莲花山斑岩型钨-金矿床蚀变矿化过程中元素迁移定量研究

广东莲花山斑岩型钨-金矿床蚀变类型可以分作钾化、云英岩化、绿泥石化、绢云母化和青盘岩化。不同原岩不同类型蚀变岩元素质量得失的定量计算结果表明,Th、TiO₂、Al₂O₃、P₂O₅、Ta和Hf等在蚀变矿化过程中基本表现出惰性特征,质量得失较少,主元素在岩石中含量的变化主要受原岩类型的影响,其次受到蚀变作用类型的影响,成矿元素及与其有关的其他微量元素在蚀变岩中则主要表现出较大程度的富集。稀土元素在蚀变矿化过程中迁移作用不明显。本文结合蚀变矿化的地质特征及镜下观察结果对不同蚀变带中元素质量得失作了详细解释。

ELEMENT GAINS AND LOSS IN THE PROCESS OF ALTERATION IN LIANHUASHAN W-Au PORPHYRY-TYPE DEPOSIT

Lianhuashan porphyry-type W-Au deposit,Guandong Province,is formed in the endo and exo contact zone of quartz sandstone and Mesozoic quartz syenite,quartz diorite.Characteristics of alteration and mineralization show that the deposit is of porphyry-type deposit.Alterations include k-feldspar and biotite alteration,greisenization,sericitization,chloritization and propylitization.Mineral associations of ore include wolframite,scheelite-arsenopyrite-pyrrhotite,polymetallic sulfides and pyrite.The percentage of gains and losses of elected elements for different types of original and altered rocks,through calculation based on the formula given by Grant (1986),show that Th,TiO₂,Al₂O₃,P₂O₅,Ta,Hf are immobile in the process of alteration.Gains and losses of main elements are controlled predominantly by types of original rocks and secondarily by the types of alteration.The content change of main elements reflects element redistribution in porphyry system,with the exception of MnO,which may be controlled by both element redistribution and deposition as wolframite of deep-sourced ore fluid.Mineralization related elements,such as Au,WO₃,Cu,Zn,etc.,are greatly enriched in the altered rocks and the enrichment factor in quartz sandstone is up to 5.If mass balance is taken into account,enrichment of mineralization-related elements is formed through ore deposition of deep-sourced fluid,rather than element redistribution.REE has mainly less than 25% change of mass in the process of alteration.