...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >The Hydrothermal Geochemistry of Tungsten in Granitoid Environments: I. Relative Solubilities of Ferberite and Scheelite as a Function of T, P, pH, and m_(NaCl)
【24h】

The Hydrothermal Geochemistry of Tungsten in Granitoid Environments: I. Relative Solubilities of Ferberite and Scheelite as a Function of T, P, pH, and m_(NaCl)

机译：钨在花岗岩环境中的热液地球化学：I.镁铁矿和白钨矿的相对溶解度随T，P，pH和m_（NaCl）的变化

获取原文
获取原文并翻译 | 示例
   

获取外文期刊封面封底 >>

       
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The characteristics of granitoid-related tungstendeposits hosted in siliceous (carbonate-free) rocks (e.g.,Panasqueira, Cligga Head, Pasto Bueno) are reviewed and theranges of physicochemical parameters of the ore-forming fluidsare summarized. The two important tungsten minerals in thesedeposits are wolframite and scheelite, which were depositedmostly between and 200 deg and 500 deg C and 200 and 1,500bars. The salinities of the mineralizing fluids were typically lessthan 15 wt percent but commonly were significantly higher (upto 55 wt percent). The two predominant dissolved componentsare Na~+ and Cl~- with subordinate Ca~ (2+), K~+, andcarbonate species (CO_3~ (2-)/HCO_3~-). The contents ofCO_2 are highly variable, but X_(CO_2) values typically rangefrom 0 to 0.1. limited pH and fo_2 estimates indicate amoderately acidic fluid with oxygen fugacities between those ofthe QFM and HM buffers. These parameters were used to guidesolubility and speciation modeling of W in hydrothermal fluidsin granitoid environments.Experimentally derived thermodynamic data for scheelite,ferberite, aqueous Ca, Fe, and W species, and other requiredaqueous species were critically evaluated and the most reliabledata were adopted. Where necessary, missing data wereestimated. The resultant thermodynamic database provides abasis for solubility and speciation calculations in the system Ca-Fe-W-Cl-O-H. The simultaneous solubilities of scheelite andferberite in NaCl-HCl-H_2O solutions were calculated attemperatures from 200 deg to 600 deg C, pressures from 500 to1,000 bars, pH from 3 to 6, and m_(Nacl) from to 0.1 to 5.0moles/kg H_2O. The solubility model takes account of thespecies H~+, OH~-, Na~+, Cl~-, NaCl~0, HCl~0, NaOH~0,H_2WO_4~0, HWO_4~-, WO_4~(2-), Fe~(2+), FeCl~+,FeCl_2~0, FeOH~+, FeO~0, HFeO_2~-, Ca~(2+), CaCl~+,CaCl_2~0, CaOH~+, NaHWO_4~0, and NaWO_4~-. Thecalculations indicate the following: (1) solubilities of scheeliteand/or ferberite can attain values as high as hundreds tothousands of parts per million as the tungstate speciesH_2WO_4~0, HWO_4~(2-), WO_4~(2-), NaHWO_4~0, andNaWO_4~-; thus, tungsten-chloride, -fluoride, or -carbonatecomplexes, or more exotic species are not required to transportsufficient W to form an ore deposit; (2) the tungstenconcentration in equilibrium with scheelite and ferberiteincreases strongly with increasing temperature, increasing NaClconcentration and decreasing