| Waifangshan area is located in the southern margin of the North China plate, is an attractive place for molybdenum, lead-zinc deposit. The deposits is next to the north side of the Taishanmiao multiple intrusive rock masses, Rock and molybdenum, lead-zinc deposit mineralization ages were115±2Ma,116±1. OMa,110.1±9Ma, The last period of Taishanmiao complex rock form Donggou Mo deposit rocks (Xiapu porphyry mass), from first to late its constituent change:SiO2(×10-2)71.33'72.84'76.50'77.41, Mo (×10-6)0.96'0.98'1.57'18.72,Cu (PPM)13.55'8.08'5.05'5.78, Pb (×10-6)24.30'41.73'25.53'14.33, Zn (×10-6)42.2'38.2'19.5'10.65; have a loss in MREE, have obvious negative Eu anomaly,∑REE (×10-6) decreased gradually from337.6'222'150'62, Rb (×10-6) increased gradually from194'198'392'401, Cs (×10-6) has a chage1.52'1.56'2.15'1.92,however, K/Rb has a change224'227'103'127; Nd, Hf isotope, later diagenesis is more mantle materials; from early to late, The main evolution tendency of rock is in crustal extension environment, magmatic source is changing from shallow to the deep, from lithosphere source to the mantle source,during the diagenetic process, the high magmatic differentiation has changed, ore-forming elements of Mo changed obviously enrichment, Pb,Zn, Cu, S, Fe have become selective escape from the magma.206Pb/204Pb of molybdenum, lead-zinc deposit and rock mass is change in the range of17.298～17.829,207Pb/204Pb is15.412～15.672,208Pb/204Pb is37.446～38.897,δ34S is change in range of4.11-8.90‰, which has a characteristic of the crust mantle mixed source; the value of δ13C is-3.57～-3.87%, the value of δ18O (SMOW) is6.32～10.30‰, its carbon-oxygen isotopic composition similar to magmatic origin. The minerals origin of molybdenum、lead-zinc deposits is from the magmathe which crust and mantle mixed.The early fluid inclusion types of Donggou Mo deposit are mainly water solution,multi crystal and CO2-H2O gas, its homogenization temperature is380-550°C, salinity is7.07～18.20%NaCLeqv, pressure is63～117MPa, the magma is in the magma hydrothermal stage. Wangpingxigou、 Laodaizhanggou、Xizaogou Pb-Zn deposit, the fluid homogenization temperature of ore-forming stage (280-350℃'200-320℃'180-260℃), the salinity of later metallogenic stage (3～14% NaCLeqv'2-6%NaCLeqv'1-4%NaCLeqv) change all from high to low; hydrogen-oxygen isotope δ18Oquartz is9.4～14.2‰,10.0～13.3‰,18.82‰;δ18Ow is1.6～3.7‰,2.9～9.3‰,-0.95‰;εD is-84.7～-88.7,-81～-84,-113. The ore fluid of molybdenum, lead-zinc ore deposits is evolution from the heterogeneous magmatic fluid of middle-high temperature, high salinity,rich in CO2to surface water of the low temperature, low salinity, lacking CO2.Under the action of the early magmatic fluid lifted and crust stretched, the rock rised upward and formed horizontal tensile cracks, and it was filled by quartz-potassium feldspar veins which were made by the high temperature minerals, metallogenic magma was differentiation of vapor+brine phase hydrotherm, Cu, S preferentially entered the vapor phase, K,Na, Pb, Zn, Fe preferentially entered the brine phase,the Mo which carried by magma was rich in the residual magma. Two phase fluid moved to structural fracture zone where is outside the rock mass and is a low pressure open space by the hydrostatic pressure of wall rock, ore mineral precipitated on condition that the reduced pressure and was boiling and mixed surface water, formed vein type lead-zinc deposit of low-middle temperature hydrotherm. Meanwhile The permeability of wall rock reduced because of alteration, and made the magma cooling differentiation lage of mixed fluid, which gathed the top of the dome space of magma formation, when the still water pressure is greater than the lithostatic stress, suddenlly, the top rock burst fragmentation, release of pressure, Magmatic fluid which is rich in Mo run away from magma, magma, and it is the accompaniment of fluid intensely boiling, fluid ore-forming elements molybdenum formed deposit in wall rock crack of the top of magma, formed thick molybdenum ore bodies which was in the top of magma and was controlled by crack. |
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