Research On Isotope Geology Of The Lengshuikeng Ag-Pb-Zn Deposit, Jiangxi Province

The Lengshuikeng Ag-Pb-Zn deposit is located in the south of Yangtze blockand the South China block matching belt，the northeast margin of the South Chinaplate, belong to east china Pacific-rim metallogenic domain, the QinHangmetallogenic belt in the south. Its Ag-Pb-Zn scale is oversize, and associated copperand gold metal with influence in the world. It has a unique style of mineralizationcharacteristics, not only has the typical porphyry-type Ag-Pb-Zn mine body, and thereis a layered silver lead and zinc body, existing stratiform silver lead-zinc mine body.The porphyry-type orebodies is located in three ore block: Yinluling,Baojia,Yiinzhu-shan, the stratiform orebodies buried under the porphyry-type ore body, composingof Yinglin, Xiabao, Yinkeng three ore block.1. The porphyry ore body according to the useful ore components was dividedinto following categories: Ag-Pb-Zn, Cu,Au ore body, Ag-Pb-Zn ore body is the mainpart, copper ore body and gold ore body scattered distribution, they spatialoverlapping output. The Ag-Pb-Zn ore body produced in the frontal zone of graniteporphyry, the main belt and near the contact zone, Cu ore body is produced near theroot of the ore-bearing granite porphyry rock, gold ore body scattered in the lowerpart of the contact zone, consistent with the occurrence of granite porphyry. Mostlylenticular orebodies, the shape is relatively regular, ore-forming temperature is120⁴90°C, ore fabric shaped granular structure fine-grained semi-euhedral, veinletdisseminated structure-based, the rock from center to outside sericitization andchloritization-zone, sericite-carbonate-silicification of pyrite with carbonate-sericite zone, this deposit have the characters that low grade, large-scale. Ore formingmaterials directly come from containing mine granite porphyry which originated from the melting of the crust, belonging to the sub-volcanic hydrothermal mineralization ofthe structure-rock-porphyry-type deposits trinity Ag-Pb-Zn （Cu,Au） ore body.2. The stratiform ore body has completely different characteristics fromporphyry-type ore body, which is strictly controlled by a large set of the volcanicbreccia layer within Jurassic volcanic rocks. The ore body and surrounding rock wasdeposited conformable contact relationship, was bedded rules lenticular beddingoutput, ore-forming temperature is170⁴00°C or lower, with rich ore grade, thicknessand many kinds of useful substances. Most of ore fabrics are fine-grainedsemi-euhedral, accountable structures mainly are brecciated and disseminatedstructure. wall-rock alteration to carbonate, weak sericitization and linearchloritization. The stage of ore forming has experienced a volcanic eruption-sedimentary mineralization and hydrothermal mine period. According to the study onhydrogen-oxygen, carbon-oxygen, sulfur, lead isotope geological of the Xiabao mineore body we consider that:Hydrogen and oxygen isotopes of Iron and manganese carbonate minerals andquartz the δ¹⁸O_矿物value range from1.43¹5.09‰, average in7.48‰; volcaniceruptions-deposition stage with the δ¹⁸O_矿物value changes in the range of7.07¹1.48‰, average in9.63‰; hydrothermal mineralization of the the δ¹⁸O_矿物mineral values in the range of1.43¹5.09‰, average in4.90‰. Volcaniceruptions-the sedimentation of the delta δ¹⁸O_H2Ovalue is2.42⁴.83‰range change,averages1.25‰, hydrothermal ore-forming period delta δ¹⁸O_H2Ovalue is10.25¹1.78‰range change, averages9.09‰; δD_H2Ovalue in the-37.10⁹3.50‰range change, averages65.30‰. The hydrogen and oxygen isotope tracer fluid, theore-forming fluid is the ground water, precipitation of the combined action of theresults.