Abstract
The Xialiugou polymetallic deposit is located in the North Qilian Orogenic Belt, Northwest China, of which the main ore-bearing strata are the Middle Cambrian Heicigou Group. The mineralization is zoned with “black” orebodies (galena–sphalerite), which are stratigraphically above the “yellow” orebodies (pyrite–chalcopyrite–tennantite) at the lower zone, corresponding to the alteration assemblages of quartz–sericite in the ore-proximal zone and chlorite in the ore-distal zone. The Xialiugou mineralization can be divided into three stages: (1) Stage I (pyrite); (2) Stage II (chalcopyrite–tennantite–sphalerite); and (3) Stage III (galena–sphalerite). Fluid inclusions data indicate that the physicochemical conditions that lead to ore formation were the medium–low temperature (157–350 °C) and low salinity (0.17–6.87 wt % NaCleqv), and that the ore-forming temperature tended to decrease with the successive mineralization processes. Taking the H–O isotopic compositions (δDV-SMOW = −51.0‰ to −40.5‰, δ18OH2O = −0.4‰ to 8.6‰) into consideration, the ore-forming fluids were most likely derived from seawater with a small amount of magmatic- and meteoric-fluids input. In addition, the combined S (−3.70‰ to 0.10‰) and Pb isotopic (206Pb/204Pb = 18.357 to 18.422, 207Pb/204Pb = 15.615 to 15.687, 208Pb/204Pb = 38.056 to 38.248) data of pyrite indicate that the ore-bearing volcanic rocks may be an important source of ore-forming materials. Finally, we inferred that the Xialiugou deposit shares similarities with the most important volcanogenic massive sulfide (VMS) deposits (Baiyinchang ore field) in China and typical “black ore” type VMS deposits worldwide.
Highlights
Volcanogenic massive sulfide (VMS) deposits are an important source of copper, lead, and zinc [1]
12 deposits have been found in the Guomisi–Bailiugou district located in the western region of the North Qilian OrogenicBelt (NQOB), namely Dongtiegou, Haxionggou, Wuminggou, Xuejigou, Xishanliang, Xialiugou, Wanyanghe, Xiagou, Bailiugoiu, Guomisi, Gadaban and Xiangzigou polymetallic deposits
We present a dataset of the fluid inclusions and H–O–S–Pb isotopes from the Xialiugou deposit, coupled with field and alteration/mineralization constrain the Xiaotieshan orebodies withobservations metal reserves of 1.14 Mt Cu + Zn + paragenesis, Pb, and the to Tongchanggou origin of theare new studies can provide insight into the occur ore-forming orebodies) associated with These the intermediate-felsic volcanicbetter rocks, and mostly in the processes in the eastern NQOB [5,7,11,21]
Summary
Volcanogenic massive sulfide (VMS) deposits are an important source of copper, lead, and zinc [1]. Previous studies on various Paleozoic to Cenozoic VMS deposits have revealed their most significant features, which primarily include: (1) an extensional geotectonic environment for their formation such as midocean ridges, back-arc basins, continental rifts and island-arcs [2]; (2) zonation from a layered massive sulfide unit to a footwall stockwork mineralization zone [3,4]; (3) extensive and intensive proximal alteration assemblages including quartz, chlorite, white mica (sericite) and pyrite [2,4], (4) moderate-temperature ore-forming fluids derived from heated seawater leaching into the surrounding and underlying volcanic rocks and/or magmatic–hypothermal fluids [2,4]. The Qilian Block in the south (Figure 1a) It is well-known for its abundant metal resources, especially the Early Paleozoic copper polymetallic deposits [5,6,7,8,9]. The ore-forming psychochemical conditions in which the ores are formed and the ore-forming material sources have not been effectively elucidated [10,12,16], meaning that the genesis of ores is unclear
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