Fluid Inclusions and Daughter Minerals of Taibai Gold Deposit, ShaanXi Province, China

A discovery of daughter minerals in fluid inclusions of Taibai gold deposit, Shaanxi province has been focused on, which is a unique breccia-cemented gold-bearing system. The breccia zone strikes NWW-SEE, occurring in Devonian strata of Southern Qinling Mountains. The cement is mainly composed of ankerite, pyrite, calcite and quartz, which may be divided into four main tectonic-mineralizing stages. Gold mainly occurs in pyrite and ankerite of stage II and IV. It is found that three types of fluid inclusions can be distinguished: (1) aqueous inclusions (type B); (2) CO₂-rich inclusions (type C); (3) daughter minerals-containing inclusions (type A). LRM. (Laser Raman Micro-probe) analyses shows that the content of CO₂ occupies 54.4%-70.7% (mole fraction, so as the follows) in vapor phases of different type fluid inclusions. CH₄ (5.2%-7.3%) and H₂S (6.0%-12.7%) exist in both vapor and liquid phases. Many daughter minerals in fluid inclusions of ankerite and quartz have been found. Several kinds of daughter minerals, including ankerite, pyrite, arsenopyrite and halite, were determined by using SEM (scanning electron microscope)/EDS (energy dispersive spectrometer) technique. EPMA (electron probe micro-analysis) technique was also applied to study the daughter minerals exposed to the surface of polished thin sections.