http://www.sciencedirect.com/science/article/pii/S1674987112000072

The Abor volcanics outcroping in the core of the Siang window in the Eastern Himalaya comprise voluminous mafic volcanics（47%—56%w（SiO₂））,with subordinate felsic volcanics （67%—75%w（SiO₂））.The felsic volcanics are dacitic to rhyolitic in composition and are typically enriched in LREE（La/Sm_N=3.09-3.90） with high REE contents（256-588 ppm）,moderately fractionated REE patterns（Ce_N/Yb_N=6.54-9.52） and pronounced negative Eu anomalies（En/Eu^*=.55- 0.72）.Wide variations in Rb/Zr.K/Rb and La/Sm ratios suggest that they were derived from magmas which were randomly contaminated with crustal material.Chemical characteristics and petrogenetic modelling indicate that the dacites were generated by～15%partial melting of a mafic source leaving a residue with 55%plagioclase.14%’ orthoclase,18%clinopyroxene.5%orthopyroxene.8%hornblende. The silica-rich rhyodaciles and rhyolites were derived from a dacite magma source by a higher degree （>45%） fractional crystallization of an assemblage consisting of 70%plagioclase,12%clinopyroxene. 7%amphibole and 11%magnetite.The associated LREE-LILE enrichment and pronounced negative anomalies for HFSE（Nb,P,and Ti） exhibited by these felsic volcanics are characteristic of continental rift volcanism.implying that they were emplaced during lithospheric extension.