Search Results (8)

The North China Craton (NCC), one of the oldest cratons worldwide, may provide information on the evolution and geodynamic processes of the early Earth, especially during the pre-Mesoarchean period. Many ancient zircons have been discovered in the Jiapigou terrane of the northeastern NCC on the basis of our recent studies, providing an excellent opportunity to trace the early crustal evolution trend of the NCC. Here, we present a detailed study of the petrography, mineralogy, zircon U–Pb dating and Lu–Hf isotopes of supracrustal rocks (biotite schist) obtained from the Jiapigou terrane. Geochronology combined with the internal structures and Th/U ratios of the zircons reveal that the zircons acquired from the supracrustal rock can be divided into the following two types: magmatic zircons and metamorphic zircons. Among the magmatic zircons, the youngest zircon age (2.49 Ga) is considered to represent the time at which the protolith of the supracrustal rock (i.e., Neoarchean) crystallized, whereas the others were likely captured or inherited from their magma sources. The zircon Hf isotopes reveal that unexposed Hadean–Paleoarchean crust (4.18–3.57 Ga) is present beneath the Jiapigou terrane, and its growth history can be traced back to the Hadean period. Moreover, the evidence derived from this and previous studies indicates that the Jiapigou terrane underwent two crustal recycling events (3.37–3.20 Ga and ~2.96 Ga) during the Paleoarchean, two crustal reworking episodes (2.53 Ga and 2.49 Ga) during the Neoarchean, and later metamorphism at 2.41 Ga. Thus, the Jiapigou terrane has undoubtedly recorded multiple episodes of early crustal growth and/or reworking that are similar to, but not limited to, those of the northern and southern margins of the NCC. Full article

The Jiapigou mining district, a world-famous gold-producing district with a capacity that greatly exceeds 180 t Au, has a mining history longer than 200 years. The large amount of Jurassic Au mineralization in this district significantly differs from that in other districts of the North China Craton (130–115 Ma). However, the deep-seated dynamic processes and mechanisms that triggered the unique Jurassic mineralization in the Jiapigou district are poorly understood. Here, we present new data on the geology, petrography, and zircon U–Pb and Lu–Hf isotopes of the typical Huangnihe pluton in the Jiapigou district to address the above issues. The results revealed the following: (1) The Huangnihe pluton comprises mainly fine-grained granite and porphyritic granite, which were emplaced at 187 ± 2 Ma (n = 13) and 166 ± 2 Ma (n = 15), respectively. (2) The Hf isotope data indicate that the two episodes of granites exhibit distinct origins: the former (εHf(t) = −1.4 to +5.3; T_DM2 = 1784–1181 Ma) originated from juvenile lower crust, whereas the latter (εHf(t) = −14.9 to −9.7; T_DM2 = 2987–2518 Ma) was derived from Archean crust. (3) On the basis of published geochemical data, the estimated crustal thicknesses of the Jiapigou district ca. 187 Ma, ca. 175 Ma, and ca. 166 Ma ranged from 45 to 52 km, 43 km, and 58 to 63 km, respectively. Combined with regional observations, the results of this study further reveal the following: (1) The Jurassic magmatism in the Jiapigou district can be subdivided into three episodes: 187–186 Ma, ca. 175 Ma, and 166–165 Ma. (2) The crust in the Jiapigou district gradually thickened during the Jurassic and underwent partial melting during multiple episodes of Paleo-Pacific Plate subduction, thereby generating arc-like calc-alkaline (ca. 187 Ma), adakite-like (ca. 175 Ma), and adakite magmas (ca. 166 Ma) that were emplaced to form corresponding granitoids. Moreover, syn-ore magma mixing between the ca. 175 Ma adakite-like felsic magma and mantle-derived mafic magmas was considered a crucial process in magma evolution. This process in turn promoted the enrichment of ore-forming elements within the magma system, which significantly contributed to the formation of the large Au mineralization in the Jiapigou district. Full article

