Cu ∼68,000 t @ 1.5%; Zn ∼59,000 t @ 2.0%
Skarn type

The local geology at the Longtougang deposit is relatively simple, dominated by metamorphic rocks of the Mesoproterozoic Zhoutianyan Formation and sedimentary rocks of the Upper Carboniferous Outangdi Formation. The former crops out in the northeastern and southwestern parts of the ore district, whereas the latter crops out in a roughly NW-trending belt and is about 400-m-thick. Rocks of the Upper Carboniferous Outangdi Formation rest unconformably on the Mesoproterozoic Zhoutianyan Formation to the south, whereas thrust faults separate the two units to the north. The Zhoutianyan Formation is composed of biotite–plagioclase granulite, plagioclase amphibolites, and sericite–quartz schist. The Upper Carboniferous Outangdi Formation is dominated by sandstones, which are interbedded with limestones that have been partially metamorphosed to marble or metasomatized to skarn close to the contact with plutons. Five belts of mineralization are exposed in the deposit area, including six steeply and seven gently dipping orebodies, most of which are hosted by rocks of the Upper Carboniferous Outangdi Formation. The mineralization is zoned, with a lower zone of Cu-rich veins and Cu–Zn skarns and an upper zone of bands of Zn–Pb mineralization in massive epidote altered rocks. The mineralization styles can be subdivided into vein, skarn, and carbonate-hosted mineralization.
The vein orebodies are dominant, enriched in Cu ores, and generally crosscut both skarns and marble. The largest economic orebody is the II-1 orebody, which is about 600-m-long and 10-m-wide, and contains Cu ore in quartz gangue. In addition, disseminated Cu ores are present in wall rocks surrounding the veins. Skarn orebodies are subdivided into pyroxene skarn associated mainly with Cu–Zn mineralization and epidote alteration associated mainly with Zn–Pb mineralization. The banded Zn–Pb ores, associated with epidote alteration, mainly contain sphalerite and galena. Carbonate-hosted orebodies contain Cu–Zn–Pb bands and account for a minor proportion of the total ore. The parallel Cu–Zn–Pb bands are generally present as 2- to 5-cm-wide zones. The hypogene ore-forming events at the Longtougang deposit can be divided into four stages. These include 1) formation of pyroxene, garnet, and epidote skarn; 2) retrograde alteration of the skarn; 3) the filling of fractures and alteration of surrounding rocks by metal-rich fluids; and galena and sphalerite in banded ores (Fig. 5e); and 4) calcite, quartz, galena, sphalerite, pyrite, and chalcopyrite deposited during carbonate alteration. Subsequent supergene events formed malachite and limonite.

Other Regions, Features and Areas containing this locality

References