The world-class San Rafael tin (-copper) deposit (central Andean tin belt, southeast Peru) is an exceptionally large and rich (>1 million metric tons Sn; grades typically >2% Sn) cassiterite-bearing hydrothermal vein system hosted by a late Oligocene (ca. 24 Ma) peraluminous K-feldspar-megacrystic granitic complex and surrounding Ordovician shales affected by deformation and low-grade metamorphism. The mineralization consists of NW-trending, quartz-cassiterite-sulfide veins and fault-controlled breccia bodies (>1.4 km in vertical and horizontal extension). They show volumetrically important tourmaline alteration that principally formed prior to the main ore stage, similar to other granite-related Sn deposits worldwide. We present here a detailed textural and geochemical study of tourmaline, aiming to trace fluid evolution of the San Rafael magmatic-hydrothermal system that led to the deposition of tin mineralization. Based on previous works and new petrographic observations, three main generations of tourmaline of both magmatic and hydrothermal origin were distinguished and were analyzed in situ for their major, minor, and trace element composition by electron microprobe analyzer and laser ablation-inductively coupled plasma-mass spectrometry, as well as for their bulk Sr, Nd, and Pb isotope compositions by multicollector-inductively coupled plasma-mass spectrometry. A first late-magmatic tourmaline generation (Tur 1) occurs in peraluminous granitic rocks as nodules and disseminations, which do not show evidence of alteration. This early Tur 1 is texturally and compositionally homogeneous; it has a dravitic composition, with Fe/(Fe + Mg) = 0.36 to 0.52, close to the schorl-dravite limit, and relatively high contents (10s to 100s ppm) of Li, K, Mn, light rare earth elements, and Zn. The second generation (Tur 2)—the most important volumetrically—is pre-ore, high-temperature (>500°C), hydrothermal tourmaline occurring as phenocryst replacement (Tur 2a) and open-space fillings in veins and breccias (Tur 2b) and microbreccias (Tur 2c) emplaced in the host granites and shales. Pre-ore Tur 2 typically shows oscillatory zoning, possibly reflecting rapid changes in the hydrothermal system, and has a large compositional range that spans the schorl to dravite fields, with Fe/(Fe + Mg) = 0.02 to 0.83. Trace element contents of Tur 2 are similar to those of Tur 1. Compositional variations within Tur 2 may be explained by the different degree of interaction of the magmatic-hydrothermal fluid with the host rocks (granites and shales), in part because of the effect of replacement versus open-space filling. The third generation is syn-ore hydrothermal tourmaline (Tur 3). It forms