Abstract
The large Xinqiao Cu–S–Fe–Au deposit in the Tongling ore district, Eastern China, is characterized by a large-scale stratiform orebody, in which garnet is widely distributed as the main gangue mineral associated with mineralization. Xinqiao garnet can be divided into early (Grt1) and late (Grt2) generations based on extensive back-scattered electron (BSE) imaging observations. Laser ablation (LA)-ICP-MS trace element and U–Pb isotope composition analyses indicate that uranium occurs homogeneously within the Xinqiao garnet, and Grt1 and Grt2 have weighted average 207Pb-corrected 206Pb/238U ages of 137.0 ± 7.8 Ma (Mean standard weighted deviation (MSWD) = 4.9) and 129.6 ± 7.1 Ma (MSWD = 1.6), respectively, similar to the zircon U–Pb age (139.6 ± 1.5 Ma) of the Jitou intrusion. These garnet U–Pb ages, combined with the low MnO content and various Y/Ho ratios, suggest that the Xinqiao garnet is likely to have a magmatic hydrothermal replacement origin associated with the Jitou stock. Based on previous studies of the Xinqiao deposit, we infer that the Xinqiao stratiform orebody may have formed from the Early Cretaceous magmatic hydrothermal fluids associated with the Jitou stock, and may have been generated by the Early Cretaceous tectono-thermal event in Eastern China.
Highlights
Skarn deposits are an abundant ore type and represent a globally important source of Cu, Fe, Pb, Zn, W, Ag, and Au [1,2]
This study focuses on the garnet from the Xinqiao Cu–S–Fe–Au deposit (0.5 Mt Cu @ 0.71%, 75.5 Mt of sulfur @ 29.3%, 24.9 Mt Fe @ 46%, and 11.2 t Au @ 4.7 g/t; [43]) with the aim of constraining its mineralization age by using newly developed garnet U–Pb geochronology based on detailed field and mineralogical observations, discusses its implications on the Xinqiao ore genesis, and further introduces a new dating method for the skarn ore deposit type
A total of 86Element spot analyses for Laser ablation (LA)-ICP-MS trace element compositions were conducted on XQ37-1
Summary
Skarn deposits are an abundant ore type and represent a globally important source of Cu, Fe, Pb, Zn, W, Ag, and Au [1,2]. The direct and precise dating of skarn mineralization is commonly conducted by Re–Os of molybdenite [3,4], U–Pb of titanite [5,6], 40 Ar/39 Ar of micas [7] and K-feldspars [8,9], and Sm–Nd of calcite [10]. Due to the lack of suitable datable minerals, direct dating of skarn-type mineralization is still locally unsuccessful. Garnet is a common mineral in skarn systems [11], and its distinct oscillatory chemical zonation can track the fluid–rock interaction history and provide a continuous physicochemical record of the hydrothermal evolution [12,13,14,15,16,17,18].
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