Stable isotopes (H, C, O) and 3D fluid flow modeling constraints on gold endowment along the Augmitto-Bouzan orogenic gold deposit (Abitibi subprovince, Quebec)

IF 4.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Guillaume Raymond, Georges Beaudoin, Benoît Quesnel, Christophe Scheffer, Crystal LaFlamme, René Therrien, John W. Molson
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Abstract

The Augmitto-Bouzan deposit is a 12 km long segment of the Larder Lake-Cadillac Deformation Zone (LLCDz) south of Rouyn-Noranda (Québec, Canada) that is characterized by an uneven gold distribution hosted in quartz-carbonate ± tourmaline veins within Piché Group ultramafic rocks. This study compares the fluid flow conditions between the variable gold-endowed sectors to identify deposit-scale processes responsible for gold endowment. Stable isotopes indicate that quartz and tourmaline have equilibrium temperatures (228–⁠420 °C) that likely define a high vertical thermal gradient (~ 30 °C/100 m) along the LLCDz. Covariation between temperature and computed δ18OH2O and δDH2O is interpreted to result from mixing between a high temperature (> 420 °C), high δ18O (> 10.8‰), and low δD (< –29‰) deep-seated metamorphic fluid, and a low temperature (< 230 °C), low δ18O (< 4‰) and high δD (~ 0‰) upper crustal pore fluid. Local upwelling of auriferous deep-seated fluid, shown by interpolation of δ18OH2O in the gold-endowed Augmitto-Cinderella and Astoria segments, was likely focused along higher permeability deformation-related pathways. Sectors of low gold endowment have lower δ18OH2O and fluid/rock ratios, likely reflecting a larger proportion of upper crustal fluid and differences in fluid-flow behavior. Modeling of fluid flow shows that this is due to 1) weaker metamorphic fluid flux in the thinner band of Piché Group rocks and 2) more porous volcanic rocks north of the LLCDz, drawing more pore fluid into the fault. We suggest that most of the variation of gold endowment is related to variations in advection of auriferous metamorphic fluid along the segment, whereby a weaker metamorphic fluid flux or increased admixture of upper crustal fluids decrease the gold potential along the LLCDz.

Abstract Image

稳定同位素(H、C、O)和三维流体流动模型对奥格米托-布赞(Augmitto-Bouzan)成因金矿床(魁北克阿比提比省)沿线金赋存的制约因素
Augmitto-Bouzan矿床是加拿大魁北克省鲁因-诺兰达(Rouyn-Noranda)以南的拉德尔湖-卡迪拉克变形带(LLCDz)的一个12公里长的区段,其特点是金分布不均,赋存于皮切组超基性岩中的石英-碳酸盐±电气石矿脉中。这项研究比较了不同赋金区之间的流体流动条件,以确定造成赋金的矿床规模过程。稳定同位素表明,石英和电气石的平衡温度(228-420 °C)很可能决定了沿LLCDz的高垂直热梯度(约30 °C/100米)。温度与计算δ18OH2O和δDH2O之间的差异被解释为高温(420 °C)、高δ18O(10.8‰)和低δD(-29‰)深层变质流体与低温(230 °C)、低δ18O(4‰)和高δD(约0‰)上地壳孔隙流体之间混合的结果。金赋存的奥格米托-辛德瑞拉和阿斯托里亚区段的δ18OH2O内插法显示,含金深层流体的局部上涌很可能集中在与变形有关的高渗透率通道上。金禀赋低的区段δ18OH2O和流体/岩石比值较低,可能反映了上地壳流体比例较大以及流体流动行为的差异。流体流动模型显示,这是由于:1)较薄的皮切组岩石带变质流体通量较弱;2)LLCDz 北部火山岩孔隙较多,将更多的孔隙流体吸入断层。我们认为,金蕴藏量的大部分变化与沿断层段含金变质流体的吸入变化有关,变质流体通量减弱或上地壳流体掺入量增加会降低LLCDz沿线的金潜力。
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来源期刊
Mineralium Deposita
Mineralium Deposita 地学-地球化学与地球物理
CiteScore
11.00
自引率
6.20%
发文量
61
审稿时长
6 months
期刊介绍: The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.
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