A Research On The Multiple Mineralization In The Dayingezhuang Gold-silver Polymetallic Deposit, Jiaodong Peninsula

The Jiaodong ore concentration area is one of the largest gold producing regeion, famous by its world-class structural-altered gold deposit and quartz-vein gold deposit. Its proven reserves and annual output of the gold resources account for about 25% of the whole country. The majority of the gold mine is in the Jiaobeilongqi. This thesis choses Dayingezhuang gold deposit, which located in the middle of the Zhaoyuan-Pingdu fault, as the research object. Focusing on the important influence of superimposed mineralization, this study made a comparison between the No.Ⅰ ore body and No. Ⅱ ore body. Based on observation of optical microscope and analyses through SEM, as well as other published research results, we identified the mineralization stages, described the occurrence of gold and silver, and then discussed the effects of superimposed mineralization on deposit. This can not only give a complement for the research data on the superimposed mineralization, but also is an important reference for the research on the ore-forming mechanism of Dayingezhuang.The research shows that the types of gold ore of Dayingezhuang deposit mainly include the disseminated pyrite sericited and quartz-vein. The two ore bodies are controlled by the Zhaoyuan-Pingdu fault, therfore they are almost consistent in metallogenic tectonic. Polymetallic sulfide ore contain high grade silver, which exists in the form of electrum, argentite and a small amount of volynskite, polybasite. Silver mineral are concentrated in the polymetallic sulfide vein and obviously formed by the late superimposed mineralization.Using optical microscope and electron microscope, we made a summary of mineral paragenetic association. We divided the mineralization process of Dayingezhuang deposit’ No.Ⅰ ore body mineralizations into seven stages: potassium feldspar- quratz stage, sericite-pyrite stage, gold-quratz-pyrite stage, gold-chalcoprite stage, main ore-forming period quartz-calcite stage, silver-polymetallic sulfide stage and quartz-calcite-barite stage. Gold mineralization mainly occurs in the early stage, whereas the silver mineralization took place in the late stage. Compared to the No.Ⅰ ore body, No.Ⅰ ore body has only six mineralization stage, lacking the quartz-calcite-barite stage.Dayingezhuang fault occurred after the gold mineralization and produced the difference between the two ore bodies. The northern one was displaced from the prime fault and distribution pattern altered obviously. Later hydrothermal infiltration controlled by Dayingezhuang fault imposed metasomatism on the early alteration ore.