Geologic Characteristics Of The SEDEX Lead-Zinc Deposits In North Eastern Margin Of Lanping Basin And Metallogenetic Prognosis

Lanping Basin is one of the most important polymetallic Deposit zones in "Sanjiang" metallog enic belt,China. there is great potential for exploration. Sanhedong Group limestone which is near the Weixi-Qiaohou fault at the north eastern margin of the Lanping basin, output of a series of medium-sized Pb-Zn deposits, and mineralization has great vision. Genesis type of the lead-zin c deposits in the area is uncertain, Research work for the genesis of these Pb-Zn deposit is very i mportant,which can provide a theoretical basis for regional metallogenic regularity and exploratory forecast. Based on the field investigation of Qingdianwan-Caizidi Pb-Zn deposits, and the data coll ection and analyzed indoor, microscope identification of slices, electron microprobe analysis, stable isotope analysis and trace rare earth elements in ore and mineral analysis,The writer obtain the foll owing conclusions:1. The main ore bodies of Qingdianwan-Caizid Pb-Zn deposits are layered, stratiform or lentic ular in the Upper Sanhedong Group limestone, strictly contr-olled by the formation. A large numbe r of typical signs of the synsedimentary deposit are founded such as:laminated structure,striped b and structure, the soft sedimentary pyrite band structure, strawberry-like structure,colloidal structure of pyrite, sphalerite concentric structure et al.2. Sulfide in the hand specimen and slices are fine-grained reflecting the characteristics of ra pid deposition. Mineral composition is simple.There are sphalerite +galena+pyrite+arsenopyrite+dolo mite+calcite+barite+quartz. Components of the electron microprobe analysis of sulfide, sphalerite, p yrite, galena compositional types reflect the characteristics of sedimentary origin.3. S isotopic compositions of Qingdianwan depositsδ34S‰values range from 3.7～10‰, range of only 6.3‰, an average of 6.55‰(N= 14), and sulfur mainly from the inorganic redu ction of seawater sulfate. REE composition of ores and minerals:low total REE, LREE enrichment and positive Eu anomalies,reflecting the characteristics of Sedimentary Exhalative Deposit.4. comprehensive comparison of the Qingdianwan-Caizidi deposits to MVT and SEDEX deposi-ts educe that Qingdianwan-Caizidi Pb-Zndeposit is Sedimentary Exhalative Deposit.5. According to SEDEX mineralization characteristics, extracted Sanhedong group from the dis tribution of basin, combine to geochemical anomalies within the basin, carved out of a combinatio n of Pb-Zn anomalies Sanhedong groups are distributed, as prospecting areas.