Temporal Emplacement Sequence of the South Nam Xe Carbonatites (Northwest Vietnam)  

作　　者：Thuy Nguyen Thi Hideki Wada 

机构地区：[1]Hue University of Sciences,Hue University,No.77 Nguyen Hue St.,Hue City 49100,Vietnam [2]Institute of Geosciences,Shizuoka University,Ohya 836,Suruga-ku,Shizuoka 422-8529,Japan

出　　处：《Journal of Geological Resource and Engineering》2021年第1期13-24,共12页地质资源与工程（英文版）

摘　　要：South Nam Xe carbonatites are located in northwest Vietnam and include calcio-and ferro-carbonatite dikes.This investigation on their petrography,mineralogy and whole rock chemistry aims to constrain temporal emplacement sequence of the carbonatites during their evolution.The calciocarbonatites are supposed to be formed in the first or second stage due to massive coarse-grained texture with an assemblage of calcite,typical magmatic alkaline silicates(aegirine,arfvedsonite),biotite,fluorapatite and magnetite.Their calcites show a high CaO/(MgO+Fe_(2)O_(3)+MnO)ratio and a predominance of SrO over MnO(SrO=3.81-3.98 wt.%;MnO=0.66-0.78 wt.%).Rare earth elements(REE)tend to participate in rock-forming minerals rather than in isolated REE minerals.The ferrocarbonatites are composed of magmatic and hydrothermal varieties and assumed to be formed in the third and/or fourth stage.Major minerals of the former include zoned ankerite,Sr-rich calcite,subhedral feldspar crystals,phlogopite and magnetite;fluorapatite,monazite and REE carbonates are minor resulting in a moderate REE concentration of 43,200 ppm.Meanwhile,the latter is predominant by syntax-texture REE fluorcarbonates and(Ba,Sr)sulphates.Further,the highest REE concentration(163,900 ppm)of the rock coupled with abundance of volatile minerals(fluorite,fluorcarbonates,sulphides)and ^(18)O enrichment in the calcites(δ^(18)O_(V-SMOW)=12.01-13.26‰)is probably attributed to hydrothermal subjection in the last stage.

关 键 词：CARBONATITE South Nam Xe emplacement sequence 

分 类 号：P59[天文地球—地球化学]