pH, but is only weakly dependenton pressure; (3) the Ca/Fe ratio of a solution in equilibrium withboth scheelite and ferberite decreases strongly with increasingtemperature, i.e., the field of stability of scheelite expands withincreasing temperature; the implication, therefore, is that simplecooling of a solution with a constant Ca/Fe ratio cannot result inthe replacement of ferberite by scheelite, and that fieldobservations of the late-stage replacement of ferberite byscheelite require an increase in the Ca/Fe ratio concomitant withcooling; (4) the Ca/Fe ratio is relatively independent of pH; and(5) the effect of NaCl concentration on this ratio changes as afunction of temperature and pressure. At less than 400 deg C theratio is independent of, or decreases with, increasing NaClconcentration; at higher temperatures the ratio first decreasesand then increases with increasing NaCl concentration.Experimental data on the solubility of scheelite and the Ca/Feratio of fluids in equilibrium with scheelite + ferberite, andwhich are not used in parameterizing our model, generally agreewith the results of calculations performed using ourthermodynamic database within an order of magnitude.However, our critical examination of available thermodynamicdata reveals that significant uncertainty remains in severalparameters (e.g., the solubility products of scheelite andferberite and the association constants for alkali tungstate ionpairs). This uncertainty can only be reduced via carefullyconceived, executed, controlled, and interpreted experiments,taking into account t
机译：综述了含硅（无碳酸盐）岩石（例如，Panasqueira，Cligga Head，Pasto Bueno）中与类花岗岩相关的钨矿床的特征，并概述了成矿流体的理化参数范围。这些矿床中的两种重要的钨矿物是黑钨矿和白钨矿，它们的最大沉积温度在200摄氏度至500摄氏度以及200巴和1,500巴之间。矿化液的盐度通常小于15 wt％，但通常显着较高（高达55 wt％）。两种主要的溶解成分是Na〜+和Cl〜-，下级为Ca〜（2 +），K〜+和碳酸盐种类（CO_3〜（2-）/ HCO_3〜-）。 CO_2的内容高度可变，但是X_（CO_2）值通常在0到0.1的范围内。有限的pH和fo_2估计值表明中等酸性流体，其氧逸度介于QFM和HM缓冲液之间。这些参数被用于指导花岗岩环境中水在热液中的溶解度和形态模拟。严格评估了白钨矿，辉铁矿，Ca，Fe和W物种以及其他所需水物种的实验热力学数据，并采用了最可靠的数据。必要时，估计丢失的数据。所得的热力学数据库为Ca-Fe-W-Cl-O-H系统中的溶解度和形态计算提供了依据。在200到600摄氏度的温度，500到1,000巴的压力，3到6的pH值和m到（Nacl）的0.1到5.0moles /的温度下计算白钨矿和硅铁矿在NaCl-HCl-H_2O溶液中的同时溶解度千克H_2O。溶解度模型考虑了以下物种：H〜+，OH〜-，Na〜+，Cl〜-，NaCl〜0，HCl〜0，NaOH〜0，H_2WO_4〜0，HWO_4〜-，WO_4〜（2-）， Fe〜（2 +），FeCl〜+，FeCl_2〜0，FeOH〜+，FeO〜0，HFeO_2〜-，Ca〜（2 +），CaCl〜+，CaCl_2〜0，CaOH〜+，NaHWO_4〜0，和NaWO_4〜-。计算结果表明：（1）白钨矿和/或镁橄榄石的溶解度可以达到与钨酸盐物种H_2WO_4〜0，HWO_4〜（2-），WO_4〜（2-），NaHWO_4〜0高达百万分之十的值。 ，以及NaWO_4〜-;;因此，不需要使用氯化钨，-氟化物或-碳酸盐络合物或更多外来物种来运输足够的W以形成矿床; （2）白钨矿和白铁矿平衡态下的钨浓度随温度升高，NaCl浓度升高和pH值降低而强烈增加，但与压力的关系很小。 （3）白钨矿和钙铁矿在平衡状态下的溶液中Ca / Fe比随温度的升高而急剧下降，即白钨矿的稳定性场随温度的升高而扩大;因此，这意味着具有恒定Ca / Fe比的溶液的简单冷却不会导致白钨矿替代钙铁矿，而现场观察到白钨矿对白铁矿后期置换的要求伴随冷却而增加了Ca / Fe比。 ; （4）Ca / Fe比值相对独立于pH值; （5）NaCl浓度对该比例的影响随温度和压力的变化而变化。在低于400摄氏度的温度下，NaCl的浓度独立于或随NaCl浓度的增加而降低;白钨矿的溶解度和白钨矿+镁铁矿在平衡状态下流体的Ca / Feratio的实验数据并未用于模型化，一般与计算结果相符。但是，我们对可用热力学数据的严格检查显示，在几个参数（例如，白钨矿和硅铁矿的溶解度产物以及碱金属钨酸盐离子对的缔合常数）中仍然存在明显的不确定性。只有通过精心构思，执行，控制和解释的实验，并考虑到

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号