The Quetico Intrusions of Western Superior Province: Neo-Archean examples of Alaskan/Ural-type mafic-ultramafic intrusions
The Quetico Intrusions of Western Superior Province: Neo-Archean examples of Alaskan/Ural-type mafic-ultramafic intrusions
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DOI：
10.1016/j.precamres.2006.06.004
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发表时间：
2006-09
影响因子：
3.8
通讯作者：
N. Pettigrew;K. Hattori
中科院分区：
文献类型：
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作者：
N. Pettigrew;K. Hattori
奎蒂科侵入体是一系列超镁铁质-镁铁质火成岩，沿着北方奎蒂科次省边界出现。这些侵入体显示出从含橄榄石的超镁铁质岩的核部到角闪石岩和辉长岩的边缘的岩性分带，并且它们通常伴随有Cu-Ni-铂族元素（PGE）硫化物矿化。我们在Quetico次省的中部和南部确定了另外三个Quetico入侵，使整个Quetico入侵阵列在整个次省的长度超过125公里。萨缪尔斯湖侵入体的U-Pb年龄为2688+6/− 5 Ma，与北方边界上沿着奎蒂科侵入体的U-Pb年龄2690 Ma相似，表明所有奎蒂科侵入体可能是同期的。侵入岩的母岩浆以橄榄石和单斜辉石的高镁为基础，富镁，并以丰富的角闪石、早期单斜辉石结晶和常见的镁铁质伟晶岩为证据，证明其为含水岩浆。大块岩石显示弧地球化学特征，包括高浓度的大离子亲石元素结合低浓度的高场强元素。辉石和角闪石的矿物组成也显示出弧火成岩的特征。这些数据表明，衍生的母岩浆从地幔楔或耐火地幔，以前交代在俯冲设置。奎蒂科侵入体显示出许多与阿拉斯加/乌拉尔型带状镁铁质-超镁铁质侵入体的相似之处，这些侵入体沿着中生代造山带的主要缝合线。其共同特征包括地球动力学背景、内部岩性分带、矿物学和矿物化学，以及与铂族元素矿化的共同联系。两者之间惊人的相似之处表明，晚太古代奎蒂科侵入体可能形成于类似于阿拉斯加/乌拉尔型侵入体的构造环境中。我们建议，母岩浆的Quetico侵入体形成在非常早期阶段的增生的瓦瓦弧的瓦比贡subprovince。瓦瓦弧的斜向吸积可能使俯冲角变陡，从而使热的软流圈地幔上涌。这导致了地幔楔高度的部分熔融，产生了奎蒂科侵入体。
The Quetico Intrusions are a series of ultramafic–mafic igneous rocks that occur along the northern Quetico subprovince boundary. These intrusions show lithological zoning from cores of olivine-bearing ultramafic rocks to margins of hornblendite and gabbroic rocks, and they are commonly accompanied by Cu–Ni–platinum group element (PGE) sulphide mineralization. We identified three additional Quetico Intrusions in the centre and southern part of the Quetico subprovince, bringing the entire Quetico Intrusion array to be over 125km in length across the subprovince. The Samuels Lake intrusion in the centre of the subprovince has an U–Pb age of 2688+6/−5Ma, which is similar to the age of ∼2690Ma for the Quetico Intrusions along the northern subprovince boundary, suggesting that all the Quetico Intrusions are likely to be contemporaneous. The parental magmas of the intrusions were Mg-rich based on the high Mg of olivine and clinopyroxene, and they were hydrous as evidenced by abundant hornblende, early crystallization of clinopyroxene, and the common occurrence of mafic pegmatite. The bulk rocks show arc geochemical signatures, including a high concentration of large ion-lithophile elements combined with a low concentration of high field-strength elements. The mineral compositions of pyroxene and hornblende also plot in the field of arc igneous rocks. The data suggest the derivation of the parental magmas from a mantle wedge or a refractory mantle that was previously metasomatized in a subduction setting. The Quetico Intrusions display many similarities with Alaskan/Ural-type zoned mafic–ultramafic intrusions along major sutures of Phanerozoic orogenic belts. Common features include their geodynamic settings, internal lithological zoning, mineralogy and mineral chemistry, and common association with PGE mineralization. The striking similarities between the two indicate that the late Archean Quetico Intrusions likely formed in a tectonic setting similar to that of the Alaskan/Ural-type intrusions. We propose that the parental magmas for the Quetico Intrusions formed during the very early stage of accretion of the Wawa arc to the Wabigoon subprovince. Oblique accretion of the Wawa arc likely steepened the subduction angle, which allowed upwelling of hot asthenospheric mantle. This resulted in high degrees of partial melting in the mantle wedge to produce the Quetico Intrusions.