New constraints on the genesis of the giant Dayingezhuang gold (silver) deposit in the Jiaodong district, North China Craton

Abstract

Abstract The Dayingezhuang gold (silver) deposit in the Jiaodong district, eastern margin of North China Craton, is hosted in the NE to NNE-trending Zhaoping Fault along the contact between Precambrian metamorphic rock (Jiaodong Group) and Mesozoic intrusion (Linglong granite). Although many studies have addressed the genesis of this deposit, the mineralization age, the sources of ore-forming fluids and materials, the ore genesis is still controversial, particularly on the relationship between Au and Ag. In this paper, new dating and in-situ isotopic data are presented to provide tight constraints on the timing and ore-forming processes of the Dayingezhuang deposit. Mineral assemblages of Dayingezhuang deposit can be divided into four stages: the quartz-pyrite stage (I), the Au-bearing quartz-siderite-pyrite stage (II), the Ag-bearing quartz-siderite-polymetallic sulfide stage (III), and the quartz-carbonate stage (IV). The Ag mineralization is texturally later than the gold mineralization, and only develops locally in the orebody I. Sericite from sulfide-bearing ores has a 40Ar/39Ar plateau age of 119.1\u202f±\u202f1.2\u202fMa, and pre-ore mafic dikes yield a zircon U-Pb age of 122.7\u202f±\u202f2.6\u202fMa. The new dating results consistently indicate that the Dayingezhuang deposit formed at ~120\u202fMa and is synchronous with the regional gold mineralization event in the Jiaodong district. The C and O isotopic values of siderite and calcite from stage II to IV vary from −5.4 to −2.2‰ (δ13CV-PDB) and 7.8 to 12.1‰ (δ18OV-SMOW), respectively, and the calculated values of them for ore-forming fluids are −7.1 to −2.9‰ and −4.1 to 5.7‰, respectively. The δ34SCDT values of pyrite from stage I to III range from 4.8 to 9.0‰. Pyrite from stage I to III has 206Pb/204Pb values of 17.181–17.339, 207Pb/204Pb of 15.414–15.504, 208Pb/204Pb of 37.729–37.984. These isotopic results combined with geological and geochronological evidence collectively indicate that the ore-forming fluids and metals of Dayingezhuang were mainly derived from the deep mantle-derived magma typically represented by intermediate-mafic dikes, and mixed with meteoric water subsequently. These data also indicate that the stage III Ag mineralization was not a late event independent from the stage I and II Au mineralization. The Dayingezhuang deposit may not be related to the activation of detachment faults around the Linglong massif at 130\u202f±\u202f4\u202fMa as previously suggested, but a product of the destruction of NCC accompanied with the crust-mantle interaction and lithospheric thinning at ~120\u202fMa.