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0 引言
球状石墨是一种罕见的天然石墨.日本北海道广尾郡广尾町音调津有镍铁硫化物矿床,为一基性岩浆岩成因矿床[2-4],其中存在石墨矿体.音调津矿山产出块状、球状和脉状等类型的石墨[2].块状和脉状石墨矿受地质构造,沿断层和剪切带分布.球状石墨与镍铁硫化物矿紧密共生,主要出现在辉长岩体中[2-4].本文采用体视显微镜、光学显微镜、X射线衍射仪、透射电子显微镜等手段,观察分析了日本北海道日高带音调津天然形成的球状石墨. 相似文献
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铜陵地区几个铜矿床中磁黄铁矿的成因和演化 总被引：1，自引：0，他引：1
<正> 在复杂的Fe—S矿物系列中,磁黄铁矿是主要的矿物之一。它广泛分布在不同地质作用下形成的硫化物矿床中。本世纪四十年代前后,国外已开始了磁黄铁矿的矿物学研究;六十年代以来,有关资料大增。不少研究者通过对人工合成的磁黄铁矿进行热力学和相平衡的实验研究,获得了磁黄铁矿矿物学、结晶学等方面的丰富资料,指出磁黄铁矿存在着六方相和单斜相两种结构型式,它们之间除具有共同的基本结构型式外,在不同温度条件下,其成分和超结构等又显示出一系列差异。在对比中发现天然产出的磁黄铁矿同样存在这两个相,其成分范围、形成温度及超结构型式与人工合成磁黄铁矿极相近似。 相似文献
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黄羊山石墨矿床位于新疆东准噶尔造山带南部的卡拉麦里地区东南段,是近年来新发现的国内外首个产于花岗岩体中的超大型石墨矿床。成矿地质条件、矿床地质特征研究表明,该矿床与黄羊山碱性花岗岩体具有密切的时空及成因联系,矿石具独特的球状构造,球体中石墨与长英质矿物及磁黄铁矿、黄铜矿等金属硫化物密切共生。为确定黄羊山石墨矿床的成因和成矿物质来源,本文开展了球状矿石中的石墨拉曼光谱分析和C同位素测试,对与石墨密切共生的金属硫化物开展S-Pb同位素分析。结果表明,黄羊山矿床球状矿石不同部位石墨的拉曼谱峰相似,显示具有很高的结晶程度,估算结晶温度为750～800℃;7件石墨样品的δ~(13)C值在-19.27‰～-19.90‰,分布非常集中,介于岩浆碳值和有机碳值之间,表明具有两者的混合来源。4件磁黄铁矿样品的δ~(34)S值集中在-2.3‰～-2.9‰之间,接近原始地幔值;在Pb同位素构造环境判别图解上,Pb同位素比值(~(206)Pb/~(204) Pb=18.114～19.040,~(207)Pb/~(204) Pb=15.448 ～ 15.543,~(208) Pb/~(204)Pb=38.253～38.915)显示较好的线性关系,延伸方向与地幔演化曲线的延伸方向基本一致;S-Pb同位素测试结果表明,与石墨共生金属硫化物具有幔源特征。综合黄羊山矿床成矿地质条件、成矿特征、石墨及共生硫化物的物质来源等研究结果,本文初步认为,黄羊山石墨矿床形成于碱性花岗岩的岩浆作用阶段,矿石中的金属硫化物来自岩浆混合作用中的幔源基性端元,碳质由于岩浆同化混染作用达到饱和,在硫化物的催化下沉积形成石墨。 相似文献
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以2010年11月“长江口及东海海洋综合考察”的基金委公共航次期间采集的长江口外不同站位的水体悬浮体颗粒为对象,使用扫描电镜和能谱仪相结合的方法对其进行了系统观察和研究,发现了铁氧化物和铁硫化物两种自生矿物集合体.铁氧化物集合体由纤铁矿微晶构成,形态不规则;铁硫化物集合体由大小均一的胶黄铁矿微晶构成,呈莓球状.纤铁矿的形成与周围水体的物理化学条件相关,而胶黄铁矿的形成则与有机质包裹的局部微环境有关.水体中所形成的两类自生铁矿物沉降到海底后,会受到底质物理化学条件的制约.本研究表明陆架泥质沉积体中的一部分莓球状铁硫化物属于水体沉积成因,当利用沉积物中黄铁矿莓球体进行环境分析时,需要充分考虑该部分自生铁硫化物的影响. 相似文献
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金属硫化物半导体矿物在地壳中分布广泛,其中一些禁带宽度较窄的硫化物矿物,如黄铁矿、黄铜矿和斑铜矿等,在地热梯度下产生的天然热电势可将地球内部热能转化为电能。本文选取黄铁矿、磁黄铁矿、方铅矿、黄铜矿、斑铜矿以及斑铜矿-赤铁矿-辉铜矿集合体等天然硫化物矿物样品,研究了其热电特性。研究结果表明,300～700K下,除磁黄铁矿具有低塞贝克系数和超高电导率而表现出金属导体的电输运行为外,黄铁矿和黄铜矿为n型半导体,斑铜矿和斑铜矿-赤铁矿-辉铜矿集合体为p型半导体,具有150～500μV/K的显著塞贝克系数和5～95 S/cm的电导率,说明样品在地热梯度下具有产生显著热电效应的能力。根据激光闪射法测得的热扩散率以及样品的理论比热、密度计算热导率,斑铜矿及硫化物矿物集合体样品表现出小于1 W/(m·K)的低热导率,说明样品在局部热源影响下可形成较大温差。根据热电基本理论和地热梯度构建天然热电效应模型,对硫化物半导体矿物集合体产生的天然热电势、额外地表电流密度及热电转换效率进行了模拟计算得出经验公式,发现硫化物半导体矿物在300～650 K条件下能产生100 m V左右的天然热电势,产生的最大热电转化率可达4‰,且可以通过偶极电流源模型计算矿物体产生的额外地表电流密度。研究认为硫化物半导体矿物可能作为天然热电转换介质深刻影响地球内部能量的转化与传递过程。 相似文献
