Petrological study for origin of Nanshanling garnet peridotite from Dabie Mountain

作者：Lu FengXiang^*; Jin ZhenMin; Sang LongKang; Chu LingLin; Jin ShuYan

来源：Acta Petrologica Sinica, 2007, 23(11): 2757-2765.

• garnet peridotite
• mafic-ultramafic complex
• perogenetic genesis
• residual mantle block
• luotian dome

The Nansharding gamet-bearing peridotite body ( - 173 x 133 M(2)) is located in southeast slop of Luotian dome in Southern Dabie Mountain, Yuexi County, Anhui province, east central China. Based on the study of petrology and geochemistry and comparison with different types of peridotite in Dabie Mountain such as Bixiling, Maowu, Raobazhai and Zhimafang and in other places such as Yuanbaoshan and Hongge mafic-ultramafinc complex; Hebi and Wudalianchi residual mantle samples indicate that Nanshanling peridotites are a portion of mafic-ultramafic body intruding into the continental crust as basic magmas. Peridotite is composed of olivine (75%), clinopyroxe ( 10%) and garnet ( 15%) and shows massive structure, homogeneous distribution of minerals in the rock, and typical igneous texture. Garnet peridotites are high in FeO(T) (21. 36%), low in Mg(#)(0. 77), Mg + Ni/Fe + Mn (3. 06) < 7, and the abundances of V ( 177. 8 x 10(-8)) are higher than the that of residual mantle block. Nanshanling peridotites are low in total REE, (La/Yb)(N) = 3.1 which is lower than that of residual mantle block in Raobazhai and Zhimafang. Nanshanling peridotites show Ba, U, Pb,Zr,Eu enrichment and negative Nb anomaly in primitive mantle-normalized trace element plots. Rb-Sr and Sm-Nd isotopic analysis of whole-rock samples and mineral separates have been carried out and indicate high (87) Sr/(86) Sr ( 0.7088, 0. 7086) and low epsilon(Nd) (t) ( - 6.55, - 6.01) values implying that the resource of magmas contain crust components. Although both Nanshanling and Bixiling have same perogenetic genesis and nearby each others, they have different rock texture, BEE pattern, history of deformation and isotopic features indicating that they have different magma sources and experiences. In a diagram of epsilon(Nd) (t) _( (87) Sr/(86) Sr)(t), the plots of Nansharding whole rock and Cpx fall within elongation direction of mantle reservoir and close to the range of the plots from Zhujiapu pyroxenite-gabbros bodies which occurred at northwest slop of Luotian dome. It may be possible to infer that Nanshanling basic magmatism has some correlation with Zhujiapu mafic-ultramafic magmatism.

• 出版日期2007-11
• 单位中国地质大学（北京）