CAJ | 학술논문

沃溪矿床位于湖南雪峰山金锑(钨)成矿带中段,是该带最大的、也是惟一发育Au-Sb-W成矿元素组合的矿床。尽管该矿的研究程度较高,但人们对该矿中重要的含钨矿物--黑钨矿的研究很少。在详细的野外地质调研基础上,对该矿黑钨矿的地质特征和微量元素进行了研究,以期揭示其矿床成因、成矿流体性质及物质来源等信息。沃溪矿床黑钨矿矿脉以顺层的含矿石英脉为主,同时发育各种节理脉；节理脉常相互交错,表现出多阶段成矿特征。矿脉中黑钨矿常与石英、碳酸盐及硫化物共生,形成具有热液充填特征的矿石构造。该矿黑钨矿的REE含量很低(1.62~4.58μg/g),明显低于南岭与花岗岩有关的黑钨矿；其HREE相对富集,并具有 Eu、Sm、Gd、Tb 异常及 MW 复合型四分组效应等特征,这可能与成矿流体的氧逸度及络合物的稳定性有关。同时,该矿黑钨矿的 Y/Ho 值均小于28,指示其成矿流体中以 CO2-3(HCO-3)络合物为主。与南岭地区黑钨矿相比,该矿黑钨矿中S c含量高而N b和Ta含量很低,这可能与该区黑钨矿形成时的物理化学条件以及成矿流体对深部岩石的淋滤作用有关。沃溪矿床中黑钨矿的地质特征、化学成分及微量元素组成明显有别于南岭石英脉型黑钨矿,为其成矿作用与岩浆活动无直接成因关系提供了新的证据。
옥계광상위우호남설봉산금제(오)성광대중단,시해대최대적、야시유일발육Au-Sb-W성광원소조합적광상。진관해광적연구정도교고,단인문대해광중중요적함오광물--흑오광적연구흔소。재상세적야외지질조연기출상,대해광흑오광적지질특정화미량원소진행료연구,이기게시기광상성인、성광류체성질급물질래원등신식。옥계광상흑오광광맥이순층적함광석영맥위주,동시발육각충절리맥；절리맥상상호교착,표현출다계단성광특정。광맥중흑오광상여석영、탄산염급류화물공생,형성구유열액충전특정적광석구조。해광흑오광적REE함량흔저(1.62~4.58μg/g),명현저우남령여화강암유관적흑오광；기HREE상대부집,병구유 Eu、Sm、Gd、Tb 이상급 MW 복합형사분조효응등특정,저가능여성광류체적양일도급락합물적은정성유관。동시,해광흑오광적 Y/Ho 치균소우28,지시기성광류체중이 CO2-3(HCO-3)락합물위주。여남령지구흑오광상비,해광흑오광중S c함량고이N b화Ta함량흔저,저가능여해구흑오광형성시적물이화학조건이급성광류체대심부암석적림려작용유관。옥계광상중흑오광적지질특정、화학성분급미량원소조성명현유별우남령석영맥형흑오광,위기성광작용여암장활동무직접성인관계제공료신적증거。
The Xuefeng Uplift Belt in western Hunan is an important Au-Sb(-W) mineralization belt in South China. The Woxi deposit, as the largest deposit with a unique element association of Au-Sb-W in this region, has attracted attentions of numerous geologists. Researches on ore genesis, fluid inclusion, stable isotope, ore fabric, ore-controlling tectonic and mineralogy have been well conducted in this deposit;however, wolframite in this well studied deposit receives less attention. In this study, geological characteristics of wolframite in the Woxi deposit are described in details, and its trace element concentrations are analyzed by ICP-MS in order to constrain its ore genesis, the nature of the ore-forming fluid and the source of the ore-forming materials. In the Woxi deposit, most wolframite-bearing ore veins occur as bedding quartz veins, whereas the others appear as joint veins of various types indicating there exist multi-stage tungsten mineralization events in this area. Besides, the ore commonly exhibits open-space filling structure and the wolframite is frequently intergrown with carbonate and sulfide in this deposit. The results show that the REE concentrations of wolframites from the Woxi deposit (1.62-4.58μg/g) are distinctly lower than those of wolframites from granite-related tungsten deposits in the Nanling Range. The REE geochemistry of the Woxi wolframite is characterized by HREE enrichment, Eu-, Sm-, Gd-and Tb-anomalies, as well as a peculiar composite M- and W-type tetrad effect. All of these features are probably controlled by the oxygen fugacity and the stabilities of complexing agent in the ore-forming fluid. Moreover, the Y/Ho ratios (<28) of wolframites from the Woxi deposit reveal REE and Y speciation is dominated by (bi)carbonate-complexes in wolframite-precipitating fluid. In addition, the content of Sc of wolframite from this deposit is high but the contents of Nb and Ta are low, which probably resulted from high pH, low Eh conditions during the crystallization of wolframite and from the leaching of the underlying older continental rocks by the hydrothermal fluid. Generally, the geological and geochemical characteristics of wolframite in the Woxi deposit, which are obviously different from that of those quartz vein-type wolframite deposits associated with granite intrusions in the Nanling Range, provide new evidences for no direct relationship between the tungsten mineralization and magmatism in the Woxi deposit.