CAJ | 학술논문

对苦橄岩中橄榄石斑晶及其中熔体包裹体的电子探针分析表明，峨眉山大火山岩省的原始岩浆具高镁(MgO>16％)特征。玄武岩的REE反演计算揭示，参与峨眉山玄武岩岩浆作用的地幔具有异常高的潜能温度(1550℃)。这些特征以及峨眉山玄武岩的大面积分布和一些熔岩所显示的类似于洋岛玄武岩(0IB)的微量元素和Sr-Nd同位素特征均为地幔热柱在能量和物质上参与峨眉山溢流玄武岩的形成提供了确凿证据。峨眉山两个主要岩类(高钛和低钛玄武岩)可能是不同地幔源区物质在不同条件下的熔融产物。低钛玄武岩形成于温度最高、岩石圈最薄的地幔柱轴部。地幔(Isr≈0.705，εNd(t)≈+2)熔融始于140km，并一直延续到较浅的深度(60km，尖晶石稳定区)，部分熔融程度为16％，这类岩石可能代表了峨眉山玄武岩的主体。而高钛玄武岩的母岩浆的形成基本局限在石榴子石稳定区(>70km)，其源区特征为：Isr≈0.704，εNd(t)≈+5，可能代表了热柱边部或消亡期地幔小程度部分熔融(1.5％)的产物。
대고감암중감람석반정급기중용체포과체적전자탐침분석표명，아미산대화산암성적원시암장구고미(MgO>16％)특정。현무암적REE반연계산게시，삼여아미산현무암암장작용적지만구유이상고적잠능온도(1550℃)。저사특정이급아미산현무암적대면적분포화일사용암소현시적유사우양도현무암(0IB)적미량원소화Sr-Nd동위소특정균위지만열주재능량화물질상삼여아미산일류현무암적형성제공료학착증거。아미산량개주요암류(고태화저태현무암)가능시불동지만원구물질재불동조건하적용융산물。저태현무암형성우온도최고、암석권최박적지만주축부。지만(Isr≈0.705，εNd(t)≈+2)용융시우140km，병일직연속도교천적심도(60km，첨정석은정구)，부분용융정도위16％，저류암석가능대표료아미산현무암적주체。이고태현무암적모암장적형성기본국한재석류자석은정구(>70km)，기원구특정위：Isr≈0.704，εNd(t)≈+5，가능대표료열주변부혹소망기지만소정도부분용융(1.5％)적산물。
Electron microprobe analyses on olivine phenocrysts in picritesand their trapped melt inclusions confirmed the existence of high magnesian (MgO > 16% ) primary magmas for the Emeishan basaltic province. The application of McKenzie and O'Nions' (1991) rare earth element inversion scheme to the geochemistry of the Emeishan basalts reveals an enhanced mantle potential temperature of 1 450～1 550 ℃. These, together with the vast volume of basalts and the OIB-like signatures preserved in some samples, strongly suggest the involvement of mantle plumes in the generation of the Emeishan basalts. It is further suggested that two distinct mantle components may have been involved in generation of the low-Ti and high-Ti lavas, respectively. Whereas the high-Ti basalts originated most likely from an OIB-like mantle source (lsr ≈ 0. 704, εNa(t) ≈ +5), a slightly enriched mantle component ( lsr≈0. 705, εNa (t) ≈ + 2) is required for the low-Ti lavas. The low-Ti lavas were generated in the plume axis where the mantle temperature is high and the lithosphere is relatively thin. The melting was initiated at a relatively great depth ( 140 kmn, garnet stability) and continued to the shallow level (60 km, spinel stability). The total degree of partial melting is 16%. The low-Ti lavas may thus represent the main phase of this large igneous province. In contrast, the high-Ti lavas resulted from melting of the mantle at plume periphery or during a waning stage of plume activity. The low mantle potential temperature and thick lithosphere led the depth to the top of melting column confined within the garnet stability field and a relatively low degree of melting ( 1.5% ).