关键词: 黄钾铁矾, K-Ar, 青藏高原隆升, 季风-干旱环境, 东天山

Abstract: Eastern Tianshan area is an extremely arid desert zone,with the average rainfall of 25mm/y and evaporation capacity of 1500mm/y. The vegetation is very spare here with strong aeolian action. So the denudation and aeolian transportation is very intense in eastern Tianshan. The timing of formation of this superarid climate is very important to the research of the relationship between plateau uplift and climate change. Jarosite is a widespread secondary mineral in oxidization zones of sulfide metal deposits in eastern Tianshan. There is considerable amount of potassium containing in the crystal of jarosite,so it is suitable to K-Ar(⁴⁰Ar/³⁹Ar)geochronology. The K-Ar data obtained from 7 samples indicate three age stages:11Ma,56～66Ma and 113～193Ma. Considering the contaminations of primary minerals(such as,Illite,Microcline,Albite and Quartz),the age of formation of jarosite in eastern Tianshan can be determined at～11Ma,which indicates the climate change from arid-semiarid to superarid in eastern Tianshan. It is consistent with the strengthening of Asian north-westerly winter monsoon and the records of large scale aeolian sediments. It also accords with the time of uplift and lateral expansion of Tibetan plateau along its northern and northeastern margins. The age of jarosite's formation in eastern Tianshan supports the climate-model that simulates the atmospheric circulation change caused by the uplift of 1～2km and lateral extension of Tibetan plateau.

Key words: jarosite, K-Ar, uplift of the Tibetan plateau, Asian monsoon-arid environment, eastern Tianshan