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首页> 外文期刊>Journal of Asian earth sciences >Magma oxygen fugacity of Permian to Triassic Ni-Cu sulfide-bearing mafic-ultramafic intrusions in the central Asian orogenic belt, North China
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Magma oxygen fugacity of Permian to Triassic Ni-Cu sulfide-bearing mafic-ultramafic intrusions in the central Asian orogenic belt, North China

机译：中国中部亚洲造山带二叠系至含三叠纪含镍-硫化铜的黑铁质-超镁铁质侵入体的岩浆氧逸度

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摘要

A number of Permian to Triassic mafic-ultramafic intrusions along the central Asian orogenic belt (CAOB) host either economically important or potential Ni-Cu sulfide mineralization. These intrusions were proposed to have emplaced in a post-subduction, extensional setting. In this study, we chose rocks from the Poyi, Huangshanxi, Huangshandong, and the Hongqiling No. 2 intrusions in the CAOB that contain olivine and spinel pairs to calculate the fO(2) of magma using olivine-spinel equilibria. The obtained fO(2) of the magmas overall range from FMQ + 0.3 to FMQ + 2.6, much higher than those for MORBs (FMQ-1 to FMQ). In addition, the obtained magma fO(2) of the Poyi intrusion is progressively elevated with the decrease of Fo contents of olivine. The fO(2) of the mantle source of the Hongqiling No.2 intrusion in the eastern part of the CAOB was calculated to be similar to FMQ + 0.5 with the compositions of olivine and spinel during partial melting of the mantle being simulated by an inverse model. The fO(2) of the mantle source of the Poyi intrusion in the western part of the CAOB was calculated to be similar to FMQ + 0.3 using the ultramafic rocks containing Fo(90-91) olivine in the intrusion. In addition, the V/Sc of the mantle peridotite and basalts from Paleozoic (533-260 Ma) ophiolites in the CAOB yielded the fO(2) of FMQ-1.5 to FMQ, which can be taken as the fO(2) of the mantle either prior to or after the closure of the paleo-Asian ocean. The calculated fO(2) for the mantle sources of the two intrusions are slightly higher than the upper fO(2) limit of the mantle sources (FMQ-1.5 to FMQ) obtained from Paleozoic ophiolites in the CAOB and the mantle sources for MORBs (FMQ-2.5 to FMQ). Permian to Triassic Ni-Cu sulfide-bearing, mafic-ultramafic intrusions in the CAOB are therefore considered to have formed from relatively oxidized mafic magmas that may have been derived from the metasomatized mantle sources. The magmas may have become more oxidized with the fractionation process until they were reduced by organic-rich crustal components to reach sulfide saturation, forming economically important Ni-Cu sulfide deposits.
机译：沿中亚造山带（CAOB）的许多二叠系至三叠系镁铁质-超镁铁质侵入体具有重要的经济意义或潜在的镍-铜硫化物矿化作用。这些入侵被提议置于俯冲后的延伸环境中。在这项研究中，我们选择了包含橄榄石和尖晶石对的CAOB坡伊，黄山西，黄山洞和红旗岭2号侵入岩，利用橄榄石-尖晶石平衡来计算岩浆的fO（2）。所获得的岩浆整体的fO（2）范围为FMQ + 0.3至FMQ + 2.6，远高于MORB（FMQ-1至FMQ）的fO（2）。此外，随着橄榄石中Fo含量的降低，获得的坡伊岩浆岩浆fO（2）逐渐升高。计算出CAOB东部红旗岭2号侵入地幔源的fO（2）与FMQ + 0.5相似，其中地幔部分熔融过程中橄榄石和尖晶石的组成通过反演模拟模型。使用包含Fo（90-91）橄榄石的超镁铁质岩石，计算出CAOB西部Poyi侵入的地幔源fO（2）与FMQ + 0.3相似。此外，CAOB中古生代（533-260 Ma）蛇绿岩中地幔橄榄岩和玄武岩的V / Sc产生了FMQ-1.5至FMQ的fO（2），可以看作是FMQ的fO（2）。古亚洲洋封闭之前或之后的地幔。对于两次侵入的地幔源的计算出的fO（2）略高于从CAOB中的古生代蛇绿岩和MORB的地幔源获得的地幔源（FMQ-1.5至FMQ）的fO（2）上限（ FMQ-2.5至FMQ）。因此，CAOB中含二叠纪至三叠纪含Ni-Cu硫化物的镁铁质-超镁铁质侵入体是由相对氧化的镁铁质岩浆形成的，这些氧化质岩浆可能是由交代地幔源产生的。岩浆可能会在分馏过程中被进一步氧化，直到被富含有机物的地壳成分还原成硫化物饱和为止，形成了具有经济意义的重要的Ni-Cu硫化物沉积物。

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