The ca. 1.85 Ga Sudbury Igneous Complex (SIC) is the igneous remnant of one of the oldest, largest, and best-preserved impact structures on Earth and contains some of the world’s largest magmatic Ni-Cu-PGE sulfide deposits. Most of the mineralization occurs in Sublayer, Footwall Breccia, and inclusion-bearing quartz diorite (IQD), all of which contain significant (Sublayer and IQD) to minor (Footwall Breccia) amounts of olivine-bearing mafic-ultramafic inclusions. These inclusions have only rare equivalents in the country rocks and are closely associated with the Ni-Cu-PGE sulfide mineralization. They can be divided into three groups on the basis of petrography and geochemical characteristics. Group I (n = 47) includes igneous-textured olivine melanorite and olivine melagabbronorite inclusions in the Whistle and Levack embayments on the North Range with Zr/Y, Zr/Nb, Nb/U, and Zr/Hf similar to igneous-textured Sublayer matrix. Group I inclusions are interpreted to be anteliths that crystallized from a mixture of SIC impact melt and a more mafic melt, probably derived by melting of ultramafic footwall rocks. Group II includes Group IIA (n = 17) shock metamorphosed wehrlite and olivine clinopyroxenite inclusions in the Levack embayment and Group IIB (n = 2) shock metamorphosed olivine melanorite inclusions in the Foy Offset on the North Range. Group II inclusions have similar trace element patterns (e.g., negative Th-U, Nb-Ta-(Ti), Sr, and Zr-Hf anomalies) and overlapping Nb/U with a layered mafic-ultramafic intrusion in the footwall of the Levack and Fraser deposits, which together with their limited distribution suggests that Group II inclusions are locally-derived xenoliths. Group III (n = 21) includes phlogopite lherzolite and feldspar lherzolite inclusions with igneous, recrystallized, and shock-metamorphic textures in the Trill, Levack, and Bowell embayments and the Foy Offset dike on the North Range. They have no equivalents in the exposed country rocks. The calculated parental magma is similar to continental arc basalt formed by approximately 5% partial melting of garnet peridotite. Ol-Cpx-Pl thermobarometry of several Group III inclusions indicate equilibration at 900 - 1120 ºC and 210 ± 166 MPa to 300 ± 178 MPa, suggesting crystallization in the upper-middle crust (7.7 ± 6.6 to 10.9 ± 6.5 km), prior to being incorporated into the lower parts of the impact melt sheet during impact excavation. The exotic xenoliths provide information about the depth of impact and composition of middle-upper crust in the Sudbury region at 1850 Ma, the local xenoliths provide information about the thermomechanical erosion process that followed generation of the impact melt, the anteliths provide information about the early crystallization history of the SIC, and all of the inclusions provide constraints on the genesis of Sublayer, IQD, footwall breccia, and associated Ni-Cu-PGE mineralization.

中文翻译：

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加拿大萨德伯里火成岩群下垫层和胶结堤坝中镁铁质和超镁铁质包裹体的地球化学和岩石成因

该ca。1.85 Ga Sudbury火成岩（SIC）是地球上最古老，规模最大和保存最完好的撞击构造之一的火成残余物，其中包含一些世界上最大的岩浆Ni-Cu-PGE硫化物矿床。大多数矿化发生在亚层，下壁角砾岩和含夹杂物的石英闪长岩（IQD）中，所有这些矿物都含有大量（亚层和IQD）到少量（足底角砾岩）含橄榄石的镁铁质-超镁铁质包裹体。这些夹杂物在乡村岩石中只有很少的等价物，并且与Ni-Cu-PGE硫化物矿化密切相关。根据岩石学和地球化学特征，它们可以分为三类。第I组（n = 47）在北范围的Whistle和Levack包埋物中包含火成岩质橄榄石黑素岩和橄榄石美拉贝硼铁矿包裹体，其Zr / Y，Zr / Nb，Nb / U和Zr / Hf与火成岩质亚层相似矩阵。第I组夹杂物被解释为是从SIC冲击熔体和更多镁铁质熔体的混合物中结晶出来的前岩，可能是由于超镁铁质底盘岩的熔化而产生的。第二组包括Levack沉积物中的IIA组（n = 17）冲击变质白云母和橄榄石辉绿岩包裹体，以及北部山脉的福伊偏移中的IIB（n = 2）组冲击变质的橄榄石黑闪石包裹体。II类夹杂物具有相似的痕量元素模式（例如，负Th-U，Nb-Ta-（Ti），Sr，和Zr-Hf异常）和重叠的Nb / U以及Levack和Fraser矿床下盘的层状镁铁-超镁铁质侵入体，加上其有限的分布，表明II类包裹体是局部衍生的异岩。第III组（n = 21）包括金云母水辉石和长石水辉石夹杂物，在北岭的Trill，Levack和Bowell沉积物中具有火成岩，重结晶和冲击变质质地。在裸露的乡村岩石中，它们没有类似物。计算出的母岩浆类似于由大约5％的石榴石橄榄岩部分熔融形成的大陆弧玄武岩。几种III类夹杂物的Ol-Cpx-Pl热压法表明在900-1120ºC和210±166 MPa至300±178 MPa时达到平衡，表明在上中地壳中有结晶（7。7±6.6至10.9±6.5公里），然后在冲击挖掘过程中将其并入冲击熔体板的下部。外来的异种石块提供有关萨德伯里地区1850 Ma的撞击深度和中上地壳成分的信息，当地的异种石块提供有关随冲击熔体生成而发生的热机械侵蚀过程的信息，前石块提供有关早期的信息。 SIC的结晶史，以及所有夹杂物都对亚层，IQD，下盘角砾岩和相关的Ni-Cu-PGE矿化的成因提供了限制。