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Paleoproterozoic banded iron formation (BIF) iron ore of the Zhengjiapo region of the Changyi metallogenic belt, Eastern Block of North China Craton contains abundant coexisting antiperthite and mesoperthite textures. The antiperthite and mesoperthite occur in felsic domains of the Zhengjiapo BIF ore and enable derivation of peak temperature metamorphic conditions. Thermodynamic phase modeling shows that equilibrium conditions of corresponding textures, considering the related mineral assemblage of Pl + Qz + Kfs + Mag + Opx + L, are in the range of 870–940 °C and 5.0–6.8 kbar. Ternary feldspar thermometry using reintegrated compositions of antiperthite and mesoperthite in the felsic domain of the studied BIF iron ore reveals even higher peak metamorphic temperatures of 1045–1080 °C. The ultra-high temperature–low pressure conditions of Precambrian BIF have not yet been reported from the North China Craton. The documented ultra-high temperature metamorphism of the Zhengjiapo BIF iron ore in the Changyi metallogenic belt indicates that the BIF was involved in the collision-related tectonic process during Paleoproterozoic to have occurred in the Jiao-Liao-Ji orogenic belt. [ABSTRACT FROM AUTHOR]

• Metapelites of the Fenzishan Group were formed in a back-arc basin of an active continental margin. • Three age groups of detrital zircon: ∼ 3019–2816 Ma, 2761–2610 Ma and ∼ 2261–2128 Ma. • The minimum depositional age of metapelite precursor is ∼ 2261 – 2128 Ma. • Apatite U-Pb age ∼ 1923 – 1893 Ma reflects to the post peak collisional metamorphism. • Metapelites record the UHT metamorphism, showing an anticlockwise P-T path. Metapelites from the Fenzishan Group of the Zhengjiapo banded iron formation (BIF) iron mine studied have undergone high-pressure and ultrahigh-temperature (UHT) metamorphism. The rocks occur in the Changyi metallogenic belt that belongs to the Jiaobei terrane, Jiao-Liao-Ji Belt, North China Craton. P-T estimates using pseudosection modeling, mineral compositio isopleths and two-feldspar geothermometry of observed mesoperthite and antiperthite intergrowth textures of Bt-Grt-Mag-Amp gneisses, three different metamorphic stages were obtained: A prograde stage M1 at ∼ 600–610 °C/5.5–6.1 kbar, a peak metamorphic stage M2 at ∼ 899–1062 °C/8.6–9.15 kbar, an early retrograde stage M2́at 780–792 °C/8.6–9.15 kbar and a retrograde decompression stage M3 at 466–493 °C/4.5–5.8 kbar. Thus an anticlockwise trajectory can be defined indicating that granulite facies UHT-metamorphic peak conditions have been reached, followed by fast cooling during rapid exhumation. Geochemical characteristics of the metapelites indicate that the Fenzishan Group of the Zhengjiapo BIF iron mine was formed in a back-arc basin system of an active continental margin in a convergent/collisional geological setting.. Magmatic U-Pb ages (LA-ICP-MS) of detrital zircon from metapelites are ∼ 3096 – 2816 Ma and 2761 – 2610 Ma, indicating a source of the Archean basement which delivered clastic material for pelitic protolith. A zircon age of ∼ 2261 – 2128 Ma constrains the minimum depositional age of the metapelitic precursor, while an apatite U-Pb age of ∼ 1923 – 1893 Ma dating demonstrates a metamorphic age of ∼ 1923 – 1893 Ma, is indicated to represent a late Paleoproterozoic post peak metamorphic event that corresponds to the collision of the Jiao-Liao-Ji orogenic belt. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Sanshandao is a representative visible gold deposit. • The remobilization of gold induced the formation of high-grade ore zone and coarse visible gold. • The combined effect of CDR and LMCE melt makes gold remobilization occur. • Extensive reduction of marine sulfates are the main source of sulphur in the Jiaodong gold deposits. The Sanshandao is a typical altered-rock-style gold deposit (>260 t @ 3.96 g/t). The deposit is located at the northernmost end of the NE-trending Sanshandao fault in the northwestern Jiaodong Peninsula. The orebodies are mainly hosted by the footwall (minor in hanging-wall) of the fault, which cut Jurassic granites. According to the mineral assemblage and crosscutting relationship, five hydrothermal/mineralization stages were identified: (I) veinlet-disseminated quartz + pyrite ± chalcopyrite, (II) quartz + pyrite + chalcopyrite + native Au veining, (III) quartz + pyrite + galena + sphalerite + native Au + chalcopyrite veining, (IV-a) veinlet-disseminated siderite + pyrite + galena + sphalerite, (IV-b) ore-barren siderite, and (V) ore-barren calcite veining. Stages II and III auriferous pyrite contains visible native gold, and can be divided into four generations (Py2a, Py2b, Py3a, and Py3b). Py2a contains little native gold, whereas Py2b, Py3a, and Py3b contain much coarse-grained native gold. Gold in these pyrite generations correlates positively with the As content. Typical Py2a and Py3a porous/sieve-like texture indicates that Au remobilization has occurred, which may have controlled mainly by coupled dissolution-reprecipitation (CDR). Relative Sb-Te enrichments in Py2b and Py3a imply that a melt with low-melting point chalcophile elements (LMCEs) also facilitated Au remobilization by efficiently scavenging Au from preexisting minerals. Combined with the trace element compositions, we show that CDR may have liberated Au and LMCEs, and the subsequent fluid and LMCEs melt have altogether caused Au remobilization. The narrow δ34S V-CDT range of the pyrite from stages II-III (11.75–12.22‰ (Py2a), 10.83–12.39‰ (Py2b), 11.63–12.88‰ (Py3a), 11.91–12.67‰ (Py3b)), together with the compiled S-isotope dataset (from literature data) (δ34S V-CDT = mostly 7–10‰), indicate that reduction of marine sulfates represents the main sulfur source. