Diagenetic pyrite as a source for metals in orogenic gold deposits, Otago Schist, New Zealand
Diagenetic pyrite as a source for metals in orogenic gold deposits, Otago Schist, New Zealand
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DOI：
10.1080/00288306.2012.682282
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发表时间：
2012-06
影响因子：
2.2
通讯作者：
R. Large;Helen Thomas;D. Craw;A. Henne;S. Henderson
中科院分区：
文献类型：
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作者：
R. Large;Helen Thomas;D. Craw;A. Henne;S. Henderson
摘要在奥塔哥片岩东北缘的低品位浊积岩中发现了一种框状成岩黄铁矿。激光烧蚀电感耦合等离子体质谱（ICP-MS）分析这些framboids显示，除了Fe，存在的主要金属是As，Pb，Zn，Te，Ag和Mo; Au是在0.5和2 ppm之间。浊积岩基质中也有少量的Au和As异常。附近Macraes矿的斑状变晶黄铁矿含有微米级的自然金和高达30 ppm的固溶体金。这些黄铁矿变斑晶还富集As、W、Ni、Co和Bi。铅、锌、碲、钼含量明显低于低品位草莓。这些结果表明，低品位浊积岩是Macraes等造山型金矿床中Au和As的良好来源。黄铁矿向磁黄铁矿的转变主要发生在绿片岩相条件下，可能是中生代变质作用中最有效的As和Au活化反应。
Abstract Framboidal diagenetic pyrite occurs in low-grade turbidites on the northeast margin of the Otago Schist. Laser ablation inductively coupled plasma mass spectrometry (ICP-MS) analyses of these framboids show that the main metals present, in addition to Fe, are As, Pb, Zn, Te, Ag and Mo; Au is present at between 0.5 and 2 ppm. Minor Au and As anomalies also occur sporadically in the turbidite matrix. Porphyroblastic pyrite at the nearby Macraes mine contains micron-scale native gold and solid solution gold up to 30 ppm. These pyrite porphyroblasts are also enriched in As, W, Ni, Co and Bi. Lead, Zn, Te and Mo contents are distinctly lower than in the low-grade framboids. These results show that low-grade turbidites were a fertile source for Au and As for orogenic gold deposits such as Macraes. The pyrite to pyrrhotite transition, which occurred mainly under greenschist facies conditions, was probably the most effective As and Au mobilisation reaction during Mesozoic metamorphism.