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The first run of the ultracryogenic resonant bar detector AURIGA is in progress. Diagnostics on the cryogenics, the data acquisition system and on the noise characteristics have been performed, with results in accord with the design. The bar reached 140 mK. In tests down to 2 K the detector noise was very close to `Brownian'.

Stromatolites of the ∼3.5 billion-year-old Dresser Formation (Pilbara Craton, Western Australia) are considered to be some of Earth’s earliest convincing evidence of life. However, uniquely biogenic interpretations based on surface outcrops are precluded by weathering, which has altered primary mineralogy and inhibited the preservation of microbial remains. Here, we report on exceptionally preserved, strongly sulfidized stromatolites obtained by diamond drilling from below the weathering profile. These stromatolites lie within undeformed hydrothermal-sedimentary strata and show textural features that are indicative of biogenic origins, including upward-broadening and/or upward-branching digitate forms, wavy to wrinkly laminae, and finely laminated columns that show a thickening of laminae over flexure crests. High-resolution textural, mineralogical, and chemical analysis reveals that the stromatolites are dominated by petrographically earliest, nano-porous pyrite that contains thermally mature, N-bearing organic matter (OM). This nano-porous pyrite is consistent with a formation via sulfidization of an originally OM-dominated matrix. Evidence for its relationship with microbial communities are entombed OM strands and filaments, whose microtexture and chemistry are consistent with an origin as mineralized biofilm remains, and carbon isotope data of extracted OM (δ13COM = −29.6‰ ± 0.3‰ VPDB [Vienna Peedee belemnite]), which lie within the range of biological matter. Collectively, our findings provide exceptional evidence for the biogenicity of some of Earth’s oldest stromatolites through preservation of OM, including microbial remains, by sulfidization.

With growing interest in the application of in situ multiple sulfur isotope analysis to a variety of mineral systems, we report here the development of a suite of sulfur isotope standards for distribution relevant to magmatic, magmatic-hydrothermal, and hydrothermal ore systems. These materials include Sierra pyrite (FeS2), Nifty-b chalcopyrite (CuFeS2), Alexo pyrrhotite (Fe(1-x)S), and VMSO pentlandite ((Fe,Ni)9S8) that have been chemically characterized by electron microprobe analysis, isotopically characterized for δ 33 S, δ 34 S, and δ 36 S by fluorination gas-source mass spectrometry, and tested for homogeneity at the micro-scale by secondary ion mass spectrometry. Beam-sample interaction as a function of crystallographic orientation is determined to have no effect on δ 34 S and Δ 33 S isotopic measurements of pentlandite. These new findings provided the basis for a case study on the genesis of the Long-Victor nickel-sulfide deposit located in the world class Kambalda nickel camp in the southern Kalgoorlie Terrane of Western Australia. Results demonstrate that precise multiple sulfur isotope analyses from magmatic pentlandite, pyrrhotite and chalcopyrite can better constrain genetic models related to ore-forming processes. Data indicate that pentlandite, pyrrhotite and chalcopyrite are in isotopic equilibrium and display similar Δ 33 S values +0.2‰. This isotopic equilibrium unequivocally fingerprints the isotopic signature of the 2 magmatic assemblage. The three sulfide phases show slightly variable δ 34 S values (δ 34 Schalcopyrite = 2.9 ± 0.3‰, δ 34 Spentlandite = 3.1 ± 0.2‰, and δ 34 Spyrrhotite = 3.9 ± 0.5‰), which are indicative of natural fractionation. Careful in situ multiple sulfur isotope analysis of multiple sulfide phases is able to capture the subtle isotopic variability of the magmatic sulfide assemblage, which may help resolve the nature of the ore-forming process. Hence, this SIMS-based approach discriminates the magmatic sulfur isotope signature from that recorded in metamorphic-and alteration-related sulfides, which is not resolved during bulk rock fluorination analysis. The results indicate that, unlike the giant dunite-hosted komatiite systems that thermo-mechanically assimilated volcanogenic massive sulfides proximal to vents and display negative Δ 33 S values, the Kambalda ores formed in relatively distal environments assimilating abyssal sulfidic shales. HIGHLIGHTS  Characterisation of four sulfide standards for multiple sulfur isotope analysis: pyrite, chalcopyrite, pyrrhotite, and pentlandite for distribution  Analysis of orientation effect in pentlandite  Natural sulfur isotope fractionation between pentlandite and pyrrhotite  Case study multiple sulfur isotope analysis of three sulfide phases within world-class Long-Victor komatiite-hosted nickel-sulfide deposit KEYWORDS Multiple sulfur isotopes, SIMS, in situ, sulfide minerals, ore genesis 1.