LA-ICP-MS zircon U-Pb dating and geochemical characteristics of ore-bearing granite in skarn-type iron polymetallic deposits of Duoba area,Baingoin County,Tibet,and their significance
LA-ICP-MS zircon U-Pb dating and geochemical characteristics of ore-bearing granite in skarn-type iron polymetallic deposits of Duoba area,Baingoin County,Tibet,and their significance
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发表时间：
2012
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通讯作者：
Yang Yong-qiang;M. Key
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作者：
Yang Yong-qiang;M. Key
多巴地区位于西藏班戈县西北部，靠近班公湖-怒江成矿带中部，分布有大量夕卡岩型铁铜多金属矿床（矿化点），找矿前景良好。由于海拔高、交通不便、开采量少，仅开展了少量工作。显微研究、锆石LA-ICP-MS U-Pb定年及主量和微量元素分析。作者选择了苏沙夕卡岩矿化点和再阿夕卡岩铁多金属矿床，开展了岩石成因与成矿关系的研究。苏沙地区主要发育细粒斑状花岗闪长岩，再阿地区主要发育细粒花岗闪长岩。锆石LA-ICP-MS定年表明，细粒斑状花岗闪长岩的年龄为77.37±0.55 Ma，细粒花岗闪长岩的年龄为79.78±0.99 Ma，推测是晚白垩世岩浆作用的产物。它们的A/CNK值变化在0.78～1.29之间，A/NK值变化在0.88～1.51范围内。岩石属于弱岩石。富含大离子不相容元素Rb、Th、U、K，贫Nb，总体与班公湖-怒江成矿带同期花岗岩相同。Σ REE范围为199.82×10-6～274.64×10-6，LREE/HREE=3.552～7.199，δEu=0.20～0.82，中负Eu异常。这些资料表明，岩浆演化过程中可能发生了斜长石结晶的分离。苏沙和再阿岩体的成矿过程可能与班公湖-怒江洋盆向南俯冲有关，是闭合后岩浆活动的产物。该区具有良好的铁、铋多金属成矿地质和地球化学条件，值得进一步找矿重点关注。和评价工作。
Located in northwestern Baingoin County of Tibet,Duoba area is near the middle of Bangong Co-Nujiang River metallogenic belt with the distribution of a large number of skarn iron-copper polymetallic deposits(mineralization spots) characterized by good prospecting potential.Due to high elevations,traffic inconvenience and less mining,only a small amount of work has been carried out.This research is based on the systematic field geological survey,indoor petrographic and ore microscopic studies,zircon LA-ICP-MS U-Pb dating and analysis of major and trace elements.The authors chose Sousha skarn mineralization spot and Zai'a skarn iron polymetallic deposit to conduct researches on the relationship between the petrogenesis and the mineralization.There are mainly fine grained porphyritic granodiorites in Sousha area and fine grained granodiorites in Zai'a.Zircon's LA-ICP-MS dating indicates that the age of the fine grained porphyritic granodiorite is 77.37±0.55 Ma,whereas that of the fine grained granodiorite is 79.78±0.99 Ma,suggesting products of late Cretaceous magmatism.Their A/CNK values change between 0.78 and 1.29,and A/NK values change in the range of 0.88～1.51.The rocks belong to weakly peraluminous.They are enriched in big ion incompatible elements Rb,Th,U and K,and depleted in Nb,identical overall with the same period granite in Bangong Co-Nujiang River metallogenic belt.∑ REE range from 199.82×10-6 to 274.64×10-6,LREE/HREE= 3.552～7.199,δEu=0.20～0.82,with medium negative Eu anomalies.These data indicate that the separation of plagioclase crystallization might have occurred in magmatic evolution processes.The ore-forming processes of Sousha and Zai'a rock bodies might have had something to do with the southward subduction of the Bangong Co-Nujiang Ocean Basin and acted as the products of magmatic activity after closing.With favorable iron and bismuth polymetallic ore-forming geological and geochemical conditions,this area deserves more attention in further prospecting and evaluation work.