华中超高压变质带中榴辉岩的稀土元素地球化学

REE GEOCHEMISTRY OF ECLOGITES FROM THE ULTRA-HIGH PRESSURE METAMORPHIC BELT IN CENTRAL CHINA

根据REE含量及其分配模式 ,华中超高压变质带中榴辉岩可大体分为六种类型 ,即LREE富集型、LREE富集 +Eu正异常型、LREE富集 +Eu负异常型、REE平坦型、MREE(中稀土 )富集型和HREE富集型 ,主要为LREE富集型和LREE富集 +Eu正异常型 ,不同地区榴辉岩REE类型可进行对比 ,不同地区同REE类型榴辉岩的REE特征相似。原岩恢复结果表明榴辉岩的原岩主要为来源于相对富集地幔的大陆拉斑玄武岩及其结晶分异产物 ;LREE富集型、LREE富集 +Eu正异常型、LREE富集 +Eu负异常型榴辉岩原岩之间和REE平坦型、MREE富集型榴辉岩原岩之间具有较好的演化关系 ,前三者产于大陆环境 ,后二者相对靠近大洋环境 ;

Based on their REE contents and REE patterns, eclogites from the ultra\|high pressure metamorphic belt in central China may be roughly divided into six types including LREE\|rich, LREE\|rich+positive Eu anomaly, LREE\|rich, LREE\|rich+negative Eu anomaly, REE pattern\|smooth, MREE\|rich and HREE\|rich. The LREE\|rich, LREE\|rich+positive Eu anomaly and LREE\|rich+negative Eu anomaly types of eclogites are dominant. REE types of eclogites in different areas can be compared and the REE features of the same REE type of eclogites in different areas are similar. The results of reconstruction of the primary rocks show that the primary rocks of eclogites possibly are dominated by continental tholeiites which are the product of partial melting of relatively fertile mantle and the rocks of tholeiite crystallization\|differentiation. There is perfect evolution relationship among the primary rocks of the LREE\|rich, LREE\|rich+positive Eu anomaly and LREE\|rich+negative Eu anomaly types of eclogites and among those of the REE pattern smooth and MREE\|rich types of eclogites, the former three types were derived from continental settings and the latter two from nearly oceanic settings. Meanwhile, it is concluded that the mantle sources of primary rocks of the eclogites are inhomogeneous and the primary rocks of eclogites in this area appear to have undergone varying degree of crustal contamination.