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Fang W.-X.,China University of Geosciences | Fang W.-X.,Sino Technology Mineral Exploration Joint stock Company | Huang Z.-Y.,China University of Geosciences
Geology in China | Year: 2012

The studied apart-pull basin was formed during the oblique-direction subduction and collision of the Huabei and Yangtze Plates. The tectonic deformation history, styles, dynamics, records of tectonic lithofacies and large-scale migration of fluids in the apart-pull basin constitute some of the most important problems in the continental dynamics, and the study of these problems are helpful to the detailed investigation of the mineralization regularity and the controlling factors of polymetallic deposits, Carlin-type gold deposits and similar ore deposits in the West Qinling orogeny. The Late Paleozoic apart-pull basin in Shaanxi is the high-density area which hosts not only Sedex-type polymetallic deposits but also Carlin-type gold deposits and similar deposits. Tectonic deformation history, styles and dynamics of the Fengxian-Taibai apart-pull basin and the driving factors of fluid migration in the basin were studied by the authors based on the tectonic lithofacies. Sequences of tectonic deformation for the apart-pull basin have been classified into three main deformation stages although it has more complicated tectonic deformation history. The first stage was tectonic inversion and superimposition of hydrothermal fluid in Carboniferous-Middle Triassic period (DS1), the second stage was compressive and shrinking deformation of the basin, faulting and folding, hydrothermal superimposition by magmatic intrusion, and brittle-ductile shear deformation (DS2) during the Indo-China main orogeny resulting from the full-scale continent-continent collusion, and the third stage was tectonic taphrogeny and brittle compressed deformation of the basin during the Yanshanian intracontinent orogeny (DS3). Styles of tectonic inversion and superimposition of hydrothermal fluids during the Carboniferous-Middle Triassic period (DS1) included layering shear rheology tectonics, zone of hydrothermal brecciation, and hydrothermal fluid superimposed lithofacies in the Devonian fill-up of the basin. At the same time, Wenjiangsi-Liufengguan apart-pull and taphrogeny basin of the second-order was formed in the southern part of the basin. Inside the apart-pull basin, associations of tectonic styles are composed of multiple folds and compression-shear faults, brittle-ductile shear zone, thrusting-napping structure, recoil faults and up-recoil-ramp fault. However, thrusting-napping fault zones with the ramp-faulting style in conversion direction were formed on both sides of the apart-pull basin. These deformation tectonic associations resulted in driving force for the basin fluid in the apart-pull basin, and coupled with regional hydrothermal fluid superimposition with stable hydrothermal field supported by Xiba compound medium-acidic magmatic intrusion in the eastern part of the apart-pull basin. Different styles of tectonic deformation might have had different controlling roles in localization of gold and polymetallic deposits in the apart-pull basin. Polymetallic deposits were probably mainly controlled by "M-W"- type multiple anticline-fault associations. However, zonation of gold and polymetallic deposits was controlled by the ramp-faulting area of up-ramp-faulting style. The Carlin-type and similar gold deposits were controlled by "W-M"-type multiple syncline plus brittle-ductile shear zone. Moreover, the Baguamiao gold deposit characterized by multiple stages of gold mineralization, a deposit similar to Carlin -type gold deposit, was controlled by overturned syncline and brittle-ductile shear zone, while the Wenjiangsi gold deposit, a Carlin-type gold deposit, was controlled by syncline and brittle fault zone.

Lu J.,Kunming University of Science and Technology | Lu J.,Sino Technology Mineral Exploration Joint stock Company | Fang W.X.,Kunming University of Science and Technology | Fang W.X.,Sino Technology Mineral Exploration Joint stock Company
Advanced Materials Research | Year: 2014

Through the work of measuring magnetic susceptibility of the cores in Yinmin mining area, Yunnan, one can draw a conclusion that different strata have different magnetic susceptibility, and variations of magentic susceptibility as a whole have significant changes, concerned primarily with mafic ferruginous lava, iron ore, ferruginous dolomite and fine grained diabase in the Luoxue Group and the Yinmin Group. The study of magnetic susceptibility of the rocks is not only relevant to magnetic prospecting and the boreholetricomponent magnetic, but also a rapid and effective means of geological exploration for the iron-oxide copper gold (IOCG) deposit in Yinmin mining area. © (2014) Trans Tech Publications, Switzerland.

