Integrated analysis of environmental and genetic influences on cord blood DNA methylation in new-borns

Epigenetic processes, including DNA methylation (DNAm), are among the mechanisms allowing integration of genetic and environmental factors to shape cellular function. While many studies have investigated either environmental or genetic contributions to DNAm, few have assessed their integrated effects. Here we examine the relative contributions of prenatal environmental factors and genotype on DNA methylation in neonatal blood at variably methylated regions (VMRs) in 4 independent cohorts (overall n = 2365). We use Akaike’s information criterion to test which factors best explain variability of methylation in the cohort-specific VMRs: several prenatal environmental factors (E), genotypes in cis (G), or their additive (G + E) or interaction (GxE) effects. Genetic and environmental factors in combination best explain DNAm at the majority of VMRs. The CpGs best explained by either G, G + E or GxE are functionally distinct. The enrichment of genetic variants from GxE models in GWAS for complex disorders supports their importance for disease risk

District-scale targeting for gold in the Yilgarn Craton: part 2 of the Yilgarn Gold Exploration Targeting Atlas

Part 2 of the Yilgarn Gold Exploration Targeting Atlas evaluates 22 targeting criteria that are considered useful for targeting prospects for more-detailed exploration within a project area. As in Part 1, the emphasis is on a conceptual approach, targeting mineralization that is either not exposed at the surface or is exposed as a 'distal footprint' that might provide a vector to buried 'proximal' mineralization. Gold in the Yilgarn Craton is found in a diverse range of host rocks, so host-rock lithology is not an efficient targeting criterion. Virtually all gold mineralization is controlled by proximity to lithological contacts, particularly contacts between units of strongly contrasting rheological properties. Targeting 'rheological contacts' within a specific range of orientations increases discovery efficiency, but the optimum contact orientations vary from district to district and may differ for small deposits versus large deposits. Analyses presented here for the Wiluna, Laverton, and Kalgoorlie – Ora Banda districts of the Eastern Goldfields Superterrane show a strong association between gold mineralization and Mafic Group intrusions. Proximity to district-scale faults is an effective targeting criterion, but is generally not as efficient as targeting rheological contacts. Fault intersection density, and proximity to fault jogs and faults bends, provide effective district-scale targeting tools. Although fault density is generally an effective targeting criterion, 50% or more of the gold endowment in some districts is within domains identified by the software as having zero fault density. These deposits are in fact controlled by faults or fractures that are too small to appear at the scale of the shape files used in the analyses. There is little advantage in targeting right-stepping over left-stepping jogs, or clockwise over anticlockwise fault bends. Fold axes are a powerful targeting criterion. Targeting anticlinal fold axes is two to three times more effective than targeting undivided fold axes. In high-temperature metamorphic settings such as the Southern Cross district, boudinage at all scales represents an important (perhaps the most important) targeting element for gold. Subjected to regional deformation, folds and boudins create stress heterogeneity, and computer-based techniques for predicting variations in minimum stress (paleostress modelling and stress transfer modelling) are other useful approaches for district-scale gold exploration in all metamorphic settings. District-scale maps of maximum downhole gold concentrations highlight the flow paths of gold-bearing ore fluids and provide a striking validation of published models relating fluid flow to heterogeneous stress distribution. Arsenic distribution is partially decoupled from gold, and anomalous arsenic may be partly controlled by proximity to thick sequences of metasedimentary (including felsic volcaniclastic) rocks. In regional shear zones, arsenic footprints are more extensive along strike than gold anomalies. Pathfinder element suites can be used to determine the extent of oxidized/alkaline (W+Mo+Bi) and reduced/acid (As+Sb) hydrothermal activity. The oxidized suite has potential for location of buried or poorly exposed intrusions. Oxidized and reduced hydrothermal cells can also be distinguished on the basis of white-mica species by using multispectral and hyperspectral mineral data or chemical parameters that identify albite-rich versus muscovite-rich hydrothermal alteration. However, the more useful spectral parameters for targeting gold mineralization are white-mica intensity and Fe-chlorite abundance. A chalcophile index (e.g. W+Mo+Bi+As+Sb) or the rare alkali index ([Rb+Cs]/Th)N are as effective or more so than using juxtaposed or overlapping oxidized and reduced pathfinder element suites. Geological complexity (expressed as fractal dimension) was not shown to be effective for targeting gold mineralization at district scale

Regional-scale targeting for gold in the Yilgarn Craton: part 1 of the Yilgarn Gold Exploration Targeting Atlas

The Yilgarn Craton of Western Australia is well known for its gold endowment (more than 324 Moz, or 9730 t), including the giant Golden Mile deposit at Kalgoorlie (67.3 Moz, or more than 2000 t). Despite considerable success in the identification of near-surface gold during the periods 1890–1910 and 1985–2005, the discovery rate for gold in the Yilgarn has since slowed, a situation that is commonly attributed to exhaustion of economic near-surface resources. This view has led to a greater focus on exploration for ‘blind’ orebodies with tonnages and grades in excess of modern nearsurface resources. Exploration for blind orebodies relies on identification of a geophysical expression of subsurface ore, a geochemical expression of the ore in overlying transported sediments or sedimentary rock, or a conceptual approach that predicts the presence of ore on the basis of the geological controls of known near-surface mineralization. Although each approach has both advantages and limitations, this Atlas focuses on the conceptual approach. Eighteen targeting criteria for gold exploration at regional scale are addressed in the Atlas, with individual criteria ranging from well-established geological controls such as intersecting faults to more recent suggestions (e.g. proximity to late-stage basins). Each criterion (and sub-criteria, in some cases) is examined in relation to gold distribution, at scales ranging from craton to domain, using a GIS platform. The results of the spatial analyses are summarized in the form of maps, and histograms (containment analyses) or curves (proximity analyses) showing ounces per square kilometre and deposits per square kilometre. Full results of the spatial analyses are presented in the Appendix. \ud \ud The results of this study suggest that the four most effective targeting criteria for gold in the Yilgarn Craton are proximity to intrusions of Mafic Group granites, elevated fault density, proximity to regional fault bends, and the well-known preference for gold to be found in greenstone belts rather than in intervening areas of granite. A fuzzy logic approach has been used to combine and weight the results of spatial analyses for these four criteria to produce spatial arrays of prospectivity values that have then been used to produce regional prospectivity maps for gold in the Yilgarn Craton and in the Eastern Goldfields Superterrane. Correlation coefficients relating gold endowment to prospectivity values range from 0.38 to 0.78, depending on the parameter used to measure endowment. The results for the Yilgarn Craton as a whole are better than those for the Eastern Goldfields Superterrane, and results expressed in terms of deposit density are better than those expressed as ounces per square kilometre. Although spatial analyses for domes (containment) and late-stage basins (proximity) suggest a relationship to gold mineralization, prospectivity maps produced after their addition to the previous fuzzy logic analysis compromised the correlation between gold endowment and prospectivity value. \ud \ud This report forms the first part of a three-part Atlas. Parts two and three deal with district-scale and deposit-scale targeting, respectively