Sulfide melts–graphite interaction at HPHT conditions: Implications for diamond genesis
Sulfide melts–graphite interaction at HPHT conditions: Implications for diamond genesis
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DOI：
10.1016/j.epsl.2006.06.049
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发表时间：
2006-10
影响因子：
5.3
通讯作者：
Yuri N. Palyanov;Y. Borzdov;A. Khokhryakov;I. Kupriyanov;N. Sobolev
中科院分区：
文献类型：
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作者：
Yuri N. Palyanov;Y. Borzdov;A. Khokhryakov;I. Kupriyanov;N. Sobolev
在持续 2 至 65 小时的实验中，在 P=6.3–7.5 GPa 和 T=1450–2200 °C 下研究了石墨与 (Fe,Ni)9S8 和 FeS 硫化物熔体的相互作用。已经发现镍黄铁矿和磁黄铁矿熔体与石墨相互作用表现出相似的行为。在 <7.5 GPa 和 1450–1800 °C 以及在 7.5 GPa 和 <1600 °C 下，碳主要结晶为亚稳态石墨，少量在籽晶上结晶为金刚石。只有在 7.5 GPa 的压力和 1600 °C 或更高的温度下，硫化物熔体才能在熔体-石墨界面处以及直接在碳饱和的硫化物熔体内提供自发金刚石成核。在这种情况下，产品中没有发现亚稳态石墨。在 (Fe,Ni)9S8–C 系统中合成的金刚石晶体被发现含有浓度为 1000 ppm 数量级的氮杂质，并且由于氢而表现出红外吸收峰。发光测量揭示了与晶体中的镍杂质相关的特定光学中心。结论是，与碳酸盐、碳酸盐-硅酸盐-流体和流体系统相比，硫化物熔体是效率较低的金刚石形成介质。研究结果表明，在大多数天然钻石形成的超高压条件下，钻石成因硫化物模型中所假设的碳过饱和硫化物熔体中的钻石成核似乎不太可能。
The interaction of graphite with (Fe,Ni)9S8and FeS sulfide melts has been studied at P=6.3–7.5 GPa and T=1450–2200 °C in experiments with a duration from 2 to 65 h. It has been found that both pentlandite and pyrrhotite melts interacting with graphite show similar behavior. At <7.5 GPa and 1450–1800 °C and at 7.5 GPa and <1600 °C carbon crystallizes predominantly as metastable graphite and to the minor extent as diamond on the seed crystals. Only at a pressure of 7.5 GPa and a temperature of 1600 °C and higher, sulfide melts provide spontaneous diamond nucleation at the melt–graphite interface and directly within carbon-saturated sulfide melt. In this case no metastable graphite was found in the products. Diamond crystals synthesized in the (Fe,Ni)9S8–C system were found to contain nitrogen impurity with concentrations of an order of 1000 ppm and exhibited IR absorption peaks due to hydrogen. The luminescence measurements revealed specific optical centers related to nickel impurity in the crystals. It is concluded that sulfide melts are less efficient diamond forming media as compared to carbonate, carbonate–silicate–fluid and fluid systems. The results of the study suggest that diamond nucleation from carbon-supersaturated sulfide melt as supposed in the sulfide model of diamond genesis seems improbable at the UHP conditions of the formation of most natural diamonds.