摘要
赣南会昌地区中基性火山岩的斜长石斑晶具有钾长石环边,基质中存在大量钾长石微晶的矿物组合特征,为其归属于橄榄玄粗岩系列提供了矿物学证据。基质中钾长石微晶与斜长石微晶共存暗示了会昌橄榄玄粗岩的地幔源区混合成因,与根据Sr-Nd-O-Pb同位素地球化学特征研究得到的结果一致。电子探针分析表明会昌橄榄玄粗岩中的角闪石属于钙质角闪石亚类,为镁绿钙闪石。采用3种钙质角闪石Al地质压力计及CaO地质温度计估算会昌橄榄玄粗岩中角闪石的形成压力约为8.03×108Pa,温度为985℃。角闪石的晶体化学特征表明会昌镁绿钙闪石形成于上地幔,从而为会昌橄榄玄粗岩的幔源成因提供了重要依据。
The intermediate to basic volcanic rocks in Huichang area,southern Jiangxi province,show typical mineral assemblages for shoshonitic series such as porphyritic crystals of plagioclase with orthoclase rims and a large amount of orthoclase micro-crystals in the matrix. The coexistence of orthoclase and plagioclase micro-crystals in the matrix implies a mixing mantle source of depleted and enriched lithologies,which has been suggested by previous study of Sr-Nd-O-Pb isotopes on the shoshonite. Using electron probe analysis,amphibole in Huichang shoshonite was identified as magnesiohastingsite,a subtype of calcic amphibole. The P-T conditions of magnesiohastingsite were estimated to be around 8.03×10^8 Pa and 985 °C by three kinds of calcic amphibole Al geobarometers and CaO geothermometer. The chemical-structural features of the magnesiohastingsite reveal that it was formed in the upper mantle which provide important mineralogical evidence for the mantle origin of the shoshonite in Huichang.
出处
《铀矿地质》
CAS
CSCD
2010年第3期145-151,186,共8页
Uranium Geology
基金
中国核工业地质局十一五科研项目(2006YG026)资助成果之一
