The Dongguashan copper (gold) deposit in Anhui Province is one of the largest copper (gold) deposits in the Tongling ore district, which is the most important region in the Middle–Lower Yangtze River Metallogenic Belt, Eastern China. Stratiform and lamellar orebodies are the major deposit types. Pyrite and pyrrhotite from the stratiform deposit type (Py I, Po I) and lamellar deposit type (Py II, Po II) are investigated using Electron-probe Microanalyses (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Py I, Py II, Po I and Po II have high contents of Cu, Co, Au and Se, low contents of As, Pb and Zn, with Co/Ni ratios of 0.50−48.00, 4.00−45.00, 1.55−14.45 and 1.02−1.36, respectively, most of which are greater than 1 and vary widely; these characteristics are consistent with those of pyrite with a magmatic–hydrothermal origin. The higher Au/Ag and Fe/(S + As) ratios of pyrite and crystallization temperatures (286–387 °C) of hexagonal pyrrhotite indicate that the mineralization occurrs in environments with medium- to high-temperatures, high sulfur fugacity and medium-shallow depths. Therefore, we suggest that the Dongguashan copper (gold) deposit is a stratabound skarn-type ore deposit associated with magma intrusion activity during the Yanshanian Period.

The Huanggangliang deposit is a super-large Sn-Fe deposit in the Huanggangliang–Ganzhuermiao metallogenic belt in the southern section of the Great Hinggan Range. The Sn-Fe deposits mainly occur in the skarn contact zone and were formed via the interaction of biotite-bearing alkali feldspar granite with limestone strata of the Permian Dashizhai and Zhesi Formations. Based on the intersecting relations among the ore-bearing veins and the different types of mineral assemblages within these veins, the Sn-Fe mineralization could be divided into two periods and four stages: the skarn period, which includes the garnet–diopside–magnetite (T1) stage (stage 1) and epidote–idocrase–cassiterite–magnetite (T2) stage (stage 2); and the quartz–magnetite period, which can be divided into the quartz–cassiterite–magnetite (T3) stage (stage 3) and quartz–magnetite (T4) stage (stage 4). In this paper, we discuss the genesis of magnetite, controlling factors for magnetite compositions, and type of ore genesis based on petrographic studies and LA-ICP-MS analyses of trace elements in these four types of magnetite from the Huanggangliang Sn-Fe deposit. The results demonstrate that the four types of magnetite are generally depleted in Ti (0.002–3.030 wt %), Al (0.008–1.731 wt %), and Zr (<1.610 ppm). In addition, the low Ni and Cr contents and relatively high and stable Fe contents in the four types of magnetite are indicative of hydrothermal genetic features. Compositions of the ore fluids and host rocks, formation of coexisting minerals, and other physical and chemical parameters (such as fO₂) may have influenced the variable magnetite geochemistry in the different Huanggangliang ore types, with fluid compositions and fO₂ probably playing the most important roles. The geological, petrographic, and geochemical characteristics of magnetite of the Huanggangliang Sn-Fe deposit lead us to conclude that the deposit is a skarn-type Sn-Fe deposit associated with Yanshanian medium-acidic magmatic activities.

The Xiajinbao gold deposit is located at the northern margin of the North China Craton. Hydrothermal pyrites belonging to three stages were identified: Py1; Py2; and Py3. Geochemical study of these pyrites was conducted using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry to investigate the distributions of minor and trace elements, constrain pyrite genesis, and to obtain an improved understanding of the ore-forming processes. Py1 and Py2 contain high concentrations of Au and are interpreted to have been deposited from fluids from a dominantly magmatic source. Py3 grains have the lowest Co/Ni ratios. All generations of pyrite were deposited by mixing of meteoric waters with magmatic-hydrothermal fluids. Boiling of early ore-forming fluids led to the precipitation of Py1 and gold. Decreasing fO₂ in the ore-forming system resulted in the formation of Py2 and gold. Fluid mixing was the dominant controlling factor for the precipitation of Py3 together with small amounts of gold.

