面体｛１１１｝的聚形和菱形十二面体｛１１０｝与八面体｛１１１｝的聚形。在双筒显微镜和扫描电镜下可… 相似文献
10.
金刚石产地来源的确定是国际性难题,其中由于砂矿金刚石可能存在搬运过程的混合,其产地来源的确定更加具有争议性。巴西金刚石绝大部分来源于砂矿,从成矿地质背景、形貌和颜色、内部结构、矿物包裹体、微量元素、C同位素组成分布等六个要素总结分析了巴西金刚石研究的相关成果,为国际砂矿来源金刚石产地辨识提供参考。研究结果显示,巴西大部分矿区金刚石的特征与世界范围其它矿区的相似,以橄榄岩型为主,难以相互区分。但其中Juina地区和Machado河产地的金刚石具有独特的氮含量（无氮的Ⅱ型为主）和聚集状态,内部结构、矿物包裹体组合及温压环境特征均显示出深部地幔来源的特点,和巴西其它产地具有一定的区分度。与世界范围不同产地砂矿来源金刚石的基本特征对比显示,不同国家具体地区砂矿金刚石在上述不同要素的组合上存在一定的差异性,但总体上要借助现有资料进行产地来源的准确判断还非常困难,需要进行更深入细致的工作。 相似文献
11.
山东蒙阴金刚石的形成时代及地质环境 总被引：4，自引：0，他引：4
对山东蒙阴胜利1号岩管的金刚石样品进行了CL、FTIR、RAMAN等测试。结果表明,除部分样品阴极发光显示平直的生长色带外,多数金刚石显示均一的CL颜色,说明金刚石生长过程连续,未遭受明显的溶(熔)蚀,不同于复县的多数金刚石。依据金刚石中N的聚集状态,估算了蒙阴金刚石主要形成于三个时期:1·8~1·7 ,1·3 ~1·1和0·9 ~0·6 Ga。有意义的是,这三个时期与华北克拉通三次伸展事件时间相吻合。通过金刚石中橄榄石包裹体拉曼漂移,计算出源区压力为4·6 ,5和5·5 GPa ,得出蒙阴金刚石形成的深度分别为:152 ,165和181 km,靠近岩石圈底部。上述成果为蒙阴金刚石的形成提供了时间、空间、压力等重要地质信息。 相似文献
12.
N. V. Sobolev F. V. Kaminsky W. L. Griffin E. S. Yefimova T. T. Win C. G. Ryan A. I. Botkunov 《Lithos》1997,39(3-4):135-157
The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO2 content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m2 conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle. 相似文献
13.
The results of the study of diamonds with inclusions of high-pressure modification of SiO2 (coesite) by Raman spectroscopy are reported. It is established that the octahedral crystal from the Zapolyarnaya pipe is characterized by the highest residual pressure (2.7 ± 0.07 GPa). An intermediate value of this parameter (2.1 ± 0.07 GPa) was obtained for a crystal of transitional habit from the Maiskaya pipe. The minimal Raman shift was registered for coesite in diamond from the Komsomol’skaya–Magnitnaya pipe and provided a calculated residual pressure of 1.8 ± 0.03 GPa. The residual pressures for crystals from the placer deposits of the Kuoika and Bol’shaya Kuonamka rivers are 2.7 ± 0.07 and 3.1 ± 0.1 GPa, respectively. Octahedral crystals were formed in the mantle at a higher pressure than rhombododecahedral diamonds. 相似文献
14.
S. S. Ugap’eva A. D. Pavlushin S. V. Goryainov V. P. Afanasiev N. P. Pokhilenko 《Doklady Earth Sciences》2016,468(1):473-477
The results of morphological examination and the character of the structural orientation and estimation of residual pressure calculated from spectra of combination dispersion in olivine inclusions within diamonds of the Ebelyakh placer and kimberlite pipes of the Yakutian Diamondiferous Province are presented. The data analysis aimed at revealing indications of similarity and/or differences between diamonds from the pipes and the placer. Differences in the structural orientation and spectra of combination dispersion of the inclusions of olivine in dodecahedroids of placers of the northeastern part of the Siberian Platform support the assumption of their non-kimberlite nature. 相似文献
15.
