新甘交界红柳河地区下二叠统玄武岩地球化学特征及其形成的构造背景

The Geochemical Characteristics and Tectonic Setting of the Lower Permian Basalts in Hongliuhe Area at the Border between Xinjiang and Gansu Provinces

红柳河地区下二叠统拉斑玄武岩 ,主要表现为低Mg和全碱 (Na2 O +K2 O)以及高Fe和Ti的特征 ,微量元素Rb ,K ,Sr和Ba等大离子亲石元素富集 ,轻稀土元素 (LREE)相对富集。La/Yb =10 .6 1～ 16 .87,Th/Ta =1.0 3～ 1.99,Fe/Ti=5 .30～ 6 .39,Ti/P =5 .6 1～ 7.30 ,Ti/Zr =38.83～ 4 6 .30 ;Zr=(2 5 4～ 32 8)× 10 - 6 ,Zr/Y =5～ 10 ,Y/Nb =1.5 2～ 2 .4 5。这些地球化学特征表明它们主要为板内玄武岩 ,其岩浆主要源于亏损地幔 (DM)和富集地幔 (EM)组分的混合 ,其中富集地幔 (EM)为主要端元 ,且部分熔融程度低 。

The major elements geochemical characteristics of the Lower Permian tholeiitic basalts from Hongliuhe area show lower Mg, total alkali (Na_2O+K_2O), and higher Fe, Ti. The large ion lithophile elements (LILE), such as Rb,K,Sr and Ba are enriched. The light rare earth elements (LREE) are enriched relative to heavy rare earth elements (HREE). In addition, La/Yb=10.61～16.87, Th/Ta=(1.03)～1.99, Fe/Ti=5.30～6.39, Ti/P=5.61～7.30, Ti/Zr=38.83～46.30, Zr=(254～328)×10^(-6), Zr/Y=5～10 and Y/Nb=1.52～2.45. These characteristics indicate that the magma source of the lower Permian basalts were derived from mixed components of depleted mantle (DM) and enriched mantle (EM). The latter is the major end-member which reflects a low degree of partial melting of mantle source and a slight crustal contamination.