| 论阿尔泰3号伟晶岩脉的成因 |
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| 引用本文：.1986.The Origin Of No.3 Pegmatite In Altayshan,Xinjiang[J].Mineral Deposits,5(4):34~48 |
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| The Origin Of No.3 Pegmatite In Altayshan,Xinjiang |
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| Abstract:Being of muscovite-microcline-albite-spodumene type, No. 3 pegmatite is composed of 80 minerals which make up 36 mineral assemblages and 10 textutal zones, showing typical structure of concentric rings. No. 3 pegmatite was formed as a result of prolonged slow crystallization differentiation with isotopic ages ranging from 330 Ma to 200 Ma, decreasing gradually from the margin towards the center of the vein. The stable isotope values of No.3 pegmatite are as follows: δ18O (quartz) +11.84‰ - +13.87‰, δD ( water in fluid inclusions) -86.6‰～ -48.4‰, δ13C (CO2 in fluid inclusions) -6.4‰, 87Sr/86Sr (whole rock) 0.7512, and 87Sr/86Sr (apatite) 0.7522. In outer part of the pegrnatite (graphic pegmatite), the primary inclusions consists of silicate aggregates containing some 20-30 percent (in volume) gaseous phase with homogenization temperatures being 930-1100℃. In contrast, the fluid inclusions have homogenization temperatures of 620-500℃ and salinity of 9.77-0.35 ( in weight percentage). The spodumene-quartz assemblage seems to be the unique lithium alumino-silicate mineral assemblage in No. 3 pegmatite, implying the formation of the rocks through magmatic crystallization under comparatively high P-T-conditions. The conclusion can therefore be reached that No.3 pegmatite was produced by differentiation of magmas formed through anatexis of upper continental crust. |
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