滇西富碱斑岩中特殊包体岩石的流体包裹体幔源不混溶特征  

Immiscible characteristics of mantle-derived fluid inclusions in special xenoliths from Cenozoic alkalic-rich porphyry in west Yunnan

作　　者：赵甫峰[1] 刘显凡[1,2] 楚亚婷[1] 李春辉[1] 宋祥峰[1] 吴冉[1] 肖继雄[1] 

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]南京大学内生金属矿床成矿机制研究国家重点实验室,江苏南京210093

出　　处：《地球化学》2011年第4期305-323,共19页Geochimica

基　　金：国家自然科学基金(40773031;40473027);南京大学内生金属矿床成矿机制研究国家重点实验室开放研究基金项目(14-08-3);成都理工大学矿物学岩石学矿床学国家重点(培育)学科建设项目(SZD0407)

摘　　要：滇西地区沿金沙江-哀牢山断裂带产出了一套新生代富碱斑岩,其中发现了与镁铁-超镁铁质深源包体岩石共生的含石英的方解石包晶(体)、石英钠长石伟晶岩包体和含玻璃包裹体的纯石英包晶(体)以及富铁熔浆包体。流体包裹体地球化学研究表明,该四类特殊包体的形成与富含CO2流体持续减压而造成的不混溶作用有关;而玻璃包裹体与水溶液包裹体以及CO2包裹体共生,表明它们被捕获时是一种熔体与液体共存的不混溶状态。稀土和微素元素地球化学研究显示流体源自富集地幔;纯石英包晶(体)和富铁熔浆包体的Zr、Hf含量呈现相反的异常,表明这些特殊包晶(体)为同一地幔流体(熔体或流体)伴随上升减压引发不混溶作用的产物,同时也显示了地幔流体在上涌至地表的过程中由熔体向液体转化的可能事实。There are a series of Cenozoic alkali-rich porphyries along Jinshajiang-Ailaoshan fault belt in western Yunnan Province. Quartz calcite peritectic, quartz-albite pegmatitic xenolith, glass inclusions-bearing pure quartz peritectic and Fe-rich melt xenoliths have been discovered from alkali-rich porphyries. All of these are paragenesis with mafic-ultramafic deep xenoliths. Geochemistry of fluid inclusions show that formation of pure quartz peritectic, quartz calcite peritectic and pegmatitic xenolith of quartz-albite is related to immiscibility, which is caused by continuous decompressing of CO2-rich fluid. The paragenetic relationship, with paragenesis of glass H2O-NaCl and CO2 inclusions, indicates the immiscibility of melt and liquid fluid. REE and trace elements indicate that fluid came from enriched mantle. Reversed anomalies of Zr and Hf in pure quartz peritectic and iron-rich melt xenoliths shows special peritectic （xenoliths） are immiscible products of mantle fluid or melt, because of the decompression in upwelling, implying that mantle fluids might change from melt to liquid fluid.

关 键 词：特殊包体岩石 玻璃包裹体 流体包裹体 微量元素地球化学 不混溶作用 地幔流体 流体演化 

分 类 号：P59[天文地球—地球化学] P594[天文地球—地质学]