黑龙江省多宝山Cu-Mo矿床成矿斑岩锆石U-Pb年龄及地球化学特征

摘要

The Duobaoshan deposit,located in northern Da Hinggan Muntains,is the largest porphyry Cu-Mo deposit in Northeast China.In this study,the authors report LA-ICP-MS zircon U-Pb age,major,trace elements,and Hf isotopic compositions of the ore-related granodiorite porphyry in the Duobaoshan deposit.LA-ICP-MS zircon U-Pb dating yielded crystallization age of (474.9 ± 1.8) Ma for the granodiorite porphyry.Geochemical results indicate that the w(SiO2) values are in the range of 70.73％ ～73.45％,whereas w(K2O) and w(Na2O) range from 2.99 ％ to 3.88 ％ and from 3.86 ％ to 4.38 ％,respectively,suggesting that the rocks belong to high-K calc-alkalne series.The trace elements are characterized by enrichment of Ba,K,La,Sr,Zr,Hf,Sm,and depletion of Th,Ta,Nb,Ce,P,Ti.The REE characteristics are LREE enrichment with (La/Yb)N ratios of 6.32～12.76.The zircon Hf isotope analysis shows εHf(t) values vary from 10.3 to 14.6.The geochemical results indicate that the Duobaoshan granodiorite porphyry was probably formed in a continental marginal arc setting,and originated from partial melting of juvenile lower crust materials that were derived from the depleted mantle under the thickened crust condition.%多宝山矿床位于大兴安岭北部,是中国东北地区规模最大的斑岩型Cu-Mo矿床.文章对该矿床中与成矿关系密切的花岗闪长斑岩进行了详细的LA-ICP-MS锆石U-Pb定年、主量元素、微量元素及Hf同位素研究.结果表明,花岗闪长斑岩的LA-ICP-MS锆石U-Pb年龄为(474.9±1.8) Ma,其w(SiO2)为70.73％～73.45％,w(K2O)和w(Na2O)分别为2.99％～3.88％、3.86％ ～4.38％,属高钾钙碱性系列.岩石富集轻稀土元素,(La/Yb)N=6.32～12.76,显示出Ba、K、La、Sr、Zr、Hf、Sm等元素富集,Th、Ta、Nb、Ce、P、Ti等元素亏损的特征.锆石εHf(t)值介于10.3～14.6.详尽的元素和同位素地球化学特征表明多宝山花岗闪长斑岩可能形成于大陆边缘弧环境,来源于加厚陆壳条件下亏损地幔新增生的年轻地壳物质的部分熔融过程.