CAJ | 학술논문

滇西富碱斑岩型多金属矿区黄铁矿和石英脉流体包裹体中 R/Ra 值主要为0.1608~3.4700,远高于地壳特征值,而整体略低于地幔特征值；20 Ne/22 Ne 和21 Ne/22 Ne 平均值分别为11.2710和0.0322,接近地幔同位素组成；40 Ar/36 Ar 和38 Ar/36 Ar 平均值分别为395.5100和0.1976,均高于大气比值,而低于 MORB 比值；与大气相比,128 Xe/130 Xe、129 Xe/130 Xe、131 Xe/130 Xe、132 Xe/130 Xe、134 Xe/130 Xe、136 Xe/130 Xe 值均表现出过剩的特征；富硅成矿流体的δ30 Si 值为-2.4‰~-0.1‰,表现出几乎未经动力分馏的原始地幔流体性质,而富碱岩浆的δ30 Si 值为0.0‰~0.4‰,表现出历经强烈动力分馏的交代富集地幔流体性质。综合研究表明：滇西地区硅同位素组成与包裹体稀有气体同位素组成在显示含矿流体的幔源特征的同时,又表现出强烈的地壳特征；成矿物质主要来自地幔交代作用形成的富集地幔分异产物,即富碱岩浆和与之伴随的富硅成矿流体,二者携带成矿物质沿断裂进入地壳,伴随富硅成矿流体在富碱岩浆的成岩过程中对富碱斑岩与地层岩石的交代蚀变,从而引发壳幔物质叠加混染。正是这种流体作用构成了滇西新生代富碱斑岩多金属成矿的内在统一制约因素。
전서부감반암형다금속광구황철광화석영맥류체포과체중 R/Ra 치주요위0.1608~3.4700,원고우지각특정치,이정체략저우지만특정치；20 Ne/22 Ne 화21 Ne/22 Ne 평균치분별위11.2710화0.0322,접근지만동위소조성；40 Ar/36 Ar 화38 Ar/36 Ar 평균치분별위395.5100화0.1976,균고우대기비치,이저우 MORB 비치；여대기상비,128 Xe/130 Xe、129 Xe/130 Xe、131 Xe/130 Xe、132 Xe/130 Xe、134 Xe/130 Xe、136 Xe/130 Xe 치균표현출과잉적특정；부규성광류체적δ30 Si 치위-2.4‰~-0.1‰,표현출궤호미경동력분류적원시지만류체성질,이부감암장적δ30 Si 치위0.0‰~0.4‰,표현출력경강렬동력분류적교대부집지만류체성질。종합연구표명：전서지구규동위소조성여포과체희유기체동위소조성재현시함광류체적만원특정적동시,우표현출강렬적지각특정；성광물질주요래자지만교대작용형성적부집지만분이산물,즉부감암장화여지반수적부규성광류체,이자휴대성광물질연단렬진입지각,반수부규성광류체재부감암장적성암과정중대부감반암여지층암석적교대식변,종이인발각만물질첩가혼염。정시저충류체작용구성료전서신생대부감반암다금속성광적내재통일제약인소。
R/Ra values of fluid inclusions from pyrite and quartz veins from alkali-rich porphyry molymetallic deposits in western Yunnan are mainly in the range of 0.1 60 8 3.470 0,being much higher than the corresponding values of the crust,but a little lower than those of the mantle;the average 20 Ne/22 Ne values and 2 1 Ne/22 Ne values are averaged at 1 1.271 0 and 0.032 2,being close to those of the mantle;40 Ar/3 6 Ar values and 38 Ar/3 6 Ar values are averaged at 395.5 10 0 and 0.1 97 60 respectively,being higher than the air ratio but are lower than the MORB ratio;compared with air, 1 28 Xe/1 30 Xe,1 2 9 Xe/1 30 Xe,1 3 1 Xe/1 30 Xe,1 32 Xe/1 30 Xe,1 34 Xe/1 30 Xe,1 3 6 Xe/1 30 Xe values show a surplus characteristics;δ30 Si values of the silicon-rich ore-forming fluids vary from -2.4‰ to -0.1‰,showing a characteristic feature of the original mantle fluids almost without isotopic kinetic fractionation,whileδ30 Si values of the alkali-rich magma range from 0.0‰ to 0.4‰,showing a feature of the metasomatic enriched mantle fluids with drastic isotopic kinetic fractionation.So noble gas and silicon isotopic compositions reveal that ore-bearing fluids have both mantle-derived and the crust-modified characteristics in western Yunnan.The ore-forming materials mainly derived from the differentiation products of the metasomatized enriched mantle.These alkali-rich magma and related silicon-rich ore-forming fluids carried the ore-forming materials upwards into the crust through the deep faults.The replacement and alteration of the alkali-rich porphyry and their host strata by the silica-rich ore-forming fluids during the crystallization processes of the alkali-rich magmas led to the overprinting and contamination of the mantle and crust materials.It is such a process of fluids that makes up the key controlling factors for the Cenozoic alkali-rich porphyry polymetallic deposits in western Yunan.