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<p>The Makeng iron deposit is the largest Fe deposit in eastern China. It is hosted within Middle Carboniferous to Lower Permian limestones. The Cretaceous Juzhou and Dayang granites intruded on both sides of the Makeng mining area. The main mineral assemblage within the Makeng iron orebody is characterized by magnetite, pyroxene, and garnet, with lesser amounts of quartz. Two types of garnet associated with magnetite occur in the skarn: isotropic garnet (And<sub>92.0−99.9</sub>Gro<sub>0.0−3.4</sub>Pyr<sub>0.1−4.7</sub>) with a narrow compositional range and anisotropic garnet (And<sub>92.3−98.2</sub>Gro<sub>0.0−5.2</sub>Pyr<sub>1.8−2.6</sub> to And<sub>8.9−71.9</sub>Gro<sub>23.7−87.8</sub>Pyr<sub>2.2−4.4</sub>) with andradite–grossular compositions. Three kinds of pyroxene were further identified in the deposit: type 1 hedenbergite (Di<sub>6.6−37.5</sub>Jo<sub>7.0−10.4</sub>Hd<sub>55.1−84.9</sub>), type 2 diopside (Di<sub>83.1−95.9</sub>Jo<sub>1.5−7.3</sub>Hd<sub>2.7−9.6</sub>), and type 3 johannsenite (Di<sub>0.7−2.1</sub>Jo<sub>82.9−93.2</sub>Hd<sub>4.8−16.4</sub>) replacing andradite. Type 1 pyroxene (hedenbergite) is replaced by the andradite, magnetite, and quartz assemblage, indicating the following replacement reaction: 9Hd + 2O<sub>2</sub> = 3Ad + 9Qz + Mt. Type 2 pyroxene (diopside) together with magnetite occurs as interstitial grains between garnet crystals. Based on mineralogical and textural evidence, the magnetite and related skarn minerals (diopside and andradite) were formed under more oxidizing conditions with a Log <i>f</i>O<sub>2</sub> of − 26 to − 15. The type 1, 2, and 3 pyroxenes have high Mn/Fe ratios, which are characteristics of pyroxenes from distal skarn deposits. The Re-Os dating of molybdenite coexisting with magnetite yielded an age of 143.2 ± 3.3&#xa0;Ma, which indicates the age of the iron mineralization. These lines of evidence indicate that the Makeng iron deposit is a distal skarn–type iron deposit and that it is genetically associated with Cretaceous intrusions.</p>

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The makeng deposit, Southeastern China: a distal skarn iron deposit constrained by skarn mineralogy and molybdenite Re-Os geochronology

  • 期刊论文

  • 发表日期：

    2026年4月14日

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  • Guofeng Wang,
  • Kai Zhang,
  • Shiwei Zhang,
  • Zhilong Deng

摘要

The Makeng iron deposit is the largest Fe deposit in eastern China. It is hosted within Middle Carboniferous to Lower Permian limestones. The Cretaceous Juzhou and Dayang granites intruded on both sides of the Makeng mining area. The main mineral assemblage within the Makeng iron orebody is characterized by magnetite, pyroxene, and garnet, with lesser amounts of quartz. Two types of garnet associated with magnetite occur in the skarn: isotropic garnet (And92.0−99.9Gro0.0−3.4Pyr0.1−4.7) with a narrow compositional range and anisotropic garnet (And92.3−98.2Gro0.0−5.2Pyr1.8−2.6 to And8.9−71.9Gro23.7−87.8Pyr2.2−4.4) with andradite–grossular compositions. Three kinds of pyroxene were further identified in the deposit: type 1 hedenbergite (Di6.6−37.5Jo7.0−10.4Hd55.1−84.9), type 2 diopside (Di83.1−95.9Jo1.5−7.3Hd2.7−9.6), and type 3 johannsenite (Di0.7−2.1Jo82.9−93.2Hd4.8−16.4) replacing andradite. Type 1 pyroxene (hedenbergite) is replaced by the andradite, magnetite, and quartz assemblage, indicating the following replacement reaction: 9Hd + 2O2 = 3Ad + 9Qz + Mt. Type 2 pyroxene (diopside) together with magnetite occurs as interstitial grains between garnet crystals. Based on mineralogical and textural evidence, the magnetite and related skarn minerals (diopside and andradite) were formed under more oxidizing conditions with a Log fO2 of − 26 to − 15. The type 1, 2, and 3 pyroxenes have high Mn/Fe ratios, which are characteristics of pyroxenes from distal skarn deposits. The Re-Os dating of molybdenite coexisting with magnetite yielded an age of 143.2 ± 3.3 Ma, which indicates the age of the iron mineralization. These lines of evidence indicate that the Makeng iron deposit is a distal skarn–type iron deposit and that it is genetically associated with Cretaceous intrusions.