Insights into fluid evolution and Re enrichment by mineral micro-analysis and fluid inclusion constraints: Evidence from the Maronia Cu-Mo ± Re ± Au porphyry system in NE Greece
Jan J. Falkenberg, Manuel Keith, Vasilios Melfos, Max Hohl, Karsten M. Haase, Panagiotis Voudouris, Alica Höss, Julia Wenske, Reiner Klemd, Christoph Beier, Martin Kutzschbach, Harald Strauss
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引用次数: 0
Abstract
Porphyry-epithermal veins hosting Re-rich molybdenite and rheniite (ReS2) from the Maronia Cu-Mo ± Re ± Au porphyry in Thrace, NE Greece, provide new insights into the hydrothermal processes causing extreme Re enrichment. Quartz trace element chemistry (Al/Ti, Ge/Ti), Ti-in-quartz thermometry, and cathodoluminescence imaging reveal multiple quartz generations in consecutive hydrothermal quartz-sulfide veins associated with potassic, sericitic, and argillic alteration. Fluid inclusions in different quartz generations indicate that phase separation and fluid cooling are the main ore-forming processes in the porphyry stage (~ 500 – 350 °C), whereas mixing of a vapor-rich fluid with metalliferous (e.g., Pb, Zn, Au) meteoric water forms the epithermal veins (~ 280 °C). These processes are recorded by trace element ratios in pyrite that are sensitive to changes in fluid temperature (Se/Te), fluid salinity (As/Sb, Co/As), and mixing between fluids of magmatic and meteoric origin (Se/Ge). Highly variable intra-grain δ34S values in pyrite record S isotope fractionation during SO2 disproportionation and phase separation, emphasizing the importance of in situ δ34S analysis to unravel ore-forming processes. High δ34S (~ 4.5‰) values of sulfides are indicative of low SO42−/H2S fluid ratios buffered by the local host rocks and mixing of the magma-derived fluid with meteoric water. The formation of Re-rich molybdenite (~ 6600 ppm) is favored by cooling and reduction of a magma-derived, high-temperature (~400 °C), oxidized, and Re-rich fluid triggering efficient Re precipitation in early veins in the potassic alteration zone. The systematic temporal fluid evolution therefore reveals that coeval cooling and reduction of oxidized Re-rich fluids cause extreme Re enrichment at the Maronia porphyry system.
希腊东北部色雷斯的 Maronia Cu-Mo ± Re ± Au 斑岩中富含辉钼矿和铼矿 (ReS2) 的斑岩热液矿脉,为了解造成极端 Re 富集的热液过程提供了新的视角。石英痕量元素化学成分(Al/Ti、Ge/Ti)、石英钛热测定法和阴极发光成像揭示了连续热液石英硫化物矿脉中的多代石英,这些矿脉与钾盐化、绢云母化和镁质化有关。不同石英代中的流体包裹体表明,相分离和流体冷却是斑岩阶段(约 500 - 350 °C)的主要成矿过程,而富含蒸汽的流体与含金属(如铅、锌、金)的流星水混合则形成了热液矿脉(约 280 °C)。黄铁矿中的微量元素比率记录了这些过程,这些比率对流体温度(Se/Te)、流体盐度(As/Sb、Co/As)以及岩浆流体和陨石流体之间的混合(Se/Ge)的变化非常敏感。黄铁矿中晶粒内δ34S值的高度变化记录了二氧化硫歧化和相分离过程中的S同位素分馏,强调了原位δ34S分析对揭示成矿过程的重要性。硫化物的高δ34S(~ 4.5‰)值表明,SO42-/H2S流体比率低,受到当地寄主岩的缓冲,以及岩浆衍生流体与陨石水的混合。富 Re 辉钼矿(约 6600 ppm)的形成是由于岩浆衍生的高温(约 400 °C)、氧化和富 Re 流体在钾盐蚀变带早期矿脉中的冷却和还原引发了有效的 Re 沉淀。因此,系统的时间流体演化显示,氧化富Re流体的共时冷却和还原导致了Maronia斑岩系统的极度Re富集。
期刊介绍:
The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.