The Miocene aged polymetallic (Ag-Zn-Sn-Pb) Pirquitas deposit of NW Argentina, hosted in an uplifted horst of Ordovician metaturbiditic rocks, defines the southern extent of the Andean Tin Belt. The nearby and recently discovered Cortaderas breccia-hosted Ag-Zn deposit contrasts markedly with the main Pirquitas deposit. To address these differences, a comprehensive geological, mineralogical, and geochemical study was undertaken and here reported. Ore formation commenced with brecciation and clay alteration of host rocks followed by six polymetallic ore stages and a waning stage. The complex mineralization (Ag, Sb, As, Sn, Fe, Zn, Cu, Pb, and Bi) consists of pyrite, marcasite, sphalerite, arsenopyrite, galena, cassiterite, quartz, dickite, siderite, hydrous phosphate minerals, and various sulfosalts and sulfides; metal assays indicate a telescoped system. Sphalerite-rich domains are characterized by massive, colloform, dendritic, and cockade textures. Silver and Sn principally occur in various sulfosalts (tetrahedrite, pyrargyrite, miargyrite, pirquitasite-hocartite, and canfieldite). Fluid inclusions reflect mixing of a ca. 5 wt% eq. NaCl fluid having a maximum Th value of 340 °C with heated meteoric water; in addition, fluid unmixing and flashing are documented to have accompanied ore formation. The δ 34 S values for pyrite and sphalerite constrain δ 34 S H2S to ≈ 5‰ which suggests a magmatic reservoir. Collectively the data support a model, whereby the Cortaderas breccia reflects focusing of magmatic-sourced mineralizing fluids along an episodically dilating fault zone. Fluids ascended and depressurized following brecciation of the host rocks which initiated fast and slow boiling. The latter processes accounts for the intimate association of colloform- and dendritic-textured sphalerite. Subsequent sealing of the system allowed temperature gradients to rise which resulted in telescoping of the system and generation of this polymetallic ore zone.

中文翻译：

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多阶段超热液 Ag-Zn-Pb-Sn 矿床的起源：中新世 Cortaderas 角砾岩体，Pirquitas 矿，阿根廷西北部

阿根廷西北部的中新世多金属 (Ag-Zn-Sn-Pb) Pirquitas 矿床位于奥陶纪变浊积岩隆起的地幔中，定义了安第斯锡带的南部范围。附近和最近发现的 Cortaderas 角砾岩含银锌矿床与主要的 Pirquitas 矿床形成鲜明对比。为了解决这些差异，进行了全面的地质、矿物和地球化学研究，并在此进行了报告。矿石形成开始于围岩的角砾化和粘土蚀变，然后是六个多金属矿阶段和一个衰落阶段。复杂的矿化（Ag、Sb、As、Sn、Fe、Zn、Cu、Pb 和 Bi）由黄铁矿、白铁矿、闪锌矿、毒砂、方铅矿、锡石、石英、地开石、菱铁矿、水合磷酸盐矿物和各种硫盐组成和硫化物；金属化验表明一个望远镜系统。富含闪锌矿的区域的特征是块状、胶状、树枝状和冠状纹理。银和 Sn 主要存在于各种磺盐（四面体陨石、pyrargyrite、miargyrite、pirquitasite-hocartite 和 canfieldite）中。流体包裹体反映了大约的混合。5 重量％当量 具有最大 Th 值为 340 °C 的 NaCl 流体与加热的大气水；此外，据记载，流体分离和闪蒸伴随着矿石的形成。黄铁矿和闪锌矿的 δ 34 S 值将 δ 34 S H2S 限制为 ≈ 5‰，这表明存在岩浆储层。数据共同支持一个模型，其中 Cortaderas 角砾岩反映了岩浆来源的矿化流体沿着间歇性扩张断层带的聚集。在主岩发生角砾化作用后，流体上升和减压，从而开始快速和缓慢沸腾。后一过程解释了胶状和树枝状纹理闪锌矿的密切关联。系统的后续密封使温度梯度上升，导致系统伸缩并生成该多金属矿区。