摘要
寨背顶富重稀土花岗岩位于南岭纬向构造带中段,呈岩祩状侵位于大东山花岗岩基东北侧边缘带上。其岩石化学特征属于一种富硅、富钾、铝过饱和的钙碱性系列花岗岩。该岩石以富含重稀土元素(HREE/LREE=3.78),显著的铕负异常(δEu=0.04)为特征,显示出一种高度分异演化的特点。通过相图分析及包裹体研究,确定该岩石的形成温度为700℃～760℃,压力为500b,成岩深度大约在3km 左右。岩浆结晶时有流体存在,其流体的 pH=7.1,Eh=-0.26V。综合其岩石化学及地球化学特点,认为寨背顶富重稀土花岗岩属于地壳重熔型花岗岩。它与大东山花岗岩体有着密切的成因联系,是该花岗岩浆结晶演化的晚期侵入体。
In the middle section of the Nanling Latitudinal tectonic zone, Zhaibeiding HREE-rich granite intrudes into the northeastern lateral margin of the Dadongshan granite batholith,being stock-like bodies, Chemically,it belongs to a silicon and potassium-rich calcium-alk- ailic granite with oversaturated aluminium.It is also characterized by containing abundent HREE(HREE/LREE=3.78)and having a minus europium anomaly-(δEu=0.04),showing it has been undergone a strong differentiation. By analysing the facies map and studying the inclusion it might be concluded that the granite bodies were formed at a temperature of 700-760℃,at a pressure of 500 bar or so and at a depth of aronnd 3 km.When the magma was crystallized there was a fluid(with a pH value of 7.1 and an Eh of-2.26)in it. It is suggested that the Zhaibeiding HREE-rich granite shonld belong to remelted-type granite judging from the petrochemical and geochemical features.It is closely related with Dadongshan granite in cause of formation,being late intrusions of its crystallization caurse.