microscopic veinlets and overgrowths, partly cutting previous tourmaline generations, and is locally intergrown with cassiterite, chlorite, quartz, and minor pyrrhotite and arsenopyrite from the main ore assemblage. Syn-ore Tur 3 has schorl-foititic compositions, with Fe/(Fe + Mg) = 0.48 to 0.94, that partly differ from those of late-magmatic Tur 1 and pre-ore hydrothermal Tur 2. Relative to Tur 1 and Tur 2, syn-ore Tur 3 has higher contents of Sr and heavy rare earth elements (10s to 100s ppm) and unusually high contents of Sn (up to >1,000 ppm). Existence of these three main tourmaline generations, each having specific textural and compositional characteristics, reflects a boron-rich protracted magmatic-hydrothermal system with repeated episodes of hydrofracturing and fluid-assisted reopening, generating veins and breccias. Most trace elements in the San Rafael tourmaline do not correlate with Fe/(Fe + Mg) ratios, suggesting that their incorporation was likely controlled by the melt/fluid composition and local fluid-rock interactions. The initial radiogenic Sr and Nd isotope compositions of the three aforementioned tourmaline generations (0.7160–0.7276 for ⁸⁷Sr/⁸⁶Sr_(i) and 0.5119–0.5124 for ¹⁴³Nd/¹⁴⁴Nd_(i)) mostly overlap those of the San Rafael granites (⁸⁷Sr/⁸⁶Sr_(i) = 0.7131–0.7202 and ¹⁴³Nd/¹⁴⁴Nd_(i) = 0.5121–0.5122) and support a dominantly magmatic origin of the hydrothermal fluids. These compositions also overlap the initial Nd isotope values of Bolivian tin porphyries. The initial Pb isotope compositions of tourmaline show larger variations, with ²⁰⁶Pb/²⁰⁴Pb_(i), ²⁰⁷Pb/²⁰⁴Pb_(i), and ²⁰⁸Pb/²⁰⁴Pb_(i) ratios mostly falling in the range of 18.6 to 19.3, 15.6 to 16.0, and 38.6 to 39.7, respectively. These compositions partly overlap the initial Pb isotope values of the San Rafael granites (²⁰⁶Pb/²⁰⁴Pb_(i) = 18.6–18.8, ²⁰⁷Pb/²⁰⁴Pb_(i) = 15.6–15.7, and ²⁰⁸Pb/²⁰⁴Pb_(i) = 38.9–39.0) and are also similar to those of other Oligocene to Miocene Sn-W ± Cu-Zn-Pb-Ag deposits in southeast Peru. Rare earth element patterns of tourmaline are characterized, from Tur 1 to Tur 3, by decreasing (Eu/Eu*)_N ratios (from 20 to 2) that correlate with increasing Sn contents (from 10s to >1,000 ppm). These variations are interpreted to reflect evolution of the hydrothermal system from reducing toward relatively more oxidizing conditions, still in a low-sulfidation environment, as indicated by the pyrrhotite-arsenopyrite assemblage. The changing textural and compositional features of Tur 1 to Tur 3 reflect the evolution of the San Rafael magmatic-hydrothermal system and support the model of fluid mixing between reduced, Sn-rich magmatic fluids and cooler, oxidizing meteoric waters as the main process that caused cassiterite precipitation.

