The Shuangwang gold deposit, located in the Fengxian-Taibai fore-arc basin in the western Qinling Orogen of Central China, has yielded over 70 tons of gold. It is an orogenic gold deposit occurring in an NW-trending b...The Shuangwang gold deposit, located in the Fengxian-Taibai fore-arc basin in the western Qinling Orogen of Central China, has yielded over 70 tons of gold. It is an orogenic gold deposit occurring in an NW-trending breccia belt. Most of the ores are hydrothermal breccia type containing fragments of adjacent strata cemented by ankerite and pyrite. Pyrite is the most abundant metallic mineral and the major gold-bearing mineral in the ores. A total of 58 pyrite samples from main ore bodies of the Shuangwang gold deposit have been analysed for 44 trace elements by HR-ICP-MS. Sb, Ba, Cu, Pb, Zn, Bi, Mo, Co are selected as indicator elements to investigate the potential usefulness of trace elements in pyrite as an indicator in gold exploration. The results show that the supra-ore halo elements Sb and Ba, which may have been more active than other near-ore halo elements and sub-ore halo elements, are best to characterize the shape of ore bodies. Five target areas are pointed out for deep ore exploration based on a comprehensive study of supra-ore, near-ore and sub-ore halos. This study provides evidence that trace elements in pyrite can be used to depict the deep extension of ore bodies and to vector towards undiscovered ore bodies.展开更多
Macro-microscopic tectonic analysis and lithologic features show that the gold-bearing breccia bodies in the Shuangwang gold deposit, for hydrofracturing of the deep-sourced and alkali-rich fluids in the Devonian sodi...Macro-microscopic tectonic analysis and lithologic features show that the gold-bearing breccia bodies in the Shuangwang gold deposit, for hydrofracturing of the deep-sourced and alkali-rich fluids in the Devonian sodic rock series, are identified as hydrofracturing breccia bodies. Since the Indosinian, intracontinental collisional orogenesis results in multiple fracturings and magmatic emplacements in the Qinling area. Deep-sourced fluids resulting from deep fractures and granitoid magmatic intrusion are of a supercritical nature. Joint action between the fluid-rock system and structures leads to hydrofracturing and ore formation of the gold deposit. Firstly, the progressive coaxial compression caused the competent sodic rock series and the incompetent pelitic rock series to be deformed and partitioned. Lens-like weak-strain domains are hence formed and distributed at the approximate equidistance zones and the linear strong-strain zones, respectively. Subsequently, the progressive non-coaxial shearing and right-lateral and high-angle oblique thrusting lead to the most developed fracture system in the core of the weak-strain domain to turn from compression to extension and to link up with the deep fracture systems. The periodical huge pressure decline in the pumping center causes the deep-sourced confined fluids to develop periodic tectonic pumping, hydrofracturing and precipitation-healing in the sodic rock series. The gold-bearinghydrofracturing breccia bodies are hence ultimately formed at near-equidistance tectonic lenses. On the basis of the above model, the predicted concealed gold-bearing hydrofracturing breccia bodies have been preliminarily validated by latest drillings.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41230311,41272106,41030423)the Special Program on Mineral Resources Survey from CGS(No.1212011220923)
文摘The Shuangwang gold deposit, located in the Fengxian-Taibai fore-arc basin in the western Qinling Orogen of Central China, has yielded over 70 tons of gold. It is an orogenic gold deposit occurring in an NW-trending breccia belt. Most of the ores are hydrothermal breccia type containing fragments of adjacent strata cemented by ankerite and pyrite. Pyrite is the most abundant metallic mineral and the major gold-bearing mineral in the ores. A total of 58 pyrite samples from main ore bodies of the Shuangwang gold deposit have been analysed for 44 trace elements by HR-ICP-MS. Sb, Ba, Cu, Pb, Zn, Bi, Mo, Co are selected as indicator elements to investigate the potential usefulness of trace elements in pyrite as an indicator in gold exploration. The results show that the supra-ore halo elements Sb and Ba, which may have been more active than other near-ore halo elements and sub-ore halo elements, are best to characterize the shape of ore bodies. Five target areas are pointed out for deep ore exploration based on a comprehensive study of supra-ore, near-ore and sub-ore halos. This study provides evidence that trace elements in pyrite can be used to depict the deep extension of ore bodies and to vector towards undiscovered ore bodies.
基金the 305 State Key Sci&Tech Program(Grant No.2003BA612A-06-01)the Key Innovation Oriented Program(GrantNo.KZCX3-SW-137)of the Chinese Academy of Sciences.
文摘Macro-microscopic tectonic analysis and lithologic features show that the gold-bearing breccia bodies in the Shuangwang gold deposit, for hydrofracturing of the deep-sourced and alkali-rich fluids in the Devonian sodic rock series, are identified as hydrofracturing breccia bodies. Since the Indosinian, intracontinental collisional orogenesis results in multiple fracturings and magmatic emplacements in the Qinling area. Deep-sourced fluids resulting from deep fractures and granitoid magmatic intrusion are of a supercritical nature. Joint action between the fluid-rock system and structures leads to hydrofracturing and ore formation of the gold deposit. Firstly, the progressive coaxial compression caused the competent sodic rock series and the incompetent pelitic rock series to be deformed and partitioned. Lens-like weak-strain domains are hence formed and distributed at the approximate equidistance zones and the linear strong-strain zones, respectively. Subsequently, the progressive non-coaxial shearing and right-lateral and high-angle oblique thrusting lead to the most developed fracture system in the core of the weak-strain domain to turn from compression to extension and to link up with the deep fracture systems. The periodical huge pressure decline in the pumping center causes the deep-sourced confined fluids to develop periodic tectonic pumping, hydrofracturing and precipitation-healing in the sodic rock series. The gold-bearinghydrofracturing breccia bodies are hence ultimately formed at near-equidistance tectonic lenses. On the basis of the above model, the predicted concealed gold-bearing hydrofracturing breccia bodies have been preliminarily validated by latest drillings.