The Jiapigou mining district (>180 t Au) is an important gold district in China. For a long time, the ore genesis of the gold deposits in the Jiapigou district has been a subject of controversy and differing opinions, which has severely hindered metallogenic theories and mineral exploration. Here we present a comprehensive investigation including geology, fluid inclusions (FIs), and H–O–S isotopic data for the Naizhigou deposit in the Jiapigou district to elucidate the sources of orefluids and metals, as well as the metallogenic mechanism. The results show the following: (1) The Naizhigou deposit is characterized by quartz vein-type ores and is hosted in the Middle Jurassic granitic pluton. Native gold and sulfides were mainly deposited in the second stage (quartz–polymetallic sulfides) compared with the first (quartz–pyrite–molybdenite) and third (quartz–calcite) stages. (2) The FI studies indicated that the orefluids evolved from the early–main-stage CO₂–H₂O–NaCl system to the late-stage H₂O–NaCl system and have homogenization temperatures of 289–363, 210–282, and 124–276 °C and salinities of 4.1–20.9, 5.8–16.4, and 6.1–12.7 wt% NaCl equivalent, respectively. Fluid boiling and fluid mixing collectively controlled the precipitation of gold and ore-forming elements. (3) The δD values of the FIs hosted in quartz from the three stags range from −81 to −75 ‰, from −99 to −86 ‰, and from −110 to −101 ‰, while δ¹⁸O_water values of these FIs range from 5.3 to 5.9 ‰, from 1.1 to 5.2 ‰, and from −2.1 to −0.7 ‰, respectively. Pyrite samples from the three stages in the Naizhigou deposit have δ³⁴S values of 2.1 to 2.5 ‰, 3.1 to 4.3 ‰, and 3.8 to 3.9 ‰, respectively. The stable isotopes indicate that the orefluids and metals mainly originated from magma. A comparative study of regional observations reveals that the Naizhigou deposit is a magmatic-related mesothermal gold deposit, rather than a metamorphism-related orogenic gold deposit. The estimated ore-forming depths are 4.0–20.7 km, with exhumation depths of 4.1–5.5 km, which indicated that the deposit has been well preserved. Regionally, the new exploration strategies should place greater emphasis on work concerning ore-related plutons, ore-controlling faults, and hydrothermal alteration. Full article

The Cuyu gold deposit in central Jilin Province in Northeast China is located in the eastern segment of the northern margin of the North China Craton (NCC), as well as the eastern segment of the Xing’an–Mongolian Orogenic Belt (XMOB). Gold ore-bodies are controlled by NW-trending faults and mainly occur in late Hercynian granodiorite. The mineralization process in the Cuyu deposit can be divided into three stages: quartz + coarse grained arsenopyrite + pyrite (stage I), quartz + sericite + pyrite + arsenopyrite + electrum + chalcopyrite + sphalerite (stage II), and quartz + calcite ± pyrite (stage III). Stage II is the most important for gold mineralization. We conducted analyses including petrography, microthermometry, laser Raman spectroscopy of fluid inclusions, and H–O–S–Pb isotopic analysis to elucidate the mineralization processes in the Cuyu deposit. Five types of primary fluid inclusions (FIs) are present in the hydrothermal quartz and calcite grains of the ore: liquid-rich two-phase aqueous fluid inclusions (L-type), vapor-rich two-phase aqueous fluid inclusions (V-type), CO₂-bearing two- or three-phase inclusions (C1-type), CO₂-rich two- or three-phase inclusions (C2-type), and pure CO₂ mono-phase inclusions (C3-type). From stages I to III, the fluid inclusion assemblages changed from L-, C2-, and C3-types to L-, V-, C1-, C2-, and C3-types and, finally, to L-types only. The corresponding homogenization temperatures for stages I to III were 242–326 °C, 202–298 °C, and 106–188 °C, and the salinities were 4.69–9.73, 1.63–7.30, and 1.39–3.53 wt.% NaCl equiv., respectively. The ore-forming fluid system evolved from a NaCl-H₂O-CO₂ ± CH₄ ± H₂S fluid system in stage I and II with immiscible characteristics to a homogeneous NaC-H₂O fluid system in stage III. Microthermometric data for stages I to III show a decreasing trend in homogenization temperatures and salinities. The mineral assemblages, fluid inclusions, and H–O–S–Pb isotopes indicate that the initial ore-forming fluids of stage I were exsolved from diorite porphyrite and characterized by a high temperature and low salinity. The addition of meteoric water in large quantities led to decreases in temperature and pressure, resulting in a NaCl-H₂O-CO₂ ± CH₄ ± H₂S fluid system with significant immiscibility in stage II, facilitating the deposition of gold and associated polymetallic sulfides. The Cuyu gold deposit has a similar ore genesis to those of gold deposits in the Jiapigou–Haigou gold belt (JHGB) of southeastern Jilin Province indicating potential for gold prospecting in the northwest-trending seam of the JHGB. Full article

