| 钦杭成矿带大瑶山地区晚白垩世斑岩型铜矿床: 锆石U-Pb定年及Hf同位素制约 |
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| 引用本文： | 毕诗健,杨振,李巍,梁培,唐克非.钦杭成矿带大瑶山地区晚白垩世斑岩型铜矿床: 锆石U-Pb定年及Hf同位素制约[J].地球科学,2015,40(9):1458-1479. |
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| 作者姓名： | 毕诗健 杨振 李巍 梁培 唐克非 |
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| 作者单位： | 1.中国地质大学资源学院, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金项目41202052中央高校基本科研业务费专项资金项目CUG120102广西壮族自治区地质矿产开发局科研项目2012026193 |
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| 摘 要： | 钦杭成矿带是华南地区重要的斑岩铜成矿带.前人研究表明区内斑岩铜矿床主要形成于中-晚侏罗世(180~155 Ma), 含矿斑岩为壳-幔相互作用的产物.对区内新近发现的钦杭带西南段大瑶山地区的宝山斑岩铜矿床进行研究, 结果表明其成岩成矿时代集中在晚白垩世.其中, 隐伏含矿花岗斑岩体的锆石LA-ICP-MS U-Pb年龄为91.1±0.6 Ma(1σ), 出露地表不含矿的两个花岗斑岩锆石U-Pb年龄分别为91.3±0.8 Ma(1σ)和90.1±1.0 Ma(1σ).含矿斑岩和不含矿斑岩的锆石Hf同位素组成相似, 初始εHf(91 Ma)为-8.74~-5.13, 两阶段Hf模式年龄TDM2集中在1 210~1 394 Ma.以上U-Pb-Hf同位素分析结果表明, 宝山铜矿床是一个晚白垩世早期(约91 Ma)形成的斑岩型铜矿床, 其含矿斑岩体的成因可能与中元古代地壳物质的部分熔融有关.结合前人的研究成果可知, 钦杭成矿带存在两期斑岩铜矿床成矿作用, 分别为中-晚侏罗世和晚白垩世, 其中晚白垩世成矿作用可能与华南板块边缘后碰撞伸展构造背景有关; 钦杭带西南侧大瑶山及邻区可能广泛发育有与燕山晚期岩浆活动(80~100 Ma)有关的钨-钼-铜(金)多金属矿床.
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| 关 键 词： | 钦杭成矿带 大瑶山 宝山铜矿床 花岗斑岩 晚白垩世成矿作用 地球化学 |
| 收稿时间： | 2015-05-02 |
Discovery of Late Cretaceous Baoshan Porphyry Copper Deposit in Dayaoshan,Qinhang Metallogenic Belt:Constraints from Zircon U-Pb Age and Hf Isotope |
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| Abstract: | The Qinzhou Bay-Hangzhou Bay suture zone is an important porphyry copper metallogenic belt in southern China. Previous studies suggest that the ages of regional diagenesis and mineralization are mainly concentrated in the Late-Middle Jurassic (180-155 Ma), and the ore-bearing granite porphyry shows distinctly crust-mantle contamination. The Baoshan copper deposit is a porphyry-type Cu deposit newly discovered in the Dayaoshan region in the southwestern of the Qinhang metallogenic belt in recent years. The granite porphyry is dominated as small stock into Sheshan granodiorite, including two outcropped and one concealed magmatic emplacement. And the copper ore body is all hosted in the Baoshan concealed granite porphyry. In this paper, laser ablation (MC)-ICPMS U-Pb dating and Hf isotopic compositions of zircons from three granite porphyry samples in the Baoshan copper deposit are presented. Highly precise U-Pb results indicate that zircons from one concealed and two outcropped granite porphyries give weighted mean 206Pb/238U age of 91.1±0.6 Ma (1σ), 91.3±0.8 Ma (1σ) and 90.1±1.0 Ma (1σ), respectively. And the zircons crystallized in the late Yanshannian granites give εHf (91 Ma) values ranging from -8.74 to -5.13 and Hf model ages (TDM2) of 1 210-1 394 Ma. U-Pb and Hf isotopic data can be interpreted as the crystallization time of these granites and the mineralization age, indicating it was formed in the ~91 Ma and may be developed by reworking of Mesoproterozoic crust closely related to partial melting. Together with other published geochronological data, it is proposed that the late Yanshannian magmatite and related Cu (Au)-W-Mo deposit are widely developed in the Dayaoshan and its adjacent areas. Moreover, two epochs of porphyry copper mineralization are confirmed in this study, including the Middle-Late Jurassic and the Late Cretaceous, in the Qinhang metallogenic belt, and it is concluded that Late Cretaceous mineralization possibly resulted from the post-collisional crustal extension setting in the continental margin of the South China. |
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