Genetic Mineralogy And Deep Ore Prospecting Of The Songjiazhuang Gold Depositin Rushan County,Shandong Province

The Songjiazhuang gold deposit is a new deposit found recently which is located in the south of Mouping-Rushan gold-deposit belt of Jiaodong Peninsular. It is a transition gold deposit between pyrite-quartz vein and rotten-rock, occuring in the contact zone of the Jinshan group and the Kunyushan granitic complex body. The gold deposit is in the controlling of the south of Qinghushan-Tangjiagou fault which strikes in NNE, whose average gold grade is 2.82×10-6g/t. Basing on field observations and test analysis indoor, the paper which conducts a genetic mineralogy study of pyrite, gold-silver minerals and telluride in No. I orebody, discuss the forming material source, the physical and chemical conditions and the probable metallogenic model.The quartz-pyrite ores and polymetallic sulfide ores are the mainly ore-types. The ore is composed of metal sulfide minerals, quartz and carbonate minerals. The mainly textures of ores are granular texture and cataclastic texture, the structures of ores are massive structure, dense disseminated structure and vein structure. The gold minerals including kustelite, electrum and gold mainly occur in the form of enclosed gold. The telluride include rhombic calaverite, hessite, and tetradymite. The mineralization stages are pyrite-quartz, quartz-pyrite, polymetallic sulfides and quartz-carbonate stages.The morphological characteristic of pyrite is mainly pentagonal dodecahedron and the combination form of pentagonal dodecahedron and cube2 The combination and the crystal shape become complicated during the major ore-forming stage or the deeper part. The composition of pyrite is depleted in sulfur on the analysis of major element which demonstrates that pyrite are magmatic origin. The analysis of trace element indicates that the ore-forming fluid are maily magmatic hydrothermal. The analysis of REE reveals that the REE distribution pattern of pyrite is right deviation pattern and is unanimous in the samples of major metallogenic stage. The thermoelectric coefficient of pyrite ranges from-331～349 uV/℃. The conduction type is mainly mixture of type P and type N and the average appearace rate of type P is 59.8%.The fineness of gold-silver minerals ranges from 345.47-932.97 and the average fineness is 745.25. The telluride has been observed include rhombic calaverite, hessite, and tetradymite. It is thought the telluride and gold-silver minerals formation order presumably is pyrite-tetradymite-hessite-rhombic calaverite-electrum-gold. Basing on the combination and characteristic of telluride, the sulphur fugacity is probably less than 10-16.8, and the tellurium fugacity is more than 10-19.5 and less thanl10-1By combining the characteristics of pyrite, gold-silver minerals and telluride, it is thought that the gold deposit is formed in mid-shallow and mid-low temperature. The ore forming fluid is the mixture of crust origin and mantle origin fluid, occur strong crust-mantle interactions with wall rock with the evolution of the metallogenic stage, and in reduction conditions. The temperature of the ore forming is lowering with the increasing of the mineralization.