摘要
丹巴地区位于川西松潘－甘孜造山带东缘，出露较多的斜长角门岩类．这些岩石通常里透镜状与碳酸盐岩、泥质岩相伴生。地球化学研究表明，这类斜长角闪岩为正斜长角闪岩，原岩主要为钙碱性玄武岩类．岩石富Ｆｅ，Ｍｇ，Ｃａ和Ｔｉ，大离子亲石元素Ｓｒ，Ｂａ，Ｔｈ，Ｎｂ，Ｔａ等比较富集；轻稀土稍富集，铕亏损不明显（δＥｕ＝０．８２～０．９９），稀土总量变化在１１９．４～２０９．９９×１０－６之间．岩石的地球化学特征与拉张构造背景下形成的玄武岩类非常相似．古构造环境研究表明，这类玄武岩形成于晚元古代活动大陆边缘的弧后盆地内，玄武岩浆来自地幔，在上升过程中受到大陆地壳物质混染。
Danba area is located in the eastern margin of the main body of Songpan-Gauze orogenic belt. As acomplex basement of orogenic belt, the matamorphic rocks of Danba area attaining up to high-grade amphibolite factes, seem to be the highest in the entire orogenic belt. In terms of difference of metamorphism amphibolite of Danba area can be subdivided into epidote amphibolite, biotite amphibolite and plagioclase amphibolite. All these amphibolites occurred as lens and are associated with carbonatite, pelite and silicolites. Themineralogy of amphibolite is rather simple. Major minerals are bornblende and plagioclase which formed lepidoblastic structure. Zircon is one of the accessory minerals. which occurred as prism-developing bipyramide.U-Pb isotopic dating on single zircon from plagioclase amphibolites gives an age of 800 Ma ;it is suggested thatamphibolites are the products of the late Proterozoic volcanism. Based on petrochemistry, trace element andREE data, this paper discusses petrogenesis of plagioclase amphibolite in Danba area. A combination of geochemical characters. such as high contents of Fe, Mg, Ca and Ti in rock, enrichment of lithophile elements(Sr,B,Th,Nb,Ta etc. ). slight enrichment of LREE and deption of Eu, may indicate that plagioclase amphibolite is similiar to island arc basalt. They formed at active continental margin and are contaminated by continental crustal in process of uplift.
出处
《南京大学学报（自然科学版）》
CSCD
1996年第3期507-514,共8页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金
国家教委博士点基金
关键词
斜长角闪岩
地球化学
古构造环境
大地构造
Plagioclase amphibolite, Pettocbemistry, Palaeotectonic environment, Denba area