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东升庙多金属硫化物矿床是狼山成矿带最大和最典型的铅锌多金属硫化物矿床,目前该矿床硫的来源及成矿过程仍存在争议。本文对矿区常见硫化物矿石和最重要的赋矿围岩——绢云石墨片岩中的硫化物分别进行硫同位素分析。结果显示东升庙矿床的硫化物普遍富集硫的重同位素,且矿石与围岩中的硫化物的硫同位素分布范围均较为集中。绢云石墨片岩中的黄铁矿的δ~(34)S值在+19.4‰~+23.4‰之间,具有和当时海水硫酸盐相似的硫同位素组成,指示围岩中的不规则黄铁矿是孔隙水(海水)中的硫酸盐被完全还原后形成的。矿石硫化物的δ~(34)S值在+28.3‰~+31.3‰之间,相比围岩中的黄铁矿明显富集硫的重同位素,指示两者具有不同的硫源。矿石中的硫可能源自基底地层中蒸发岩的溶解,由此形成的硫酸盐占主导的热液流体可萃取大量铅、锌等金属,当遇到狼山群地层中富含有机质的沉积岩时发生热化学还原反应,从而造成硫化物的大量卸载,形成金属硫化物矿床。 相似文献
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黄铁矿表面溶解——不容忽视的研究领域 总被引：2，自引：0，他引：2
矿物表面反应存在于结晶、溶解、成岩成矿、蚀变和风化等一系列地质过程中,在环境科学和材料科学也有着重要的应用,因此,表面矿物学已成为国际地学研究的热点。本文概括了近年来黄铁矿等硫化物表面反应的研究进展,指出了黄铁矿的表面溶解研究存在的问题,并重点阐述了黄铁矿表面溶解研究在诸多方面的重要意义,包括黄铁矿表面溶解研究的理论意义、黄铁矿的表面溶解对矿山环境评价的意义、尾矿堆中绝大多数黄铁矿处于酸性还原环境、黄铁矿表面溶解控制着海洋中硫的循环。本文还报道了笔者通过实验所获得的黄铁矿溶解反应动力学的初步研究结果。 相似文献
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本文报道了内蒙古狼山成矿带内两个最大的铅锌多金属硫化物矿床——东升庙矿床和炭窑口矿床中黄铁矿、黄铜矿单矿物的铁同位素研究结果。东升庙矿床绢云石墨片岩中不规则状黄铁矿的铁同位素组成δ~(56)Fe_(-IRMM)值在+0.04‰~+1.11‰之间,呈现铁的重同位素富集,指示了海水中的铁以氧化态沉淀并在成岩期转化成黄铁矿的矿化过程。东升庙和炭窑口矿床富硫化物矿石中黄铁矿和黄铜矿的铁同位素组成δ~(56)Fe_(-IRMM)值的变化范围为-1.33‰~+0.08‰,具有热液成矿特征,指示金属成矿物质来源于热液流体。另外,绢云石墨片岩中脉状黄铁矿的铁同位素组成δ~(56)Fe_(-IRMM)值的变化范围为-0.39‰~-0.04‰,处于矿石黄铁矿和围岩不规则状黄铁矿之间,指示脉状黄铁矿是热液矿化的产物,并在成矿过程中混入了围岩中早先形成的富集铁的重同位素的黄铁矿。绢云石墨片岩中广泛发育的不规则状黄铁矿与赋存在绢云石墨片岩中的富硫化物矿体具有完全不同的铁同位素组成,指示热液活动对不规则状黄铁矿没有明显成矿物质贡献,因此同沉积热液活动成矿的可能性不大。结合赋存在白云石大理岩中硫化物矿体的顶、底部常见硅化的白云石大理岩角砾,本文提出后生矿化是东升庙多金属硫化物矿体的主要成矿方式。另外,东升庙矿床和炭窑口矿床的矿石硫化物具有相似的铁同位素组成特征,指示两者的成矿物质来源具有相似性。 相似文献
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Mineralogical structures of carbon phases within the ureilite North West Africa 4742, a recent find, are investigated at various scales by high-resolution transmission electron microscopy (HRTEM), Raman microspectrometry and X-ray diffraction. Ureilites are the most carbon-rich of all meteorites, containing up to 6 wt.% carbon. Diamond, graphite and so-called “amorphous carbon” are typically described, but their crystallographic relationships and respective thermal histories remain poorly constrained. We especially focus on the origin of “amorphous carbon” and graphite, as well as their relationship with diamond.Two aliquots of carbon-bearing material were extracted: the insoluble organic matter (IOM) and the diamond fraction. We also compare the observed structures with those of laboratory-shocked graphite.Polycrystalline diamond aggregates with mean coherent domains of about 40 nm are reported for the first time in a ureilite and TEM demonstrates that all carbon phases are crystallographically related at the nanometre scale.Shock features show that diamond is produced from graphite through a martensitic transition. This observation demonstrates that graphite was present