摘要
位于华北克拉通南缘河南省方城县的大庄铌-稀土矿是近年来新发现的一例具有中型规模的铌-稀土矿床.该矿床赋存于新元古代双山碱性侵入岩中,黑云母正长岩和角闪霞石正长岩是铌-稀土矿的主要赋矿岩石.通过电子探针与LAICP-MS等方法对大庄铌-稀土矿碱性岩中的榍石开展了主量、微量元素、U-Pb年代学和微区Nd同位素研究.大庄铌-稀土矿碱性岩中榍石的SiO_(2)(28.597%~31.169%)、CaO(25.492%~28.949%)、TiO_(2)(34.126%~38.940%)平均含量明显低于理论值,含有相对较高的F(0.141%~1.086%)、Al_(2)O_(3)(1.573%~2.817%)和FeO(0.446%~2.147%).榍石具有极高的稀土元素总量(∑REE=781.47×10^(-6)~31766.59×10^(-6)),球粒陨石标准化稀土配分曲线呈明显的右倾型,轻重稀土分馏明显,样品具有明显的负δEu异常(0.27~0.86)和不明显的δCe异常(0.97~1.22),Th/U值介于1.40~11.86,暗示大庄铌-稀土矿碱性岩中榍石为岩浆成因榍石,榍石Zr温度计获得大庄碱性岩的形成温度为667~964℃,平均为933℃.大庄铌-稀土矿碱性岩中的榍石具有极高的Nb和REE含量,表明榍石是大庄铌-稀土矿的重要成矿矿物,铌、稀土等元素是伴随岩浆演化逐步富集的结果.富铌榍石样品获得848±35 Ma、849±22 Ma、843±30 Ma、845±20 Ma、845±24 Ma和849±40 Ma的形成年龄,限定大庄铌-稀土矿化富集的时代为新元古代,与Rodinia超大陆裂解事件相关.榍石具有较为均一的Nd同位素值(ε_(Nd)(t)=-3.25~-0.66),表明方城地区霞石正长岩的原始岩浆形成于富金云母的地幔源区.
The Dazhuang deposit is a newly discovered medium-scale Nb-REE deposit which is located at the Fangcheng County of Henan Province on the southern margin of the North China craton.The Nb-REE orebodies are hosted in biotite syenite and hornblende nepheline syenite of Neoproterozoic Shuangshan alkaline pluton.In this paper,major and trace elements,U-Pb geochronology and in-situ Nd isotope studies were carried out on the titanite from the alkaline rocks by EPMA and LA-ICP-MS.The average contents of SiO_(2)(28.597%-31.169%),CaO(25.492%-28.949%)and TiO_(2)(34.126%-38.940%)in titanite are significantly lower than the theoretical values,whereas it contains relatively high contents of F(0.141%-1.086%),Al_(2)O_(3)(1.573%-2.817%)and FeO(0.446%-2.147%).The titanite in Dazhuang deposit has a very high total amount of REE(∑REE=781.47×10^(-6)-31766.59×10^(-6)).In the chondrite-normalized REE patterns,the rare earth distribution curve is obviously right-leaning,and the light and heavy rare earth fractionation is obvious.There are obvious negativeδEu anomalies(0.27-0.86)and inconspicuousδCe anomalies(0.97-1.22),with Th/U values ranging from 1.40 to 11.86,suggesting that the titanite is magmatic origin.The formation temperature of Dazhuang alkaline rocks obtained by the titanite Zr thermometer is 667-964℃,with an average of 933℃.The titanite in Dazhuang deposit has very high Nb and REE contents,indicating that the titanite is an important ore-bearing mineral,and the Nb and REE are the result of the gradual enrichment of magma evolution.Formation ages of 848±35 Ma,849±22 Ma,843±30 Ma,845±20 Ma,845±24 Ma,and 849±40 Ma were obtained from the Nb-rich titanite samples,constraining that the mineralization age of Dazhuang Nb-REE deposit is Neoproterozoic,of which related to the breakup of the Rodinia supercontinent.Titanite has a relatively uniform Nd isotope(ε_(Nd)(t)=-3.25 to-0.66)value,indicating that the original magma was derived from mantle where rich in phlogopite.
作者
李志丹
李山坡
郭虎
曾威
崔玉荣
李效广
陈俊魁
张哨波
Li Zhidan;Li Shanpo;Guo Hu;Zeng Wei;Cui Yurong;Li Xiaoguang;Chen Junkui;Zhang Shaobo(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Tianjin Center of China Geological Survey,Tianjin 300170,China;North China Center of Geoscience Innovation,Tianjin 300170,China;Henan Geological Survey Institute,Zhengzhou 450001,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2022年第4期1415-1434,共20页
Earth Science
基金
河南省自然资源科研项目(No.豫财招标采购-2020-165-3)
中国地质调查局项目(Nos.DD20211191,DD20200148,DD20221686,DD20190119,DD20221871)
国家自然科学基金项目(No.41502082)。
关键词
大庄铌-稀土矿
U-PB年龄
ND同位素
榍石
华北克拉通南缘
矿床
Dazhuang Nb-REE deposit
U-Pb age
Nd-isotopic compositions
titanite
southern margin of the North China craton
ore deposit
