Fluid-Rock Reaction Process And Gold Metallogenic Mechanism Of The Sizhuang Gold Deposit, Northwest Jiaodong Peninsula, China

The Sizhuang gold deposit is a super-large altered rock type gold deposit which is proved recent years. It is located in the south tip of Jiaojia gold field, Jiaodong gold deposits concentration area. All orebodies are located in the alteration zone. However, the fluid-rock reaction process and gold metallogenic mechanism has not been identified up to now. The author definite the alteration type and mineralization type, found out the alteration-mineralization structure and studied gold metallogenic mechanism using systematically field and laboratory study. Few preliminary understanding are as follows:(1) 4 alteration types(potash feldspathization, sericite-quartz alteration, beresitization) and 3 mineralization types(altered rock type, transitional type, quartz-vein type) were definited.(2) Alteration and mineralization zoning obviously. Form the Jiaojia fault surface to its’ footwall distributed beresite zone, sericite-quartz alteration zone, potash feldspathization zone and Linglong biotite granite. Corresponding ore bodies are altered rock type, transitional type, quartz-vein type, none ore bodies. Alteration and mineralization have the pulse, overlapping characteristics. From early to late, there are potash feldspathization, sericite-quartz alteration and beresitization associated with altered rock type mineralization, quartz-vein type ore body, carbonatization alteration.(3) Mass balance calculation in altered rocks indicates during the potash feldspathization, Si O2, Al2O3, Fe2O3, Fe O, Mg O, Na2 O, Au, Ag, As, Hg, Pb and rare earth elements emigrated, K2 O immigrated. During the sericite-quartz alteration and beresitization, Si O2, Fe2O3, Fe O, K2 O, Au, Ag, As, Hg, Cu, Sb, Bi and light rare earth elements immigrated, Al2O3, Na2 O and heavy rare earthelements emigrated. Au coefficient of variation during the beresitization process is 14073.49% which is 16 times than the sericite-quartz alteration process and 283 times than the potash feldspathization process.Metallogenic material came from the Linglong biotite granite. High potassium and low silicon magmatic fluid form the potash feldspathization, high silicon and ferrum magmatic fluid form the sericite-quartz alteration and beresitization.(4) Two-feldspar geo-thermomete calculation indicates the temperature of potash feldspathization range from 349℃ to 449℃, while ore-forming temperature range from 200℃ to 300 ℃. Eu anomaly indicates the potash feldspathization is occurred in oxidation environment, while the sericite-quartz alteration and the beresitization were occurred in reduction environment. Au may be transferred by Au-S complex basing on the mineral assemblages and correlation between Au and S, Cl. Au precipitated when quartz and pyrite crystalling during the sericite-quartz alteration and beresitization.