Against the background of an ongoing debate on the genetic relationship between orogenic gold and granitic magmatism, we studied the evolution of a gold-mineralizing system in shear zone-hosted veins that are spatially associated with a syn- to late tectonic 2.69 Ga granite at the Satinoco deposit in the Archean Pitangui greenstone belt (Iron Quadrangle, Brazil). Detailed underground mine mapping, petrography, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and elemental mapping of sulfide grains revealed a complex polyphase history, with at least three gold-bearing stages: (1) A syntectonic arsenopyrite (Apy₁)-löllingite-pyrrhotite assemblage I that formed during prograde metamorphism from ca. 475° to 650°C at 3 to 4 kbars; (2) further fluid circulation during syn- to late tectonic retrograde metamorphism from ca. 510° to 445°C, which led to a pyrrhotite-arsenopyrite (Apy₂) ± löllingite ± galena assemblage II; and (3) a pyrite-pyrrhotite-galena ± chalcopyrite ± sphalerite ± ullmannite assemblage III formed during a later post-tectonic brittle deformation event from ca. 350° to 300°C at 1 to 2 kbars. Ascending granitic magma acted as a heat engine for peak metamorphic temperatures locally, that is at the immediate contact, reaching as much as 730°C and, together with the dehydration of mafic and ultramafic host rocks, generated the sulfide assemblage I. Crosscutting field relationships, together with existing S isotope data, indicate a metamorphic origin for all the sulfide stages with a contribution from granite-derived magmatogenic fluids to the mineralizing system at stage II. New X-ray element maps together with LA-ICP-MS spot analyses document oscillatory zoning of As, Fe, and Ni in Apy₁ and enrichment in Ni, Mn, Zn, and V. The large amount of pyrrhotite in assemblage II is explained by granite-related Fe metasomatism. This stage led to an enrichment in Co, Sb, and Pb and the redistribution of Au. Assemblage III involved the formation of pyrite veins and precipitation of free gold and Pb-Sb-Cu-Zn sulfides in microfractures of this pyrite. This stage was likely responsible for the remobilization of Ni, Cu, Zn, and Bi-Te minerals. Based on existing geochronological data, at least most of the gold formed between ~2.72 and 2.68 Ga. This study revealed that gold mineralization took place over a wide range of temperatures—a finding that might be not only specific to the Satinoco deposit but possibly to other orogenic-type gold deposits elsewhere as well.

中文翻译：

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与同步花岗岩浆作用有关的造山金系统中的温控矿石演化：以巴西铁四方省为例

在关于造山金与花岗岩岩浆作用的遗传关系的争论不断进行的背景下，我们研究了剪切带状脉中金矿化系统的演化，该脉空间与中晚期构造的2.69 Ga花岗岩在空间上相关萨蒂诺科（Satinoco）矿床，位于太古代的皮坦圭绿岩带（巴西铁四方矿）。详细的地下矿山制图，岩石学，激光烧蚀-电感耦合等离子体质谱（LA-ICP-MS）和硫化物晶粒的元素制图揭示了复杂的多相历史，至少有三个含金阶段：（1）同构造毒砂（Apy ₁）-钙镁铁矿-硅镁土组合物I，是在大约从Ca.进行的变质过程中形成的。3至4 kbar时为475°至650°C; （2）大约在大约从构造到晚期的构造逆行变质过程中，流体进一步循环。510°至445°C，导致产生黄铁矿-毒砂（Apy ₂）±闪锌矿±方铅矿组合II; （3）在一个较晚的构造后后期的脆性变形事件中，由铁素体-硫铁矿-方铅矿±黄铜矿±闪锌矿±钙锰矿组合III形成。在1至2 kbar的压力下为350°至300°C。上升的岩浆作用为局部变质峰温度的热力引擎，即最高接触温度，即刻接触，温度高达730°C，再加上镁铁质和超镁铁质基质岩石的脱水，生成了硫化物组合物I。横切场关系与现有的S同位素数据一起，表明了所有硫化物阶段的变质成因，其中花岗岩衍生的成岩流体对阶段II的成矿系统有贡献。新的X射线元素图与LA-ICP-MS点分析一起记录了Apy中As，Fe和Ni的振荡分区₁和富集镍，锰，锌和钒。组合II中大量的黄铁矿是由与花岗岩有关的Fe交代作用解释的。这一阶段导致了Co，Sb和Pb的富集以及Au的重新分布。组合III涉及黄铁矿脉的形成以及该黄铁矿微裂缝中游离金和Pb-Sb-Cu-Zn硫化物的沉淀。这个阶段可能是Ni，Cu，Zn和Bi-Te矿物的迁移的原因。根据现有的地质年代数据，至少大部分金形成在〜2.72至2.68 Ga之间。这项研究表明，金的矿化发生在很宽的温度范围内-这一发现可能不仅针对Satinoco矿床，而且可能对Satinoco矿床具有特殊性。其他造山型金矿床也在其他地方。