CAJ | 학술논문

内蒙古乌拉山金矿田内主要出露晚太古代乌拉山群区域变质岩和规模不一的花岗岩体以及不同时代、不同种类的脉状地质体.含金矿脉中主要矿物共生组合为碱性长石、石英、斜长石、碳酸盐矿物(方解石、白云石)和少量金属硫化物.矿床的显著特征为碱性长石交代作用强烈,碱性长石也广泛产于该地区其他各种类型的岩石中.本文采用电子显微探针分析了共生碱性长石和斜长石的化学成分,并采用三元二长石温度模型估计了碱性长石的平衡温度.结果表明,第一成矿阶段的碱性长石-石英含金矿脉中碱性长石的形成温度为353℃,第二成矿阶段石英含金矿脉中碱性长石的形成温度为281℃,矿脉碱性长石形成压力约为5 kbar.这些结果与同类矿石中平衡共生的碳酸盐矿物和云母类矿物的地质温度计估计的形成温度以及共生石英中流体包裹体的均一温度非常一致.因此,乌拉山金矿床形成和富集的温度可估测为260～380℃,压力约为5 kbar.此外,应用二长石温度计计算了本地区区域变质片麻岩和花岗岩中碱性长石的平衡温度,所得温度比采用共生铁铝榴石和黑云母温度计估计的温度要低约250℃.这表明共生的铁铝榴石和黑云母的平衡温度可能代表其寄主变质岩变质期温度及寄主花岗岩原生温度,而区域变质岩和花岗岩中的碱性长石在经历了随后多次热液作用后,可能重新平衡再生,这也与前人对乌拉山金矿的矿床地质和同位素研究的结果一致.
내몽고오랍산금광전내주요출로만태고대오랍산군구역변질암화규모불일적화강암체이급불동시대、불동충류적맥상지질체.함금광맥중주요광물공생조합위감성장석、석영、사장석、탄산염광물(방해석、백운석)화소량금속류화물.광상적현저특정위감성장석교대작용강렬,감성장석야엄범산우해지구기타각충류형적암석중.본문채용전자현미탐침분석료공생감성장석화사장석적화학성분,병채용삼원이장석온도모형고계료감성장석적평형온도.결과표명,제일성광계단적감성장석-석영함금광맥중감성장석적형성온도위353℃,제이성광계단석영함금광맥중감성장석적형성온도위281℃,광맥감성장석형성압력약위5 kbar.저사결과여동류광석중평형공생적탄산염광물화운모류광물적지질온도계고계적형성온도이급공생석영중류체포과체적균일온도비상일치.인차,오랍산금광상형성화부집적온도가고측위260～380℃,압력약위5 kbar.차외,응용이장석온도계계산료본지구구역변질편마암화화강암중감성장석적평형온도,소득온도비채용공생철려류석화흑운모온도계고계적온도요저약250℃.저표명공생적철려류석화흑운모적평형온도가능대표기기주변질암변질기온도급기주화강암원생온도,이구역변질암화화강암중적감성장석재경력료수후다차열액작용후,가능중신평형재생,저야여전인대오랍산금광적광상지질화동위소연구적결과일치.
The Wulashan gold deposit, Inner Mongolia, China, which is characterized by intensive alkali feldspar metasomati, is hosted by the late Archean gneiss, amphibolite, migmatite, and marble of the Wulashan Group and surrounded by several intrusions. The general mineral assemblage of mineralized lodes is alkali feldspar + quartz + plagioclase + carbonate (calcite and Fe-dolomite etc). Alkali feldspar is also present as a major component within country rocks. On the basis of the microprobe analyses for coexisting alkali feldspar and plagioclase, the equilibrium temperatures of the alkali feldspars are calculated using several ternary two-feldspar geothermometers. The obtained temperatures at 5 kbar are 353℃ for alkali feldspars from gold-bearing veins I (K-feldspar-quartz veins), and 281℃ for alkali feldspars from gold-bearing veins Ⅱ (quartz veins), in good agreement with the estimated temperatures for coexisting carbonates, mica minerals and gold, and with the homogeneous temperatures of fluid inclusions in quartz and alkali feldspars. Therefore, the gold mineralization in the Wulashan gold deposit formed at the temperatures ranging from 280～360℃ and the pressure of 5 kbar. On the other hand, the temperatures of alkali feldspars from regional metamorphic gneiss and granite are lower than the equilibration temperatures of coexisting almandine and biotite, indicating that the temperatures of almandine and biotite may represent the peak temperature of metamorphi and alkali feldspars in metamorphic rocks and granite may re-equilibrate after experiencing numerous overprinting thermal / magmatic events.