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The ages of Carlin-type gold deposits in the Golden Triangle of South China have long been questioned due to the general lack of minerals unequivocally linked to gold deposition that can be precisely dated using conventional radiogenic isotope techniques. Recent advances in U-Pb methods show that calcite can be used to constrain the ages of hydrothermal processes, but few studies have been applied to ore deposits. This approach can be used to constrain the timing of hydrothermal activity that generated and overprinted the giant Shuiyindong Carlin-type gold deposit in the Golden Triangle. Three stages of calcite (Cal-1, Cal-2, and Cal-3) have been recognised in this deposit based on crosscutting relationships, cathodoluminescence colours, and chemical (U, Pb, and rare earth element) and isotope (C, O, Sr) compositions. U-Pb isotope analysis, by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for U-rich Cal-1 and Cal-2 and by LA-multicollector (MC)-ICP-MS for U-poor Cal-3, yield well-defined age constraints of 204.3 to 202.6, 191.9, and 139.3 to 137.1 Ma for Cal-1, Cal-2, and Cal-3, respectively. These new ages suggest that the Shuiyindong gold deposit formed in the late Triassic (associated with the late Triassic Indochina orogeny) and was overprinted by hydrothermal events in the early Jurassic and early Cretaceous palaeo-Pacific plate subduction., The ages of Carlin-type gold deposits in the Golden Triangle of South China have long been questioned due to the general lack of minerals unequivocally linked to gold deposition that can be precisely dated using conventional radiogenic isotope techniques. Recent advances in U-Pb methods show that calcite can be used to constrain the ages of hydrothermal processes, but few studies have been applied to ore deposits. This approach can be used to constrain the timing of hydrothermal activity that generated and overprinted the giant Shuiyindong Carlin-type gold deposit in the Golden Triangle. Three stages of calcite (Cal-1, Cal-2, and Cal-3) have been recognised in this deposit based on crosscutting relationships, cathodoluminescence colours, and chemical (U, Pb, and rare earth element) and isotope (C, O, Sr) compositions. U-Pb isotope analysis, by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for U-rich Cal-1 and Cal-2 and by LA-multicollector (MC)-ICP-MS for U-poor Cal-3, yield well-defined age constraints of 204.3 to 202.6, 191.9, and 139.3 to 137.1 Ma for Cal-1, Cal-2, and Cal-3, respectively. These new ages suggest that the Shuiyindong gold deposit formed in the late Triassic (associated with the late Triassic Indochina orogeny) and was overprinted by hydrothermal events in the early Jurassic and early Cretaceous palaeo-Pacific plate subduction.

Dongping is the largest Au-Te vein deposit (ca. 120 t Au) in the North China craton, but its age, origin, and setting remain unsolved. Gold mineralisation at Dongping is hosted in the Shuiquangou alkaline complex (ca. 401–390 Ma) and dominated by quartz-sulphide veins with minor ores in adjacent alteration envelopes. Andradite to grossular garnets are recognised in pre-, syn-, and post-ore quartz veins as well as mineralised alteration envelopes and are closely associated with a variety of ore and gangue minerals. The paragenetic, textural, fluid inclusion, and compositional data suggest that garnets precipitated directly from a low-salinity fluid at 302 to 383 degrees C and 90 to 330 bar. Garnets from various veins and alteration envelopes have similar U contents ranging from 0.80 to 13.89 mg/kg and yield reproducible U-Pb dates of 142 ± 5 to 139 ± 6 Ma by LA-ICP-MS. The dating results suggest that gold mineralisation at Dongping occurred in the Early Cretaceous and thus preclude a genetic link between Au-Te mineralisation and the ore-hosting alkaline intrusion as commonly suggested. When combined with independent geologic, geochemical, and geochronological studies, the new garnet U-Pb dates classifies the Dongping Au-Te deposit as an oxidised intrusion-related gold deposit, with the causative magma likely derived from melting of an ancient enriched lithospheric mantle source due to destruction of the subcontinental lithospheric keel beneath the North China craton, a catastrophic event induced by the westward subduction of the Palaeo-Pacific plate. This study highlights garnet U-Pb dating as a potential robust geochronometer for gold vein deposits elsewhere., Dongping is the largest Au-Te vein deposit (ca. 120 t Au) in the North China craton, but its age, origin, and setting remain unsolved. Gold mineralisation at Dongping is hosted in the Shuiquangou alkaline complex (ca. 401–390 Ma) and dominated by quartz-sulphide veins with minor ores in adjacent alteration envelopes. Andradite to grossular garnets are recognised in pre-, syn-, and post-ore quartz veins as well as mineralised alteration envelopes and are closely associated with a variety of ore and gangue minerals. The paragenetic, textural, fluid inclusion, and compositional data suggest that garnets precipitated directly from a low-salinity fluid at 302 to 383 degrees C and 90 to 330 bar. Garnets from various veins and alteration envelopes have similar U contents ranging from 0.80 to 13.89 mg/kg and yield reproducible U-Pb dates of 142 ± 5 to 139 ± 6 Ma by LA-ICP-MS. The dating results suggest that gold mineralisation at Dongping occurred in the Early Cretaceous and thus preclude a genetic link between Au-Te mineralisation and the ore-hosting alkaline intrusion as commonly suggested. When combined with independent geologic, geochemical, and geochronological studies, the new garnet U-Pb dates classifies the Dongping Au-Te deposit as an oxidised intrusion-related gold deposit, with the causative magma likely derived from melting of an ancient enriched lithospheric mantle source due to destruction of the subcontinental lithospheric keel beneath the North China craton, a catastrophic event induced by the westward subduction of the Palaeo-Pacific plate. This study highlights garnet U-Pb dating as a potential robust geochronometer for gold vein deposits elsewhere.