δ¹³C_PDBvalue in iron and manganese carbonate minerals range from3.844^-8.389‰, with an average in-6.108‰, δ¹⁸O_PDBvalue from-12.978-19.522‰, withan average in-15.667‰, δ¹⁸O_SMOWvalue in the range of10.736¹7.481‰, with anaverage in14.709‰, by calculating the Z value and carbon tracer to infer theformation of the sedimentary environment belongs to the continental deep lakeenvironment, Fe, Mn has the characteristics of the magma source.The mineral δ³⁴S_CDToverall value change in the range of-6.34⁴.61‰, theoverall average in-0.32‰, frequency histogram showed tower distribution, comparedthe ore body sulfur isotope with deep mantle rich in sulfur-heavy isotopes³⁴S, mayreflect that ore hydrothermal product by remelting of the crust, the sulfur isotope in the volcanic strata is relative loss³⁴S, and has a fierce volcanic eruption phase withhigh H2S gas or bio-participatory.²⁰⁶Pb/²⁰⁴Pb value of the ore minerals of lead isotopes in the range from17.663¹7.810, average in17.735,²⁰⁷Pb/²⁰⁴Pb value changes in the range of15.448¹5.628, in the average15.534,²⁰⁸Pb/²⁰⁴Pb value changes in the range of37.907⁸.977, average in38.216, μ value changes within the range of9.250⁹.600, average in9.418; ω values change from37.090⁴1.950, in the average38.872, the Th/U value inthe range of3.880⁴.370, average in3.994; vector eigenvalue V₁in the range of56.680⁸4.200, in the average69.973, V₂changes from27.370⁴8.940, average in42.888. With a low μ value, the lead sources have characteristics of the crust-mantlemixing, and mainly composed by crustal source material, mantle source followed.To sum up, layered ore body of ore-forming materials mainly comes frommagma source of crust-mantle mixed, Jurassic volcanic also provide some of thethings of the source.3. The Lengshuikeng mineralization process can be summarized as follows:intra-continental Triassic-Late Jurassic （220¹50Ma） intra continental subductioncollage collision orogenic environment. Jurassic volcanic eruptions alternating withdeposition. At the interval of volcanic eruptions, geothermal systems carrying themagma source of iron, manganese slow deposition in the deep lake formed in the ironand manganese carbonate rocks; about154¹57Ma, the formation of the Jurassic LawDepartment, Daguding group （J₃d） and E’huling group （J₃e）, the deposition of ironand manganese carbonate rocks was brust into iron and manganese carbonate breccia（agglomerate） by strong volcanic eruption, the breccia （agglomerate） filling withpyroclastic material, then deposited to forming volcanic breccia layer, with theweakening of volcanic eruptions, high temperature volcanic gas-liquid which carrywith minerals migrate up to superficial, the participation of atmospheric promote thephysical and chemical conditions change, as minerals precipitate to form the originalsource of ore; deep magmatic activity is very strong in the original source of oreformation, when the downward infiltration of groundwater along the fissure, andcirculation, with interaction between the flows with volcanic rock, ore-bearinghydrothermal formed by continuously extracted from the flow through thesurrounding rock, volcanic breccia filled with account of the original source of ore,gradually enriched minerals, and precipitation.Late Jurassic （145±5Ma） fromcompression to extension, expansion change of surroundings. Regional tectonics, theformation of the mine F2nappe structure, cut through the stratiform ore body. parts of structure collapse Invaded. about146Ma volcanic hydrothermal with thecharacteristics of crustal remelting source（granite porphyry） flowed along the F2nappe structure, and rise to superficial of earth, occurred strong crypto explosion, withthe precipitation of minerals, eventually including the leading edge of the mine graniteporphyry belt, silver-lead-zinc deposits formed in the main band and contact belt,copper ore body mainly distribute in the rock roots, sporadic gold ore bodies locatedin the lower part of the rock contact zone.4. The Lengshuikeng deposit, stratiform orebodies are volcanic deposition-hydrothermal Ag-Pb-Zn body and the granite porphyry containing ore body belong toporphyry-type Ag-Pb-Zn （Cu,Au）.