摘要
在中国西南和东南亚领域内存在一条南北延伸的花岗岩岩基带,滇西的临沧岩体(LG)和平和街岩体(PMG)是这一巨型同碰撞岩基带最北段的二个岩体,出露面积共约11000平方公里。具壳源(S型)花岗岩许多特征。根据Sr、Nd同位素的上陆壳一下陆壳两端员混合摸拟,这两个岩体的源区岩石相当于由70—80％上陆壳物质加上20—30％的下陆壳物质构成的混合物。根据Rb、Sr、Rb/Sr等微量元素和微量元素对比值在部分熔融中的行为,计算了这一源区物质约30—35％的部分熔融形成当时的平和街和临沧岩体的初始岩浆。
In the territory of SW China and SE Asia, between 100-120° east longitude, there is a NS trending syncollision tybe granite belt. At the northern end this granite belt begins with Lincang granite body (LG) and Pinghejie granite body (PG), W Yunnan. It runs southwards to join the medial granite zone of Thailand and the western granite zone of Malaysia. These two granite bodies with total exposure of 11000 km^2 have typical features of continental crust-derived origin. The main characteristics are: (1) Peraluminous, with ANKC values greater than 1.00 (1.082 for PG and 1.106 for LG); (2) Rich in potash relative to sodium, with Na/K ratios less than 1.00 (0.88 for PG and 0.95 for LG); (3) Relatively lower in Sm/Nd ratios (0.17 for PG and 0.20 for LG); (4) Relatively higher in Rb/Sr ratios (1.35 for PG and 2.03 for LG); (5) Enriched in Sn (13.7ppm for PG and 14,6ppm for LG); (6) Higher in initial Sr ratios (0.7205 for PG and 0.7340 for LG); (7) Negative ε_(Nd)~t values (-12.6 for LG) etc.The source materials for these two granite bodies are considered to be a mixture of about 70-80% upper continental crust and 20-300% lower continental crust materials by modelling using mixing two different Sr and Nd isotope isotope compositions proposed by Faure (1986). The magma for LG and PG was generated from 30-35% partial melting of this source material based on the partial melting equation of Rb, St, Rb/Sr proposed by Shaw.
出处
《岩石矿物学杂志》
CAS
CSCD
1989年第1期1-12,共12页
Acta Petrologica et Mineralogica
关键词
定量模拟
花岗岩
源区物质
continental crust-derived syncollision granite
Sr-Nd isotope composition
source materials
quantitative modelling of mixing
partial melting
