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 orefield, were studied using the electron paramagnetic resonance method. Relationship between the isomorphic substitution and the dynamic recrystallization of quartz was studied by optical and scanning electron microscopy. Analysis of the plots of interdependency between the concentrations of various substitutional impurities in quartz (isogens) provided an opportunity to detect isomorphic substitution development trends. Two isomorphic substitution stages were recognized, one associated with mineral crystallization and the other, with its subsequent dynamic recrystallization. The first stage leads to Al impurity incorporation into the quartz crystal lattice, and the second, to Ti impurity incorporation. The Ge impurity is the isomorphic substitution catalyst, 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 quartz genetic groups, which are described by individual isogens, have been recognized in the Darasun orefield. Two of them correspond to the quartz crystallized from a magmatogenic fluid directly or redeposited with its participation, and the other two correspond to the quartz crystallized from an altered fluid. The facts that substitutional Al concentrations are retained in quartz after redeposition, whereas substitutional Ti impurity concentrations fall dramatically, are demonstrated. Mineral formation processes at each gold deposit are discussed. Two types of temperature zoning, the normal and the reverse, have been recognized at the Darasun deposit. Each zoning is characterized by an individual quartz genetic group and the extent of mineralization system closedness. The genetically similar magmatogenic quartz samples found at the Darasun and Talatui deposits attest to the uniformity of mineralization process in the Darasun orefield. The established trends of isomorphic substitution in quartz are applicable in the studies of ore formation histories of gold and other ore deposits. Keywords: Darasun; Teremkinskoe; and Talatui deposits of the Darasun orefield; mineral formation; auriferous quartz; dynamic recrystallization; substitutional impurities; genetic analysis; isogens; isomorphic substitution stages; quartz redeposition; temperature zoning; EPR method; scanning electron microscopy