The parental magma composition, crustal contamination process, and metallogenesis of the Shitoukengde Ni‐Cu sulfide deposit in the Eastern Kunlun Orogenic Belt, NW China
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Abstract Shitoukengde is an important magmatic Ni–Cu sulfide deposit in the Eastern Kunlun Orogenic Belt (EKOB). It comprises several mafic–ultramafic complexes and contains different kinds of mafic–ultramafic rocks. Lherzolite and olivine websterite are the most significant Ni–Cu‐hosted rocks. The No. I complex hosts six Ni–Cu ore bodies, and the depth of the intrusion has great exploration potential. Therefore, geochronology, geochemistry, and mineral chemistry of the Shitoukengde deposit were studied to constrain its mineralization time, parental magma composition, and crustal contamination process. Zircon U–Pb dating of olivine websterite shows the magmatic origin (Th/U = 0.40–1.05) and an age of 418.1 ± 8.7 Ma (MSWD = 0.01), which is coeval with the Xiarihamu, Akechukesai, and other Cu–Ni deposits in the EKOB. Geochemically, the mafic–ultramafic rocks are characterized by low SiO 2 , TiO 2 , and Na 2 O + K 2 O and high MgO (9.49–36.02%), with Mg # values of 80–87. They are relatively enriched in LREE and LILEs (e.g., K, Rb, and Th), with weakly positive Eu anomalies (δEu = 0.83–2.26), but depleted in HFSEs (e. g., Ta, Nb, Zr, and Ti). Based on the electron microprobe analyses, all of the olivines are chrysolite (Fo = 81–86), and the pyroxenes are dominated by clinoenstatite (En = 80–84) and augite (En = 49–55) in the mafic–ultramafic rocks. Therefore, the composition of parental magma is estimated to be picritic basaltic magma with SiO 2 and MgO concentrations of 54.47 and 13.95%, respectively. The zircon ε Hf ( t ) values of olivine websterite vary from −0.8 to 4.6, with a T DM1 of 0.84–1.06 Ga, indicating that the parental magma was derived from relatively high degree partial melting (about 13.4%) of a depleted mantle source and experienced significant crustal contamination (about 12–16%). We propose that crustal assimilation, rather than fractional crystallization, played a key role in triggering the sulfide saturation of the Shitoukengde deposit, and the metallogenesis of “deep liquation–pulsing injection” is the key mechanism underlying its formation. The parental magma, before intruding, underwent liquation and partial crystallization at depth, partitioning into barren, ore‐bearing, and ore‐rich magma and ore pulp, and was then injected multiple times, resulting in the formation of the Shitoukengde Ni–Cu deposit.Keywords:
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Mafic-ultramafic 建筑群在在中央 JinlinProvince 的 Hongqiling 是普遍的， NE 中国。Hongqiling 建筑群包括辉岩，橄榄石 websterite， lherzolite，斑粝岩和 leucogabbro。基于最近的 geochronological 结果，这些侵入产出大约 216 妈的锆石 U-Pb 年龄，暗示那他们在晚三叠纪的时期的 emplaced 并且 mafic-ultramafic 建筑群是在起源的 post-orogenic。这些年龄与在区域的 A 类型花岗石的炮兵阵地是同时代的，但是比 syn-orogenic graniticmagmatism 稍微年轻。父母岩浆的作文与高 MgO 在结晶的积累的橄榄石的使平衡期间是玄武岩的，并且它来自弄空或少年石版印刷球的披风，根据痕量元素和 Sr-Nd 同位素的结果。外壳的材料的数量污染了 magmatic 来源，暗示 mafic-ultramafic 岩石从导出外壳、导出披风的岩浆的混合产品发源。因此， magmatic 来源被外壳的材料的数量污染，并且随后的水晶分别导致了 Cu-Nimineralization。动态分析显示在北方中国古地台 andJiamusi 山岳的碰撞以后，石版印刷球的分层在期间造山运动以后导致了起来岩流圈并且团并且在导出披风的岩浆的 plating 下面侵入的 welling ，它由于导出披风的岩浆并且下地壳的部分融化导致了主要 mafic-ultramafic 岩浆的形成。这结果建议 mafic-ultramafic 建筑群属于在 post-orogenic 期间演变，并且他们作为在 post-orogenic 扩展环境存在的 mafic-ultramafic 塘群被暴露那处理的一间典型地重要的 magmatic 套房。Italso 暗示 orogenic 过程在这个地区性的地质的背景最终完成了。在 Xing 的 mafic-ultramafic 建筑群的 Thewidespread 出现“一 -- 在 NEChina 并且在在北 Xinjiang 的 Altay-Tianshan-Junggar Orogenic 的蒙古 Orogenic 显示 maficintrusions 是在 post-orogenic 过程期间演变的一间重要 magmatic 套房。这 mafic 岩浆的部分能在 plated 下面有下地壳，并且当热为 associatedlate 阶段采购花岗石的岩浆�
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Abstract Over most of the area, the McLean Basalt, southwest of Cooktown, and the Piebald Basalt, north of Cooktown, were erupted on to a land surface generally similar to that of the present day. The basalts form horizontal flows, and a number of vents have been identified. In the main, the lavas consist of olivine basalt; these are shown by chemical analysis to be alkaline, transitional to olivine tholeiite. In the McLean Basalt, several flows consisting of olivine analcimite have been discovered. An olivine nephelinite flow is associated with the Piebald Basalt. Chemical analyses of olivine analcimites and the olivine nephelinite are presented and discussed.
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The δD values of hornblendes from some granites and ultramafic-mafic rocks suggest that the water in granitic magma and the water equilibrated with hornblendes in ultramafic-mafic rocks associated with peridotites seem to be the same with respect to δD values which range from -29 to -37‰. Water contents of hornblendes in ultramafic-mafic rocks are clearly higher than those in granitic rocks. The δD values and water contents of hornblendes from nodules in some alkali basalts and possibly metamorphosed ultramafic-mafic rocks are quite different from those of the rocks mentioned above.
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