【摘要】 对阿尔泰造山带南缘喀拉通克和锡泊渡两个杂岩体的Sr-Nd-O同位素研究表明,两个杂岩体的同位素特征相似,均具有低的(87Sr/86Sr)t和高的εNd(t)值(6.3~9.1),表明其来源于亏损的软流圈地幔,但是其δ18O值(‰)大多大于6(5.4~10.2),表明有地壳物质的加入。Sr和O同位素表明,这种地壳物质的混入主要是源区的混入。根据Nd同位素模式年龄以及区域构造演化特征,可能是混入有早期俯冲的洋壳(可能是早古生代)的亏损地幔熔融的结果。然而,与锡泊渡杂岩体不同的是,喀拉通克杂岩体局部还经历了上部地壳的混染作用。此外,额尔齐斯深大断裂南北两侧镁铁质-超镁铁质杂岩体源区特征的相似性可能暗示了该断裂可能不是阿尔泰造山带和准噶尔造山带的分界线。更多还原

【Abstract】 The Sr, Nd and O isotopic compositions of the Kalatongke and Xibodu mafic-ultramafic complexes from the south margin of Altay orogenic belt show that they have similar isotopic compositions, characterized by low (~ 87 Sr/~ 86 Sr)_t and high ε_ Nd (t) value (6.3～9.1). It suggests that they were derived from depleted asthenospheric mantle. However, most of the samples have the δ~ 18 O values >6‰ (5.4‰～10.2‰), indicating the involvement of crustal materials. A combination of Sr and O isotopic data shows the incorporation of crustal materials into depleted mantle. They were produced by the melting of depleted mantle by the incorporation of subducted oceanic crust, and this incorporation might occur in the Early Paleozoic time in the light of their Nd model ages and regional tectonics. The Kalatongke complex might have undertaken the contamination of upper crust whereas the Xibodu complex had not been had any signature of contamination of upper crust. In addition, the similarities of the sources of the two complexes, which were located at the north and south sides of the regional Irtysh fault zone respectively suggest that this fault might not be the boundary between the Altay and Zhunggar orogenic belts.更多还原