Helium isotope studies of the Central Tien Shan

Abstract

The research shows new results of isotope-helium studies carried out in the Tien Shan - Naryn and Atbashi basins. Sampling of thermal mineral springs in the Eastern Tien Shan was carried out in order to identify traces of mantle emanations in fluids and to assess the degree of permeability of the Earth’s crust for the introduction of deep masses, which would make it possible to clarify the nature of the interaction of the crust and mantle in the zone of recent orogeny. Concentrations of helium isotopes were measured in gas and water samples from 6 thermal mineral springs in the Central Tien Shan. It was found that fluids from three sources contain an abnormally high amount of mantle helium. In the gases of the Narzan source, the ratio 3He/4He in the gas phase (597÷600) × 10−8 reaches the Central Asian maximum found earlier on the Fergana ridge in the Kyzyl-Beles source (510÷630) × 10−8. The obtained results support the ideas on the existence of two sublatitudinal positive helium isotope anomalies on the northern and southern flanks of the Eastern Tien Shan - in the zones of junction of the epiplatform neoorogene with more ancient tectonically stable structures.