新疆准噶尔北缘索尔库都克铜钼矿氦-氩同位素组成及地质意义

Helium and Argon Isotopes Tracing of Ore-forming Fluid in the Suoerkuduke Cu-Mo Deposit in the Northern Margin of Junggar,Xinjiang

索尔库都克铜钼矿床位于准噶尔北缘，矿体呈似层状、透镜状、脉状产于中泥盆世北塔山组安山岩和矽卡岩中。采用稀有气体同位素质谱法，对矿床中绿帘石矽卡岩、安山岩和矿石3种产状的黄铁矿中流体包裹体氦和氩同位素组成进行测试分析。测试结果显示，黄铁矿中流体包裹体的4 He含量为（0.8821～13.3410）×10-8 cm3 STP/g，3 He/4 He为0.88～1.76 Ra（Ra为大气中的3 He/4 He，Ra＝1.4×10-6），幔源He占13.27％～26.93％，表明成矿流体中氦主要来源于地壳。40Ar含量为（4.2376～13.970）×10-8 cm3 STP/g，40Ar/36 Ar为301.07～331.55，40Ar＊含量占1.71％～10.87％，表明成矿流体中Ar主要来源于大气降水。3种产状的黄铁矿中氦、氩同位素组成及特点相似，结合矿床流体包裹体和稳定同位素研究，认为成矿流体来源于壳-幔相互作用的岩浆流体和大气降水，矿床的形成与安山岩和矽卡岩关系密切，暗示矿床成因为矽卡岩型。

The Suoerkuduke Cu-Mo deposit located in the northern margin of Junggar Terrane,is hosted by skarn and andesite of Middle Devonian volcanic rocks of Beitashan Formation.The orebodies are stratoid,len-ticular and vein types.Helium and argon isotopic compositions of fluid inclusions in pyrite from epidote skarn, andesite and ore were analyzed by using an inert gas isotopic mass spectrometer.The analysis results indicated that the 4He content ranges from 0.882 1 ×10 -8 cm3 STP/g to 13.341 0 ×10 -8 cm3 STP/g,the 3He/4 He ranged from 0.88 Ra to 1.76 Ra,the He content from mantle varied from 13.27%to 26.93%,all of these chara-cteristics showed that the He in ore-forming fluids derived mainly from crust.The 40 Ar content varied from 4.237 6 ×10-8 cm3 STP/g to 13.970 ×10-8 cm3 STP/g,the 40Ar/36Ar was 301.07 to 331.55,and the radiogenic 40Ar＊varied from 1.71%to 10.87%,indicated Ar in the ore-forming fluid was mainly from atmospheric water.The＆amp;nbsp;composition of He and Ar in three kinds of pyrite was similar.Combining deposit fluid inclusion and isotopic char-acteristics,we suggested that helium and argon isotopes of fluid inclusions in pyrite were mixture of crust fluid, mantle fluid and atmospheric water.The formation of deposit closely related with skarn and andesite,which imply that the ore genesis was skarn type Cu-Mo deposit.