when the shock occurred and is consequently a precursor of diamond. The structure of what is commonly described as the “amorphous carbon” has been identified. It is not completely amorphous but only disordered and consists of nanometre-sized polyaromatic units surrounding the diamond. Comparison with laboratory-shocked graphite, partially transformed into diamond, indicates that the disordered carbon could be the product of diamond post-shock annealing.As diamond is the carrier of noble gases, whereas graphite is noble gas free, graphite cannot be the sole diamond precursor. This implies a multiple-stage history. A first generation of diamond could have been synthesized from a noble gas rich precursor or environment by either a shock or a condensation process. Thermally-induced graphitization of chondritic-like organic matter could have produced the graphite, which was then transformed by shock processes into polycrystalline nanodiamond aggregates. The formation of the disordered carbon occurred by diamond post-shock back-transformation during post-shock heating. The noble gases in the first generation diamond could then be incorporated directly into the disordered carbon during the transformation. 相似文献
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为了探究煤系石墨形成过程中结构演化及不同石墨化程度无烟煤和石墨的热反应行为，选取湖南新化系列变质程度无烟煤和煤系石墨为研究对象，通过X射线衍射（XRD）和高分辨率透射电子显微镜（HRTEM）对其结构进行表征，并结合程序控制升温法（TPO）分析不同变质程度无烟煤和煤系石墨的热反应行为。结果表明，随变质程度的增加，碳结构由无烟煤中的无定形态转变成石墨的三维有序C原子点阵。系列石墨化煤是由多种有序度不同的碳结构相组成，体现了其结构非均质性，碳结构相含量及分布随变质程度而逐渐变化，石墨化程度最高的煤系石墨中主要为石墨微晶集合体，但依旧含有结构缺陷。无烟煤和煤系石墨中碳结构的多相性和不均匀分布是影响其热反应行为的重要原因。 相似文献
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Carbon isotope fractionations between calcite and graphite in the Panamint Mountains, California, USA, demonstrate the importance of mass balance on carbon isotope values in metamorphosed carbon-bearing minerals while recording the thermal conditions during peak regional metamorphism. Interbedded graphitic marbles and graphitic calcareous schists in the Kingston Peak Formation define distinct populations on a δ13C(gr)–δ13C(cc) diagram. The δ13C values of both graphite and calcite in the marbles are higher than the values of the respective minerals in the schists. δ13C values in both rock types were controlled by the relative proportions of the carbon-bearing minerals: calcite, the dominant carbon reservoir in the marble, largely controlled the δ13C values in this lithology, whereas the δ13C values in the schists were largely controlled by the dominant graphite. This is in contrast to graphite-poor