《International Geology Review》2012,54(13):1658-1667
The identification of syngenetic inclusions in diamond (i.e. inclusions of minerals that crystallized at the same time and by the same genesis as their host) has long been of paramount importance in diamond studies. However, the widespread assumption that many or most inclusions in diamonds are syngenetic is based on qualitative morphological criteria and few direct measurements. In order to provide statistically significant information on inclusion–host genetic relations for at least one kimberlite, we have determined the crystallographic orientations of 43 olivine inclusions with diamond-imposed morphology, a feature generally interpreted to indicate syngenesis, in 20 diamonds from the Udachnaya kimberlite (Siberia). Our unprecedented large data set indicates no overall preferred orientation of these olivines in diamond. However, multiple inclusions within a single diamond frequently exhibit similar orientations, implying that they were derived from original single monocrystals. Therefore, regardless of the possible chemical re-equilibration during diamond-forming processes, at least some of the olivines may have existed prior to the diamond (i.e. they are protogenetic). Our results imply that a diamond-imposed morphology alone cannot be considered as unequivocal proof of syngenicity of mineral inclusions in diamonds. 相似文献
16.
F. Kaminsky O. Zakharchenko R. Davies W. Griffin G. Khachatryan-Blinova A. Shiryaev 《Contributions to Mineralogy and Petrology》2001,140(6):734-753
Alluvial diamonds from the Juina area in Mato Grosso, Brazil, have been characterized in terms of their morphology, syngenetic mineral inclusions, carbon isotopes and nitrogen contents. Morphologically, they are similar to other Brazilian diamonds, showing a strong predominance of rounded dodecahedral crystals. However, other characteristics of the Juina diamonds make them unique. The inclusion parageneses of Juina diamonds are dominated by ultra-high-pressure ("superdeep") phases that differ both from "traditional" syngenetic minerals associated with diamonds and, in detail, from most other superdeep assemblages. Ferropericlase is the dominant inclusion in the Juina diamonds. It coexists with ilmenite, Cr-Ti spinel, a phase with the major-element composition of olivine, and SiO2. CaSi-perovskite inclusions coexist with titanite (sphene), "olivine" and native Ni. MgSi-perovskite coexists with TAPP (tetragonal almandine-pyrope phase). Majoritic garnet occurs in one diamond, associated with CaTi-perovskite, Mn-ilmenite and an unidentified Si-Mg phase. Neither Cr-pyrope nor Mg-chromite was found as inclusions. The spinel inclusions are low in Cr and Mg, and high in Ti (Cr2O3<36.5 wt%, and TiO2>10 wt%). Most ilmenite inclusions have low MgO contents, and some have very high (up to 11.5 wt%) MnO contents. The rare "olivine" inclusions coexisting with ferropericlase have low Mg# (87-89), and higher Ca, Cr and Zn contents than typical diamond-inclusion olivines. They are interpreted as inverted from spinel-structured (Mg, Fe)2Si2O4. This suite of inclusions is consistent with derivation of most of the diamonds from depths near 670 km, and adds ilmenite and relatively low-Cr, high-Ti spinel to the known phases of the superdeep paragenesis. Diamonds from the Juina area are characterized by a narrow range of carbon isotopic composition ('13C=-7.8 to -2.5), except for the one majorite-bearing diamond ('13C=-11.4). There are high proportions of nitrogen-free and low-nitrogen diamonds, and the aggregated B center is predominant in nitrogen-containing diamonds. These observations have practical consequences for diamond exploration: Low-Mg olivine, low-Mg and high-Mn ilmenite, and low-Cr spinel should be included in the list of diamond indicator minerals, and the role of high-Cr, low-Ti spinel as the only spinel associated with diamond, and hence as a criterion of diamond grade in kimberlites, should be reconsidered. 相似文献
17.
