Uplift of northwest margin of Tibetan plateau: Indicated by zircon LA ICP-MS U-Pb dating of conglomerate from Mazartagh, Tarim basin

Abstract

Radiometric age dating of detrital zircons is highly advantageous for analysis of the depositional environment and to identify source areas. Aiming at the uplift and denudation of the surrounding ranges, LA ICP-MS U-Pb analysis has been performed on zircon grains from a conglomerate collected at the Lower Pliocene of Mazartagh, which is in the center of the Tarim basin, Xinjiang (新疆), China. A wide range of ages mainly falling into three groups was yielded: 200–500, 800–1 100, and 1 800–2 000 Ma. Zircon features principally indicate magmatic origin. According to the comparison between the analyzed zircons with those from surrounding orogenic belts, the younger grains are mainly related to the west while the older ones are to the regions more eastward. The variations might imply the W-E propagation tectonic activation and uplift of the surrounding orogenic belts. The west segment uplifted and was denuded firstly, driven by the approximate W-E height difference, upon the denudation, transportation and deposition, acting as the source of young zircons analyzed. With the eastward spreading of tectonic movement, the segment more to the east rose, the meridional relief increased rapidly and began to control the flow direction, then more zircons joined in the Pliocene in Mazartagh. It is difficult to definitely explain the source of grains with similar values to that from the Altyn Mountain region, more detailed data and chronological ages with higher precision will be helpful for making more credible conclusion.

Keywords

Zircon / Tibetan Plateau / 206Pb / Pliocene / Tarim Basin

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