High pressure phase relations for much of the Cu-Fe-S system have not previously been determined experimentally. Experimental studies have concentrated on low-pressure phase relations and cannot explain high pressure sulfide mineral inclusion assemblages in some natural blueschists and eclogites. In particular, the co-existence of pyrite + covellite at 1.0 GPa, and pyrite + bornite at 1.9 GPa, observed in New Caledonian rocks, is precluded by tie lines between S and bornite, and S and the intermediate solid solution (iss), in the published low-pressure experimental topologies at corresponding temperatures. In addition, the Cu-content (up to ∼10 at%) of pyrrhotite in eclogite exceeds the experimentally determined maximum for Cu in solid solution with pyrrhotite at low pressures and at corresponding temperatures. We have performed six experiments in which natural chalcopyrite starting material was equilibrated at conditions ranging from 1.0 to 1.7 GPa and 500 to 650 °C. At 1 GPa chalcopyrite is replaced by iss. The iss phase undergoes a terminal breakdown reaction between 1.0 and 1.7 GPa, being replaced by a new assemblage of bornite, pyrite, and pyrrhotite. Our experimental results confirm predictions from the SUPCRT thermodynamic database (Johnson et al., 1992; Computers & Geosciences18, 899-947) but not that of Robie and Hemmingway (1995; United States Geological Survey Bulletin2131). The former database is therefore recommended for calculation of high-pressure sulfide phase relations. Chalcopyrite and its high-temperature, low fS₂ equivalent, iss are not stable at pressures corresponding to much of blueschist-eclogite facies metamorphism. These results are also applicable to sulfide assemblages in the lithospheric mantle along both oceanic and continental geotherms; the subsolidus Cu-rich mineral in the lithosphere at depths of 30 to > 65 km must be bornite-digenite solid solution (bn-ss) rather than iss as is commonly assumed.

中文翻译：

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高压Cu-Fe-S相平衡：俯冲带和岩石圈地幔中硫化物的一些实验和热力学约束

先前尚未通过实验确定许多Cu-Fe-S系统的高压相关系。实验研究集中在低压相关系上，无法解释某些天然蓝晶岩和榴辉岩中的高压硫化物矿物包裹体组合。特别是，在新喀里多尼亚岩石中观察到的1.0 GPa的黄铁矿+玄武岩和1.9 GPa的黄铁矿+堇青石的共存被S和褐铁矿，S和中间固溶体（iss）之间的连接线所阻止，在相应的温度下已发表的低压实验拓扑结构中。此外，榴辉岩中黄铁矿的Cu含量（至多约10 at％）超过了在低压和相应温度下与黄铁矿固溶体中Cu的实验确定的最大值。我们进行了六个实验，其中天然黄铜矿原料在1.0至1.7 GPa和500至650°C的条件下达到平衡。在1 GPa时，黄铜矿被iss取代。iss相经历1.0 GPa至1.7 GPa的最终击穿反应，被新的堇青石，黄铁矿和黄铁矿组合所取代。我们的实验结果证实了SUPCRT热力学数据库的预测（Johnson等，1992；计算机与地球科学18，899-947），但不是罗宾和海明威（1995年，美国地质调查局2131）。因此，建议使用前一个数据库来计算高压硫化物的相位关系。黄铜矿及其高温，低fS ₂当量在一定的压力下不稳定，而压力对应于大量的蓝片岩-榴辉岩相变质作用。这些结果也适用于沿海洋和大陆地热的岩石圈地幔中的硫化物组合。岩石圈中深30至> 65 km的富含亚固相的矿物必须是钙长石-地长岩固溶体（bn-ss），而不是通常认为的iss。