湖南宝山-大坊矿区成矿花岗闪长斑岩的锆石U-Pb年龄、Hf同位素及微量元素组成对区域成矿作用的指示  

Zircon U-Pb ages,Hf isotope and trace element characteristics of the granodiorite porphyry from the Baoshan-Dafang ore district,Hunan: Implications for regional metallogeny

作　　者：弥佳茹 袁顺达[1] 轩一撒 张东亮[2] MI JiaRu;YUAN ShunDa;XUAN YiSa;ZHANG DongLiang(MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;Earth Science ＆ Geophysics Information College,Central South University,Changsha 410083,China)

机构地区：[1]中国地质科学院矿产资源研究所、国土资源部成矿作用与矿产资源评价重点实验室,北京100037 [2]中南大学地球科学与信息物理学院,长沙410083

出　　处：《岩石学报》2018年第9期2548-2564,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41672095、41373047); 中国地质科学院基本科研业务费专项经费(YYWF201711)联合资助

摘　　要：钦-杭成矿带是华南地区新近识别出的一条重要的中生代斑岩-矽卡岩型铜多金属成矿带。宝山矿床处于铜山岭-宝山-水口山矿区的中部,是湘南地区最大的铜多金属矿床,而大坊金矿床与宝山Cu-Mo-Pb-Zn矿相邻,在空间上亦与花岗闪长斑岩密切相关。矿区内岩浆活动复杂,矿化类型齐全,成矿元素多样。我们对宝山成矿花岗闪长斑岩、花岗闪长质隐爆角砾岩和大坊成矿花岗闪长斑岩进行了LA-MC-ICP-MS锆石U-Pb测年,结果表明宝山花岗闪长斑岩、花岗闪长质隐爆角砾岩和大坊花岗闪长斑岩的侵位年龄分别为156. 3±0. 9Ma、157. 1±1. 8Ma和154. 5±1. 0Ma,三者在误差范围内一致,均为晚侏罗世岩浆活动的产物;锆石Hf同位素研究表明,宝山和大坊矿床的成矿岩体均主要为古元古代地壳物质部分熔融的产物,并有幔源组分的加入;锆石微量元素分析结果显示,上述三类岩石的锆石具有相似的稀土元素配分模式,显示它们可能是同一期岩浆作用的产物。宝山矿区花岗闪长斑岩中锆石的Ce^(4+)/Ce^(3+)比值平均为355,与全球典型的含铜斑岩的Ce^(4+)/Ce^(3+)比值(> 300)相似。而大坊矿区花岗闪长斑岩中锆石的δEu平均为0. 48,与宝山岩体δEu平均值(0. 42)相近,指示二者具有相对较高的氧逸度,均为与铜金多金属矿化有关的斑岩体。锆石U-Pb年龄、Hf同位素及微量元素特征表明,大坊金矿和宝山铜多金属矿床均与矿区花岗闪长斑岩具有时空及成因联系,共同构成钦杭成矿带中段一套与花岗闪长斑岩有关的Cu(Mo)-Pb-Zn-Au-Ag成矿系统。Qinzhou-Hangzhou ore belt is an economically important Mesozoic porphyry-skarn Cu-polymetallic metallogenic belt recently recognized in South China. The Baoshan Cu-Mo-Pb-Zn-Ag deposit associated with granodiorite porphyry in genesis is located in the central part of the famous Tongshanling-Baoshan-Shuikoushan ore district,which is also the largest Cu deposit in southern Hunan Province. The Dafang Au deposit is adjacent to the Baoshan deposit. There are various kinds of magmatic rocks distributed in this mining area,which are associated with Cu-Pb-Zn-Au-Ag polymetallic mineralization. The zircon LA-MC-ICP-MS U-Pb dating results show that the zircon U-Pb ages of the Baoshan granodiorite porphyry,granodioritic cryptoexplosion breccia and the Dafang granodiorite porphyry are 156. 3 ± 0. 9 Ma,157. 1 ± 1. 8 Ma and 154. 5 ± 1. 0 Ma,respectively. They are well coincident with each other within acceptable errors,indicating that they are the products of the Late Jurassic magmatism; The Hf isotope values of the Baoshan and Dafang deposits indicate that the granodiorite porphyry was formed by the partial melting of Paleoproterozoic crustal material with a mixed source of crust and mantle. According to LA-ICP-MS trace element analyses on zircons from all three granitiod rocks,they share similar chondrite-normalized REE patterns,indicating that they have similar sources. The zircons from the Baoshan granodiorite porphyry have an average Ce4＋/Ce3＋ ratio of 355,similar to the values of zircons（〉 300） from the granitiod rocks related to typical porphyry Cu-Au mineralization. The δEu values of zircons from the Baoshan and Dafang granodiorite porphyry are 0. 42 and 0. 48,respectively,suggesting that they have relatively high oxygen fugacity, and are genetically related to the Cu-Au polymetallic mineralization. By integrated analysis on the zircon U-Pb ages,Hf isotope and trace element characteristics,it suggested that both the Dafang Au deposit and the Baoshan Cu polymetallic deposit are spatio-temporal and geneticall

关 键 词：锆石U-PB年龄 HF同位素 微量元素 Ce4+/Ce3+比值 花岗闪长斑岩 钦杭成矿带 

分 类 号：P612[天文地球—矿床学] P588.13[天文地球—地质学]