摘要
本文首次报道了攀西裂谷南段云南省鸡街碱性超基性岩中铂族元素(PGE)的地球化学特征。采用改进的Carius管法测定了霞霓钠辉岩、霓霞岩和磷霞岩中的低含量PGE。PPGE与IPGE呈现强烈分馏,推断幔源岩在低程度部分熔融过程中Pt、Pd表现为相似的不相容性,而Ir、Ru表现为相容性,这种分馏效应随着结晶分异作用的进行而逐渐增强。3种岩石均出现Ru的负异常及Pt、Pd的解耦,说明母岩浆经历了早期的橄榄石晶出,在结晶分异过程中Pd较Pt更不相容。由于岩浆上升过程中的压力减小和结晶分异作用导致的成份变化使岩浆可以达到硫的局部饱和而熔离,表现为部分样品中Cu/Pd远高于原始地幔值。本文通过碱性超基性岩与金伯利岩、煌斑岩和邻区碱性、过碱性玄武岩PGE特征的对比,探讨了其岩浆源区及演化特征。
This paper reports the geochemical characteristics of platinum-group elements (PGE) of Jijie alkaline-ultrabasic intrusive rock complex,in the southern part of Panxi rift,Yunnan Province,Southwest of China. Trace PGE concentrations in melteigite,ijolites and urtites were measured by ID-ICP-MS coupled with a modified Carius tube digestion. The significant fractionation between PPGE and IPGE of these alkaline-ultrabasic rocks,suggest that Pt and Pd are incompatible while Ir,Ru and Rh are compatible during low degree partial melting. The negative Ru anomalies on primitive mantle-normalized PGE patterns of all these samples indicate the removal of olivine during the magma ascent. Pd show more incompatible than Pt during crystal fractionation. Most of the Cu/Pd ratios are much higher than prime mantle,suggesting the parent magma may reach partial sulfide saturation and then segregation due to the change of pressure and crystal fractionation,. The characteristics of the prime magma source and magma evolvement were discussed by comparison with the PGE characteristics of typical kimberlites,lamprophyres and alkaline basalts.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第3期938-946,共9页
Acta Petrologica Sinica
基金
中国科学院"项目百人计划"项目(KZCX2-YW-BR-09)
国家自然科学基金项目(40773070
40573049)资助
关键词
碱性超基性岩
铂族元素
金伯利岩
碱性玄武岩
Alkaline-ultrabasic rock
Platinum-group elements
Kimberlite
Alkaline basalt
