山东土堆-沙旺金矿床同位素组成特征及矿床成因讨论

Isotopic Composition Features and Ore-forming Mechanism of the Tudui-Shawang Gold Deposit in Shandong Province

土堆-沙旺金矿床位于胶莱盆地东北缘,为胶东东部牟平-即墨成矿带的重要组成部分。石英流体包裹体Rb-Sr等时线年龄为119±10 Ma,与胶东大规模成矿时间一致。矿石硫化物硫同位素组成δ34S介于8.50‰～12.72‰之间,成矿热液δ34S∑S=10.03‰,铅同位素组成中206Pb/204Pb=17.12～17.86,且具有低μ高ω特征,指示成矿物质来源于下地壳或地幔。氢氧同位素δ18OH2O值为+1.96‰～+7.71‰,δD为–68.64‰～–86.47‰,显示成矿流体主体为岩浆水,并有部分后期大气水的参与。矿石铅同位素与同期脉岩组成接近,且具有线性特点,指示二者可能与早白垩世华北克拉通东部构造体制转化所引起的壳幔岩浆混合作用有关。

The Tudui-Shawang gold deposit lies in the northeastern margin of the Jiaolai basin and is located at the center of the Rushan-Mouping gold belt in Jiaodong Peninsula.The Rb-Sr isochron age of the fluid inclusions in quartz is about 119±10 Ma,which is consistent with the main stage of the extensive gold mineralization in the Jiaodong gold province.The sulfur isotopic composition of ores ranges from 8.5‰ to 12.72‰,implying an ore fluid with δ34S∑S equal to10.03‰.Ore sulfides have 206Pb/204Pb of 17.12~17.86 and exhibit low μ but high ω val-ues,indicating the derivation of ore-forming materials from the lower crust or the mantle.δD and recalculated δ18OH2O values vary from –68.64 to –86.47‰ and from ＋1.96‰ to ＋7.71‰ respectively,implying that the ore fluid was dominated by magmatic water with the participation of some later meteoric water.Pb isotopes of ore sulfides are coincident with those of contemporaneous dikes and their linear array suggests that both of them might have been related to the change of tectonic regime of the eastern North China craton during the Early Cretaceous.