calcsilicate systems where carbon isotope shifts in carbonate minerals are controlled by decarbonation reactions. The marbles record a peak temperature of 531±30 °C of a Jurassic low-pressure regional metamorphic event above the tremolite isograd. In the schists there is a much wider range of recorded temperatures. However, there is a mode of temperatures at c. 435 °C, which approximately corresponds to the temperatures of the principal decarbonation metamorphic reactions in the schists, suggesting that the carbon exchange was set by loss of calcite and armouring of graphite by newly formed silicate minerals. The armouring may explain the relatively large spread of apparent temperatures. Although the modal temperature also corresponds to the approximate temperature of the Cretaceous retrograde event, retrograde exchange is thought less likely due to very slow exchange rates involving well-crystallized graphite, armouring of graphite by silicates during the earlier event, and because of other barriers to retrograde carbon exchange. Thus, only the calcite–graphite carbon isotope fractionations recorded by the marbles demonstrate the high-temperature conditions of the low-pressure Jurassic metamorphic event that was associated with the emplacement of granitic plutons to the west of the Panamint Mountains. 相似文献
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D.J. Barber 《Geochimica et cosmochimica acta》1981,45(6):945-970
TEM, HRTEM, HVEM and SEM methods, coupled with energy dispersive X-ray analysis, have been used to study the microstructure and the phases comprising the matrix of carbonaceous chondrites Murchison, Cold Bokkeveld, Nawapali and Cochabamba. A wide variety of phyllosilicate morphologies occurs in each. Very small crystals and clasts of olivine, pyroxene and other unhydrated minerals are mixed intimately with the phyllosilicates. Intergrowths of carbonates and Sulfides within the phyllosilicates also occur, as well as a ubiquitous spongey material which is difficult to characterize, but contains elementary phyllosilicate units and embryo crystals. The identifiable large crystalline phyllosilicates are principally Fe-rich serpentine-group minerals and intermediate more Mg-rich chrysotilelike group members, with characteristic ~ 7.0–7.4 Å basal layer spacings. Complex interlayered and intergrown hydrous minerals also occur associated with the spongey material, and other poorly crystalline silicates and finely divided Fe-Ni sulphides. Fe/Si and Mg/Si ratios vary on a sub-micron scale, and the