Tectonic activities in Dongshangen polymetallic ore district, eastern Kunlun Mountains, Qinghai-Tibet Plateau: Evidences from fission track thermochronology

Abstract

The Dongshangen polymetallic ore district is located in east section of the Eastern Kunlun Mountains, the south eastern margin of the Qaidam Basin, and is one of the most important polymetallic mining regions. However, there is a relatively lower research degree on the district, especially lack of thermochronology data. Using zircon and apatite fission track thermochronology, this article reveals the tectonic activities experienced in Dongshangen polymetallic ore district. It is shown that the 6 age groups of geological thermal events, i.e., 197 Ma, 182–170 Ma, 160–110 Ma, 110–80 Ma, 80–23 Ma and 23–0 Ma. Combining with the geological characteristics, we consider that the 6 age groups belong to 6 periods of tectonic activities in the Dongshangen ore district. The first age group of 197 Ma mainly resulted from the South Kunlun fault strike-slip and the Qiangtang block collided with the Kunlun block; the second age group of 182–170 Ma was related to the Songpan-Ganzi-Bayan Har Basin closure; the third age group of 160–110 Ma was bound up with the left-lateral strike-slip took place in the North Kunlun fault, and the squeezing and collaging activities of both the Qiangtang block and the Lhasa block toward the Eurasian plate; the event during the 110–80 Ma responded to northward subduction of the Neo-Tethys Ocean and strong strike-slip in the Altyn Tagh fault zone; the Late Cretaceous to Miocene (80–23 Ma) was affected by the northward napping of the Central Kunlun terrane and the northward subduction of Neo-Tethys Ocean continued; from 23 Ma to present, the collision of the Indian plate toward the Eurasian plate occurred, leading to the Qinghai-Tibet Plateau uplifting as a whole. Synthesizing the geological characteristics and the tectonothermal events, we discriminate 4 metallogenic periods of 197 Ma, 182–170 Ma, 155–112 Ma and 109–88 Ma in the district, better reflecting the characteristics of multi-stage metallogenic events.