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The parental magma composition, crustal contamination process, and metallogenesis of the Shitoukengde Ni-Cu sulfide deposit in the Eastern Kunlun Orogenic Belt, NW China
Resource Geology ( IF 1.4 ) Pub Date : 2021-06-09 , DOI: 10.1111/rge.12267
Liang Li 1, 2 , Dexin Zhang 3 , Shucheng Tan 1 , Fengyue Sun 4 , Chao Wang 4 , Tuofei Zhao 4 , Shijin Li 3 , Yanqian Yang 3
Affiliation  

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 SiO2, TiO2, and Na2O + K2O 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 SiO2 and MgO concentrations of 54.47 and 13.95%, respectively. The zircon εHf(t) values of olivine websterite vary from −0.8 to 4.6, with a TDM1 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.

中文翻译:

东昆仑造山带石头坑德镍铜硫化物矿床母岩浆成分、地壳污染过程及成矿作用

石头坑德是东昆仑造山带(EKOB)重要的岩浆镍铜硫化物矿床。它由几个镁铁质-超镁铁质杂岩组成,并含有不同种类的镁铁质-超镁铁质岩石。Lherzolite 和橄榄石 websterite 是最重要的 Ni-Cu 承载岩石。Ⅰ号杂岩体有6个镍铜矿体,侵入深度大,勘探潜力大。因此,对石头坑德矿床的年代学、地球化学和矿物化学进行了研究,以限制其成矿时间、母岩浆成分和地壳污染过程。橄榄石韦氏橄榄石锆石 U-Pb 定年显示为岩浆成因 (Th/U = 0.40-1.05),年龄为 418.1 ± 8.7 Ma (MSWD = 0.01),与夏日哈木、阿克楚克赛等铜镍矿床共生在 EKOB。地球化学上,2、TiO 2、Na 2 O + K 2 O 和高 MgO (9.49–36.02%),Mg #值为 80–87。它们相对富集 LREE 和 LILE(例如 K、Rb 和 Th),Eu 呈弱正异常(δEu = 0.83-2.26),但缺乏 HFSE(例如 Ta、Nb、Zr 和 Ti)。根据电子探针分析,所有橄榄石都是橄榄石(Fo = 81-86),辉石以斜辉石(En = 80-84)和辉石(En = 49-55)为主,在镁铁质-超镁铁质岩石中. 因此,母岩浆的成分估计为苦味玄武质岩浆,SiO 2和MgO 浓度分别为54.47% 和13.95%。锆石ε Hf ( t) 橄榄石韦氏橄榄石的值从 -0.8 到 4.6 不等,T DM1为 0.84 至 1.06 Ga,表明母岩浆来源于相对高度部分熔融(约 13.4%)的枯竭地幔源,并经历了显着的地壳污染(约 12-16%)。我们认为,地壳同化作用而非分步结晶作用是触发石头坑德矿床硫化物饱和的关键,“深层液化-脉动注入”的成矿作用是其形成的关键机制。母岩浆侵入前在深部发生液化和部分结晶,划分为贫瘠、含矿、富矿的岩浆和矿浆,然后多次注入,形成石头坑德镍铜矿床.
更新日期:2021-06-09
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