CHARACTERISTICS AND EVOLUTION OF ORE FLUIDS IN GUILAIZHUANG GOLD DEPOSIT, SOUTHWEST SHANDONG
Shen Kun1, Ni Pei2, Lin Jingqian3
1. Shandong Institute of Geological Sciences, Jinan 250013; 2. State Key Laboratory of Mineral Deposit Research, Nanjing University, Nanjing 210093; 3. Department of Geology, Jilin University, Changchun 130061
The Guilaizhuang gold deposit, discovered recently in southwest Shandong province, China, is one of cryptoexplosive breccia type. The deposit occurs in the lower Paleozoic carbonate strata and is associated genetically with the Tongshi subalkaline igneous complex. Based on the fluid inclusion study of the gold deposit and of the igneous rocks and combined with the information obtained from exploration and research on the gold deposit, it is suggested that the ore fluids responsible for the Guilaizhuang gold deposit are the mixtures of magmatic water with a large quantity of meteoric water from the country rocks which were the high-temperature, halogen-and CO2-rich hydrothermal solutions with low to medium salinity during the early stage and evolved to the low temperature aqueous solutions containing minor volatiles with various salinities in the later stages. During the deposition of gold the fluid pressure was no more than 40～60 MPa while the temperature from 250℃ to less than 200℃. The decrease of temperature and fluid unmixing accompanied with the cryptoexplosion are the important factors causing gold deposition.