摘要
The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratization. Major element data show that lamprophyres in theorefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres. The rocks are enriched in rare-earth elenlents as compared with the primary mantle andmid-ocean ridge basalts(MORB). Modelled calculations by the least squares method of Petrological Mixing show that the mantle source for the lamprophyres is enriched in rare-earth elements. The geotectonic development of western Yunnan, Sr and Nd isotopic compeitions, incompatible element patterns and linear programing calculations indicate that the fluids were de-rived from dehydration of submaine sediments which are enriched in ALK, LREE and incompatible elements and then were carried to mantle wedges as a result of plate subduction. That isthe main factor leading to the formation of a metasomatic fertile mantle in the area studied.
The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratization. Major element data show that lamprophyres in theorefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres. The rocks are enriched in rare-earth elenlents as compared with the primary mantle andmid-ocean ridge basalts(MORB). Modelled calculations by the least squares method of Petrological Mixing show that the mantle source for the lamprophyres is enriched in rare-earth elements. The geotectonic development of western Yunnan, Sr and Nd isotopic compeitions, incompatible element patterns and linear programing calculations indicate that the fluids were de-rived from dehydration of submaine sediments which are enriched in ALK, LREE and incompatible elements and then were carried to mantle wedges as a result of plate subduction. That isthe main factor leading to the formation of a metasomatic fertile mantle in the area studied.
关键词
金矿田
云南
稀土元素
煌班岩
古化学
成矿作用
Laowangzhai gold orefield
Yunnan
Iamprophyre
rare-earth element
genesis
