摘要
河北金家庄地区产出的长英质碱性杂岩,由两套岩石组成(早期正长质杂岩和晚期钾长石岩),空间上与超基性岩密切伴生,均受东西向断裂控制。长英质碱性杂岩的岩石化学成分,高SiO_2和K_2O+Na_2O,低FeO,Fe_2O_3和MgO;里特曼指数为7.14～9.75;FeO/MgO为1.73～2.18;稀土总量偏低,无铕亏损;^(87)Sr/^(88)Sr值为0.706;δ^(18)O为8.10‰～10.3‰;熔融包裹体的均一温度为925℃。早晚两期岩石的同位素年龄分别为260Ma和187.5Ma。这套长英质碱性杂岩属幔源玄武岩浆分异的产物。
The felsic alkali complex consists of two sets of rocks: the early-stagesyenite complex and the late-stage potash feldspatite, in Jinjiazhuang, Hebei.They are intimately associated with the ultrabasic rocks in space and arecontrolled by EW-striking faults. Petrochemically, the syenitc complex andpotash feldspatite possess high SiO_2 and K_2O+Na_2O, low FeO, Fe_2O_3and MgO. The Rittman index is 7.14 to 9.75. The FeO/MgO ratio is 1.73 to2.18. The total amounts of REE are lower, without the depletion in Eu.The initial ^(87)Sr/^(86)Sr ratio is 0.706. The δ^(18)O is 8.10‰ to 10.30‰.Thehomogenization temperature of the melt inclusions is 925℃.The felsic alkalicomplexes were formed through mantle-source basalt magma differentiation,being the typical product of magma intrusion.