The newly discovered Erdaodianzi gold deposit in southern Jilin Province, Northeast China, is located in the eastern segment of the northern margin of the North China Craton (NCC). It is a large-scale gold deposit with reserves of 38.4 tons of gold. Gold mineralization in the ore district primarily occurs in gold-bearing quartz–sulfide veins. The gold ore occurs mainly as vein, veinlet, crumby, and disseminated structures. The hydrothermal process can be divided into three stages: stage I, characterized by quartz, arsenopyrite, and pyrite; stage II, featuring quartz, arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite, and native gold; and stage III, consisting of quartz, pyrite, sphalerite, galena, electrum (a naturally occurring Au–Ag alloy), and calcite. Electrum and native gold primarily occur within the fissures of the polymetallic sulfides. To determine the enrichment mechanism of the Au element and the genetic types of ore deposits in the Erdaodianzi deposit, sourcing in situ trace element data, element mapping and sulfur isotope analysis were carried out on sphalerites from different stages using LA-ICP-MS. Minor invisible gold, in the form of Au–Ag alloy inclusions, is present within sphalerites, as revealed by time-resolved depth profiles. The LA-ICP-MS trace element data and mapping results indicate that trivalent or quadrivalent cations, such as Sb³⁺ and Te⁴⁺, exhibit a strong correlation with Au. This correlation can be explained by a coupled substitution mechanism, where these cations (Sb³⁺ and Te⁴⁺) replace zinc ions within the mineral structure, resulting in a strong association with Au. Similarly, the element Pb exhibits a close relationship with Au, which can be attributed to the incorporation of tetravalent cations like Te⁴⁺ into the mineral structure. The positive correlation between Hg and Au can be attributed to the formation of vacancies and defects within sphalerite, caused by the aforementioned coupled substitution mechanism. A slight positive relationship between Au and other divalent cations, including Fe²⁺, Mn²⁺, and Cd²⁺, may result from these cations simply replacing Zn within the sphalerite lattice. The crystallization temperatures of the sphalerite, calculated via the Fe/Zn ratio, range from 238 °C to 320 °C. The δ³⁴S values are divided into two intervals: one ranging from −1.99 to −1.12‰ and the other varying from 10.96 to 11.48‰. The sulfur isotopic analysis revealed that the ore-forming materials originated from magmatic rock, with some incorporation of metamorphic rock. Comparative studies of the Erdaodianzi gold deposit and other gold deposits in the Jiapigou–Haigou gold belt have confirmed that they are all mesothermal magmatic–hydrothermal lode gold deposits formed at the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate during the Middle Jurassic. The Jiapigou–Haigou gold belt extends northwest to the Huadian area of Jilin province. This suggests potential for research on gold mineralization in the northwest of the belt and indicates a new direction for further gold prospecting in the region. Full article

