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A trace metal, stable isotope (H, O, S), and geochronological (U-Pb titanite) characterization of hybridized gold orebodies in the Missanabie-Renabie district, Wawa subprovince (Canada)
Mineralium Deposita ( IF 4.4 ) Pub Date : 2020-06-11 , DOI: 10.1007/s00126-020-00983-9
Jordan A. McDivitt , Daniel J. Kontak , Bruno Lafrance , Joseph A. Petrus , Mostafa Fayek

Mineralized shear zones in the Archean Missanabie-Renabie gold district (~ 1.1 Moz Au; Wawa, Ontario, Canada) locally define composite orebodies that record three hydrothermal events: (1) a pre-orogenic Au 1 event (pre-D 1 and pre-prograde-metamorphic); (2) a syn-orogenic, post-peak-metamorphic Retrograde event (syn-D 3 ); and (3) a late syn-to post-orogenic Au 2 event (late syn- to post-D 4 ). Genetic considerations indicate the orebodies are hybrids with early intrusion-related (Au 1 ) and later orogenic (Retrograde + Au 2 ) events. Pearson product-moment correlation coefficients (log 10 ) of whole-rock and LA-ICP-MS pyrite trace metal datasets distinguish Au 1 from Au 2 mineralization by Au-Ag, Au-Bi, and Au-Te correlations > 0.7 ( p < 0.05) in the former, irrespective of sample medium and analytical method. An Au-Mo correlation in whole rock data (0.58–0.76; p < 0.05) further distinguishes Au 1 from Au 2 and supports an independently inferred intrusion-related origin for Au 1 . Sulfur isotope data is similar for both Au 1 and Au 2 pyrite with average δ 34 S values of − 5.5‰ ± 0.2‰ (1σ) and − 3.5‰ ± 0.3‰ (1σ) and average Δ 33 S values of 0.4‰ ± 0.1‰ (1σ) and − 0.3‰ ± 0.2‰ (1σ), respectively. SIMS δ 18 O quartz values for the Au 1 , Retrograde, and Au 2 events largely overlap and, like δ 18 O carbonate values of previous studies, tend to be lower than values typical of Archean gold deposits. The results of this study suggest that correlation coefficients in trace metal datasets are useful in discriminating and characterizing different gold events. Caution is emphasized with the use of S- and O-isotope datasets for these purposes. The presence of low δ 18 O values in vein quartz and carbonate is best explained by an 18 O-depleted fluid formed during the Retrograde hydrothermal event. The latter is inferred at 2580 ± 21 Ma based on U-Pb geochronlogy of hydrothermal titanite, and relates to deformation and metamorphism in the nearby, amphibolite- to granulite-grade Kapuskasing metamorphic belt. Geochronological and geochemical evidence suggest that the 18 O-depleted fluid may have formed via the devolatilization of biotite-bearing granitoids during deep-crustal metamorphism.

中文翻译:

瓦瓦省(加拿大)Missanabie-Renabie 区杂化金矿体的痕量金属、稳定同位素(H、O、S)和年代学(U-Pb 钛铁矿)表征

太古宙 Missanabie-Renabie 金区(~ 1.1 Moz Au;Wawa,加拿大安大略省)的矿化剪切带局部定义了记录三个热液事件的复合矿体:(1)造山前 Au 1 事件(前 D 1 和前-prograde-变形);(2) 同造山、峰后变质逆行事件 (syn-D 3 );(3) 一个晚期同向到造山后 Au 2 事件(晚期同向到后 D 4 )。遗传考虑表明矿体是具有早期侵入相关(Au 1 )和后期造山(逆行+ Au 2 )事件的混合体。全岩和 LA-ICP-MS 黄铁矿痕量金属数据集的 Pearson 积矩相关系数 (log 10) 通过 Au-Ag、Au-Bi 和 Au-Te 相关性区分 Au 1 和 Au 2 矿化 > 0.7 ( p < 0.05) 在前者中,与样品介质和分析方法无关。全岩数据中的 Au-Mo 相关性 (0.58–0.76; p < 0.05) 进一步将 Au 1 与 Au 2 区分开来,并支持独立推断的 Au 1 侵入相关成因。Au 1 和 Au 2 黄铁矿的硫同位素数据相似,平均 δ 34 S 值为 − 5.5‰ ± 0.2‰ (1σ) 和 − 3.5‰ ± 0.3‰ (1σ),平均 Δ 33 S 值为 0.4‰ ± 0.1 ‰ (1σ) 和 − 0.3‰ ± 0.2‰ (1σ)。用于 Au 1 、逆行和 Au 2 事件的 SIMS δ 18 O 石英值在很大程度上重叠,并且与先前研究的 δ 18 O 碳酸盐值一样,往往低于太古代金矿床的典型值。这项研究的结果表明,痕量金属数据集中的相关系数可用于区分和表征不同的金事件。出于这些目的使用 S 和 O 同位素数据集时要格外小心。石英脉和碳酸盐岩中存在低 δ 18 O 值的最佳解释是在逆行热液事件期间形成的 18 O 耗尽流体。后者根据热液钛铁矿的 U-Pb 年代学推断为 2580±21 Ma,与附近角闪岩至麻粒岩级 Kapuskasing 变质带的变形和变质作用有关。年代学和地球化学证据表明,18 O 耗尽流体可能是通过深地壳变质过程中含黑云母花岗岩的脱挥发分形成的。角闪岩至麻粒岩级 Kapuskasing 变质带。年代学和地球化学证据表明,18 O 耗尽流体可能是通过深地壳变质过程中含黑云母花岗岩的脱挥发分形成的。角闪岩至麻粒岩级 Kapuskasing 变质带。年代学和地球化学证据表明,18 O 耗尽流体可能是通过深地壳变质过程中含黑云母花岗岩的脱挥发分形成的。
更新日期:2020-06-11
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