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Xiaotongjiapuzi is a representative invisible gold deposit. • Gold exists mainly as solid solution (Au+) in the pyrite lattice and nanoparticles (Au0). • Paleoproterozoic sedimentary and metamorphism may have formed the initial sulfur reservoir. • The Xiaotongjiapuzi gold deposit has undergone a remarkable multi-step enrichment process of ore-forming materials. Most gold ores have variable sulfur isotopic and trace elemental compositions at micro-/nano-scale, which makes the understanding of the gold formation process more challenging. The advancement of in-situ analytical techniques offer opportunity to gain insight into gold mineralization processes and ore-material source. The Xiaotongjiapuzi is a representative intrusion-related gold deposit in the Qingchengzi orefield of the Liaodong Peninsula, Eastern China. Alteration and gold mineralization comprise four stages: (I) quartz-pyrite-Au, (II) quartz-pyrite-biotite-Au, (III) Au-barren quartz-pyrite, and (IV) post-ore quartz-calcite. Detailed scanning electron microscope (SEM) backscattered electron (BSE) imaging, electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) elemental and LA–multi-collector (MC)–ICP–MS sulfur isotope analyses were conducted to reveal the ore-material source and mineralization process. Three texturally distinct auriferous pyrite generations were identified: Py1 and Py2 (in both stage I and II) and Py3 (in stage II and III). Py1 is porous and weakly fragmented, poorly crystallized, and overgrown by Py2. Py2 is commonly intergrown with arsenopyrite and marcasite, whilst Py3 overgrew around Py2 or replace it. Gold exists mainly as solid solution (Au+) in the pyrite lattice and nanoparticles (Au0), as well as (rare) micron-scale inclusions along the Py2-Py3 interface. Py2 has the highest gold content (mean 47 ppm, max 344 ppm), especially when intergrown with marcasite (Mrc1). The δ34S values of pyrite (5.71–15.31‰, n = 18) and marcasite (-19.59 to 7.45‰. n = 6) are the highest and lowest, respectively, and the values increase steadily from Py1 to Py3 (Py1: 5.71–7.54‰ → Py2: 7.44–9.55‰ → Py2 + Mrc1: 12.88–13.92‰ → Py3: 15.17–15.31‰). The Paleoproterozoic Dashiqiao and Gaixian formation host rocks contain large amount of sulfate minerals (e.g., barite and gypsum), and the coeval global sulfate has heavy sulfur isotope enrichment, suggesting that sulfate reduction may have provided H 2 S-rich fluids [Au(HS)2- and/or Au(HS)0] for the Mesozoic mineralization. For the multistage gold enrichment at Xiaotongjiapuzi, we suggest that the Paleoproterozoic sedimentary and metamorphic rocks may have formed the initial sulfur reservoir, which was then reactivated by Mesozoic magmatic-hydrothermal events. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Jiudian large quartz vein gold system occurs in the southern Jiaobei uplift. • Cathodoluminescence images show 4 generations of quartz associated with 4 stages. • The ore-fluid system is mesothermal, low salinity, low density, and CO 2 -rich. • Hosted in Mesozoic granite, but ore-fluids partly come from Precambrian rocks. The Jiudian large-size gold deposit occurs as quartz veins in the footwall of the ZhaoPing Fault, and belongs to the southern section of the ZhaoPing metallogenic belt in Jiaodong Peninsula, eastern China. This study presents new fluid inclusion, geochemical, stable isotopic, and mineralogical data that provide insights into the sources of the ore metals, the temperature of mineralization, and the nature of the fluids involved in four different ore-forming stages. Cathodoluminescence imaging indicates four stages of quartz: the early-stage euhedral quartz that unrelates to mineralization and contains small-size fluid inclusions (Qz-1), the quartz containing abundant fluid inclusions and coexisting with pyrite (Qz-2 and Qz-3), and the late-stage quartz occurring as sulfide-barren veinlets crosscutting previous veins or mineral assemblages (Qz-4). Fluid inclusions include three types: H 2 O–CO 2 ± CH 4 (Type 1), two-phase aqueous inclusions (Type 2), and liquid aqueous inclusions (type 3). Fluid inclusions in Qz-1 are dominated by type 1, but in Qz-4 are only type 3; whilst Qz-2 and Qz-3 contain all three types fluid inclusions. Type 1 inclusions comprise three phases (liquid H 2 O + liquid CO 2 + vapor CO 2), with two carbonic phase ratios cluster at 10 %–30 % and 60 %–90 %. Type 2 inclusions also comprise two types, with vapor/liquid ratios focusing at 10 %–40 % and 60 %–80 %, respectively. All the fluid inclusions have homogenization temperatures of 198.5–329.2 °C, salinities of 3.95–12.39 wt% NaCl equivalent, and densities of 0.72–0.96 g/cm3. The quartz of main mineralization stages recorded the highest salinity, although the density of the fluids did not change markedly over time. These fluid inclusion data indicate that the Jiudian deposit has been formed from a mesothermal fluid system enriched in CO 2 and CH 4 , and genetically belongs to the orogenic-type. The C, H, O and Pb isotopic data indicate that the ore-forming metals and fluids were mainly sourced from Precambrian metamorphic basement and Mesozoic granites, with a small contribution from the mantle. This suggests that the Early Precambrian host-rocks significantly contributed metals to the ore-forming system. Therefore, a new genetic model for the Jiudian gold deposit is proposed to incorporate the Early Precambrian basement, Mesozoic intrusive rocks and ZhaoPing fault system. [ABSTRACT FROM AUTHOR]