As stated above, the Hongqiling Cu-Ni deposit consists of the No.1 and No.7 orebodies. Cu–Ni sulfide ores are hosted in the olivine websterite unit and the No. 1 orebody contains 15,200 t of Cu and 71,600 t of Ni, based upon average ore grades of 0.54% Ni and 0.11% Cu [21
]. The No.7 orebody is hosted in the orthopyroxenite, norite and peridotite units and contains 204,000 t of Ni and 39,000 t of Cu, based upon the average ore grades of 2.30% Ni and 0.63% Cu [21
]. In addition, 3,100 t of Co may be recovered as by-products [21
Mineralogically, the ore minerals of the Hongqiling Cu-Ni deposit are dominantly pyrrhotite, pentlandite, chalcopyrite, violarite, pyrite, valleriite, millerite, nickeline, ilmenite, galena and magnetite, and the gangue minerals are olivine, pyroxene, plagioclase, hornblende, biotite, chlorite and serpentine.
The textures of the ore minerals include euhedral, subhedral, anhedral, subhedral-anhedral, gabbroic, poikilitic, reaction rim, sideronitic, interstitial and corrosion textures, and the ore structures are mainly massive, disseminated, sparsely disseminated, spotted and banded.
Based on cross-cutting relationships between minerals and mineral assemblages, mineralization in the Hongqiling orebody can be subdivided into the following three stages (Figure 4). The first is the magmatic crystallization
stage, characterized by disseminated and massive ores with pentlandite+violarite+millerite+magnetite. The second is the auto-metamorphic stage that is characterized by the formation of massive and vein-like high grade Cu and Ni ores, and forming Cu- and Ni-bearing minerals, represented by chalcopyrite and pyrrhotite. The third is the magmatic–hydrothermal stage that is characterized mainly by chlorite and carbonate alteration, forming the carbonate+pyrite+chalcopyrite assemblage that occurs as veins.
Wall–rock alteration related to mineralization
in the Hongqiling Cu–Ni ore deposit includes chloritization, carbonatization, serpentinization, talcization, uralitization, sericitization, tremolitization [23
]. Characteristic minerals in the alteration zones are talc, chlorite, serpentine, sericite and carbonate.