| Xiaotazigou gold deposit is located in the southwest of Nuluerhu uplifted belt, which situates at the east of Menggu structure axis, the northeastern of Yanshan platformal fold belt, and the northern edge of Huabei platform. Approximating the south of Yanliao subsiding belt, the rhombus area is enclosed by the Chifeng-Kaiyuan ultra-lithosphere fracture-belt, the Chengde-Beipiao ultra-lithosphere fracture-belt and the Balihan fracture, with the major structure lines directing towards the NE-NNE and EW and coming through Lvliang moving ,Haixi moving,Yinzhi moving and Yanshan period mass structures or magma function. The major exposed layers were rather complicated in this zone, which are the archean basic-acidic lava-clastic rock-carbonate construction, the proterozoic Changcheng series clastic sediment, the under-palaeozoic group neritic facies carbonate and a bit of clastic rock, the mesozoic group continental facies lava- sedimentary rock group and the congeries of caenozoic era terrigenous detrital sedimentary rock. The host rock of Xiaotazigou gold mine was the amphibolite facies- pyroxene granulite facies metamorphic rocks of Jianping group Xiaotazigou team of junior Archean Eonothem in this zone.After the upheaval of the later Proterozoic Eon, the Mongolian structure axis has not witnessed much fluctuation till late neopaleozoic, when structure magma movement was engendered due to joint of the Siberian and North China plain. What deserves special mention was that the strong Yanshan movement broke out the east-west structure pattern from Proterozoic Eon. As a result of twist, it gave rise to a series of faults, and discordogenic faults that have deepened in the mantle cut through the whole lithosphere in this zone, subsequently supplied the useful ways of rising and exerting for mineralized stuff or liquid which were from the mantle; thus produced the magma movement of extending to northeast and triggered the formation of around a hundred different granitoid intrusions, which supplied the heat source and mineralized liquid and useful physical-chemical condition for shaping the gold deposit.Continually on the move in the zone, the magma almost located itself in the Nuluerhu uplifted belt, which is usually spotted in palaeozoic mid-acidic rocks and followed by the Mesozoic intrusion. From the Yanshan period, with the expansion and massing of magma intrusion, miscellaneous petrographic categories have been formed. The diversified dike rocks thus fell into a magnitude of varieties in the diggings,the styles were iorite-porphyrite, syeniteporphyry, andesite-porphyrite,rhyolite-porphyrite, quartz-porphyry and granite- porphyry and so on. The spreading direction of dike rocks was directed far more northeastern, with the latter spreading northwestern and few N-S. The phenomenon was due substantially to mineralizing as well as the cut-through relationship. Dike rocks were prior to mineralizing, posterior to slightly or forming at one time nearly.The total number of categories for veins is around 20, and the No.1 lode was the most important yield, the second were 5,6,7 lodes, besides the No .2,3 lodes were prospecting in sap. The most veins expanded towards the direction of N-E approximately, with the others extending nearly W-E. In the diggings, in these industrial mineral lodes, No.2 vein was dip-dyed pyrite-quartz vein rock pattern, No.3 got part pyrite-metallizing, No.5 was fabaceous quartz vein rock pattern,No.6 was pyrite- chalcopyrite style quartz vein rock pattern. Based upon our microscopical identification, pyrite,chalcopyrite,pyrrhotite and sphalerite were dominant ore minerals, secondary ore minerals aregalena,bornite,magnetite,malachite and limonite etc. Aurum in the ore was unattached occurrence forms, and its attitude was packed-gold, cranny-gold and crystal- clearance gold. Quartz is primary gangue mineral, and secondary gangue minerals are calcite,sericite and a spot of chlorite. We separate metallogenesis of Xiaotazigou gold mine into four stages of mineralization according to ore fabric and the relation of minerals: the first one, quartz vein stage; the second one,pyritestage;the third one, polymetallic sulfide stage; the last one, carbonate stage.The results of Co-related analysis ,R-style cluster analysis and R-style factor analysis of ore samples indicate: Au has positive coorelation with Ag,Bi,Cu,Zn,Hg elements, and sulfophile element Ag,Bi,Cu,Pb,Zn,As,Hg,Sb,(Co) get positive coorelation obviously among themselves. The positive coorelation are rather obviously between lithophile (oxide) CaO,MgO,K2O,Na2O,Ba and the oxyphilic element Al2O3 ,or among themselves,and the same as the negative correlation between lithophile and oxyphilic element. Drawn from the space distribution characters of element Au in No.1 vein as well as the space distribution of the indicator elements and the result of multi-analysis, it showed rarely strong equidistance character ,and the distance directed upright of the center of ore shoot is about 160m,uprising the relative impoverishing plat in modest, then shows sublevel concentration rule of vein-style gold deposit.Indicating from microelement characteristic of intrusive rock, The Au content of all kinds of dike rocks also was upper in the diggings. It Indicated Beidashan monzonitic granite, granite porphyry, diorite-porphyrite and relative magma rocks might be the one of Au source of mineralized stuff. Analyzing by the information of rare earth element, the change current of REE was about the same in the part of LREE between Beidashan monzonitic granite and quartz vein, some different in HREE,the data of Eu were 0.07,0.63 in single, with the same character in negative anomaly, these characters indicated the definite relationship in mineralized matter between Beidashan monzonitic granite and quartz vein.The research of hydrogen and oxygen from the fluid inclusions indicates that ore-forming fluid mostly derived from magmatic water. The homogenization temperature of the fluid inclusion varied remarkably, so the temperatures of the ore-forming fluid in different veins are in different stages. The temperature of the head mineralization progress was about 330℃,which varied from 280℃to380℃.And the relevant salinity was 1.5%,which varied mostly from 0% to 3%. The analysis of the components of ore-forming fluid indicates its chemical components is similar with the characteristic of high sulfidation gold deposit which is related with gas- liquid phase inclusion,triphase inclusion with carbon dioxide,pure carbon dioxide inclusion and liquid inclusion.Fluid inclusion can be signed as microcosmic mark for orefinding. In the veins of No.3,4,5,6, owing to the unmixing phenomenon of ore fluid unhappening, the metallization is rather bad.Although the upgrowth of inclusion is not good in the No.2 vein,all kinds of them are in existence ,so the strength of metallization is likely to stronger than the veins of No.3,4,5,6. The same , in the No.18,19 middle pieces of the deepen of No.1vein, the upgrowth of inclusion is worse, the phase state is singlet, rather without gas- liquid phase inclusion, never occurs the unmixing phenomenon of ore fluid, so the possibility that appearing the large scale make of ore is much rarely in the underside of No.19 middle piece.The range ofδ34S of Xiaotazigou gold deposit is from 1.19‰to 6.31‰, the average ofδ34S is 3.747‰, which is similar with theδ34S of granite and basalt in the nature, which demonstrates that the source of sulfur of the ore deposit bears a close relationship with granitic magma. Combining with the tectonic movement in the zone, it can be easily seen that the sulfur may come from basaltic magma and the magma melting from igneous rock source area in the lithosphere, thus becoming ore bearing hydrothermal fluid after the period of magma intrusion. Therefore, generalizations could be made that Xiaotazigou gold deposit is a mesothermal Audeposit that is related with neutral-acid intrusive rock.
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