Re os dating arsenopyrite
The former finds the minimum age of the extraction event assuming the elemental Re/Os ratio equals 0 (komatiite residues have Re/Os of 0, so this is assuming a xenolith was extracted from a near-komatiite melt).The latter gives the age of the melting event inferred from the point when a melt proxy like Al Os of modern plume related magmas show simultaneous enrichment which implies a source that is supra-chondritic in Pt/Os and Re/Os.While the 2.707 /- 0.008 Ga highly radiogenic arsenopyrite provides firm support for an early mineralisation event, a mixing origin cannot yet be excluded for the 2.71 /- 0.05 Ga isochron.
Re tends to enter the melt phase (incompatible) while Os remains in the solid residue (compatible).Re-Os data are best explained by relatively short crustal residence times of less than 0.1 Ga, wherein the Os, and associated metals, were extracted from the mantle at a time younger than 2.8 Ga, and in which the 2.64 /- 0.02 Ga stage formed by mobilisation of an earlier mineralisation.Name: Arsenopyrite RRUFF ID: R070585 Ideal Chemistry: Fe As S Locality: Standard Consolidated mine, Sumpter District, Baker County, Oregon, USA Source: James Shigley [view label] Owner: RRUFF Description: Tin-yellow, metallic striated crystal associated with calcite Status: The identification of this mineral is confirmed by single-crystal X-ray diffraction and chemical analysis. A 2.71 /- 0.05 Ga arsenopyrite isochron and 2.707 /- 0.008 Ga highly radiogenic arsenopyrite from a mineralisation along a rock contact, together with a 2.64 /- 0.02 Ga arsenopyrite isochron along the axial plane of the fold core indicate a two-stage mineralisation process. (More)The Storo greenstone belt in Godthabsfjord, southern West Greenland consists of juxtaposed rock units of different age and origin, and hosts gold mineralisation that is associated with arsenopyrite along a contact between lithological units and along the axial plane of a large fold core.A 2.71 /- 0.05 Ga arsenopyrite isochron and 2.707 /- 0.008 Ga highly radiogenic arsenopyrite from a mineralisation along a rock contact, together with a 2.64 /- 0.02 Ga arsenopyrite isochron along the axial plane of the fold core indicate a two-stage mineralisation process.