摘要
滇西地区新生代碱性侵入岩中广泛分布的麻粒岩包体可以代表该地区的下地壳岩石,为了确定滇西下地壳岩石的铅同位素组成,我们系统采集了该区碱性岩中的麻粒岩包体,挑选出其中的长石、石榴子石等造岩矿物,测定了其铅同位素组成,在Zartman等的铅构造演化模式图上,剔除个别异常的铅同位素组成,圈出投影于下地壳铅同位素演化趋势线上及附近的铅同位素分布范围,由此确定了该区下地壳的铅同位素组成的区域,并进一步结合作者先前确定的该区上地壳及上地幔铅同位素组成,构建了该区三维岩石圈铅同位素组成,并将这一结果用于滇西金顶超大型铅锌矿床的成矿物质来源的研究中,发现颇受争议的金顶铅锌矿床中的铅并非来自上地幔,而相当于下地壳来源的铅与兰坪盆地沉积岩铅二者的混合铅。
The extensive granulite inclusions in alkaline intrusive rocks are considered as materials of lower curst in the region of western Yunnan. In order to reveal the Pb isotopic composition of lower crust in this region, the authors systematically collected samples of the granulite inclusions in alkaline intrusive rocks and selected the plagioclase and garnet et al. from them. Then the Pb isotopic composition of these minerals was determined. In the dia- gram of Zartman et al. , the data points of almost all samples fall on the lower crust Pb evolution line or are distributed in the extending direction along this evolution line except for several samples. Eliminating the Pb isotopic compositions of anomaly samples, the variation range so defined is well consistent with the lower crust Pb evolution line along the long axis. Based on the Pb isotopic composition of upper crust and mantle having been determined, the authors build the Pb isotopic composition of three - dimensional lithosphere in the region of western Yunnan. And by comparing the Pb isotopic composition of Jinding Pb -Zn deposit, the authors discovered that Pb in the Jinding Pb- Zn deposit is not the upper mantle Pb; it may be derived from the lower crust and sedimentary rocks in the Lanping Basin.
出处
《地质与勘探》
CAS
CSCD
北大核心
2009年第5期509-515,共7页
Geology and Exploration
基金
中国科学院创新项目(批准号:KZCX2-YW-111)
国家基础重点规划(973)项目(批准号:2007CB411408)
关键词
碱性岩
下地壳
多金属矿床
铅同位素组成
滇西
alkaline rock
lower crust
polymetallic deposit
lead isotopic composition
western Yunnan Province
