Arsenopyrite and As-bearing pyrite from the Roudný deposit, Bohemian Massif
Arsenopyrite and As-bearing pyrite from the Roudný deposit, Bohemian Massif
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DOI：
10.1180/0026461046810169
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发表时间：
2004-02
影响因子：
2.7
通讯作者：
Jiří Zachariáš;J. Frýda;B. Paterová;M. Mihaljevič
中科院分区：
文献类型：
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作者：
Jiří Zachariáš;J. Frýda;B. Paterová;M. Mihaljevič
摘要 采用电子探针和激光烧蚀ICP-MS 技术研究了中温Roudný 金矿床中黄铁矿和毒砂的主量元素和微量元素化学。总共区分了四代黄铁矿和两代毒砂。黄铁矿通过 Fe (AsxS1−x)2 取代机制富集 As。 Pyrite-2 的富砷区（砷含量高达 4.5 wt.%）还富含金（高达 20 ppm）、铅（通常高达 220 ppm，特殊情况下高达 1500 ppm）和锑（通常 <600 ppm，很少高达 1350 ppm）。与卡林型金矿床中富含金的含砷黄铁矿相反，所研究的黄铁矿中砷和金的正相关性并不伴随着铁的缺乏。富含砷的黄铁矿-2 与富含锑 (1−4.2 wt.%) 和富含金 (40−150 ppm) 的砷黄铁矿-1 共沉淀。较年轻的毒砂-2 中这些元素的富集度明显较低（0−70 ppm Au）。鲁德尼金矿床中黄铁矿的化学地带性反映了含矿流体的化学演化，这是在任何其他矿物相中未观察到的。现有数据表明，在较老的黄铁矿一代（pyrite-1）结晶过程中，硫的活性相对较高，而砷和金的活性较低。随后，经过黄铁矿1的特殊溶解，富金砷的黄铁矿2和毒砂沉淀出来。这些事实表明含矿流体中砷和金的活性显着增加。 Pyrite-2 的 As 含量从核心到边缘以振荡方式降低，反映了 As 活性或/和 P-T 条件的变化。根据毒砂温度计和流体包裹体数据，含砷黄铁矿是在至少 320-330°C 的温度下形成的。
Abstract The major- and trace-element chemistry of pyrite and arsenopyrite from the mesothermal Roudný gold deposits was studied by electron microprobe and laser ablation ICP-MS techniques. In total, four generations of pyrite and two of arsenopyrite were distinguished. The pyrite is enriched in As through an Fe (AsxS1−x)2 substitution mechanism. The As-rich zones of pyrite-2 (up to 4.5 wt.% As) are also enriched in gold (up to 20 ppm), lead (commonly up to 220 ppm, exceptionally up to 1500 ppm) and antimony (commonly <600 ppm, rarely up to 1350 ppm). Positive correlation of As and Au in the studied pyrites is not coupled with an Fe deficiency, in contrast to Au-rich As-bearing pyrites in Carlintype gold deposits. The As-rich pyrite-2 coprecipitated with the Sb-rich (1−4.2 wt.%) and Au-rich (40−150 ppm) arsenopyrite-1. The younger arsenopyrite-2 is significantly less enriched in these elements (0−70 ppm of Au). The chemical zonality of pyrites in the Roudný gold deposits reflects the chemical evolution of ore-bearing fluids that are not observed in any other mineral phases. The data available suggest relatively high activity of sulphur and low activities of arsenic and gold during crystallization of the older pyrite generation (pyrite-1). Later, after particular dissolution of pyrite-1, Au-rich As-bearing pyrite-2 and arsenopyrite precipitated. These facts suggest a marked increase in the arsenic and gold activities in ore-bearing fluids. The As-content of pyrite-2 decreases in an oscillatory manner from the core to the rim, reflecting changes in the As activity or/and in the P-T conditions. The As-bearing pyrites were formed at temperatures of at least 320-330ºC, based on arsenopyrite thermometers and fluid inclusion data.