Abstract:

Rhyolite porphyry in Hetaoba, Inner Mongolia, is closely associated with uranium mineralization of the area. In order to strengthen the theory research and seek the prospecting breakthrough, this article focuses on the relationship between uranium mineralization and rhyolite porphyry, structure by the methods of geochemistry and magma and tectonic evolution. The pluton is located in the southern of Zhenzishan caldera in Duolun volcano basin. The rock has high SiO₂ content (70.15%-78.58%), high K₂O (5.28%-9.30%) and are enriched in alkali contents (Na₂O+K₂O=7.49%-10.82%). It belongs to the alkaline rhyolite as shown in the plot of TAS. Rhyolite porphyry in Hetaoba shows high REE contents and is relatively enriched in LREE, Rb, Th, with evidently negative Eu and Sr anomalies. Especially, U element content is extremely high (6.66×10^-6-966.00×10^-6). The magma came from partial melting of the lower crust materials, and the pluton, belonging to A2 subtype granite, was likely emplaced in the extensional post-collision setting. Eventually, these factors including emplacement of rhyolite porphyry, the ore-forming structure in the late stage, the emplacement and extraction of hydrothermal with rich uranium, have led to the formation of the Hetaoba uranium deposit.

Key words: Hetaoba, rhyolite porphyry, geochemistry, structure, uranium