morphologies of the larger phyllosilicate crystals correlate broadly with these variations. Small crystals of sodium chloride and potassium chloride have been identified, occluded within a predominantly organic mass.The matrix minerals have a multistage history of formation in which the effects of aqueous alteration are dominant. Few, if any, of matrix minerals can be unmodified nebular condensates, although some clasts and inclusions have escaped alteration and predate the alteration process. 相似文献
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The suitability of a new reagent, Kr6D, as a depressant for galena and sphalerite in a differential sulphide flotation stage has been tested. Small-scale laboratory flotation tests on pure sulphide minerals indicated that the reagent is capable of depressing both galena and sphalerite when used in small doses. At higher concentrations, chalcopyrite is also depressed. Single-stage batch-scale flotation tests have been carried out on bulk sulphide concentrates containing the three sulphide minerals. Kr6D has been compared with starch as a depressant both in the presence and in the absence of sulphur dioxide. In each case the new modifier has been shown to be more effective. When using sodium dichromate as a differential depressant in similar tests, it has been shown that the quantity necessary to achieve selectivity between chalcopyrite and galena may be considerably reduced if small quantities of Kr6D are added. 相似文献
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超无烟煤（也称变质无烟煤）中广泛发育石墨微晶，为深入分析煤中石墨微晶产出特征及成因，以福建省永安煤田典型样品为例，采用光学显微镜、扫描电镜和透射电镜等测试方法，识别并分析煤中石墨微晶的光学性质、物质组成、晶体结构等特征，并探讨其成因。结果显示:石墨微晶主要产出于煤中微裂缝和空腔内，多数具有类似于石油焦的纤维状显微结构，可见气泡膜状结构；石墨微晶最大反射率为9.29%~10.83%，远远高于煤中原有显微组分；正交偏光加石膏试板观测条件下，石墨微晶呈现一级黄、二级蓝干涉色以及镶嵌状、区域状、纤维状等显微结构，局部定向性明显。扫描电镜加电子探针探测显示，石墨微晶多呈鳞片状并见流动状结构和气孔构造，同时显示出纯碳特点。高分辨率透射电镜观测到石墨微晶晶格条纹呈平直定向排列，选区电子衍射呈现典型的石墨晶格环斑模式。初步分析认为，煤中石墨微晶的碳质来源于高度熔融的（变）壳质组和富氢（变）镜质体，热源为侵入煤田周边及盆地底部的燕山期花岗岩，熔融含碳物质在孔缝空间内汇聚流动并在高温下脱除杂质元素，然后在强大岩浆侵位压力下结晶形成秩理性显著的石墨微晶；同时，也不排除渗出沥青质体再次活化形成研究区煤中石墨微晶的可能性。移动阅读 相似文献
17.
泗滨砭石的岩石矿物研究Ⅱ:矿物组成特征与红外发射功能的关系 总被引：2，自引：0，他引：2
为进一步查明泗滨砭石的矿物组成特征与砭石良好的红外发射功能间的关系,用激光喇曼光谱和高分辨透射电镜对砭石样品进行了研究.喇曼光谱研究除证实样品含有微米晶黄铁矿、石墨和锐钛矿外,还发现方解石、黄铁矿和锐钛矿的谱图上均有石墨的两个谱峰.TEM和HRTEM观察发现方解石全由纳米品组成,并普遍有石墨纳米粒子产出.纳米晶石墨多分布于方解石晶界间.4种矿物中纳米晶方解石含量最高,热容也最大,是泗滨砭石具有良好热辐射性质最重要的矿物学背景条件.纳米晶石墨的普遍存在提高了岩石整体导热和储热性能,其优良的热红外发射性能也是造成泗滨砭石在远红外波段具有很高发射率的一个重要原因.黄铁矿具有良好的热电性,而锐钛矿的红外线吸收和反射能力都较强、光电转换效率也高,它们也是泗滨砭石具有良好的热发射性能的一个辅助原因.上述4种矿物良好物理性质的共同作用,使加热后的泗滨砭石具有疏通经络、活血化淤、调理气血等重要的理疗功效,中医砭术在医疗保健上所利用的也正是砭石能辐射对人体有益的远红外线功能. 相似文献
18.
