Impurity Elements in Quartz from Gold Deposits of the Darasun Ore Field (Eastern Transbaikalia, Russia): Electron Paramagnetic Resonance Data

The distribution of substitutional Al, Ti, and Ge impurities in quartz samples from the Darasun, Teremkinskoe, and Talatui gold deposits, located in the Darasun ore field, were studied by electron paramagnetic resonance. The relationship between the isomorphous substitution and dynamic recrystallization of quartz was studied by optical and scanning electron microscopy. It was found that analysis of the plots of interdependence between the concentrations of various substitutional impurities in quartz (isogens) can detect development trends of isomorphous substitution. Two isomorphous substitution stages were recognized, one associated with quartz crystallization, and the other, with its subsequent dynamic recrystallization. The first stage is characterized by incorporation of Al impurity into the quartz crystal lattice, and the second, by incorporation Ti impurity. A Ge impurity is a catalyst for isomorphous substitution, and its concentrations vary widely. It is noted that the second stage plays a decisive role, because it accounts for the incorporation of the larger part of substitutional impurities. This process is facilitated by the dynamic recrystallization of quartz. Four genetic quartz groups, described by individual isogens, have been recognized in the Darasun ore field. Two of them correspond to quartz crystallized directly from a magmatogenic fluid or redeposited with the melt’s participation, and the other two groups, to quartz crystallized from an altered fluid. It was found that substitutional Al concentrations are retained in quartz after redeposition, whereas substitutional Ti concentrations decrease dramatically Mineral formation processes at each gold deposit are reviewed. Two types of temperature zoning, normal and reverse, have been recognized at the Darasun deposit. Each is characterized by an individual genetic quartz group and the degree of closedness of the mineral formation system. The genetically similar magmatogenic quartz samples found at the Darasun and Talatui deposits indicate the uniformity of the mineralization process in the Darasun ore field. The established trends of isomorphous substitution in quartz are useful in studies of the ore formation histories of gold and other ore deposits.