The medium-sized Songjianghe Au deposit is located in the southeastern part of the Jiapigou-Haigou gold belt (JHGB) in central eastern Jilin Province, NE China. The gold mineralization is primarily characterized by disseminated-style ores and hosted in the low-/medium-grade metamorphic rocks of the Seluohe Group. The ore bodies are governed by NNW-striking brittle-ductile structures and spatially correlated with silicic and sericitic alterations. Four alteration/mineralization stages have been distinguished: (I) Quartz-pyrrhotite-pyrite, (II) quartz-polymetallic sulfides, (III) quartz-pyrite, and (IV) quartz-calcite. The fluid inclusion (FI) assemblage in quartz from Stage I comprises C1-type, C2-type, C3-type, and VL-type FIs, with total homogenization temperatures (Th-total) of 292.8 to 405.6 °C and salinities of 2.8 to 9.3 wt% NaCl eqv. Quartz from Stage II (main ore stage) developed C2-, C3-, and VL-type FIs, with a Th-total of 278.5 to 338.9 °C and salinities of 2.8 to 8.1 wt% NaCl eqv. Stage III is characterized by coexisting C3- and VL-type FIs in quartz, with a Th-total of 215.9 to 307.3 °C and salinities of 2.4 to 7.2 wt% NaCl eqv. Only VL-type FIs are observed in Stage IV, with a Th-total of 189.5 to 240.4 °C and salinities of 3.7 to 5.7 wt% NaCl eqv. The Laser Raman spectroscopic results demonstrated minor CH₄ in the C-type FIs from Stages I and II. The results suggest that ore fluids may have evolved from a medium-high temperature, low-salinity immiscible CO₂-NaCl-H₂O ± CH₄ system to a low temperature, low-salinity homogeneous NaCl-H₂O system. Fluid immiscibility caused by the rapid drop in pressure may have been the main trigger for gold-polymetallic sulfide precipitation. The Songjianghe Au deposit may have been formed under 352–448 °C and 850–1380 bar pressure, based on the isochore intersection for Stage II fluid inclusions. The H-O isotopic compositions (Stage I: δ¹⁸O_fluid = 5.6 to 5.8‰, δD = −96.2 to −95.7‰; Stage II: δ¹⁸O_fluid = 3.7 to 4.2‰, δD = −98.7 to −89.8‰; Stage III: δ¹⁸O_fluid = 1.2 to 1.4‰, δD = −103.5 to −101.2‰) indicate that the hydrothermal fluids are dominated by magmatic water in the early stages (Stages I and II) and mixed with meteoric water since Stage III. The pyrite S-Pb isotope data (δ³⁴S: −2.91 to 3.40‰; ²⁰⁶Pb/²⁰⁴Pb: 16.3270 to 16.4874; ²⁰⁷Pb/²⁰⁴Pb: 15.2258 to 15.3489; ²⁰⁸Pb/²⁰⁴Pb: 36.6088 to 36.7174), combined with Pb isotopic compositions of the intrusive rocks and wall rocks (the Seluohe Group) in the ore district, indicate that the ore-forming materials at Songjianghe are predominantly from a magmatic source and may have been affected by the contamination of the Seluohe Group. In accordance with the features of ore geology, ore-forming fluids and metals, and geodynamic setting, the Songjianghe Au deposit belongs to a mesothermal magmatic hydrothermal vein gold deposit, which formed in the intermittent stage of Paleo-Pacific plate subduction during the Late Jurassic. Full article

Over the years, many geological exploration reports and considerable geological data have been accumulated during the prospecting and exploration of the Jiapigou gold metallogenic belt (JGMB). It is very important to fully utilize these geological and mineralogical big data to guide future gold exploration. This work collects the original textual data of different gold deposits in JGMB and constructs a knowledge graph (KG) for deposits based on deep learning (DL) and natural language processing (NLP). Based on the metallogenic geological characteristics of deposits, a visual construction method of a KG for deposits and a calculation of the similarity between deposits are proposed. In this paper, 20 geological entities and 24 relationship categories are considered. By condensing the key KG information, the metallogenic geological conditions and factors controlling the ore in 14 typical deposits in the JGMB are systematically analyzed, and the metallogenic regularity is summarized. By calculating the deposits’ cosine similarities based on the KG, the mineralization types of deposits can be divided into two categories according to the industrial types of ore bodies. The results also show that the KG is a cutting-edge technology that can extract the rich information of ore-forming regularity and prospecting criteria contained in the textual data to help researchers quickly analyze the mineralization information. Full article

Liuhe gold orefield is being newly explored in the southeast part of the Jiapigou gold ore belt, and occurs in the Neoarchean basement composed of trondhjemite–tonalite–granodiorite (TTG). Zircon U–Pb data suggest that the ore-hosting magma emplacement in the Liuhe orefield mainly took place in two epochs: late Neoarchean to early Paleoproterozoic (ca. 2500 Ma) and early Jurassic of the Mesozoic era (ca. 170 Ma). The TTG rocks show higher A1₂O₃ (12.58 to 15.71%) and Na₂O/K₂O ratios (1.16 to 2.9), and lower MgO (0.93 to 2.73%) and Mg# values, with positive Eu anomaly and low Y and Yb content, and high Sr/Y (22.3–79.6), and the plot in the adakite field in the Sr/Y-Y discriminant diagram belongs to the modern island-arc adakite rocks. Samples in this study are plotted in the pre-plate collision area in the R1-R2 discrimination diagram, and fall into the VAG and VAG + Syn-COLG field in the Rb-Y + Nb and Nb-Y diagram, respectively, indicating that the magmatism is related to plate subduction. The ore-bearing TTGs of the late Neoarchean to early Paleoproterozoic deposits were derived from the partial melting of mafic lower crustal caused by the underplating of basaltic magma on the island-arc or active continental margin before plate collision. The magmatism of the Dajiagou deposit occurred in active continental margin setting associated with the westward subduction of the paleo-Pacific plate beneath Eurasian Plate during the early Jurassic of Mesozoic period. Full article