摘要
青藏高原东北缘的松潘-甘孜造山带发育中生代花岗岩类及花岗伟晶岩型锂矿床。本文系统收集了该区同期发育的含矿与不含矿花岗岩的地球化学数据,探索并揭示了花岗岩相关的锂矿成矿的岩浆物源条件。研究表明,含矿与不含矿花岗岩都形成于晚三叠世,其在空间分布上无明显差异。含矿花岗岩具高硅(平均71.57%)、富锂(Li含量>100×10^(-6))和弱过铝质-过铝质(A/CNK为1.04~1.63)特征,相对较低的Ba、Sr含量和Zr/Hf、Nb/Ta值,以及相对较高的Rb含量和Rb/Sr值,为相对贫水条件下形成的过铝质的高分异S型花岗岩;这些含矿花岗岩具相对低的δ^(7)Li值(-3‰~1‰)和ε_(Nd)(t)值(-10~-8),表明其具有相对较多的沉积组分和古老物质的贡献。不含矿花岗岩具变化的SiO_(2)含量,平均铝饱和指数为1.04,具相对较高的Ba、Sr含量和Zr/Hf、Nb/Ta值,其主体为准铝质到过铝质I型花岗岩;它们还具有相对高的δ~7Li值(-1‰~5‰)和ε_(Nd)(t)值(-7~0),表明其中有相对新生物质组分的贡献。综合分析和对比含矿与不含矿花岗岩的地球化学特征,含矿花岗岩主要源自古老地壳物质(ε_(Hf)(t)<0),含交代沉积组分(Th/La>0.6),且岩浆分异程度较高(Zr/Hf<35和Nb/Ta<10)。可见,这些含矿与不含矿花岗岩在地球化学特征上的差异,对认识相关锂矿的成岩成矿过程具有重要意义。
Mesozoic granite and granite-pegmatitic lithium deposits are found in the Songpan-Ganzi orogenic belt,on the northeastern margin of the Tibetan Plateau.This paper systematically collected the geochemical data of both Li-bearing and barren granites formed contemporaneously in this belt,from which the magmatic source conditions associated with lithium ore mineralization are revealed.The results indicate that both Li-bearing and barren granites were formed in the Late Triassic within a similar spatial distribution.However,Li-bearing granites are characterized by high silica content(averaged value=71.57%),elevated lithium content(>100×10^(-6)),and weakly peraluminous properties(A/CNK=1.04~1.63);they also exhibit relatively lower values for Ba,Sr,Zr/Hf,and higher Rb and Rb/Sr ratios than barren granite.These Li-bearing granites are classified as highly differentiated S-type peraluminous granites formed under relatively water-poor conditions.Additionally,they show lowδ^(7)Li(-3‰~1‰)andε_(Nd)(t)(-10~-8)values,indicating significant contributions from sedimentary components and ancient materials.The barren granites,in contrast,display variable SiO_(2)content,with an average aluminum saturation index of 1.04 and relatively high values for Ba,Sr,Zr/Hf,and Nb/Ta.They are categorized as metaluminous to peraluminous I-type granites formed under water-rich conditions.These granites have highδ^(7)Li(-1‰~5‰)andεNd(t)(-7~0)values,suggesting contributions from juvenile materials.A comprehensive analysis of the geochemical characteristics of the two types of granites reveals that the Li-bearing ones were derived from ancient crustal materials(εHf(t)<0),including metasomatic sedimentary components(Th/La>0.6),and exhibit a high degree of magmatic differentiation(Zr/Hf<35 and Nb/Ta<10).The finding on geochemical differences between Li-bearing and barren granites are crucial for understanding the lithium mineralization.
作者
邱志毅
李舢
戴梦
崔祥蝶
邓敏
QIU ZhiYi;LI Shan;DAI Meng;CUI XiangDie;DENG Min(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 101408,China;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《岩石学报》
SCIE
EI
CAS
2024年第12期3876-3890,共15页
Acta Petrologica Sinica
基金
国家自然科学基金项目(92162322)
中国科学院新百人计划项目(E3ER0401A2)联合资助。
关键词
松潘-甘孜造山带
三叠纪花岗岩
锂矿
地球化学
Songpan-Ganzi orogenic belt
Triassic granite
Lithium deposits
Geochemistry