《International Journal of Mineral Processing》2005,76(4):244-259
The effect of carbon or graphite coating on the adsorption of gold cyanide on pyrite was investigated with pure pyrite and a pyrite concentrate. In the carbon or graphite contaminated pyrite systems carbon and graphite not only acted as gold sorbents, but also enhanced gold adsorption on pyrite. The carbon coating enhanced gold adsorption on pyrite to a larger extent, in comparison with the graphite coating. The carbon or graphite coating on pyrite reduced the negativity of the pyrite surfaces, and hence improved the physical adsorption of gold cyanide on pyrite. In addition, the highly conductive coating of carbon or graphite on pyrite could enhance electron transfer in the electrochemical reactions occurring in the chemical adsorption of gold and gold reduction on pyrite. The preg-robbing by pyrite or the graphite-coated pyrite was reduced and further eliminated at higher cyanide concentrations. However, gold adsorption on the carbon-coated pyrite could not be prevented even at higher cyanide concentrations due to gold adsorption on the carbon coating. In comparison with pure pyrite, the pyrite concentrate had a higher capacity adsorbing gold, due to the presence of carbonaceous matter in the pyrite concentrate. Fine grinding intensified the smearing of carbon or graphite on the mineral particles, resulting in a larger extent of enhancement in the preg-robbing of the concentrate by the carbon or graphite coating.A diagnostic elution of the preg-robbing pyrite samples indicated that the reduction of gold at the pyrite surfaces was the dominant mechanism for gold adsorption on pyrite, followed by physical and chemical adsorption. Surface topological studies by SEM/EDX showed that gold adsorbed at defect sites on pyrite surfaces. For the pyrite with a 5% carbon coating, gold was observed to adsorb not only at the defect sites, but also at the smooth surfaces with carbon present. For the pyrite with a 5% graphite coating, carbon was also found at the pyrite surfaces, but gold was only detected at the defect sites. XPS studies revealed that part of the gold physically and chemically adsorbed on pyrite or pyrite coated with carbon or graphite. Some gold cyanide was reduced at the pyrite surfaces, with the sulphide ions of pyrite being oxidised to elemental sulphur. 相似文献
19.
《International Journal of Mineral Processing》2005,77(3):123-138
The effect of carbon or graphite coating on the adsorption of gold cyanide on pyrite was investigated with pure pyrite and a pyrite concentrate. In the carbon or graphite-contaminated pyrite systems carbon and graphite not only acted as gold sorbents, but also enhanced gold adsorption on pyrite. The carbon coating enhanced gold adsorption on pyrite to a larger extent, in comparison with the graphite coating. The carbon or graphite coating on pyrite reduced the negativity of the pyrite surfaces, and hence improved the physical adsorption of gold cyanide on pyrite. In addition, the highly conductive coating of carbon or graphite on pyrite could enhance electron transfer in the electrochemical reactions occurring in the chemical adsorption of gold and gold reduction on pyrite. The preg-robbing by pyrite or the graphite-coated pyrite was reduced and further eliminated at higher cyanide concentrations. However, gold adsorption on the carbon-coated pyrite could not be prevented even at higher cyanide concentrations due to gold adsorption on the carbon coating. In comparison with pure pyrite, the pyrite concentrate had a higher capacity adsorbing gold, due to the presence of carbonaceous matter in the pyrite concentrate. Fine grinding intensified the smearing of carbon or graphite on the mineral particles, resulting in a larger extent of enhancement in the preg-robbing of the concentrate by the carbon or graphite coating.A diagnostic elution of the preg-robbing pyrite samples indicated that the reduction of gold at the pyrite surfaces was the dominant mechanism for gold adsorption on pyrite, followed by physical and chemical adsorption. Surface topological studies by SEM/EDX showed that gold adsorbed at defect sites on pyrite surfaces. For the pyrite with a 5% carbon coating, gold was observed to adsorb not only at the defect sites, but also at the smooth surfaces with carbon present. For the pyrite with a 5% graphite coating, carbon was also found at the pyrite surfaces, but gold was only detected at the defect sites. XPS studies revealed that part of the gold physically and chemically adsorbed on pyrite or pyrite coated with carbon or graphite. Some gold cyanide was reduced at the pyrite surfaces, with the sulphide ions of pyrite being oxidised to elemental sulphur. 相似文献
20.
