Constraints on diamond formation and craton evolution from S isotopes and trace element contents in diamond sulfides

钻石是一种罕见的地幔附属矿物，可在克拉通榴辉岩等深部地幔岩性中取样。这些表明了影响岩石圈演化的主要过程，即它们是通过海洋地壳俯冲而形成的，还是由地幔内的基性熔体结晶而成的。钻石定年研究表明，许多榴辉岩钻石套件是古老的（元古代或太古代）。这一点，再加上钻石的化学惰性，使其矿物含量不受形成后地幔交代事件的影响，使得对钻石内含物的研究特别令人兴奋。由于硫化物矿物是钻石中常见的包裹体类型，除了硫外，还含有大量的亲铜和亲铁元素，因此它们适合于原位分析技术。从从奴克拉通中部岩石圈深部取样的钻石中分离出的榴辉岩硫化物包裹体，先前已被确定为约1.9 Ga，这一时期与奴克拉通边缘的俯冲相对应，但也接近于导致地幔中基性成分结晶的主要岩脉形成时期。我建议用离子探针测定硫化物包裹体上的多种S同位素，以限制地壳与深部地层的起源（S同位素可以在包括大洋板块在内的浅层岩石圈中分选，但不能在深部地幔中分选）。在流体释放和部分熔融过程中，通过激光烧蚀ICPMS对微量元素丰度进行了进一步的研究，有望深入了解硫化物的起源、钻石形成的条件以及相关岩石圈地幔的演化。

Diamonds are rare accessory mantle minerals sampling deep mantle lithologies including cratonic eclogites. These are indicative of major processes affecting lithosphere evolution, i.e. whether they were emplaced via subduction of oceanic crust or crystallized from mafic melts within the mantle. Diamond dating studies have revealed many eclogitic diamond suites to be ancient (Proterozoic or Archaean). This, combined with the chemically inert nature of diamond, which prevents its mineral content from being modified by post-formation mantle metasomatic events, makes the study of inclusions in diamonds particularly exciting. Since sulfide minerals are a frequent inclusion type in diamonds that contain high abundances of chalcophile and siderophile elements in addition to sulfur, they lend themselves to in situ analytical techniques. Eclogitic sulfide inclusions, isolated from diamonds sampling the deep lithosphere in the central Slave Craton, have previously been dated to ca 1.9 Ga, a time corresponding to subduction at the Slave craton margin, but also close to a major dike formation episode leading to the crystallization of mafic components in the mantle. I propose to determine multiple S isotopes on sulfide inclusions by ion microprobe to constrain a crustal vs deep formation origin (S isotopes can be fractionated in the shallow lithosphere including the oceanic slab but not in the deep mantle). Additional investigation of the trace-element abundances, which are fractionated during fluid release and partial melting, by laser ablation ICPMS, promises insights on the origin of the sulfides, conditions of diamond formation and evolution of the associated lithospheric mantle.