中文摘要：

藏南仲巴地区混杂岩隶属雅鲁藏布江缝合带西段增生楔构造单元,其中玄武岩与放射虫硅质岩、硅质页岩及泥岩伴生产出,多呈枕状构造,玄武岩时代由伴生硅质岩中放射虫组合约束为早白垩世.仲巴地区混杂岩内玄武岩具有高P2O5（0.34％～0.87％）,低Al2O3（13.48％～15.38％）和Mg#值（15～35）,高Fe（全Fe2O3=7.62％～13.16％）、Ti（TiO2=1.76％～3.11％）和贫Si（SiO2=43.57％～51.99％）特征,为一套Fe-Ti玄武岩,且呈碱性,是玄武岩浆依高铁贫硅趋势发生较高程度结晶分异演化的产物.轻重稀土元素分馏较为明显（（La/Yb）N=8.48～32.04）,无明显Ce、Eu异常,富集大离子亲石元素（LILE）（如Ba、Th）和高场强元素（HFSE）（如Nb、Ta、Zr、Hf）,无明显Nb、Ta异常,呈现典型OIB型地球化学特征.地球化学特征指示仲巴玄武岩形成于洋岛环境,且处于一个拉张的构造背景下,其岩浆源区为主要由石榴石橄榄岩组成的富集地幔,发生了6％～10％部分熔融,岩浆上升过程中没有或很少受到地壳混染.本文认为仲巴玄武岩可能为地幔热柱成因,指示新特提斯洋洋盆早白垩世可能存在热点.

英文摘要：

Zhongba Mé1ange in southern Tibet belongs to the accretionary wedge in the western segment of the Yarlung Zangbo suture zone.The basalts from Zhongba Mé1ange are in coexistence with radiolarian chert,siliceous shale and mudstone,showing a pillow structure.The age of basalts is constrained to the early Cretaceous by radiolarian assemblage in its companion chert.The basalts have relatively high P2O5 （0.34%-0.87%）,lower Al2O3 （13.48%-15.38%） and Mg#（15-35）.The samples are characterized by high iron （Fe2O3=7.62%-13.16%） and titanium （TiO2=1.76%-3.11%）,and poor silicon （SiO2=43.57%-51.99%）,and can be classified as Fe-Ti basalts （ferrobasalts）.And the basalts are alkaline.The Fe-Ti basalts were produced through a high degree of high iron and poor silicon trend differentiation.The REE patterns are similar to those of OIB,with LREE enrichment （（La/Yb）N=8.48-32.04） and no obvious Ce and Eu anomaly.The basalts have typical geochemical characteristics similar to those of OIB,with the enrichment of large ion lithophile elements （LILE） （Ba,Th） and high field-strength elements （HFSE） （Nb,Ta,Zr,Hf）,and no obvious Nb and Ta anomalies.The geochemical characteristics suggest that the basalts were formed in an ocean island within an extensional tectonic setting,and the magma originated from enriched mantle composed mainly of garnet peridotite with 6%-10% partial melting.Geological signatures of whole-rock trace elements indicate little or no appreciable crustal contamination for the samples.The Zhongba basalts might have been derived from the mantle plume,which suggests that there probably existed a hotspot in the Neo-Tethys.