Precise constraints on the source and evolution of ore-forming fluids of Carlin-type gold deposits in the Golden Triangle are of critical importance for a better understanding of the ore genesis and a refined genetic model for gold mineralisation. However, constraints on the source of ore fluid components have long been a challenge due to the very fine grained nature of the ore and gangue minerals in the deposits. Here, He, Ne, and Ar isotope data are presented of fluid inclusion extracts from a variety of ore and gangue minerals (arsenian pyrite, realgar, quartz, calcite, and fluorite) representing the main and late ore stages of three well-characterised major gold deposits (Shuiyindong, Nibao, and Yata). Measured He isotopes have R/RA ratios ranging from 0.01 to 0.4 that suggest a maximum of 5% mantle helium with an R/RA of 8. The Ne and Ar isotope compositions are broadly comparable to air-saturated water, with a few analyses indicating the presence of an external fluid containing nucleogenic 38Ar and radiogenic 40Ar. The main ore-stage fluids are interpreted as a mixture of magmatic fluid containing mantle He and sedimentary pore fluid or deeply sourced metamorphic fluid with predominantly crustal He, whereas the late ore-stage fluids are a mixture of sedimentary pore fluid or deeply sourced metamorphic fluid bearing crustal He and shallow meteoric groundwater containing atmospheric He. Results presented here, when combined with independent evidence, support a magmatic origin for the ore-forming fluids. The ascending magmatic fluid mixed with sedimentary pore fluid or deeply sourced metamorphic fluid in the ore stage and subsequently mixed with the meteoric groundwater in the late ore stage, eventually producing the Carlin-type gold deposits in the Golden Triangle., Precise constraints on the source and evolution of ore-forming fluids of Carlin-type gold deposits in the Golden Triangle are of critical importance for a better understanding of the ore genesis and a refined genetic model for gold mineralisation. However, constraints on the source of ore fluid components have long been a challenge due to the very fine grained nature of the ore and gangue minerals in the deposits. Here, He, Ne, and Ar isotope data are presented of fluid inclusion extracts from a variety of ore and gangue minerals (arsenian pyrite, realgar, quartz, calcite, and fluorite) representing the main and late ore stages of three well-characterised major gold deposits (Shuiyindong, Nibao, and Yata). Measured He isotopes have R/RA ratios ranging from 0.01 to 0.4 that suggest a maximum of 5% mantle helium with an R/RA of 8. The Ne and Ar isotope compositions are broadly comparable to air-saturated water, with a few analyses indicating the presence of an external fluid containing nucleogenic 38Ar and radiogenic 40Ar. The main ore-stage fluids are interpreted as a mixture of magmatic fluid containing mantle He and sedimentary pore fluid or deeply sourced metamorphic fluid with predominantly crustal He, whereas the late ore-stage fluids are a mixture of sedimentary pore fluid or deeply sourced metamorphic fluid bearing crustal He and shallow meteoric groundwater containing atmospheric He. Results presented here, when combined with independent evidence, support a magmatic origin for the ore-forming fluids. The ascending magmatic fluid mixed with sedimentary pore fluid or deeply sourced metamorphic fluid in the ore stage and subsequently mixed with the meteoric groundwater in the late ore stage, eventually producing the Carlin-type gold deposits in the Golden Triangle.