Sulfide saturation in alkaline to peralkaline igneous rocks.

硅酸盐熔体中硫的行为是一个被广泛讨论的话题：火山喷发时硫的释放影响全球气候，岩浆中硫的含量对岩浆到热液矿床的成因起着重要的控制作用。基性、中质和花岗质体系中的原生硫化物（主要是磁黄铁矿、黄铜矿和辉钼矿）和其他含硫矿物（主要是磷灰石和钠石群矿物）是近年来许多研究的重点，但在碱性至过碱性岩浆体系中尚未进行详细和系统的研究。本研究研究并比较了两个具有良好特征的碱性和过碱性深成杂岩（摩洛哥的Tamazeght和格陵兰的Ilimaussaq）及其空间相关和成因相关的脉岩的原生硫化物清单。所研究的岩石成分多样性很大，主要包括辉长岩（碱玄武岩）、二长岩（乳化质）和正长岩（粗质）以及榴石正长岩（phonolitic）。因此，本研究结果将对碱性-过碱性岩浆系统中硫的行为具有普遍意义。分析各种硫化物的主、次、微量元素组成及硫同位素组成，以跟踪其在岩浆分异过程中的组成演化。这些数据将与其他含硫矿物（磷灰石和钠石矿）中硫浓度的测定以及共存的Fe-Mg硅酸盐和Fe-Ti氧化物的成分数据结合起来，因为这对它们形成过程中主要的氧和硫逸度提供了重要的限制。硫化物的硫同位素组成将对岩浆的硫同位素组成和不同硫化物组合的结晶温度提供约束。这两个复合体内部和之间的变化有望揭示岩浆房过程的详细信息（例如，硫化物-硅酸盐熔体分离、分馏结晶、岩浆补给、岩浆分层的形成），并将破译硫化物形成对碱性到过碱性岩浆地球化学演化的影响，并可能对这类系统的矿潜力产生影响。通过对深成岩和脉岩的比较，可以详细了解与不同冷却速率和热液叠印强度有关的硫化物主要化学成分和同位素组成的保留和蚀变的潜在差异。

The behavior of sulfur in silicate melts is a widely discussed topic: Its release during volcanic eruptions affects the global climate, and the sulfur content of magmas exerts a major control on the genesis of magmatic to hydrothermal ore deposits. Primary sulfides (mainly pyrrhotite, chalcopyrite and molybdenite) and other sulfur-bearing minerals (mainly apatite and sodalite group minerals) in mafic, intermediate and granitic systems have been the focus of many recent studies, but no detailed and systematic study on this topic in alkaline to peralkaline magmatic systems has been undertaken so far.The present proposal investigates and compares the primary sulfide inventory of two otherwise well-characterized alkaline to peralkaline plutonic complexes (Tamazeght in Morocco and Ilimaussaq in Greenland) and their spatially associated and genetically related dyke rocks. The rocks to be investigated cover a large compositional diversity ranging mainly from gabbroic (alkali basaltic) via monzonitic (latitic) and syenitic (trachytic) to nepheline syenitic (phonolitic) compositions. Therefore, the results of this study will have general implications for the behavior of sulfur in alkaline to peralkaline magmatic systems. The various sulfides will be analyzed for their major, minor and trace element composition and their sulfur isotopic composition in order to track their compositional evolution during magmatic differentiation. These data will be combined with determination of sulfur concentrations in other sulfur-bearing minerals (apatite and sodalite) and with compositional data on co-existing Fe-Mg silicates and Fe-Ti oxides, since this provides important constraints on prevailing oxygen and sulfur fugacity during their formation. The sulfur isotope composition of the sulfides will provide constraints on the sulfur isotope composition of the magmas and the temperature of crystallization of the different sulfide assemblages.The variability within and between the two complexes is expected to reveal detailed insights into magma chamber processes (e.g., sulfide-silicate melt separation, fractional crystallization, magma recharge, formation of magmatic layering) and will decipher the influence of sulfide formation on the geochemical evolution of alkaline to peralkaline magmas with possible implications for the ore potential of such systems. The comparison between plutonic rocks and dyke rocks will provide detailed insight into potential differences with respect to the retention and alteration of the primary chemical and isotopic compositions of sulfides related to different cooling rates and the intensity of hydrothermal overprint.