广西大厂锡多金属矿区深部碳酸盐岩的稀土元素特征及其地质意义  

Characteristics of Rare Earth Elements in the Deep Carbonate Rocks and Their Geological Significance in the Dachang Tin-polymetallic Deposit of Guangxi

作　　者：秦燕[1] 王登红[1] 梁婷[2] 李建康[1] 侯可军[1] 

机构地区：[1]国土资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所,北京100037 [2]长安大学地球科学与国土资源学院,陕西西安710054

出　　处：《岩矿测试》2014年第2期296-302,共7页Rock and Mineral Analysis

基　　金：国家深部探测技术与实验研究专项课题(SinoProbe 0301);中国地质大调查项目(1212011120989;1212010633903;1212011120354);中央级公益性科研院所基本科研业务费专项资金(K1214;K1013)

摘　　要：广西大厂巴里地区锡多金属矿体经过多年的快速开采,导致浅部资源枯竭,深部找矿迫在眉睫.本文以广西大厂超大型锡多金属矿区深部钻探ZK39-1钻孔（钻孔深度1580 m）获得的新鲜岩心为研究对象,采用激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）详细分析了该钻孔钻遇的泥盆系中下统灰岩样品的稀土元素含量（REEs）,以期为深部找矿提供依据.研究结果表明,稀土元素总量（ΣREEs）为3.49～261.07 μg/g,稀土总量变化较大,且岩心样品在顶部与底部相差较大,其中1100 ～ 1580 m之间岩心样品ΣREEs（3.49～45.81g/g）明显低于1100 m以浅稀土总量（188.96～242.36 μg/g）,达到了区域背景值的10倍左右,且远超过普通沉积成因的石灰岩;轻稀土与重稀土比值LREEs/HREEs为2.96 ～10.04,反映了该区轻、重稀土元素分馏程度较高,δEu为0.11～1.00,δCe为0.53 ～0.99;球粒陨石标准化分布型式图呈“右倾”轻稀土富集型.10～1100 m之间样品Eu异常不明显,1100～ 1580 m之间样品Eu明显亏损,顶部到底部Ce亏损逐渐降低.1100～1580 m之间岩心样品球粒陨石标准化型式图与大厂花岗岩型式图相似,认为这套碳酸盐岩可能受到了花岗岩浆热液的蚀变作用,指示深部可能还存在岩浆热液成因或矽卡岩型多金属矿化,即在近花岗岩部位或花岗岩与围岩接触带部位存在“第三成矿空间”.After years of rapid mining,the shallow resources of the polymetallic tin ore bodies in the Bali area,Dachang,have been depleted.Therefore,deep prospecting is imminent.The REEs of limestone samples in the Middle/Upper Devonian from drill holes of ZK39-1 in the Bali area,Dachang,by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry （LA-ICP-MS） have been analysed and the process is presented in this paper.The drilling depth is 1580 m,which is one of the world＇s deepest hole drilling.The results showed that the amount of the REES （ΣREEs） is 3.49-261.07 μg/g with a large range.ΣREEs （3.49-45.81 μg/g） of drill core samples at 1100-1580 m are significantly lower than ΣREEs （188.96-242.36 μg/g） at 1100 m above,which is about 10 times the regional background values and far more than common sedimentary limestone.The ratios of light rare earth elements and heavy rare earth elements （LREEs/HREEs） had a range of 2.96-10.04,which meant that there was a high degree of fractionation between light rare earth elements and heavy rare earth elements.δEu values varied between 0.11 and 1.00 and δCe values ranged from 0.53 to 0.99.The Chondrite-normalized distribution pattern chart was ‘ right inclination’ LREE enrichment type.Samples from1100-1580 m had a negative Eu anomaly and Ce had a negative anomaly decreasing from top to bottom.The chondrite-normalized pattern chart of 1100-1580 m drill core samples was similar to that of granite from Dachang,indicating that the carbonates were altered by granite magma and that there might be deep magrnatic hydrothermal origin or silicon skarn-type polymetallic mineralization near the granite contact zone,known as the ‘third metallogenic spatial’.

关 键 词：碳酸盐岩 稀土元素 深部找矿 广西大厂超大型锡矿 

分 类 号：P588.245[天文地球—岩石学] O614.33[天文地球—地质学]