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.

Daughter minerals in fluid inclusions of garnet and diopside from Tongguanshan Copper Deposit by SEM/EDS and LRM

Tongguanshan copper deposit of Tongling large ore belt is one of the typicalskarn copper deposits. Based on careful observation under microscope many daughter mineralsincluding transparent ones and opaque ones have been distinguished in the fluid inclusions of garnetand diopside. The results of SEM/EDS (scanning electron microscope/energy dispersive spectrometer)and LRM (laser Raman microprobe) analysis show that these daughter minerals in garnet are sylvite,halite, sphalerite, chalcopyrite and carbonate. Sylvite daughter mineral is very popular in garnetand diopside. The existence of so much sylvite daughter mineral and other daughter minerals in thefluid inclusions indicates that the ore--forming fluid is of supper-high salinity and high potassiumconcentration. High potassium concentration in the fluid inclusions agrees with K-richmesotype--acid rock and K-silicate alteration that occurred widely in this area. The daughtermineral assemblage in garnet and diopside is similar to the mineral assemblage of ore-forming stagethat followed skarn stage.

Fluid-melt Inclusions in Fluorite of the Huanggangliang Skarn Iron-Tin Deposit and Their Significance to Mineralization

For the first time, fluid-melt inclusions are found in fluorite of the Huanggangliang skarn iron-tin deposit (HSID). The fluorite was formed in the main stage of mineralization, named the hydro-skarnization stage. The inclusions contain various components such as Fe, Mg and Cr from deep sources. The melts of primary inclusions are mainly Ca- and F-rich and those of secondary inclusions tend to become Si-rich. During this evolution process, the melts and iron daughter minerals decreased and even vanished. These facts reveal that the evolution of the primary mineralizing fluids and the differentiation of the fluids and melts are the main factors leading to the deposition of Fe, Sn and other elements. This discovery confirms the magmatic genesis of the HSID and has filled in the gaps in the research of magmatogenic skarn deposits and furnished new methods for such research. Furthermore, it has enlarged the scope of the research on fluid inclusions.