中文摘要：

本文在总结全球地幔橄榄岩岩石学和地球化学特征的基础上，首次提出了一个用于判别HP—UHP变质带中变质橄榄岩原岩及其成因类型的判别图解。该图主要由镁铁总量MgO＋〈FeO〉（％）和一个参数m＋f／si比值构成。另用Al2O3和CaO分别与MgO＋％FeO〉（％）制成两个辅助图解，以示方辉橄榄岩和二辉橄榄岩之间在Al2O3和CaO含量上的分界。通过原岩判别结果和研究表明，PP3孔和PP1孔两者在变质组合、原岩成因类型、地球化学和变质条件方面存在一系列的重大差异。分别代表来自两种极端的地球化学类型和两种不同大地构造环境的UHP变质体。PP3钻孔以Ol＋Gt＋Cpx＋Opx＋Sp为变质矿物共生组合的含石榴石纯橄岩，其原岩系来自地幔残余成因的方辉橄榄岩遭受UHP变质作用的产物，它以成分高度均一，富Mg（Mg′=92），极端亏损不相容元素REE（∑REE〈1×10^-6可称为超亏损型）为特征。在变质相中仍保留原岩的残余矿物铬尖晶石（Sp），其成分显示蛇绿岩地幔橄榄岩的成分趋势。并出现以Gt和Sp共存相为特征的变质相。据实验结果（klemme，2004）表明该共存相的稳定域的P—T条件Cr—Sp可达7Gpa，T1400℃，即形成于200km的地幔深度。综合研究显示该孔变质橄榄岩原岩（方辉橄榄岩）具有大洋岩石圈地幔残余成因的某些印记，而不是同深度原生地幔岩相转变的产物。PP1孔变质橄榄岩是由无水矿物相（Ol＋Opx＋Cpxq-Gt）＋含水矿物相（Phl±Chu）组成的石榴石橄榄岩杂岩，其原岩来自两种不同成因的超镁铁岩系列：一为具地幔成因的方辉橄榄岩-二辉橄榄岩系列（可能相当于地幔楔中的Al型橄榄岩），另一部分（少数）来自具岩浆成因的超镁铁岩系列（纯橄岩-异剥橄榄岩-辉石岩组合，可能相当于A2型橄榄岩）。该套变质橄榄岩，以成分高度不均一，极端富集REE（∑REE?

英文摘要：

Based on summing up of petrography and petrochemisty for mantle peridotite all over the world, we firstly propose a diagram for discriminating the protolith of meta-peridotite of HP and UHP metamorphic terrane. This diagram is constituted by total MgO＋〈FeO〉（%） versus （m＋f）/si ratio. Two additional diagrams, consisting of Al2O3 versus MgO＋〈Fe〉（%） respectively, are used to divide the boundary between harzburgite and lherzolite. By discriminating the protolith of meta-peridotite from the PP3 hole and PPlhole, we found a large sum of differences existing in metamorphic mineral assemblage, protolith genesis, geochemistry and metamorphic conditions among them, which represents two extremely differentgeochemical types and distince tectonic environment, respectively. The meta-peridotite from the PP3 hole, being garnet bearing dunite, has assemblage of Ol＋Gr＋Cpx＋Opx＋Sp. Its protolith is the product of residual mantle harzburgite which suffered UHP metamorphism. The garnet bearing dunite is characterized by highly uniform composition, enrichment in MgO （Mg′= 92）, and extreme depletion in incompatible REE （total REE abundances to lower than 1 ppm）. The residual Cr-sp, still preserved in the meta-peridotite, has the compositional features of typical ophiolitic dunite-harzburgite, with coexistence of garnet and spinel. In view of the experiments by Klemme et. Al. （2004）, spinel coexisting with garnet is stable up to 7GPa at 1400℃, which means the meta-peridotite from PP3 hole is formed no more than 200km. Comprehensive studies show that the meta-peridotite （its protolith to be harzburgite possesses theattribution of oceanic lithosphere mantle, but is not the transition phase of the mantle at 200km depth. The meta-peridotite from PP1 hole, being garnet peridotite complex, has assemblage of Ol＋Gr＋Cpx＋Opx anhydrous phase and Phl＋Ti＋Chu hydrous phase. Based on the discrimination of their protolith, they are found to derive from two different genetic ultramafic series,