湖南沅江是我国砂矿金刚石的重要产地,石榴子石和金刚石是砂矿中常见的重矿物,与金刚石相关的石榴子石特征研究,对揭示湖南砂矿金刚石的来源与形成条件有重要意义。本文随机选取湖南沅江辰溪地区金刚石砂矿中160粒碎屑石榴子石和5粒金刚石包裹体中的石榴子石,采用矿物学、地球化学并借鉴统计学方法对它们进行了分析比较。结果显示,碎屑石榴子石主要为铁铝-锰铝榴石系列,其中个别石榴子石含有金刚石包裹体。聚类分析、线性判别、逻辑回归分析计算显示,部分G3榴辉岩型石榴子石与金刚石可能具有成生联系。同时,两个采集地点的石榴子石类型、主微量元素具有一定的差异,其中一个地点的石榴子石样品DJZ-7-1具有与金刚石更强的亲缘性。基于本文碎屑石榴子石Si值大于3.02以及前人对湖南金刚石限定的温压条件进行分析,认为湖南金刚石可能形成于深度小于220 km的橄榄岩-榴辉岩混杂区,该区域系钾镁煌斑岩型金刚石来源的优势区域。据此,建议可在辰溪赤岩村河段上游区域进一步寻找幔源G3型石榴子石以及钾镁煌斑岩,以期发现原生金刚石矿床。 相似文献
18.
从金刚石成因研究,流体包裹体、表征流体存在的固态包裹体及晶格原子、流体成分组合的制约因素等方面,论述了深部地幔流体的存在。华北地台原生金刚石中与流体包裹体共存的钛铁矿+铬铁矿、金红石+金云母+橄榄石、锆石+碳酸盐+橄榄石、磷灰石+金云母+橄榄石组合。相平衡原理揭示地幔流体存在着复杂的自催化反应。华北地台由金刚石流体包裹体所反映的深部地幔组成C、H、O、S和N分别为16.87%、47.47%、30.90%、3.02%和5.38%(皆为原子百分比),与现代大气圈、水圈相比明显富H贫O。 相似文献
19.
Ben Harte John J. Gurney Jeffrey W. Harris 《Contributions to Mineralogy and Petrology》1980,72(2):181-190
Olivine, orthopyroxene and garnet grains belonging to the peridotitic suite of mineral inclusions in natural diamonds typically show compositions poorer in Ca and Al and richer in Mg and Cr than the same minerals in peridotite nodules in kimberlite. Other features suggest the crystallisation of diamonds from magmas of kimberlitic affinities, and it is suggested that the genesis of peridotitic suite diamonds is linked with that of a CO2-bearing magma. It is shown that the generation of kimberlitic magma from common garnet-peridotite (with 5 wt.% clinopyroxene) in the presence of CO2 may rapidly remove by melting all Ca-rich solid phases (clinopyroxene and/or carbonate). Further melting may form liquids in equilibrium with olivine, orthopyroxene, and garnet with the distinctive compositions of the diamond inclusions. The amount of melting and CO2 necessary for the loss of clinopyroxene (and/or carbonate) are estimated at approximately 5.0 wt.% and 0.5 wt.% respectively. 相似文献
20.
Mineral inclusions in fibrous diamonds: constraints on cratonic mantle refertilization and diamond formation 总被引：1，自引：0，他引：1
We analyzed mineral microinclusions in fibrous diamonds from the Wawa metaconglomerate (Superior craton) and Diavik kimberlites (Slave craton) and compared them with published compositions of large mineral inclusions in non-fibrous diamonds from these localities. The comparison, together with similar datasets available for Ekati and Koffiefontein kimberlites, suggest a general pattern of metasomatic alteration imposed on the ambient mantle by formation of fibrous diamond. Calcium and Fe enrichment of peridotitic garnet and pyroxenes and Fe enrichment of olivine associated with fibrous diamond-forming fluids contributes to refertilization of the cratonic mantle. Saline—carbonatitic—silicic fluid trapped by fibrous diamonds may represent one of the elusive agents of mantle refertilization. Calcium enrichment of peridotitic garnet and pyroxenes is expected in local mantle segments during fibrous diamond production, as Ca in the carbonatitic fluids is deposited into the surrounding mantle when oxidized carbon is reduced to diamond. Harzburgitic garnet evolves towards Ca-rich compositions even when it interacts with Ca-poor saline fluids. An unusual trend of Mg enrichment to Fo95–98 is observed in some olivine inclusions in Wawa fibrous diamonds. The trend may result from the carbonatitic composition of the fluid that promotes crystallization of magnesian olivine and preferentially oxidizes the fayalite component. We propose a generic model of fibrous and non-fibrous diamond formation from carbonatitic fluids that explains enrichment of the mantle in mafic magmaphile and incompatible elements and accounts for locally metasomatized compositions of diamond inclusions. 相似文献