Laser ablation ICP-MS imaging of gold and other trace elements in pyrite from four different sedimenthosted\ud gold-arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit: an early\ud synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace\ud elements, in particular, As, Ni, Pb, Zn, Ag, Mo, Te, V, and Se; and a later hydrothermal stage where gold forms\ud as either free gold grains in cracks in overgrowth metamorphic and/or hydrothermal pyrite or as narrow goldarsenic\ud rims on the outermost parts of the overgrowth hydrothermal pyrite. Compared to the diagenetic\ud pyrites, the hydrothermal pyrites are commonly depleted in Ni, V, Zn, Pb, and Ag with cyclic zones of Co, Ni,\ud and As concentration. The outermost hydrothermal pyrite rims are either As-Au rich, as in moderate- to highgrade\ud deposits such as Carlin and Bendigo, or Co-Ni rich and As-Au poor as in moderate- to low-grade deposits\ud such as Sukhoi Log and Spanish Mountain. The early enrichment of gold in arsenic-bearing syngenetic to diagenetic\ud pyrite, within black shale facies of sedimentary basins, is proposed as a critical requirement for the later\ud development of Carlin-style and orogenic gold deposits in sedimentary environments. The best grade sediment-\ud hosted deposits appear to have the gold climax event, toward the final stages of deformation-related\ud hydrothermal pyrite growth and fluid flow

Pyrite, the most abundant sulfide on Earth and a common component of gold deposits, can be a significant host for refractory gold. This is the first documentation of pore-attached, composite Au-telluride nanoparticles in “arsenic-free” pyrite. Trace elements mapping in pyrite from an intrusion-hosted Au deposit with orogenic overprint (Dongping, China) shows trails of tellurides overlapping Co-Ni-zonation. Intragranular microfracturing, anomalous anisotropy, and high porosity are all features consistent with devolatilization attributable to the orogenic event. The pyrite-hosted nanoparticles are likely the “frozen,” solid expression of Te-rich, Au-Ag-Pb-bearing vapors discharged at this stage. Nanoparticle formation, as presented here, provides the “smallest-scale” tool to fingerprint Au-trapping during crustal metamorphism

The effects of laser type (Nd:YAG and excimer lasers) and their analytical parameters on ³⁴S/³²S isotopic fractionation during LA-ICP-MS analysis were investigated. Laser fluence has a larger fractionation effect when ablating pyrite with the New Wave Nd:YAG 193 nm laser, compared to the Resonetics 193 nm excimer laser which did not produce significant fractionation over the same range of fluence (1.3–3.7 J cm⁻²). Matrix effects occurred between pyrite and bornite on both laser systems, especially at low fluence. However, matrix effects can be reduced with increasing fluence lessening the need for matrix matched reference materials. The effects of interface tubing configuration were also investigated and the addition of a ‘squid’ mixing device, a coil of small diameter Tygon tubing and a small volume glass bulb, was found to improve signal precision and reproducibility and decrease the washout time of the S signal between analyses. The degassing of air from the inner surfaces of the interface tubing can produce significant isotopic drift (8‰ h⁻¹), hence flushing the tubing prior to analyses is crucial for reproducible analyses. The isotopic composition and homogeneity of a range of sulphide minerals were characterised for use as potential reference materials. We present preliminary data for a large, isotopically homogeneous pyrite crystal (PPP-1) which could be considered as a new isotopic reference material (δ³⁴S_V-CDT = 5.3 ± 0.2‰).