德兴铜矿花岗闪长斑岩成岩过程分异的初始岩浆流体HF、HCl浓度特征

The Concentration Characteristics of HF and HCl Deriving from Early Crystal of Granodiorite Porphyry in Dexing County Jiangxi Province,China

用全岩锆饱和温度计和角闪石Al压力计计算得到德兴花岗闪长斑岩体的平均结晶温度为(790±50)℃,压力为(198±60)MPa。以此温压条件为前提,根据化学反应平衡时各组分浓度与反应吉布斯自由能的关系,在假设磷灰石中F-、Cl-与OH-理想替位的前提下,运用电子探针测试及计算得到的花岗闪长斑岩中斑晶矿物磷灰石F-、Cl-、OH-浓度,计算得到磷灰石结晶时流体中HF、HCl的活度分别为0.00079和0.196mol/L。这个浓度代表了岩浆结晶早期分异的初始岩浆流体中HF和HCl的含量特征,且HCl的有效浓度远远大于HF,暗示德兴花岗质岩浆分异的初始岩浆流体富含能与成矿元素Cu形成稳定络合物的挥发性组分Cl,有利于形成花岗质岩浆热液铜矿床。

In this research,under the assumption of ideal site mixing of F-,Cland OHin apatite,concentrations of HF and HCl in the hydrothermal fluid during the crystal of granodiorite porphyry in Dexing County,Jiangxi Province,China were tested by using electron microprobe,and calculated to be 0.00079 and 0.196 mol/L based on the relationship between Gibbs free energies and equilibrium constant,respectively.The amount of HCl exceeded that of HF,indicating that the hydrotherm derived from magma included a mount of Clthat could be stable complexes with Cu.Further more,it was evident that there was a close relationship between Cland Cu deposit.The average temperature and pressure of the granodiorite porphyry in Dexing County were calculated as 790（± 50） ℃ and 1.98（± 0.6） kbar by using the thermometer of Zr saturation and Al manometer of hornblende,respectively.