Cao, Yonghua, Wang, Christina Yan, Wei, Bo (2020) Magma oxygen fugacity of mafic-ultramafic intrusions in convergent margin settings: Insights for the role of magma oxidation states on magmatic Ni-Cu sulfide mineralization. American Mineralogist, 105 (12) 1841-1856 doi:10.2138/am-2020-7351
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Magma oxygen fugacity of mafic-ultramafic intrusions in convergent margin settings: Insights for the role of magma oxidation states on magmatic Ni-Cu sulfide mineralization | ||
| Journal | American Mineralogist | ||
| Authors | Cao, Yonghua | Author | |
| Wang, Christina Yan | Author | ||
| Wei, Bo | Author | ||
| Year | 2020 (December 1) | Volume | 105 |
| Issue | 12 | ||
| Publisher | Mineralogical Society of America | ||
| DOI | doi:10.2138/am-2020-7351Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 529760 | Long-form Identifier | mindat:1:5:529760:7 |
| GUID | 0 | ||
| Full Reference | Cao, Yonghua, Wang, Christina Yan, Wei, Bo (2020) Magma oxygen fugacity of mafic-ultramafic intrusions in convergent margin settings: Insights for the role of magma oxidation states on magmatic Ni-Cu sulfide mineralization. American Mineralogist, 105 (12) 1841-1856 doi:10.2138/am-2020-7351 | ||
| Plain Text | Cao, Yonghua, Wang, Christina Yan, Wei, Bo (2020) Magma oxygen fugacity of mafic-ultramafic intrusions in convergent margin settings: Insights for the role of magma oxidation states on magmatic Ni-Cu sulfide mineralization. American Mineralogist, 105 (12) 1841-1856 doi:10.2138/am-2020-7351 | ||
| In | (2020, December) American Mineralogist Vol. 105 (12) Mineralogical Society of America | ||
| Abstract/Notes | Abstract Oxygen fugacities (fO2) of mantle-derived mafic magmas have important controls on the sulfur status and solubility of the magmas, which are key factors to the formation of magmatic Ni-Cu sulfide deposits, particularly those in convergent margin settings. To investigate the fO2 of mafic magmas related to Ni-Cu sulfide deposits in convergent margin settings, we obtained the magma fO2 of several Ni-Cu sulfide-bearing mafic-ultramafic intrusions in the Central Asian Orogenic Belt (CAOB), North China, based on the olivine-spinel oxygen barometer and the modeling of V partitioning between olivine and melt. We also calculated the mantle fO2 on the basis of V/Sc ratios of primary magmas of these intrusions. Ni-Cu sulfide-bearing mafic-ultramafic intrusions in the CAOB include arc-related Silurian-Carboniferous ones and post-collisional Permian-Triassic ones. Arc-related intrusions formed before the closure of the paleo-Asian ocean and include the Jinbulake, Heishan, Kuwei, and Erbutu intrusions. Post-collisional intrusions were emplaced in extensional settings after the closure of the paleo-Asian ocean and include the Kalatongke, Baixintan, Huangshandong, Huangshan, Poyi, Poshi, Tulaergen, and Hongqiling No. 7 intrusions. It is clear that the magma fO2 values of all these intrusions in both settings range mostly from FMQ+0.5 (FMQ means fayalite-magnetite-quartz oxygen buffer) to FMQ+3 and are generally elevated with the fractionation of magmas, much higher than that of MORBs (FMQ-1 to FMQ+0.5). However, the mantle fO2 values of these intrusions vary from ~FMQ to ~FMQ+1.0, just slightly higher than that of mid-ocean ridge basalts (MORBs) (≤FMQ). This slight difference is interpreted as the intrusions in the CAOB may have been derived from the metasomatized mantle wedges where only minor slab-derived, oxidized components were involved. Therefore, the high-magma fO2 values of most Ni-Cu sulfide-bearing mafic-ultramafic intrusions in the CAOB were attributed to the fractionation of magmas derived from the slightly oxidized metasomatized mantle. In addition, the intrusions that host economic Ni-Cu sulfide deposits in the CAOB usually have magma fO2 of >FMQ+1.0 and sulfides with mantle-like δ34S values (–1.0 to +1.1‰), indicating that the oxidized mafic magmas may be able to dissolve enough mantle-derived sulfur to form economic Ni-Cu sulfide deposits. Oxidized mafic magmas derived from metasomatized mantle sources may be an important feature of major orogenic belts. | ||
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