| Naa tungsten deposit situated in the east of Tibet,is a very representative and typical skarn deposit in Gangdise metallogenic belt.Naa tungsten deposit is located in cuogao-demala metamorphic complex belt in the composite Longgeer-Gongbujiangda island-arc in the east of Ladake-Gangdise arc-basin system which is located in the edge of the active Gandise–Nyainqêntanglha landmass in structure.A systematic study on regional geology,characteristics of metallogenic,petrology and geochemistry of Naa tungsten deposit has been carried out in the thesis,we reached the following main achievements and understanding:1.Rock related to mineralization is a composite batholith in naa mine,which can be roughly divided into the following sequence of magma from early to late:porphyritic biotite granite and coarse-grained biotite granite formed in early's magmatism,then hypabyssal intrusive medium-grained moyite gradually evolved from early's magmatism.Hypabyssal ultra-hypabyssal intrusive micro-fine-grained monzogranite formed in metallogenic epoch.Aplite veins,felsic veins and doleritic veins formed in the late's magmatism.2.Wall rock alteration characteristics:wall rock alteration are well-developed in mine area,there are main hydrothermal alteration of the skarn alteration?garnetization,diopsidization,actinolitization,tremolite?,silicification,albitization,chloritization,epidotization,sericitization,hornfelsic,carbonatization,etc.Among them,the skarn alteration,silicification,chloritization are most correlative to metallogenesis.3.Metallogenic stage division:mineralization process in mine area are divided into two mineralization epochs,skarn period and quartz-sulfide epoch,the former includes dry skarn stage and wet skarn stage.The latter includes quartz-scheelite-sulfid stage and calcite-sulfid stage,according to the mineral combination and mutual cross-cutting relationships between minerals and minerals.Quartz-scheelite-sulfid stage is intimately related to metallogenesis.4.The studies on characteristics of main elements showed that coarse-grained,medium-grained,micro-fine-grained granite related to mineralization belong to weakly peraluminous high K calc-alkaline rocks with enriched silicon,alkali,the content of SiO2 is 71.47%75.33%,Litman index???is 1.742.41,aluminum saturation index?A/CNK?is 1.021.12,K2O/Na2O is 1.271.67.DI is 82.8692.82,them commonly underwent intensive differentiation and evolution,micro-fine-grained monzogranite is closely related to metallogenesis among them.5.The studies on characteristics of trace elements showed that coarse-grained,medium-grained,micro-fine-grained granite are rich in W,Mo,Cu,Bi,U.Rb,Th,Nd,Hf show positive anomalies,Ba,Sr,P,Ti show negative anomalies on the spider diagram of trace element;their REE patterns are all L type,which shows coarse-grained,medium-grained,micro-fine-grained granite are products gradually evolved from the same magma.There are significantly differences on the spider diagram of trace element and REE patterns between aplite veins,felsic veins and coarse-grained,medium-grained,micro-fine-grained granite,which show these two kinds of veins and coarse-grained,medium-grained,micro-fine-grained granite are probably derived from different magma system.6.Element migration rules:the content of SiO2,Al2O3,Fe2O3,MnO significantly increase;the content of CaO significantly reduce;marble mainly provides CaO,magmatic rocks mainly provides SiO2,Al2O3;W,Mo,Zn,Cd,In,Re are significantly enriched in the process of marble into skarn.7.The spider diagram and REE patterns of W-Zn ore and W-Mo ore are generally similar,which showed they may be production of the same period ore-forming hydrothermal solution.Compared with the spider diagram and REE patterns of former two kinds of ore,there are distinct difference in Mo ore,which reflected there are two periods ore-forming hydrothermal solutions in mine.Mo mineralization should be the production of late hydrothermalism.8.Studies show that ore-forming substances for Naa tungsten ore is mainly probably sourced from micro-fine-grained monzogranite,second probably from marble stratum. |
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