在峨眉山大火成岩省的攀西地区的南北向断裂带内分布着一系列层状镁铁-超镁铁质岩体,它们在时空上与峨眉山玄武岩有着密切的联系,代表了岩浆管道系统。本文选择了3个代表性岩体,含钒钛磁铁矿的攀枝花岩体,含铜镍硫化物矿床的力马河岩体...在峨眉山大火成岩省的攀西地区的南北向断裂带内分布着一系列层状镁铁-超镁铁质岩体,它们在时空上与峨眉山玄武岩有着密切的联系,代表了岩浆管道系统。本文选择了3个代表性岩体,含钒钛磁铁矿的攀枝花岩体,含铜镍硫化物矿床的力马河岩体以及同时含钒钛磁铁矿和铜镍硫化物铂族元素矿床的新街岩体进行了主要元素、微量元素和Sr-Nd同位素地球化学研究。总体上新街岩体在地球化学特征上均介于攀枝花岩体和力马河岩体之间。在主要元素特征上,攀枝花岩体相对富Fe、Ti、Ca、Al,而力马河岩体则相对富Mg。3个岩体的稀土和微量元素标准化曲线均与丽江苦橄岩相似,均显示出LREE和LILE的相对富集,但是力马河岩体有明显的负Nb、Ta和Ti异常,反映了源区有地壳物质或岩石圈地幔的混染。在log(Th/Yb)_(PM)vs.log(Ta/Th)_(PM)图解上,3个岩体显示出线性关系,其中攀枝花岩体具有高的(Ta/Th)_(PM)和低的(TH/Yb)_(PM)值,而力马河岩体则显示出相反的特征,并且该图解也暗示了攀枝花岩体有岩石圈地幔的混染,力马河岩体有上地壳物质的混染,而新街岩体则有下地壳物质的混染。在Sr-Nd同位素特征上,3个岩体也有明显的区别,其中新街岩体具有较均一的(^(87)Sr/^(86)Sr)_t(0.70610～0.70636)和ε_(Nd)(t)值(1.01 to 1.75),力马河岩体则具有高的(^(87)Sr/^(86)Sr)_t(0.70631～0.70930)和低的ε_(Nd)(t)值(-0.85 to-4.13),而攀枝花岩体则与丽江苦橄岩的Sr-Nd同位索组成(0.70434～0.70510,1.1～3.2)相似。然而,3个岩体的Sr-Nd同位素成分(除力马河岩体部分样品外)均落在峨眉山玄武岩和洋岛玄武岩(OIB)内,因此这3个岩体可能均来自于地幔柱,但地幔柱熔体在上升过程中受到了不同物质的混染,其中,攀枝花岩体的源区为地幔柱和岩石圈地幔,新街岩体为地幔柱和下地壳,而力马河岩体则为地幔柱和上地壳,其源区的特征可能反映了地幔柱熔体的演化过程。展开更多
The dunite bodies, which extend as the direction of W-E, are exposed to the southeast of Elazlg located within the Eastern Taurus Belt of Turkey. Mafic-Ultramafic section in the Guleman ophiolite consists ofdunite whi...The dunite bodies, which extend as the direction of W-E, are exposed to the southeast of Elazlg located within the Eastern Taurus Belt of Turkey. Mafic-Ultramafic section in the Guleman ophiolite consists ofdunite which containing disseminated chromites, wehrlite, gabbros （isotrope gabbro and layered gabbro） and clinopyroxenite. Dunite blocks above the harzburgite massif have irregular contacts with the enclosing peridotites. Dunite blocks are generally around a few of meters. Dunite blocks consist of gabbro and pyroxenite patches. The origin of dunite blocks are belong to the transition zone of harzburgitic ophiolites which is located at the base of the mafic layered section. They are entirely or largely magmatic formed by olivine and chromite ponds at the base of the crustal magma chamber. The rather around of rock pieces within dunite bodies are foliated such as features have been ascribed to the ophiolite being impregnated by and reacting with a melt. Rocks in the bodies show depleted in incompatible trace elements such as Ba, Nbet al., characteristic of subduction related magma. Furthermore, the high LREE/HREE and high Rb/Th ratios indicates a mantle that has been enrichmented by subduction. As a result, isotopic data, petrographic and geochemical of bodies＇s result suggest a parental magma derived from an enrichmed source of subduction zone. A few meters of the large dunite bodies, and ascribes to the central dunites a cumulative origin by fractionation from a picritic melt.展开更多
