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

摘要： 东天山地区金属硫化物矿床氧化带中黄钾铁矾的测年结果显示,红山铜金矿样品08XJ-20的K-Ar年龄为11Ma,延东铜矿、沙泉子铜矿、梅岭铜金矿及马头滩金矿样品的K-Ar年龄都在56～66Ma之间,个别样品如梅岭铜金矿和图拉尔根铜镍矿样品的K-Ar年龄分别为114Ma和194Ma。其中红山铜金矿样品08XJ-20没有其它的含钾且年龄较老的风化残留矿物成分(主要是伊利石、微斜长石、斜长石和石英)的影响,其年龄值11Ma是东天山氧化带表生矿物黄钾铁矾的形成年龄,代表了东天山地区气候向极端干旱转变的时间。这与亚洲大陆西北季风加强,黄土大面积沉积以及青藏高原在垂向上强烈隆升和在横向上向北、东北方向扩展的时间基本一致,从而支持了青藏高原在约8MaBP强烈隆升了约1～2km,并向周边扩展,同时引起大气环流改变的理论模型。

关键词: 黄钾铁矾, K-Ar, 青藏高原隆升, 季风-干旱环境, 东天山