Partial melting and melt segregation in footwall units within the contact aureole of the Sudbury Igneous Complex (North and East Ranges, Sudbury structure), with implications for their relationship to footwall Cu–Ni–PGE mineralization
Partial melting and melt segregation in footwall units within the contact aureole of the Sudbury Igneous Complex (North and East Ranges, Sudbury structure), with implications for their relationship to footwall Cu–Ni–PGE mineralization
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萨德伯里火成岩杂岩（北部和东部山脉，萨德伯里构造）接触环内下盘单元的部分熔融和熔体偏析，及其与下盘 Cu-Ni-PGE 矿化的关系
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发表时间：
2011
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通讯作者：
A. Mogessie
中科院分区：
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作者：
A. Péntek;F. Molnár;D. H. Watkinson;P. Jones;A. Mogessie
我们进行了详细的字段和钻孔岩芯映射的部分熔融功能和长英质岩石（下盘花岗斑岩，FWGRs）代表隔离和结晶部分熔体接触晕内的萨德伯里火成杂岩（SIC）在1.85 Ga萨德伯里的影响结构。我们的研究结果，来自映射内的北部（风湖，福伊，维斯纳地区）和东部山脉（斯金纳，弗罗斯特地区）的结构，揭示了部分熔融是广泛的长英质和镁铁质下盘单位的距离达500米的SIC的基底接触。在结构和矿物学上，由局部熔融形成的岩石之间存在着显著的差异。然而，一般来说，熔体主要由不同的石英-长石共生体（如花岗斑岩，图形）和直径达5厘米的晶洞。维斯纳和弗罗斯特FWGR的主量和微量元素组成表明，它们的结晶熔体主要来自于长英质Levack片麻岩和Cartier花岗岩类岩石的部分熔融，以及仅在弗罗斯特辉长岩。这些结果雅阁我们对长英质和镁铁质岩石中原位部分熔融特征和微观尺度结晶熔体的观察。我们的结论是，部分熔融发生在1.5 ± 0.5千巴的压力和温度高达750°C的维斯纳地区和高达900°C的弗罗斯特和风湖地区。在所有地方都存在部分熔融成脉和岩脉的分离现象，并由Penokean造山带中萨德伯里构造的变形促进，如主导走向所示。而静脉和岩脉反映熔体迁移过程中的脆性条件，剪切熔体豆荚在萨德伯里角砾岩基质中表示在其结晶的韧性条件。我们的研究结果表明，部分熔融，熔体分离，热液过程负责再动员的铜镍铂族元素硫化物和SIC下盘内的密切的成因协会。
We performed detailed field and drill core mapping of partial melting features and felsic rocks (footwall granophyres, FWGRs) representing segregated and crystallized partial melts within the contact aureole of the Sudbury Igneous Complex (SIC) in the 1.85 Ga Sudbury impact structure. Our results, derived from mapping within the North (Windy Lake, Foy, Wisner areas) and East Ranges (Skynner, Frost areas) of the structure, reveal that partial melting was widespread in both felsic and mafic footwall units up to distances of 500 m from the basal contact of the SIC. Texturally and mineralogically, significant differences exist between rocks formed by partial melting within and between localities. In general, however, melt bodies are dominated by different quartz-feldspar intergrowths (e.g. granophyric, graphic) and miarolitic cavities up to 5 cm in diameter. Major and trace element compositions of Wisner and Frost FWGRs imply that they crystallized from melts dominantly derived from partial melting of felsic Levack Gneiss and Cartier granitoid rocks, as well as from gabbroic rocks only at Frost. These results accord with our observations on in situ partial melting features and crystallized melt of microscopic scale in both felsic and mafic rocks. We conclude that partial melting occurred at a pressure of 1.5 ± 0.5 kbar and at temperatures up to 750°C in the Wisner area and up to 900°C in the Frost and Windy Lake areas. Segregations of partial melt into veins and dikes are present in all localities, and were promoted by deformation of the Sudbury structure in the Penokean orogeny as indicated by dominant strike directions. Whereas veins and dikes reflect brittle conditions during melt migration, sheared melt pods in the Sudbury breccia matrix indicate ductile conditions during their crystallization. Our results suggest a close genetic association of partial melting, melt segregation, and hydrothermal processes responsible for remobilization of Cu–Ni–PGE sulphides into and within the SIC footwall.