Cu-Bearing Mokama Granite Prospect of the Kibara Belt in the Maniema Province, DRC: A Preliminary Petrography, Geochemistry, and Fluid Inclusion Study

The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is disseminated inside the rock and consists of minerals (Raman, EPMA and metallographic microscopy) including chalcopyrite and bornite that are replaced by chalcocite and covellite, and the last also replaced later by malachite. The chemistry (XRF, LA-ICP-MS) of these peraluminous S-type leucogranites show SiO2 (71 wt% - 79 wt%), ASI (1.4 - 3.1 molar), and are enriched in Rb (681 - 1000 ppm), Ta (12–151 ppm), Sn (43 - 142 ppm), Cu (10 - 4300 ppm), Zn (60 - 740 ppm), U (2.2 - 20.7 ppm) while depleted in Zr (20 - 31 ppm), Sr (20 - 69 ppm), Hf (1.3 - 2.0 ppm), Th (2.2 - 18.9 ppm), W (9 - 113 ppm), Pb (5 - 50 ppm), Ge (5 - 10 ppm), Cs (21 - 53 ppm) and Bi (0.6 - 17.4 ppm) and low ratios of (La/Yb) N, (Gd/Yb) N, (La/Sm) N). Fluid inclusion assemblages (FIAs) hosted in quartz in the Mokama granites show ranges of salinities of 4 - 23 wt% (NaCl equivalent) and homogenization temperatures (Th) of 190°C - 550°C. A boiling assemblage in the granite suggests a fluid phase separation occurred at about 380 - 610 bars, and this corresponds to apparent paleodepths of approximately 1 - 2 km (lithostatic model) or 3 - 5 km (hydrostatic model). FIAs hosted in TOGM such as cassiterite (salinities of 2 wt% - 10 wt% and Th of 220°C - 340°C) helped set up the possible temperature limit of SGM (Cu sulfide) precipitations that are estimated below 200°C.

Genesis of the Xinfang Gold Deposit,Liaodong Peninsula:In-sights from Fluid Inclusions and S-Sr Isotopic Constraints

The North China Craton(NCC)has been continuously reactivated since the Mesozoic and this decratonization is responsible for its economically important gold mineralization in the Meso-zoic.The Early Cretaceous(110-130 Ma)gold mineralization in the NCC has been well-studied due to its significance,but little attention has been given to other episodes of gold mineralization related to polyphased reactivation of the NCC.The Xinfang mesozonal gold deposit(143 Ma)in the Liaodong Peninsula is related to the one of the episodes of the Yanshanian orogeny.The orebodies of the Xin-fang gold deposit were controlled by the low angle transpressive fault systems and hosted by the Neoarchean monzogranitic gneiss.Fluid inclusion microthermometry reveals that the mineralizing temperatures range from 220 to 280℃,with salinities from 6 wt.%NaCl eqv.to 15 wt.%NaCl eqv.,pressures from 199 to 321 Ma.The S isotopic characteristics of sulfides not only record a heterogene-ous source including magmatic or gneissic sulfur but also record inter-mineral isotope fractionation.The initial^(87)Sr/^(86)Sr values of pyrite(0.713480-0.729031)indicate a radiogenic crustal origin for the sources.The metamorphic dehydration of the underlying basement resulted in the genesis of the Xin-fang gold deposit.We summarize three episodes of gold mineralization in the Liaodong Peninsula re-lated to continuous reactivation of the NCC,which indicates a great exploration potential of this area.