The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t) of gold. The deposit is hosted in the 2699–2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699–2696 Ma) Mooshla Intrusive Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked, contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host rocks.The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusite-kyanite-pyrophyllite argillic to advanced argillic-style tabular envelope that is up to a few tens of meters thick.The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillic-style alteration assemblage is associated with both corridors.The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic-hydrothermal system that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system.The Westwood Au deposit represents one of the very few documented examples of an Archean magmatic-hydrothermal system—or at least of such systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor Au-rich VMS-type mineralization.

中文翻译：

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加拿大南部 Abitibi 绿岩带 Westwood 矿床：太古宙富金多金属岩浆热液系统——第二部分。热液蚀变、矿化和地质模型

Westwood 矿床位于太古宙 Abitibi 绿岩带南部的 Archean Doyon-Bousquet-LaRonde 采矿营地，含有 4.5 Moz（140 公吨）黄金。该矿床位于 2699-2695 Ma 海底、拉斑质至钙碱性火山岩、火山碎屑岩和 Bousquet 组的侵入岩中。该矿床位于同火山岩（约 2699-2696 Ma）Mooshla 侵入复合体附近，该复合体拥有与 Doyon 表带侵入相关的 Au ± Cu 矿床，而在 Westwood 矿床以东存在几个富金火山成因块状硫化物 (VMS) 矿床. Westwood 矿床由地层堆叠、对比和叠印的矿化样式组成，与营地的侵入相关矿床和 VMS 矿床具有相似性。矿区形成三个不同的，与从北（底部）到南（顶部）、2 区延伸、北走廊和韦斯特伍德走廊的分层走廊略有不一致。同晚期主区域变形和上绿片岩到下角闪岩相区域变质作用影响矿区、蚀变组合和围岩。 2 区伸展由 Au ± Cu 硫化物（黄铁矿-黄铜矿）-石英脉和播散成半块状硫化物。矿带在空间上与一系列钙碱性长英质岩床和岩脉相关，这些岩床和岩脉横切镁铁质至中间、拉斑到过渡、较低的 Bousquet 组火山岩。变质的近端蚀变由白云母-石英-黄铁矿±石膏-红柱石-蓝晶石-叶蜡石泥质至先进的泥质式板状包络组成，厚度可达几十米。北部走廊由含金半块状到块状硫化物脉组成， Bousquet 组上部底部的中间火山碎屑岩中的硫化物纵梁带和浸染性硫化物。韦斯特伍德走廊由半块状到块状硫化物透镜体、矿脉、硫化物纵梁带和浸染性硫化物组成，它们位于地层序列的较高位置，位于或靠近上部钙碱性英安岩穹顶和上覆钙碱性流纹岩之间的接触处布斯凯形成。一个大的，包括北走廊的半整合远端蚀变区存在于 Westwood 走廊的下盘和附近。这个变质的蚀变带由黑云母-锰石榴石-绿泥石-碳酸盐±白云母-钠长石的组合组成。近端白云母-石英-绿泥石-黄铁矿泥质型蚀变组合与两条走廊有关。2 区伸展矿带和相关蚀变根据横切关系和 U-Pb 年代学被认为是火山岩，并被解释为一个以同火山 Mooshla 侵入复合体上部为中心的带状岩浆热液系统。North 和 Westwood 走廊由双峰长英质富金 VMS 型矿化和蚀变组成，由改性海水的对流循环产生，其中包括同时代外带区 2 扩展岩浆-热液系统的岩浆贡献。Westwood Au 矿床代表了一个极少数记录在案的太古宙岩浆热液系统的例子——或者至少是在水下环境中形成的此类系统。对 Westwood 矿床的研究有助于更好地理解岩浆流体输入对太古宙表带侵入相关 Au ± Cu 和海底/海底富金 VMS 型矿化形成的关键作用。Westwood Au 矿床代表了极少数记录在案的太古代岩浆热液系统的例子之一，或者至少是在水下环境中形成的此类系统的例子之一。对 Westwood 矿床的研究有助于更好地理解岩浆流体输入对太古宙表带侵入相关 Au ± Cu 和海底/海底富金 VMS 型矿化形成的关键作用。Westwood Au 矿床代表了极少数记录在案的太古代岩浆热液系统的例子之一，或者至少是在水下环境中形成的此类系统的例子之一。对 Westwood 矿床的研究有助于更好地理解岩浆流体输入对太古宙表带侵入相关 Au ± Cu 和海底/海底富金 VMS 型矿化形成的关键作用。