攀枝花层状辉长质岩体的微量元素和锶钕铅氧同位素系统:地幔源区和矿床成因的证据  

Trace Element and Sr—Nd—Pb—O Isotopic Systems of the Panzhihua Layered Gabbro Intrusion:Constraints on the Mantle Source Regions and Origin of V—Ti—Fe Oxide Deposit

作　　者：艾羽[1] 张招崇[1] 王福生[2] 郝艳丽[2] 赵莉[1] 杨铁铮[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质科学院地质研究所,北京100037

出　　处：《地质学报》2006年第7期995-1004,共10页Acta Geologica Sinica

基　　金：教育部新世纪优秀人才支持计划(NCET-04-0728);国土资源部百名优秀青年计划;国家自然科学基金资助项目(编号40273020;40172026);"973"项目(编号G1999043205)的成果

摘　　要：攀枝花岩体是攀西地区一个典型含钒钛磁铁矿的层状辉长质岩体,是峨眉山大火成岩省的组成部分。其Sr、Nd、Pb同位素组成变化范围较窄,落在峨眉山玄武岩的范围内,同时也落在洋岛玄武岩范围内,说明攀枝花岩体与峨眉山玄武岩有着成因联系,均与地幔柱作用有关。其低的δ18O值(<6‰)说明没有地壳物质的混染,其高的La/Nb比值(>1)和微量元素原始地幔标准化图解出现的负Nb异常则表明源区有岩石圈地幔物质的混染。因而攀枝花岩体是地幔柱和岩石圈地幔部分熔融的产物,岩浆在岩浆房中没有经历地壳物质的混染作用。Mg#与P2O5的正相关以及P2O5与FeO含量的负相关,表明P不是导致氧化物熔体不混熔的主要原因;而Mg#与Fe2O3/FeO的负相关则说明,岩浆演化过程中氧逸度的升高可能是导致氧化物熔体不混熔的主要原因。The Panzhihua intrusion, a part of the Emeishan large igneous province, is one of typical V--Ti magnetite ore-bearing layered gabbro intrusions. The Sr, Nd and Pb isotopic data overlap the field of the Emeishan basalts and oceanic island basalts, which suggests a genetic relationship to mantle plume. The high ratio of La/ Nb values （〉1） and negative Nb anomalies on the primitive mantle-normalized trace element patterns characterize the contamination of lithospheric mantle or crustal materials. However, the low δ^18O SMOW（‰） values （〈6） suggest the absence of crustal contamination. Thus, the Panzhihua intrusion can be produced by a partial melting of mantle plume and lithospheric mantle, but not underwent crustal contamination. Positive correlation between Mg^# and PO5 and negative correlation between P2O5 and FeO suggest that addition of P is not the key role for the separation of immiscible oxide melts. In contrast, negative correlation between Mg^# and Fe2O3/FeO ratios implies that the increasing of oxygen fugacity is very likely the main factor to induce immiscibility of oxide melt.

关 键 词：辉长岩 地幔柱 岩石圈地幔 地壳混染 不混熔 氧逸度 攀枝花 

分 类 号：P611[天文地球—矿床学] P597[天文地球—地质学]