Variation of oxygen fugacity during magmatic evolution: in-situ geochemistry of mafic dikes from Jiaodong, southeastern North China Craton

Ma, Yao; Liu, Xuefei; Liang, Yayun

doi:10.1007/s00710-021-00755-x

Cited by 2 publications

(1 citation statement)

References 81 publications

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“…Notably, the economic WDS and HNT‐MPs have higher biotite X Mg ratios than the subeconomic and uneconomic granite porphyries (Figure 12b), indicating that the economic MPs formed by the partial melting of lower crust with more mantle material. The mantle‐derived magma (e.g., lamprophyre [LP]) exhibits high f O 2 (Ma et al, 2020). Hence, we proposed that the mixing between these high‐ f O 2 potassic–ultrapotassic magmas derived from the deep mantle and the melts derived from partial melting of the sulphide‐rich juvenile lower crust could be the key factor resulting in the high‐ f O 2 of the lower crust melting products at the Beiya Au deposit.…”

Section: Discussionmentioning

confidence: 99%

Geochemical and mineralogical contrasts between economic and uneconomic granite porphyries in the Beiya giant Au deposit, southwest China: Implications for petrogenesis and Cu–Au mineralization

Bao

Mao

et al. 2022

Geological Journal

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The Beiya giant porphyry Au deposit is the largest Cenozoic Au deposit in the Jinshajiang Cu–Mo–Au metallogenic belt. Many granite porphyries of ~36 Ma were exposed in the Beiya deposit, including the Wandongshan (WDS) and Hongnitang monzogranite porphyries (HNT–MPs) with economically important Au metal resources, the uneconomic WDS biotite MP, and Putaishan granite porphyry (GP), and subeconomic MPs at Nandaping (NDP) and Matouwan (MTW) prospects. To reveal the fundamental factors that lead to the different fertility of these granitic porphyries, this study uses the biotite and zircon geochemical compositions to evaluate their petrogenetic and magmatic conditions (e.g., F content, pressure, fO2). The results show that biotites from economic WDS and HNT–MPs exhibit moderate F contents (0.85%–2.16%), low n(FeT)/n(FeT + Mg) ratios (average of 0.36), and shallow emplacement depths of 0.19–1.76 km. In contrast, the uneconomic granite porphyries are characterized by variable F contents (0.17%–2.75%), high n(FeT)/n(FeT + Mg) ratios (average of 0.43), and deep emplacement depths of 2.76 to 5.02 km. Moreover, the economic WDS and HNT–MPs display higher average zircon fO2 (ΔFMQ [fayalite–magnetite–quartz] of +0.88) than uneconomic granite porphyries (ΔFMQ of −0.19), further confirming a higher fO2 of the economic granitic porphyries. These features indicate that magmatic fO2 is a critical factor controlling Cu–Au mineralization at the Beiya Au deposit. In comparison with the economic WDS and HNT–MPs, the subeconomic MPs in the MTW and NDP prospects exhibit higher average biotite n(FeT)/n(FeT + Mg) ratios of 0.47 and 0.45, and lower average zircon ΔFMQ of −0.05 and −0.23, suggesting lower magmatic fO2 and thus have relatively weak potentials to form Cu–Au mineralization. Notably, the economic WDS and HNT–MPs have higher biotite XMg ratios than those of the subeconomic and uneconomic granitic porphyries, indicating that the economic MPs were formed by the partial melting of mixed lower crustal materials with more mantle‐derived materials. Therefore, the addition of mantle‐derived materials played an important role in determining the fO2 of the granitic porphyry, thus primarily controlling its fertility of Cu–Au mineralization.

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Section: Discussionmentioning

confidence: 99%

Geochemical and mineralogical contrasts between economic and uneconomic granite porphyries in the Beiya giant Au deposit, southwest China: Implications for petrogenesis and Cu–Au mineralization

Bao

Mao

et al. 2022

Geological Journal

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Mineral chemistry of chrome-diopside bearing lamprophyre from Mesoproterozoic Settupalle igneous complex of Prakasam alkaline province: insights on the magma dynamics at shallow lithospheric mantle beneath the NE margin of the Cuddapah basin, Southern India

Sridhar,

Reddy,

Pandey

et al. 2024

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The Eastern Dharwar Craton (EDC) shows considerable variations in the activity of Kimberlite, lamproite, and lamprophyre and their related lithospheric thickness, thermal structure, and magmatic source characteristics from the innermost core to the margin. These variations have been revealed through seismic studies and the analysis of xenoliths, and xenocrysts carried in alkaline magmas, particularly kimberlites. This study reports the occurrence of chrome diopside phenocrysts from a lamprophyre of the Settupalle pluton, located on the northeastern margin of the Cuddapah basin, Prakasam Alkaline Province (PAP) in South India. Studied lamprophyre characterized by phenocrystic clinopyroxene (Cpx) and biotite, embedded in a groundmass of amphibole, biotite, opaques, calcite, feldspar, nepheline, and sodalite, with the latter minerals forming ocellar structures. Clinopyroxene displays normal zoning, with a high Mg-Cr rich diopside core (up to 1.92 wt%) and a Na 2 O, Al 2 O 3 , FeO, and TiO 2 -enriched salite rim. These chemical variations, along with elemental substitutions from core to rim, indicate the significant role of fractionation in the evolution of lamprophyre magma. The lack of chemical disparity among the studied Cpx, suggests closed-system fractionation, under high oxygen fugacity conditions. Thermobarometry results indicate polybaric crystallization for the Cpx (1206–1269 °C, 11.82–18.04 kbar) and biotite (825–856 °C, 3.49–6.94 kbar). The gradient inferred from the pressure of the Cpx suggests that its crystallization occurred at a depth of 43-66 km, implying shallow lithospheric magma contribution for the genesis of the lamprophyre magma. Supplementary material at https://doi.org/10.6084/m9.figshare.c.7249493

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Variation of oxygen fugacity during magmatic evolution: in-situ geochemistry of mafic dikes from Jiaodong, southeastern North China Craton

Cited by 2 publications

References 81 publications

Geochemical and mineralogical contrasts between economic and uneconomic granite porphyries in the Beiya giant Au deposit, southwest China: Implications for petrogenesis and Cu–Au mineralization

Geochemical and mineralogical contrasts between economic and uneconomic granite porphyries in the Beiya giant Au deposit, southwest China: Implications for petrogenesis and Cu–Au mineralization

Mineral chemistry of chrome-diopside bearing lamprophyre from Mesoproterozoic Settupalle igneous complex of Prakasam alkaline province: insights on the magma dynamics at shallow lithospheric mantle beneath the NE margin of the Cuddapah basin, Southern India

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