The Xiajinbao gold deposit is a medium-sized gold deposit in the Jidong gold province. Ore bodies mainly occur within the Xiajinbao granite porphyry and along the contact zone between the intrusion and Archean plagioclase hornblende gneiss. The zircon LA-ICP-MS age of the Xiajinbao granite porphyry yields 157.8 ± 3.4 Ma, which reflects the metallogenic age of the gold mineralization. Its petrographic features, major and trace element contents, zircon Hf isotopic model ages and compositional features all demonstrate that the Xiajinbao granitic magma is derived from partial melting of the Changcheng unit. The results of H–O isotopic analyses of auriferous quartz veins indicate that the ore-forming fluids are derived from magmatic waters that gradually mixed with meteoric waters during the evolution of the ore-forming fluids. S–Pb isotopic data indicate that the ore-forming fluids were mainly provided by the magma and by plagioclase hornblende gneisses. The gold metallogeny of the Xiajinbao gold deposit is temporally, spatially, and genetically associated with the high-K calc-alkaline-shoshonitic granitic magma emplaced during the Yanshanian orogeny and intruding the Archean plagioclase hornblende gneisses. These magmatic events mainly occurred during the period of 223–153 Ma and comprise three peak periods in the late Triassic (225–205 Ma), the early Jurassic (200–185 Ma) and the middle–late Jurassic (175–160 Ma), respectively. The metallogenic events in this area mainly occurred during the period of 223–155 Ma with the peak periods during the late Triassic (223–210 Ma) and the middle–late Jurassic (175–155 Ma), respectively. Both mineralization and magmatism occurred in a post-collisional tectonic setting related to the collision between the Mongolian plate and the North China plate at the end of the Permian. The magmatism of the early Jurassic occurred during the collision between the Siberian plate and the Mongolian plate, which caused the thickening and melting of the northern margin of the North China plate. The middle and late Jurassic magmatism and metallogenic activities are products of crustal thickening and partial melting during the Yanshanian intra-continental orogeny at the northern margin of the North China plate.

The Longmendian Ag–Pb–Zn deposit is located in the southern margin of the North China Craton, and the mineralization occurs mainly in quartz veins, altered gneissic wallrocks, and minor fault breccias in the Taihua Group. Based on vein crosscutting relations, mineral assemblages, and paragenesis, the mineralization can be divided into three stages: (1) quartz–pyrite, (2) quartz–polymetallic sulfides, and (3) quartz–carbonate–polymetallic sulfides. Wallrock alteration can be divided into three zones, i.e., chlorite–sericite, quartz–carbonate–sericite, and silicate. Fluid inclusions in all Stage 1 to 3 quartz are dominated by vapor-liquid two-phase aqueous type (W-type). Petrographic and microthermometric analyses of the fluid inclusions indicate that the homogenization temperatures of Stages 1, 2, and 3 are 198–332°C, 132–260°C, and 97–166°C, with salinities of 4.0–13.3, 1.1–13.1, and 1.9–7.6 wt% NaCl_eqv, respectively. The vapor comprises primarily H₂O, with some CO₂, H₂, CO, N₂, and CH₄. The liquid phase contains Ca²⁺, Na⁺, K⁺, SO₄²⁻, Cl⁻, and F⁻. The sulfides have δ34S=–1.42 to +2.35‰ and 208Pb/204Pb=37.771 to 38.795, 207Pb/204Pb=15.388 to 15.686, and 206Pb/204Pb=17.660 to 18.101. The H–C–O–S–Pb isotope compositions indicate that the ore-forming materials may have been derived from the Taihua Group and the granitic magma. The fluid boiling and cooling and mixing with meteoric water may have been critical for the Ag–Pb–Zn ore precipitation. Geological and geochemical characteristics of the Longmendian deposit indicate that the deposit is best classified as medium- to low-temperature intermediate-sulfidation (LS/IS) epithermal-type, related to Cretaceous crustal-extension-related granitic magmatism.