(1. 北京科技大學(xué) 土木與資源工程學(xué)院，北京 100083；
2. 北京科技大學(xué) 金屬礦山高效開采與安全教育部重點實驗室，北京 100083)
3. 中國地質(zhì)調(diào)查局武漢地質(zhì)調(diào)查中心，武漢 430205；
4. 中國地質(zhì)大學(xué)(北京)，北京 100083)
摘 要: 阿斯馬拉(Asmara)地區(qū)位于非洲東北部的厄立特里亞，是重要的VMS型礦床成礦帶。對其礦石結(jié)構(gòu)特征和成礦物質(zhì)來源的分析研究有利于區(qū)域成礦規(guī)律的總結(jié)。在分析礦床成礦地質(zhì)條件的基礎(chǔ)上，研究Emba Derho和Debarwa VMS型礦床的礦石結(jié)構(gòu)特征、礦石硫、鉛同位素組成及閃鋅礦中的流體包裹體特征。結(jié)果表明：Debarwa和Emba Derho礦床成礦作用在經(jīng)過VMS過程之后，其后期的變形變質(zhì)過程對成礦的改造和疊加作用有限。閃鋅礦中的流體包裹體研究顯示其成礦流體具有低鹽度、中-高溫的特征。Debarwa和Emba Derho礦床中黃鐵礦、閃鋅礦和黃銅礦等原生硫化物礦物的δ34SCDT值變化范圍較窄，數(shù)據(jù)集中在0.01%~0.48%之間，重晶石S同位素為高正值(δ34S=1.66%~1.73%)，具有地幔硫和海水硫的混合來源特征。Debarwa 和Emba Derho礦床礦石鉛同位素組成穩(wěn)定，顯示正常鉛的特征。對礦石鉛同位素進(jìn)行特征參數(shù)示蹤、鉛構(gòu)造模式示蹤和Δβ-Δγ圖解示蹤的結(jié)果表明：Debarwa和Emba Derho礦床中礦石鉛主要為地殼與地幔混合的俯沖鉛。
關(guān)鍵字: 硫同位素；鉛同位素；流體包裹體；VMS型礦床；厄立特里亞
（1. School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. Key Laboratory of High-Efficient Mining and Safety of Metal, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China;
3. Wuhan Center of China Geological Survey, Wuhan 430205, China;
4. China University of Geosciences, Beijing 100083, China）
Abstract:Volcanogenic massive sulfide (VMS) deposit is an important type of nonferrous deposit. In Eritrea, Neoproterozoic volcanogenic massive sulphide deposits and occurrences, to a large extent, distribute in Asmara-Nakfa Belt (ANB). The most important mineral deposits and occurrences known in Asmara-Nakfa Belt are those of the Emba Derho and Debarwa VMS deposits. Based on the research related to the Debarwa and Emba Derho deposit’s oreforming geological conditions, the compositions of S, Pb isotopes as well as the characteristics about fluid inclusions in sphalerite and ore textures were studied, and the origin of oreforming materials was discussed. The results show that the transformation and superposition of regional metamorphism for deposits are limited. Ore-bearing fluids are characterized by medium-high temperature, low salinity. The δ34SCDT values of primary sulfide ore minerals distribute narrowly (0.01%-0.48%) in Debarwa and Emba Derho deposits, δ34SCDT value of barite in Debarwa deposit is 1.66%-1.73%. The characteristics of sulfur isotopic composition show that the sulfur in these two deposits is derived from the mantle mixed seawater. Meanwhile, the Pb isotopic composition of ore sulfides is stable and the ore lead is ordinary common lead with little U and Th radiogenic lead. According to the tracer analysis regarding the characteristic parameters, lead composition model and Δβ-Δγ diagram, the conclusion is drawn that the ore lead is typically crustmantle mixed subduction lead.
Key words: sulfur isotope？ lead isotope？ fluid inclusions; VMS deposit; Eritrea
