Research On The Geochemical Feature, Genesis And Metallogenic Prognosis In The ShiHu Gold Deposit, Western Hebei Province

Guided by Diwa metallogenic theory, starting from analyses ofregional metallogenic background of Shihu gold deposit, thecharacteristics of geology geochemistry and the genesis of deposit inShihu gold deposit are studied systematically and deeply by using theknowledge of petrology, structural geology, mineral deposit, isotopegeochemistry, geochemistry of mineral deposits, etc. On the basis ofsummarizing of metallogenic regularities in detail, researches ofprospecting prognosis have been done.The author, for the first time, has proved that Shihu mining area hasundergone three big developing evolution stages, ie. Pregeosyncline,platform and Diwa stages. The pregeosyncline is a main sedimentationperiod in which the protolith stratum of Fuping group was formed; duringLvliang movement period, the region was arised and platform formed;when Yanshan movement period, the platform was moved into Diwastage by activating, large-scale tectonic and magmatic activities happenedin that region, which was considered as the significant forming stage ofShihu gold deposit.The geochemical feature of the microelement and the rare earthelement of the country rock near orebody, magmatite and ore are studiedsystemactically, these reveales the geochemical action feature of themicroelement and rare earth element in the ore-forming process anddiagenetic stage, and the main ore—forming element Au is derived fromthe source bed (Tuanbokou formation of Fuping group). The data ofsulfur, lead and carbon isotopes show that sulfur, lead and carbon arederived from the mantle, the data of the compositions of gas and liquidphases in quartz inclusion and hydrogen, oxygen isotopes suggest that ore—forming fluids is a mixture of magmatic hydrothermal fluids andmeteoric water. The physical chemical features suggest that the depositemplaced in a near—surface, relative oxidized and weakly alkaline ore—forming environment.The moving direction of the ore—forming fluids is studied by means of decrepitation temperature in the Shihu gold deposit. Measure ofdecrepitation temperature and the vertical isothermal diagram of quartzinclusions at different levels in orebody 101-4 suggests that ore—formingfluids moved from south to north and from deep to shallow, whichexplains microcosmically the forming mechanism of pitch to south.Contacting the ore—forming process with the stage of geotectonicevolution, the mechanism of mineralization in Shihu gold deposit isstudied in detail. The author puts forward that the forming of the Shihugold deposit is of the characteristics of multistage geotectonic evolution,multisource ore- forming materials, multiore- controlling factors,multimineralization, multigenesis typle. Controlled by the fault belt, theShihu gold deposit is a polygenetic compound ore deposits which wasformed in the Archean mesometamorphic rock and reconstructed bymixed hydrothermal in Yanshan Epoch. And a related minerogeneticmodel has been set up.Through the analyses of ore—controlling factors, the conditions ofthe ore—beating fault belt are put forward as follows: 1) it developed inthe Tuanpokou formation of Fuping group which is the source bed of themining area; 2) it has a certain scale, which is over 1,000m along thestrike and 400m along at the dip; 3) it should undergo multistage andmultiphase movements, more movements number, easily formedmultistage mineralization pile; 4) accompanying intrusion of the quartzdiorite veins, it made that the fault belt became the structural weak zone,which is favourable for the access and precipitation of the ore fluid; 5) itis the best to mineralization when the fault belts locate in radiating faultsystem and their strike is NW—trending or NNW to SN—trending.The isogram of thickness and grade of the orebody suggests that theconnection line of the mineral concentration area is coinciding with thepitch direction of the orebody; and the appearing rate ofα—βpeak ofquartz decrepitation temperature has a distribution regulation, whichchanges from high to low with the depth of the orebody. This regulationsuggests that the deposit bellow the 180m bears a good prospectingperspective.Through the study of metallogenic regularities of the gold deposit, based mainly on the pitch regularity of the orebody, the moving directionof the ore—forming fluids and various mineral concentration regularity, itis supposed that deep and south domains of the deposit bear a goodprospecting perspective. Then two forecasting targets at the south of theorebelt 101 and depth along the pitch direction of the present orebody areoutlined integrating with the methods of EH-4 electrial conductivityimage system. Through the verfication of ore—searching by the tunnel,industrial orebody with big thickness and high grade, has been foundrecently at 180m, 220m and 260m level in the south forecasting area.