中文摘要：

青藏高原东南缘＂三江＂地区变质杂岩带中的岩石类型十分复杂,斜长角闪岩和含角闪石斜长片麻岩是本区常见的变质岩石类型。斜长角闪岩可进一步划分为由石榴辉石岩退变而成的和基性原岩经角闪岩相-麻粒岩相变质形成的两种类型。斜长角闪岩的SiO2平均含量50.0%,具有高铝低钛的特点,轻稀土元素相对富集,铕无异常或略具负异常,Zr含量较低,Zr/Y比值较小,其原岩的主微量元素组成具有岛弧玄武岩的特点,反映其原岩形成于俯冲碰撞的构造环境。含角闪石斜长片麻岩的SiO2平均含量63.64%,MgO和TiO2含量低,轻、重稀土元素分馏,轻稀土元素明显富集而重稀土元素相对亏损,具有中等负Eu异常,大离子亲石元素K、Rb、Ba、Th强烈富集,高场强元素Ti、Zr、Hf、Nb和Ta含量较低,其原岩具有安山质岩石或安山质/玄武质岩石的特点,主要形成于板块聚敛边缘的构造环境。

英文摘要：

Abundant and complex metamorphic rocks are widespread in Sanjiang region,southeastern Tibetan plateau.Amphibole-bearing metamorphic rocks,comprising amphibolite and amphibole-bearing plagioclase gneiss,occur as lenses or thin layers within metamorphic supracrustal rocks.Amphibolite could be subdivided into two types： one is a retrogressive product of garnet-pyroxenolite,and the other is a product of mafic protolith which experienced amphibolite-to granulite-facies metamorphism.The amphibolite has an average SiO2 content of ~50.0%,with high-Al,low-Ti,Zr and Zr/Y ratio.The chondrite-normalized REE patterns show enrichment of LREE with slightly negative or no Eu anomalies.These geochemical characteristics are very similar to those of the island-arc basalt,indicating that the protolith of the amphibolites was formed in the subduction-collision tectonic setting.In contrast,the amphibole-bearing plagioclase gneiss has a higher average SiO2 content of ~63.64% with low MgO and TiO2 content,characterized by the enrichment of large ionic lithophile elements（LILE） such as K,Rb,Ba and Th,and the depletion of high field strength elements（HFSE） such as Ti,Zr,Hf,Nb and Ta.The REE patterns are characterized by relatively high fractionations of LREE and HREE with pronounced negative Eu anomalies.These geochemical features are inherited from those of andesitic or andesitic/basaltic rocks,indicating that the protolith of the amphibole-bearing plagioclase gneiss appeared in a plate convergence tectonic setting.