Mineralization And Metallogenic Prognosisof Luping Lead Polymetallic Deposit In Heqing, Yunnan, P.R.C.

Abstract:The Luping lead polymetallic deposits in Heqing, Yunnan is a large deposit found newly at the alkaline-rich porphyry mineralization zone in west edge of Yangtze platform. By studying on reginal geology, mineralizing factors, geological characters, geochemical characters and mineralization of the Luping lead polymetallic deposits, the author builts the mineralization model of the deposit and the general prospecting model, then used them to suggest the exploration targets and carry out prognosis on all targets in Luping area. The main research results are summarized as follows.1.The large Luping lead polymetallic deposits in Heqing located at north area of Beiya gold polymetallic deposits and belonged same mineralizing system concerned to intrusive activity of alkaline-rich quartz syenite porphyry. It occurred in inter-layer fracture zone outside of quartz syenite porphyry with components of lead mainly and silver and gold associated. The large hydrothermal ore-bodies of the deposits spread along axis of Beiya syncline, was a new and important discovery in Beiya gold polymetallic mineralizing system and that proved large-scale layer-like hydrothermal deposits occurred in inter-layer fracture zone around mineralizing center of alkaline porphyry and named Luping Pattern of lead polymetallic deposits.2. The rocks of Beiya Formation were divided to five parts in past research works, but it was divided to upper section consisted of grey middle-thick dolomitic limestone and dolomitic calcarenite and lower section consisted of gravel limestone, argillaceous limestone and bioclastic limestone in this paper. The new system rock divided was easy to conclude mineralizing rules.3. The tectonic activity was intense in the area. Structural features spread closely north-south to northwest and similar to the direction of regional structures. The ore-bodies occurred in inter-layer fracture zones that formed at axis of Beiya-Qinhe syncline spread northwest, which was southern part and subsidiary fracture of Heqing-Songgui complex sync line.4. First research on geochemical charaters of intrusive rocks concerned to mineralizing mainly were beschtauite and quartz syenite porphyry with main elements characteristics of rich contents of Na2O+K2O and A12O3and poor contents of Fe2O3, MnO, P2O5and TiO2, that was very similar to the characteristics of Wandongshan quartz syenite porphyry in Beiya deposit, with trace elements characteristics that partition model of both porphyries were same, enriched LILE and lacked of Nb、Ta、P、Ti, which showed porphyry magma come from island arc magma and with rock isotope geo-chemistry characteristics showed that porphyries formed by melted deep lithosphere and upper mantle together. Mensurated the porphyries age was36.28±1.6Ma and considered that both porphyries and Wandongshan quartz syenite porphyry in Beiya deposit belonged same magma activity system, they just occurred at different space in various shapes.5. The shape of ore-bodies mainly were layer-like and lens-like and occurred gently. The elevation occurred ore-bodies were increased from south to north and ore-bodies became thicker at axis of syncline and became thinner from axis to limbs in latitudinal direction. Vertically, mineralizing elements were zonal characteristic, that were Pb-Zn-Ag zone on the top to Pb-Zn-Ag-Au-Fe zone in the middle to Au-Cu zone at the bottom. Horizontally, it was Pb-Ag-Au-Cu-Fe element component from line23to line15in the south area, Pb-Ag-Au-Fe element component from line11to line42in the middle area, mainly Pb-Ag-Fe element component with decrease of gold element obviously at the north of line50in the deposits.6.The S isotopic composition was very centralized with δ34S value of sulfide from+0.81×10-3to+2.83×10-3in the Luping lead polymetallic deposits and showed obvious Tower Effect, typical character of mantle source sulfer and which was similar to characters of S isotopic composition in Beiya gold polymetallic deposits. The C and O isotopic composition of calcite was correspondingly homogeneous with δ13CPDBvalue of carbon from-5.80×10-3to-5.05×10-3and δ18OSMow value of oxygen from+13.17×10-3to+14.68×10-3in the Luping lead polymetallic deposits and showed obvieously different to the characters of C and O isotopic composition of carbonate rocks and which was similar to characters of C and O isotopic composition of early calcite in Beiya deposit. The characters of S, C and O isotopic composition showed that S in mineralizing fluid came from mantle or deep crust and not from wall rocks, C and O in mineralizing fluid mainly came from mantle or magmatic system but partly from carbonate of wall rocks.7. Lead and gold ore-bodies of the Luping lead polymetallic deposits was the result of hydrothermal fluid from Beiya gold polymetallic deposits moved, diffused and sedimentated along northwest direction of Beiya depositand also the result of high temperature hydrothermal fluid infilling mineralization in outside zone of Wandongshan quartz syenite porphyry mineralization system with the mineralizing temperature of more than300C°. Mineralizing elements come from both mantle and wall-rocks. Considered that genesis of the Luping deposits was porphyry-hydrothermal polymetallic deposits type concerned to alkaline-rich porphyry activated in Himalaya period.8. By concerning the mineralization model of Beiya Pattern of gold polymetallic deposits, the author built the genetic model and exploration model of Luping Pattern of lead polymetallic deposits, provided some exploration targets outside of Qinhe section and predicted there was prospecting potential for large to super-large scale gold and silver deposits, large scale lead deposits and middle scale copper-zinc-iron deposits in the area.