南岭中西段燕山早期北东向含锡钨A型花岗岩带  

Early Yanshanian NE Trending Sn/W-Bearing A-Type Granites in the Western-Middle Part of the Nanling Mts Region

作　　者：朱金初[1] 陈骏[1] 王汝成[1] 陆建军[1] 谢磊[1] 

机构地区：[1]南京大学地球科学和工程学院,成矿作用国家重点实验室,南京210093

出　　处：《高校地质学报》2008年第4期474-484,共11页Geological Journal of China Universities

基　　金：中国地质调查局调查项目“南岭重要金属矿床成矿机理研究和成矿潜力预测”(1212010632100);国家自然科学基金项目(40730423,40373014)资助

摘　　要：南岭中西段,发育着一条北东向的燕山早期含钨锡A型花岗岩带,该带主要由花山、姑婆山、九嶷山、骑田岭等花岗质岩基和周边岩株群所组成,延伸在250km以上,出露总面积超过3000km2,含有丰富的钨锡等金属矿产资源。这些花岗质岩体多为多阶段复式岩体,主侵入期花岗岩的侵位年龄多在165~153Ma范围内,常常与同时代的偏中性(闪长岩、花岗闪长岩、石英二长岩等)岩株或酸性火山侵入杂岩相伴生,具有岩浆混合特征的暗色包体十分常见。主侵入体多为斑状黑云母花岗岩,有时含角闪石,酸性至超酸性,弱准铝至弱过铝,富含K2O和总碱,富含大离子亲石元素和高场强元素如Rb,Cs,U,Th,LREE,Y,Nb,Ta,Zr,Hf,Ga等,Sn,W等成矿元素及F,Cl等挥发性组分亦十分丰富。在Whalen等(1987)判别A型花岗岩和未分异M,I,S型花岗岩的图解上,绝大多数落在A型花岗岩区。他们的ISr值变化较大(0.7063~0.7182),εNd(t)值偏高(-1.7^-8.0),t2DM值偏低(1.1~1.6Ga),表明花岗岩成分中有不同程度新生地幔物质的参与,尤其以花山和姑婆山花岗岩更为明显。花岗岩体往往强烈分异,晚期(或称补充侵入期)强分异细粒花岗岩的侵位年龄大多在146~151Ma范围内。与主体相花岗岩相比,他们更偏酸性,过铝,更富含Rb,Cs,U,Y,Sn,W等微量元素,但∑REE(尤其是LREE),Zr等HFSE含量明显贫化,在岩石化学成分上与S型花岗岩十分接近。成矿作用贯穿花岗岩侵位和演化的全过程,从主侵入期经补充侵入期到后来的热液期,都能形成Sn,W等金属矿床。矿化类型多样,包括云英岩型、石英脉型、矽卡岩型、Li-F花岗岩型、锡石硫化物型和绿泥石化构造蚀变带型等,规模可达大型乃至超大型。过去一般认为,Sn/W矿床主要与S型花岗岩有关,南岭地区富含Sn/W矿化的A型花岗岩带的厘定,证明了A型花岗岩与Sn/W成矿作用密切相关,为在华南乃至世界其他地区寻找新的锡钨矿床�In the western-middle part of the Nanling Mountains region there develops an Early Yanshanian （Jurassic） Sn/W bearing A-type granite belt. It is composed of Huashan, Guposhan, Jiuyishan and Qitianling granite batholiths and nearby granite stocks. This beh extends in a NE direction for more than 250 kin. The total exposure area is over 3000 km^2. These granitic bodies are usually multiple phased intrusions. The emplacement ages of their major phases are in the range of 165 - 153 Ma. The contemporaneous igneous rocks of intermediate composition （diorite, granodiorite, quartz monzonite）, acidic extrusive rocks and mafic microgranular enclaves with mingling character are very common. The major phase granites are mostly porphyritic biotite granite, sometimes contain hornblende. They are acidic to ultra-acidic, weakly metaluminous to weakly peraluminous, rich in K2O and total alkalis, rich in LILE and HFSE such as Rb, Cs, U, Th, LREE, Y, Nb, Ta, Zr, Hf, Ga, as well as Sn, W etc. oreforming elements and F, Cl etc. volatile elements. On the discrimination diagrams of Whalen et al （1987） they are plotted in the A-type granite field. Their ISr values vary in the range of 0.7063 - 0.7182, εNd（t） values in the range of-1.7 - -8.0, t2DM values in the range of 1.1 - 1.6 Ga, which indicates that different proportions of mantle component were involved in their source materials, especially for the Huashan and Guposhan granites. These granite bodies are usually strongly fractionated. The emplacement ages of the later phase （or the additional phase） fine-grained granites are in the range of 146 -151 Ma. Compared with the major phase, they are more uhra-aeidic, per-aluminous, more enriched in Rb, Cs, U, Y, Sn, W etc. trace elements, hut more depleted in LREE and Zr etc. HFSE. Petrochemically, they are close to the S-type granites. The Sn/W etc. mineralizations were found throughout the whole process of granite emplacement and evolution, beginning from the major intrusive phase, through the additional intrusive p

关 键 词：南岭 A型花岗岩 锡钨矿床 壳幔相互作用 微量元素和同位素地球化学 

分 类 号：P588.121[天文地球—岩石学]