文摘在峨眉山大火成岩省的攀西地区的南北向断裂带内分布着一系列层状镁铁-超镁铁质岩体,它们在时空上与峨眉山玄武岩有着密切的联系,代表了岩浆管道系统。本文选择了3个代表性岩体,含钒钛磁铁矿的攀枝花岩体,含铜镍硫化物矿床的力马河岩体以及同时含钒钛磁铁矿和铜镍硫化物铂族元素矿床的新街岩体进行了主要元素、微量元素和Sr-Nd同位素地球化学研究。总体上新街岩体在地球化学特征上均介于攀枝花岩体和力马河岩体之间。在主要元素特征上,攀枝花岩体相对富Fe、Ti、Ca、Al,而力马河岩体则相对富Mg。3个岩体的稀土和微量元素标准化曲线均与丽江苦橄岩相似,均显示出LREE和LILE的相对富集,但是力马河岩体有明显的负Nb、Ta和Ti异常,反映了源区有地壳物质或岩石圈地幔的混染。在log(Th/Yb)_(PM)vs.log(Ta/Th)_(PM)图解上,3个岩体显示出线性关系,其中攀枝花岩体具有高的(Ta/Th)_(PM)和低的(TH/Yb)_(PM)值,而力马河岩体则显示出相反的特征,并且该图解也暗示了攀枝花岩体有岩石圈地幔的混染,力马河岩体有上地壳物质的混染,而新街岩体则有下地壳物质的混染。在Sr-Nd同位素特征上,3个岩体也有明显的区别,其中新街岩体具有较均一的(^(87)Sr/^(86)Sr)_t(0.70610～0.70636)和ε_(Nd)(t)值(1.01 to 1.75),力马河岩体则具有高的(^(87)Sr/^(86)Sr)_t(0.70631～0.70930)和低的ε_(Nd)(t)值(-0.85 to-4.13),而攀枝花岩体则与丽江苦橄岩的Sr-Nd同位索组成(0.70434～0.70510,1.1～3.2)相似。然而,3个岩体的Sr-Nd同位素成分(除力马河岩体部分样品外)均落在峨眉山玄武岩和洋岛玄武岩(OIB)内,因此这3个岩体可能均来自于地幔柱,但地幔柱熔体在上升过程中受到了不同物质的混染,其中,攀枝花岩体的源区为地幔柱和岩石圈地幔,新街岩体为地幔柱和下地壳,而力马河岩体则为地幔柱和上地壳,其源区的特征可能反映了地幔柱熔体的演化过程。
文摘The dunite bodies, which extend as the direction of W-E, are exposed to the southeast of Elazlg located within the Eastern Taurus Belt of Turkey. Mafic-Ultramafic section in the Guleman ophiolite consists ofdunite which containing disseminated chromites, wehrlite, gabbros （isotrope gabbro and layered gabbro） and clinopyroxenite. Dunite blocks above the harzburgite massif have irregular contacts with the enclosing peridotites. Dunite blocks are generally around a few of meters. Dunite blocks consist of gabbro and pyroxenite patches. The origin of dunite blocks are belong to the transition zone of harzburgitic ophiolites which is located at the base of the mafic layered section. They are entirely or largely magmatic formed by olivine and chromite ponds at the base of the crustal magma chamber. The rather around of rock pieces within dunite bodies are foliated such as features have been ascribed to the ophiolite being impregnated by and reacting with a melt. Rocks in the bodies show depleted in incompatible trace elements such as Ba, Nbet al., characteristic of subduction related magma. Furthermore, the high LREE/HREE and high Rb/Th ratios indicates a mantle that has been enrichmented by subduction. As a result, isotopic data, petrographic and geochemical of bodies＇s result suggest a parental magma derived from an enrichmed source of subduction zone. A few meters of the large dunite bodies, and ascribes to the central dunites a cumulative origin by fractionation from a picritic melt.