Fang W.,Sino Technology Mineral Exploration Joint stock Company | Fang W.,Kunming Sino Technology Mineral Exploration LLC | Yang X.,Sino Technology Mineral Exploration Joint stock Company | Guo M.,Sino Technology Mineral Exploration Joint stock Company | And 3 more authors.
Geotectonica et Metallogenia | Year: 2013

Low-Ti iron oxide Cu-U-Au-REE deposits commonly consist of low-titanium iron ore containing variable amounts of copper, uranium, gold, and rare earth elements. However, high-Ti iron oxide Cu-Au-Ag-REE deposits were found in Yunnan and Sichuan provinces, southwestern of China. Based on petrography, geochemistry of major and trace elements, and zircon U-Pb dating, we delineated the relationships between the alkaline Ti-Fe-rich gabbros and the IOCG deposit found recently in the Baixila ore district in Yunnan province, China. Firstly, petrofacies-logging for the gabbros were done in detail for the No. 59, 179, and 219 exploration profiles at the 2360 m-shafts underground in the Baixila ore district in order to study the gabbros hosting the IOCG or otherwise. Secondly, lithofacies analysis and re-mapping were completed in office study based on the new comprehensive study methods, which include geochemical lithofacies for the rocks and ores, trace element concentrations, and mineralogy of the artificial heavy-mineral-concentrates. Thirdly, the zircons were separated from the gabbros in the Baixila ore district, and then, CL images were used to identify the metamict zircons (ZS02, ZS03 and ZS04) and pristine zircons (ZS01) from the gabbros in the Baixila ore district. Finally, SHRIMP zircon U-Pb dating was carried out. Alkaline Ti-Fe-rich gabbros in the Baixila ore district in Yunnan province, which are closely related to the iron-oxide copper-gold (IOCG) deposits, are obviously lithofacies zonated. On the contrary, the barren alkaline Ti-Fe-rich gabbros are lack of petrofacies zonation. In fact, the iron-oxide copper-gold deposit found recently was controlled by the alkaline Ti-Fe-rich gabbros with obvious lithofacies zonation, and particularly the cryptoexplosion breccia of the gabbros. The alkaline Ti-Fe-rich gabbros are characterized by low Si, and high alkaline, P, Ti-Fe, LILE, REE, and HFSE, which are similar to those of the OIBs derived from the Fe-rich mantle source. It may be supposed that the alkaline Ti-Fe-rich gabbros in this study area could be derived from the intra-plate ocean island basalt. Geodynamically, metasomatism of Fe-rich mantle melting fluid might have resulted in the upwelling of the alkaline Ti-Fe-rich gabbros. SHRIPM Zircon U-Pb dating indicated that the alkaline Ti-Fe-rich gabbros and IOCG were formed at 1067±20 Ma~1047±15 Ma, i.e., the Late Mesoproterozic (Stenian Period). The alkaline Ti-Fe-rich gabbros and IOCG in the Baixila ore district might have been formed in the syn-orogenic magmatic-tectonic event during the Grenville orogeny. They implied that IOCG metallogenic zone from the Baixila Fe-Cu ore district to the Tangdan copper-iron ore district, the east-west-trending magmatic-tectonic zone in the study area, might have attached to the syn-orogenic magmatic-tectonic event in the Grenville orogeny. In summary, this type of Fe-rich mantle source in the Baixila ore district, Yunnan province, China, might supply the abundant metallogenic materials for large-scale accumulations of iron and copper metals. It might have been the excellent metallogenic environments not only for large to superlarge iron-oxide copper-gold (IOCG) deposits, but also for the formation of titanic iron ores and copper-sulfide-PGE deposits.

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