Geological, geochronological, and H-O isotopic constraints on the genesis of the Tongjing Cu-Au deposit in the Ningwu basin, east China

The Tongjing Cu-Au deposit is a medium-sized deposit within the Ningwu volcanic basin, east China, and is hosted by Cretaceous volcanic rocks of the Dawangshan and Niangniangshan Formations. The veined and lenticular Cu-Au orebodies are spatially and temporally related to the volcanic and subvolcanic rocks of the Niangniangshan Formation in the ore district The wall-rock alteration is dominated by silicification, siderite alteration, carbonation, sericitization, chloritization, and kaolinization. On the basis of field evidence and petrographic observations, two stages of mineralization are recognized: (1) a siderite-quartz-sulfide stage (Stage 1) associated with the formation of chalcopyrite and pyrite in a quartz and siderite gangue; and (2) a quartz-bornite stage (Stage 2) cutting the Stage 1 phases. Stage 1 is the main mineralization stage. Quartz that formed in Stage 1 has delta O-18(H2O) values of -4.3%. to 3.5 parts per thousand with delta D values of fluid inclusion waters of -97.1 parts per thousand to -49.9 parts per thousand, indicating that the ore-forming fluids were derived from early magmatic fluids and may have experienced oxygen isotopic exchange with meteoric water during Stage 1 mineralization. LA-MC-ICP-MS zircon U-Pb dating of the mineralization-related nosean-bearing phonolite and nosean-bearing phonolitic brecciated tuff at Tongjing yields ages of 129.8 +/- 0.5 Ma and 128.9 +/- 1.1 Ma, respectively. These results are interpreted as the crystallization age of the volcanic rocks of the Niangniangshan Formation. A hydro thermal sericite sample associated with Cu-Au mineralization at Tongjing yields a plateau 40Ar-39Ar age of 131.3 +/- 1.3 Ma. These results confirm a genetic link between the volcanisrn and associated Cu-Au mineralization. The Tongjing Cu-Au deposit in the Ningwu basin is genetically and possibly tectonically similar to alkaline intrusion-related gold deposits elsewhere in the world. (C) 2016 Elsevier B.V. All rights reserved. The Tongjing Cu-Au deposit is a medium-sized deposit within the Ningwu volcanic basin, east China, and is hosted by Cretaceous volcanic rocks of the Dawangshan and Niangniangshan Formations. The veined and lenticular Cu-Au orebodies are spatially and temporally related to the volcanic and subvolcanic rocks of the Niangniangshan Formation in the ore district The wall-rock alteration is dominated by silicification, siderite alteration, carbonation, sericitization, chloritization, and kaolinization. On the basis of field evidence and petrographic observations, two stages of mineralization are recognized: (1) a siderite-quartz-sulfide stage (Stage 1) associated with the formation of chalcopyrite and pyrite in a quartz and siderite gangue; and (2) a quartz-bornite stage (Stage 2) cutting the Stage 1 phases. Stage 1 is the main mineralization stage. Quartz that formed in Stage 1 has delta O-18(H2O) values of -4.3%. to 3.5 parts per thousand with delta D values of fluid inclusion waters of -97.1 parts per thousand to -49.9 parts per thousand, indicating that the ore-forming fluids were derived from early magmatic fluids and may have experienced oxygen isotopic exchange with meteoric water during Stage 1 mineralization. LA-MC-ICP-MS zircon U-Pb dating of the mineralization-related nosean-bearing phonolite and nosean-bearing phonolitic brecciated tuff at Tongjing yields ages of 129.8 +/- 0.5 Ma and 128.9 +/- 1.1 Ma, respectively. These results are interpreted as the crystallization age of the volcanic rocks of the Niangniangshan Formation. A hydro thermal sericite sample associated with Cu-Au mineralization at Tongjing yields a plateau 40Ar-39Ar age of 131.3 +/- 1.3 Ma. These results confirm a genetic link between the volcanisrn and associated Cu-Au mineralization. The Tongjing Cu-Au deposit in the Ningwu basin is genetically and possibly tectonically similar to alkaline intrusion-related gold deposits elsewhere in the world. (C) 2016 Elsevier B.V. All rights reserved.