腾冲地区火山岩铀钍地球化学特征及其成因的初步探讨

A PRELIMINARY STUDY OF THE GEOCHEMICAL BEHAVIORS OF U AND Th AND THE GENESIS OF VOLCANIC ROCKS FROM TENGCHONG AREA, YUNNAN PROVINCE, CHINA

腾冲火山岩位于云南省西部，主要分布于腾冲、梁河两县境内。处于印度板块和欧亚板块之间的缝合地带，是次一级的板块——腾冲断块。在广泛分布的中新生代花岗岩之上，堆积着大量新生代喷发的火山岩。

Petrologically the volcanic rocks in theTengchong area are a continent-fades calc-alkali basalt series characterized as being high in U and Th and Th/U ratio. The con-tents of U and Th and Th/U ratio are found increasing from basic to intermediate-acid and/or from early to late in the evolutionary series of volcanic rocks. This seems to be related to the geological environment where the collision boundary of the Indian and Eurasian plates is located. It is tentatively suggested that the volcanic rocks are the result of assimilation-contamination of crustal materials by primitive basaltic magma.