地质学报2017，Vol.91Issue(4)：736-747,12.
甘肃龙首山东段小口子镁铁—超镁铁质岩体岩石学、地球化学及年代学研究
Petrology, Geochemistry and Chronology Study of the Xiaokouzi Mafic-Ultramafic Intrusion in the Eastern Section of Longshou Mountains, Gansu
摘要
Abstract
Longshou mountains at the southern margin of Alxa block are famous for hosting the Neopaleozoic Jinchuan Cu-Ni sulfide deposit,prospecting for Cu-Ni sulfide deposits surrounding the Jinchuan ore deposit has long received much attention.The Xiaokouzi mafic-ultramafic intrusions,located in the eastern segment of Longshou Moutnrain,consist mainly of serpentine rock,augite peridotite,olivine pyroxenite.Star-shaped sulfide can be found locally.Sulfide contains pyrite and chalcopyrite,and no Ni-and Cu mineralization but parital mgnetitization were found in orebodies.The previous study suggests that the Xiaokouzi intrusions were likely the product of the same magma event with the Jinchuan mafic-ultramafic intrusions.The litho-geochemical analysis in this study shows that the intrusions have fairly high MgO/FeOT values with m/f=5.31～8.74,which is higher than that of average Ni-bearing intrusions.The chondrite-normalized REE diagrams and primitive-mantle normalized trace elements diagram of the samples display a flat distribution pattern with low total REEs content,indicating olivine accumulation in the intrusions.Sr and Nd isotopic study yields εNd (t) values of 6.09～7.77,indicating the magma source is characterized by depleted mantle.Trace element ratios and modeling results also suggest that parental magma experienced weak contamination of middle-upper crust.Single zircon U-Pb age of augite peridotite from the intrusions is 284.4±3.5 Ma.Compared with regional geology,the Permian igneous rocks may be related to the closure of the Paleo-Asian Ocean,or an extensional regime after subduction.关键词
镁铁—超镁铁质岩体/年代学/岩石地球化学/构造背景/甘肃小口子Key words
mafic-ultramafic intrusion/chronology/litho-geochemistry/tectonic setting/Xiaokouzi/Gansu引用本文复制引用
焦建刚,靳树芳,芮会超,张国鹏,宁权飞,邵乐奇..甘肃龙首山东段小口子镁铁—超镁铁质岩体岩石学、地球化学及年代学研究[J].地质学报,2017,91(4):736-747,12.基金项目
本文为国家自然科学基金项目(编号:41672064,41372101) （编号:41672064,41372101）
国土资源部公益性行业科研专项(编号:200911007,201011058)的成果. （编号:200911007,201011058）
