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滇西特提斯造山带具有多块体拼合的构造特点,其中冈底斯—腾冲地层区是东特提斯造山带的重要组成部分之一,是研究全球特提斯造山带形成演化的重要窗口。腾冲和保山地块之间的高黎贡—龙陵—瑞丽断裂带西侧出露潞西三台山蛇绿岩,该岩体与围岩均呈断层接触共同构成增生杂岩,主要由纯橄榄岩和方辉橄榄岩组成,主要造岩矿物为橄榄石和斜方辉石,副矿物尖晶石发育。橄榄石为镁橄榄石(Fo90~93);斜方辉石为顽火辉石(En 89 ~ 92),以低铝(0.47% ~ 1%)和高Mg#(91 ~ 96)为特征;尖晶石主要为富铬型尖晶石(Cr# 54 ~ 78)。三台山纯橄榄岩和方辉橄榄岩具有相似的稀土配分模式曲线,为轻稀土元素富集且右倾平坦型曲线;在微量元素原始地幔标准化图解中,相对富集大离子亲石元素Rb、Cs和高场强元素Pb、U。矿物地球化学和全岩组分表明,三台山橄榄岩主要矿物与全岩地球化学成分特征具有深海橄榄岩和弧前橄榄岩的特征,为经历了25% ~ 35%部分熔融后的残余。结合与不同蛇绿岩体构造环境的对比,笔者认为三台山橄榄岩与雅鲁藏布江缝合带的蛇绿岩体具有相似的源区特征,兼具亏损地幔源区特征和俯冲带熔/流体交代特征,表明其可能经历了快速扩张大洋中脊(MOR)和俯冲带仰冲板片(SSZ)两种构造环境。
The Tethys orogenic belt in western Yunnan has the characteristics of multi-block assemblage. The Gangdise-Tengchong formation is one of the important components of the Eocene Tethys orogenic belt and is an important part of studying the formation and evolution of the Tethyan orogen in the world window. The Gaoligong-Longling-Ruili fault zone between Tengchong and Baoshan blocks exposes the Santaishan ophiolite in the Luxi area. The rock mass and the surrounding rock are all fault-connected and constitute accretionary complex, which is mainly composed of pure olives Rock and hardenite, the main rock-forming minerals are olivine and orthopyroxene, and the secondary mineral spinel is developed. Olivine is forsterite (Fo 90-93); orthopyroxene is enstatite (En 89-92), characterized by low aluminum (0.47% -1%) and high Mg # (91-96) Spinel is mainly chromium-rich spinel (Cr # 54 ~ 78). The three-mountain dunite and harzburgite have similar patterns of REE patterns, which are light-rare earth element enriched and right-flatwise-flat curves. In trace elemental primitive mantle normalization diagrams, the relative enrichment of large ion lithophile elements Rb, Cs And high field strength elements Pb, U. Mineral geochemistry and whole rock components show that the main mineral and whole rock geochemistry characteristics of the Peridot sands peridotite are characterized by deep peridotites and argillaceous peridotites, which are left after 25% -35% partial melting. In comparison with the tectonic setting of different ophiolite bodies, the authors consider that the ophiolite body of the Santai peridotite and the Yarlung Zangbo suture zone have similar source characteristics, both of the characteristics of depleted mantle source areas and the melt / fluid metasomatic characteristics of the subduction zone, Indicating that they may have experienced two kinds of tectonic settings: rapid expansion mid-ocean ridge (MOR) and subduction zone inversion plate (SSZ).