Dominic Papineau Bradley T. De Gregorio Marc D. Fries Stephen J. Mojzsis Rhonda M. Stroud 《Geochimica et cosmochimica acta》2010,74(20):5862-5883
Because all known Eoarchean (>3.65 Ga) volcano-sedimentary terranes are locked in granitoid gneiss complexes that have experienced high degrees of metamorphism and deformation, the origin and mode of preservation of carbonaceous material in the oldest metasedimentary rocks remain a subject of vigorous debate. To determine the biogenicity of carbon in graphite in such rocks, carbonaceous material must be demonstrably indigenous and its composition should be consistent with thermally altered biogenic carbon as well as inconsistent with abiogenic carbon. Here we report the petrological and spectroscopic characteristics of carbonaceous material, typically associated with individual apatite grains, but also with various other minerals including calcite, in a >3.83 Ga granulite-facies ferruginous quartz-pyroxene unit (Qp rock) from the island of Akilia in southern West Greenland. In thin sections of the fine-grained parts of Akilia Qp rock sample G91-26, mapped apatites were found to be associated with graphite in about 20% of the occurrences. Raman spectra of this carbonaceous material had strong G-band and small D-band absorptions indicative of crystalline graphite. Three apatite-associated graphites were found to contain curled graphite structures, identified by an anomalously intense second-order D-band (or 2D-band) Raman mode. These structures are similar to graphite whiskers or cones documented to form at high temperatures. Raman spectra of apatite-associated graphite were consistent with formation at temperatures calculated to be between 635 and 830 °C, which are consistent with granulite-facies metamorphic conditions. Three graphite targets extracted by focused ion beam (FIB) methods contained thin graphite coatings on apatite grains rather than inclusions sensu stricto as inferred from transmitted light microscopy and Raman spectroscopy. TEM analyses of graphite in these FIB sections showed a (0 0 0 2) interplanar spacing between 3.41 and 3.64 Å for apatite-associated graphite, which is larger than the spacing of pure graphite (3.35 Å) and may be caused by the presence of non-carbon heteroatoms in interlayer sites. Samples analyzed by synchrotron-based scanning transmission X-ray microscopy (STXM) also confirmed the presence of crystalline graphite, but abundances of N and O heteroatoms were below detection limit for this method. Graphite in the Akilia Qp rock was also found to occur in complex polyphase mineral assemblages of hornblende ± calcite ± sulfides ± magnetite that point to high-temperature precipitation from carbon-bearing fluids. These complex mineral assemblages may represent another generation of graphitization that could have occurred during the amphibolite-facies metamorphic event at 2.7 Ga. Several observations point to graphitization from high-temperature fluid-deposition for some of the Akilia graphite and our results do not exclude a biogenic source of carbon in graphite associated with apatite, but ambiguities remain for the origin of this carbon. 相似文献