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电气石作为晚岩浆到热液演化的示踪剂：秘鲁世界一流的圣拉斐尔锡（-铜）矿床

世界一流的圣拉斐尔锡（-铜）矿床（秘鲁东南部安第斯锡矿带中部）是一个异常庞大且丰富的锡矿（> 100万吨锡，品位通常> 2％锡），由锡石矿床托管晚渐新世（约24 Ma）高铝质钾长石-大晶花岗岩体及其周围的奥陶纪页岩受到变形和低品位变质的影响。矿化由西北走向，石英-锡石-硫化物脉和断层控制角砾岩体（垂直和水平延伸> 1.4 km）组成。它们显示出在体积上重要的电气石蚀变，该蚀变主要形成于主矿阶段之前，与全球其他与花岗岩相关的锡矿床相似。我们在此介绍电气石的详细结构和地球化学研究，目的是追踪圣拉斐尔岩浆热液系统的流体演化，从而导致锡矿化的沉积。根据以前的工作和新的岩石学观测，区分了岩浆和热液来源的电气石的三个主要世代，并通过电子探针分析仪和激光烧蚀-电感耦合等离子体质量对它们的主要，次要和微量元素组成进行了现场分析。质谱，多集电极-电感耦合等离子体质谱法测定它们的Sr，Nd和Pb同位素组成。早岩浆电气石世代（Tur 1）以结节和扩散的形式出现在高铝质花岗岩中，但未显示出改变的迹象。早期的Tur 1在质地和成分上是均匀的。它有剧烈运动的成分，Fe /（Fe + Mg）= 0.36至0.52，接近于小方晶界，并且Li，K，Mn，轻稀土元素和Zn的含量相对较高（10s至100s ppm）。第二代（Tur 2）（体积上最重要）是前矿石，高温（> 500°C），热液电气石（作为晶状体替代物出现）（Tur 2a）以及在静脉和角砾岩中的开放空间填充物（Tur 2b） ）和微角砾岩（Tur 2c）放置在宿主花岗岩和页岩中。矿石前Tur 2通常显示出振荡带，可能反映了热液系统的快速变化，并且具有很大的成分范围，涵盖了从气田到地下的气田，Fe /（Fe + Mg）= 0.02至0.83。Tur 2的痕量元素含量与Tur 1相似。Tur 2内的成分变化可以用岩浆热液与基质岩石（花岗岩和页岩）的不同程度的相互作用来解释，部分原因是由于置换作用与开放空间填充作用有关。第三代是syn-ore热液电气石（Tur 3）。它形成微观的小脉和过度生长，部分地切割了先前的电气石世代，并与主要矿石组合中的锡石，绿泥石，石英以及次要的黄铁矿和毒砂混合在一起。Syn-ore Tur 3具有单相成分，Fe /（Fe + Mg）= 0.48至0.94，部分不同于后期岩浆Tur 1和预矿石热液Tur2。相对于Tur 1和Tur 2 ，syn-ore Tur 3的Sr和重稀土元素含量较高（10s至100s ppm），而Sn含量异常高（最高> 1,000 ppm）。这三个主要电气石世代的存在，每个世代都有特定的质地和成分特征，反映出富硼的岩浆热液系统，反复发生水力压裂和流体辅助的重开作用，产生脉状和角砾岩。San Rafael电气石中的大多数微量元素与Fe /（Fe + Mg）的比例不相关，这表明它们的掺入很可能受熔体/流体成分和局部流体-岩石相互作用的控制。上述三个电气石世代的初始放射性Sr和Nd同位素组成（0.7160-0.7276 每种都具有特定的质地和成分特征，反映出富硼的岩浆热液系统，其中反复发生水力压裂和流体辅助的重新张开，生成脉状和角砾岩。San Rafael电气石中的大多数微量元素与Fe /（Fe + Mg）的比例不相关，这表明它们的掺入很可能受熔体/流体成分和局部流体-岩石相互作用的控制。上述三个电气石世代的初始放射性Sr和Nd同位素组成（0.7160–0.7276 每种都具有特定的质地和成分特征，反映出富硼的岩浆热液系统，反复发生水力压裂和流体辅助的重开作用，产生脉状和角砾岩。San Rafael电气石中的大多数微量元素与Fe /（Fe + Mg）的比例不相关，这表明它们的掺入很可能受熔体/流体成分和局部流体-岩石相互作用的控制。上述三个电气石世代的初始放射性Sr和Nd同位素组成（0.7160–0.7276 San Rafael电气石中的大多数微量元素与Fe /（Fe + Mg）的比例不相关，这表明它们的掺入很可能受熔体/流体成分和局部流体-岩石相互作用的控制。上述三个电气石世代的初始放射性Sr和Nd同位素组成（0.7160–0.7276 San Rafael电气石中的大多数微量元素与Fe /（Fe + Mg）的比例不相关，这表明它们的掺入很可能受熔体/流体成分和局部流体-岩石相互作用的控制。上述三个电气石世代的初始放射性Sr和Nd同位素组成（0.7160-0.7276¹⁴³ Nd / ¹⁴⁴ Nd _（i）的⁸⁷ Sr / ⁸⁶ Sr _（i）和0.5119-0.5124 _）与圣拉斐尔花岗岩的大部分重叠（⁸⁷ Sr / ⁸⁶ Sr _（i） = 0.7131-0.7202和¹⁴³ Nd / ¹⁴⁴ Nd _{（ i）} = 0.5121–0.5122）并支持热液的主要岩浆成因。这些成分也与玻利维亚锡斑岩的初始Nd同位素值重叠。电气石的初始Pb同位素组成显示出较大的变化，分别为²⁰⁶ Pb / ²⁰⁴ Pb _（i），²⁰⁷ Pb / ²⁰⁴Pb _（i）和²⁰⁸ Pb / ²⁰⁴ Pb _（i）的比率分别大多分别落在18.6至19.3、15.6至16.0和38.6至39.7的范围内。这些组合物部分地重叠圣拉菲尔花岗岩（的初始铅同位素值²⁰⁶的Pb / ²⁰⁴的Pb _（ⅰ） = 18.6-18.8，²⁰⁷的Pb / ²⁰⁴的Pb _（ⅰ） = 15.6-15.7，和²⁰⁸的Pb / ²⁰⁴的Pb _（I）= 38.9–39.0），也与秘鲁东南部其他中新世的中新世Sn-W±Cu-Zn-Pb-Ag矿床相似。从Tur 1到Tur 3，电气石的稀土元素特征是通过减少（Eu / Eu *）_N比率（从20到2）与增加的Sn含量（从10s到> 1,000 ppm）相关。这些变化被解释为反映了水热系统从还原状态向相对更多的氧化状态的演变，仍然处于低硫化环境，如黄铁矿-毒砂组合。Tur 1至Tur 3不断变化的质地和组成特征反映了San Rafael岩浆-热液系统的演化，并支持还原的，富含Sn的岩浆流体与冷却器之间的流体混合模型，这是造成陨石水氧化的主要过程锡石沉淀。