滇西上地幔铅同位素演化模式及滇西富碱斑岩铅同位素组成的诠释

The Pb Isotope Evolution Model of the Upper Mantle in Western Yunnan and Interpretation of Lead Isotopic Compositions of Regional Alkali-rich Porphyries

大量的Pb同位素数据资料表明 ,滇西上地幔铅具两阶段演化历史 ,但又不是很好地吻合Stacey Kramers的两阶段模式。本文依据Stacey Kramers建造两阶段模式的基本原理 ,结合滇西地区上地幔铅同位素组成资料 ,拟合出了能更好地反映滇西上地幔铅同位素演化历史的二阶段模式并应用此模式对滇西富碱斑岩及其相关岩石的铅同位素组成做出诠释。

Thirty Pb isotope data of the upper mantle in western Yunnan show trends similar to Stacey-Kramers′ two stage model growth curves but apparently deviate from the latter curves on the lead isotope composition programs. This may suggest that Pb isotope of the upper mantle in western Yunnan might have experienced two stages of evolution though it is not fit very well to Stacey-Kramers' two-stage model growth curves. In this paper,a two-stage growth curves model which can better fit the Pb isotope data was constructed on the basis of the lead isotope data of the upper mantle in western Yunnan. With this model,a reasonable interpretation is given to the lead isotopic compositions of the regional alkali-rich porphyries and their related rocks.