Abstract: The SiO₂ content of the mafic dikes from Gan-Hang tectonic belt ranges from 46.88% to 53.69%. The dolerites from middle and west of Gan-Hang(Jiangxi-Zhejiang) tectonic belt belong to sub-alkaline and alkaline series, respectively. The trace elements of the mafic dikes are characterized by enrichment in LREE and LILE (Ba, Rb and K) and depletion in HREE and HFSE (Ta, Nb, Zr, Hf and Ti). The REE of the mafic dikes decreases gradually from Guangfeng to Yujiang and Dongxiang, and then to Yongfeng and Xiajiang. The mafic dikes from Yongfeng have obviously Eu anomalies. The Sr and Nd isotopic composition of mafic dikes are of a wide range, (⁸⁷Sr/⁸⁶Sr)_i varying from 0.704 635 to 0.708 769, (¹⁴³Nd/¹⁴⁴Nd)_i from 0.512 173 to 0.512 758, and ε_Nd(t) from -6.8 to +5.6, revealing that the mafic dikes were derived from partial melting of different magma sources. The mafic dikes from Yujiang, Dongxiang and Xiajiang were derived from depleted mantle, while the mafic dikes from Guangfeng and Yongfeng were produced by partial melting of EMⅡ-type enriched mantle due to mantle metasomatism. In addition, there occurred fractional crystallization of olivine, clinopyroxenes, plagioclase and Ti-Fe oxide during the magma ascent. The mafic dikes were related with the subduction of the Paleo-Pacific, different tectonic locations may account fro their different petrologic characteristics.

Key words: Gan-Hang tectonic belt, mafic dikes, geochemical characteristics, metasomatism