沉积与特提斯地质2025，Vol.45Issue(2)：408-423,16.DOI:10.19826/j.cnki.1009-3850.2025.04002
西藏班公湖-怒江成矿带高保约铜金矿含矿花岗斑岩的年代学、地球化学特征及其地质意义
Chronology,geochemical characteristics and geological significance of ore-bearing granite porphyries in Gaobaoyue Cu-Au deposit,the Bangong Co-Nujiang metallogenic belt,Xizang,China
摘要
Abstract
The Gaobaoyue deposit is a newly discovered copper-gold deposit located in the middle section of the Bangong Co-Nujiang metallogenic belt.The ore deposit is primarily associated with exposed granodiorite and granite porphyry,with the latter being an ore-bearing rock.Zircon U-Pb dating results indicate that the weighted average 206Pb/238U age of the granite porphyry is(154.5±0.7)Ma,suggesting a Late Jurassic age for its formation.The granite porphyry is a calc-alkaline,metaluminous I-type granite,with an alumina saturation index(A/CNK)ranging from 0.84 to 0.98.It is enriched in large ion lithophile elements and light rare earth elements,while depleted in high field strength elements and heavy rare earth elements,with(La/Yb)N values ranging from 5.19 to 8.61.Compared to Rb and Th,Ba is depleted.In addition,it exhibits a weak negative europium anomaly,with δEu values varying from 0.70 to 0.98.These geochemical characteristics are typical of magmatic rocks in subduction zones.The porphyry contains homogeneous zircon Hf isotopes with depletion—the εHf(t)values vary from 8.49 to 10.28,and the zircon two-stage model ages(TDM2)range from 662 Ma to 564 Ma.The whole-rock(87Sr/86Sr)i values range from 0.707 2 to 0.707 7,while the εNd(t)values are from 1.69 to 2.66.The whole-rock Nd isotopic two-stage model ages(TDM2)are from 770 Ma to 640 Ma.The porphyries are enriched in radiogenic whole-rock Pb isotopes,with(206Pb/204Pb)i values varying from 18.370 to 18.437,(207Pb/204Pb)i values from 15.665 to 15.669,and(208Pb/204Pb)i values from 38.605 to 38.669.There is a certain degree of decoupling between the whole-rock Nd isotopes and zircon Hf isotopes.During the early subduction process,high oxygen fugacity fluids rich in water and ore-forming materials,which are generated by the dehydration of the oceanic crust slab,metasomatize the lithospheric mantle and undergo partial melting.Mantle-derived magmas with high oxygen fugacity,rich in water and ore-forming materials,underplate at the bottom of the lower crust,forming a newly formed lower crust.Around 154 Ma,during the northward subduction and consumption process of the Bangong Co-Nujiang oceanic crust,the underplating of mantle-derived magmas occurred,leading to the partial melting of the newly formed lower crust and forming the Gaobaoyue ore-bearing porphyry.关键词
花岗斑岩/I型花岗岩/锆石U-Pb年代学/Sr-Nd-Pb-Hf同位素/铜金矿/班公湖-怒江成矿带Key words
granite porphyry/I-type granite/zircon U-Pb geochronology/Sr-Nd-Pb-Hf isotope/Cu-Au deposit/Bangong Co-Nujiang metallogenic belt分类
天文与地球科学引用本文复制引用
李红兵,张海,刘铸,王富明,盛德波,唐沙..西藏班公湖-怒江成矿带高保约铜金矿含矿花岗斑岩的年代学、地球化学特征及其地质意义[J].沉积与特提斯地质,2025,45(2):408-423,16.基金项目
四川省冕宁县新民金矿普查(DZ202319) （DZ202319）
中国地质调查局地质调查项目(DD20230049,DD20230031,DD20240069) （DD20230049,DD20230031,DD20240069）
国家自然科学基金重点项目(91955208) （91955208）
