摘要
锂同位素作为一种示踪工具在地球化学研究中发挥着重要作用。本文首次尝试将锂同位素研究应用于四川甲基卡伟晶岩型锂多金属矿区新三号(X03)矿脉的找矿实践。新三号矿脉ZK1101的系统锂同位素分析结果显示,含矿(锂辉石)伟晶岩中的w(Li)为0.94%~1.80%,δ7 Li值为-1.5‰^-1.0‰,平均值为-1.3‰,相对稳定,变化幅度小;不含矿伟晶岩的w(Li)平均值为0.04%,δ7 Li平均值为+2.0‰,与含矿伟晶岩可区分开;围岩的w(Li)为0.02%~0.12%,δ7 Li值为-13.4‰^-0.4‰,平均值为-7.7‰,变化范围较大。锂同位素在含矿伟晶岩、不含矿伟晶岩和围岩中存在的明显差异,可作为今后找矿的"示踪剂"。锂同位素组成与锂含量之间不存在直接的线性关系,其三者之间的差异可能在于分馏机制的差异:伟晶岩中锂同位素的分馏机制属于"热力学平衡分馏";而围岩中锂同位素的分馏机制属于"动力学非平衡分馏"。新三号矿脉中伟晶岩锂同位素的组成暗示其与矿区二云母花岗岩之间具有成因联系,同时围岩中锂同位素的变化趋势也暗示其深部可能存在隐伏矿体,具有找矿潜力。
Lithium isotope is taken as a tracer tool and plays an important role in the study of geochemistry. This paper is mainly to introduce the preliminary application of lithium isotope in the new No. 3（×03）ore vein, Jiajika pegmatite-type lithium polymetallic orefield. The systematic lithium and lithium isotope study of a typical drill from the X03 ore vein shows absorbing results. The 87 Li values of the pegmatite with spodumene （10 samples, Li content ranges from 0. 94% to 1.80%） range from --1.5%o to --1.0~0, with an average of -- 1.3%0, showing a characteristic of little change. The average 87 Li value of the pegmatite without spodumene （2 samples, mean content of Li is 0.04%） is ＋2. 0‰, which is clearly different from the spodumene-bearing pegmatite. The 87Li values of country rock （6 samples, Li content varies from 0. 02% to 0. 12%） vary from -13. 4‰a to -0.4‰, with an average of -7. 7‰, showing a characteristic of wide range. Although there is no direct linear relationship between lithium isotopes and lithium contents, lithium isotopes have obvious differences in mineralized pegmatite, non-mineralized pegmatite and wall rocks, owing to the fractionation mechanism of lithium isotopes. The lithium isotopes fractionation mechanism of pegmatite belongs to ＂thermodynamic equilibration fractionation＂, while that of country rock belongs to＂dynamic non-equilibrium fractionation＇. The distribution of lithium isotopes for the X03 pegmatite vein indicates that there has genetic connection between pegmatite and granite. In addition, the change of the lithium isotopes in the wall rocks indicated that there may be concealed orebodies in the deep part with large prospecting potential, and the application of lithium isotopes is of great guiding significance. In conclusion, the lithium isotopes can be used as tracers according to their differences for future prospecting.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2017年第5期167-171,共5页
Earth Science Frontiers
基金
中国地质调查局地质大调查项目"大宗急缺矿产和战略性新兴产业矿产调查"工程"川西甲基卡大型锂矿资源基地综合调查评价"项目(DD20160055)
"华南重点矿集区稀有稀散和稀土矿产调查"项目(DD20160056)
"中国矿产地质与成矿规律综合集成和服务"(矿产地质志)项目(DD20160346)
关键词
甲基卡
新三号矿脉
伟晶岩
锂同位素
找矿
Jiajika
the X03 ore veim pegmatite
lithium isotope
prospecting
