Grønlands Geologiske Undersøgelse
Grønlands Geologiske Undersøgelse
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格伦兰地质学Undersøgelse
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发表时间：
2011
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通讯作者：
Feiko Kalsbeek
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作者：
Geologiske Undersøgelse;Feiko Kalsbeek
用光学显微镜、电子探针和X射线衍射技术研究了西格陵兰岛费斯肯塞特杂岩中63种岩石的硫化物结构和化学成分。硫化物在整个层序中均有分布，尤其集中在超镁铁质带和较高带的超镁铁质透镜中。硫化物的物相仅限于铜-铁-镍-钴-S系--五闪锌矿、磁黄铁矿、黄铜矿、黄铁矿、千里铜矿、黑钨矿、钴镍黄铁矿、聚辉铜矿、钙钛矿、紫晶石、方铜矿和闪长矿。大多数硫化物在间隙中呈圆形球状，通常含有大量的氧化物。有些集合体在硅酸盐或铬铁矿中以缺口的形式出现，作为其他相之间的锯齿状细线，或具有扇形的积云间结构。固相下反应很常见，出现了镍黄铁矿-黄铁矿、黄铜矿-黄铁矿、黄铜矿-方铅矿、镍黄铁矿-方铅矿和镍黄铁矿-蓝晶石-多辉铜矿的细小共生。斜长岩和铬铁矿中发现了四面体黄铁矿。在某些岩石中，黄铁矿-千里石似乎是一种平衡对。风化作用影响成岩序列中的主要相态：磁黄铁矿>、黄铜矿>、五辉安山岩。几种相的温度稳定性极限、平衡相组合和硫化物共生长物的织构，都表明硫化物已重新平衡到低温。常见的黄铁矿-镍黄铁矿组合的平衡温度上限为230℃，而闪长岩成分的平衡温度下限为125℃。在上部，更长英质带中的集合。表现出这些特征的硫化物分馏作用在层状火成岩侵入体中也很常见。Fiskenæsset硫化物与其他侵入岩中的Thase相似，并提醒人们不太可能通过同化或交代作用派生硫化物，这意味着硫化物来自原始岩浆。
The textures and chemistry of sulphides were investigated in 63 rocks from the Fiskenæsset complex, West Greenland, by light microscopy, electron microprobe, and X-ray diffraction techniques. Sulphides are found disserninated throughout the layered sequence, being especiaIly concentrated in the ul tramafic zone and in ultramafic lenses in the higher zones. Sulphide phases are restricted to the Cu-Fe-Ni-Co-S system - pentIandite, pyrrhotite, chalcopyrite, pyrite, millerite, heazlewoodite, cobalt-pentlandite, polydymite, godlevskite, violarite, cubanite, and digenite. Most sulphides occur interstitially as rounded globules often containing significant quantities of oxides. Some aggregates occur as inciusions in silicate or chromite, as ragged stringers between other phases, or with scalloped intercumulus textures. Subsolidus reactions are common; fine-scale inter growths of pentlandite-pyrite, chalcopyrite-pyrite, chalcopyrite-cubanite, pentlandite-heazlewoodite and pentlandite-godlevskite-polydymite occur. Euhedral pyrite is found in the anorthosites and chromitites. Pyrite-millerite appears to be an equilibrium pair in some rocks. Weathering affects the major phases in the folIowing order: pyrrhotite > chalcopyrite > pentIandite. Temperature stability limits for several of the phases, equilibrium phase assemblages, and textures of the sulphide intergrowths, all indicate that the sulphides have re-equilibrated to low temperatures. The common pyrite-pentlandite assemblage places a 230°C upper limit, and the digenite composition places a 125°C lower limit, on the temperature of equilibration. assemblages in the upper, more felsic zones. Sulphide fractionation exhibiting some af these features is also faund in ather layered igneaus intrusions. The similarity of the Fiskenæsset sulphides with thase in other intrusians, caupled with the unlikely passibility of derivation of the sulphides by assimilation or metasomatism, implies that the sulphides were derived from the original magma.