四川康定-冕宁地区变质侵入岩的地球化学及Nd同位素研究

The petro-chemistry and Nd isotopes study of metamorphic intrusions in Kangding-Mianning,Sichuan province.

通过对四川康定-冕宁地区出露的康定杂岩中基性、中性、酸性岩岩石学、微量元素地球化学、Sm-Nd 同位素等多方面系统研究,确定这套岩石形成于岛弧环境。Sm-Nd 同位素未能形成等时线,说明可能岩石形成后经历了较高温度的热扰动,ε_(Nd)(t)大于零,表明样品可能来源于一个较为亏损的地幔,其亏损地幔模式年龄集中在1.2～1.4Ga。通过对该区岩石的 AFC(同化混染结晶分离)过程模拟,说明岛弧岩浆形成后分离结晶时同化混染围岩,中-酸性深成岩体是残留岩浆,约为原始岩浆量的60%,其结晶形成的混染速率与结晶速率比值约0.9。

It was indicated that Kangding metamorphosed intrusions in Kangding and Mianning, Sichuan Province formed in island arc setting through the integrated study including whole rock chemistry, trace elements geochemistry and Nd isotopic geochemistry of plutonic rocks range from acid to basic ones. There is no isochrones formed by Sm-Nd isotopic data, which indicated these samples may have experienced a high temperature disturbance. Positive εNd （t） suggested that they may have derived from a relative depleted mantle source, and most of them had 1. 2 - 1. 4Ga depleted model ages. Through AFC （Assimilation and Fractional Crystallization ） simulation, the results show that the assimilation rate was nearly equal to the crystallization rate when the residual magma fraction was about 60% of the original one.