Peng Zidong et al.-EG: VMS-BIF Mining Combination Mechanism in the late green rock belt

The mineral formation system composed of volcanic reunion block sulfide minerals (VMS) and strip -shaped iron construction (BIF) is a unique mining combination in the ancient universe green rock belt. Product. This combination is not only an important source of metals such as copper, zinc and iron, but also records a specific structure, atmosphere and marine environment at that time. Therefore, it has important values ​​of research on research on economic and science. Focusing on the key scientific issue of VMS-BIF mining combination formation mechanism. The current research work is mainly concentrated in the space-time distribution, structural background, material source and sedimentary environment of the symbiosis of two types of minerals. Among them The deposition environment is the difficulty and hotspot of the current research.

The Qingyuan green rock belt located at the end of the northern edge of Clarong North my country is not only the only green rock belt for developing VMS CU-Zn minerals and BIF iron ore at the same time in China. -BIF Research Area of ​​Mining Combination. The Key Laboratory of the Institute of Mineral Resources of the Institute of Mineral Resources of the Institute of Geology and Geophysics of the Chinese Academy of Sciences Peng Zidong and the deputy researcher of Wang Changle, Zhang Lianchang, and Professor Simon Poulton University, and Professor Kurt Konhauser at the University of Alberta, Canada, and others. Multiple VMS and BIF minerals in the belt have carried out detailed research on geological, global chemistry, iron isotopes and polysulfonal isotope (Δ33S, Δ34s, and Δ36s), which effectively restrained the material source, sedimentary environment and complement of the VMS-BIF mineral combination combination Mining mechanism.

In terms of material source: The iron quality of the green rock band BIF iron ore mainly comes from the FE (II) accumulated in the water body accumulated in the water body. The ore-forming thermal solution system related to VMS provides a lot of iron for BIF, which is set in advanced stages; sulfur-containing BIF and layer-like VMS ore formed on the underwater deposition have non-zero Δ33S values ​​(average-average- 0.05 ‰ ± 0.007 ‰, 2sd; n = 9) and the ratio of Δ36S/Δ33S ratio consistent with typical sulfur isotope non-mass fraction (-1 ± 0.3, Figure 1b and 2A) in the early stages Sulfate provides some sulfur quality for it.

Figure 1 The characteristic of the Qingyuan green rock with VMS-BIF mining combination Fe-S isotope characteristics. (A) VMS ore pyrite and the Δ56FE value of magnets and pyrite in different levels of BIF; (B) Δ34S and Δ33S values ​​of sulfur -containing BIF and VMS ore

In terms of sedimentation environment: The development instructions of BIF with different levels of BIF with different levels of green rocks were in a state of hypoxia and rich iron. Based on the "diffusion-reaction" model (Dispersion-Reaction Model) of predecessors, the Δ56FE value of the lowest BIF positive BIF (0.48–0.69 ‰) of the lower part of the green rock belt indicates that the oxygen content of the surface seawater is about 10-4 ~ 10- 3 μmol/L (Figure 2B). The deposition layer-shaped VMS ore is close to the Δ56FE value (-0.58 ~ 0.51 ‰, Figure 1A), which is close to zero, reflecting the local sulfide body formed by the underwater heat fluid activity.

Figure 2 The original green rock with VMS-BIF ore combination iron isotopes and sulfur isotopes. (A) The pyloric ore in BIF and VMS ore with sulfur -containing ore has a Δ36S/Δ33S ratio that is consistent with typical sulfur isotope non -mass fraction (MIF) effects. (B) The lower BIF BIF and the Δ56FE value of Δ56FE values ​​and mimic calculations of the Δ56FE value of Δ56FE in different periods of the green rock belt and the possible surface water oxygen content

In terms of mining mechanism: CU content and CU/(CU+Zn) ratio of mesh, block, and layered VMS ore system reflect the transformation from the early stages of the seabed thermal fluid to the late stage. Matching differences with the FE and S of the above ore. Based on the construction model of the green rock belt, this study believes that in the early stages of pulling in the arc basin, some low -temperature thermal fluid systems developed mainly in the sea floor, and the mineralization effect is mainly based on BIF. Δ56FE value bias (Figure 3A); During the peak period, the underwater development high -temperature thermal fluid system is developed at this time. FE (II) will significantly change the iron isotope composition of the basin of the basin (Figure 3B), which is reflected in the composition of the iron isotope of the upper BIF bista (Figure 3C).

The study not only helps to improve the international understanding of the coupling mechanism between the material circulation and environmental evolution of the early earth surface system, but also provides instance support for the establishment of a VMS-BIF mining combination.

Figure 3 A schematic diagram of Qingyuan Green Rock with VMS-BIF Mining Combination Mining Mode

Geochemistic, and Iron and Multiple Sulfur (Δ33s, Δ34s, and Δ36s) isotopes [J] .economic geology, 2022, 117 (6): 1275–1298. Doi: 10.5382/Econgeo.4920).Studies were jointly funded by the Research on the Independent Research Project of the National Key Laboratory of the Rock Circle (No. 1191139), the key deployment projects (IGGCAS-201905), and the National Natural Science Foundation Youth Fund project (41902078).Beauty editor: Fu Shixu

School pair: Wanpeng

- END -