Biogeochemical anomaly response of circumboreal shrubs and juniper to the Juomasuo hydrothermal Au-Co deposit in northern Finland

Abstract Tree tissue chemistry has proven successful in guiding advanced exploration in the early stages of mineral exploration projects in Arctic and subarctic regions. In this paper, the biogeochemical response of three circumboreal shrubs, crowberry (Empetrum nigrum L.), Labrador tea (Ledum palustre) and bilberry (Vaccinium myrtillus L.), and one conifer, common juniper (Juniperus communis L.), to the underlying hydrothermal Juomasuo Au-Co deposit was assessed in southeast Finnish Lapland. A variety of contrasting spatial multi-elemental anomaly patterns were found for the elements Au and Co, along with Fe, Th, U and rare earth elements, such as Ce, La and Nd, in different plant tissue types over the subcropping lodes and also deep (blind) mineralizations down to a depth of 200 m in two seasonally varying campaigns: in late summer (August) 2013 and early summer (June) 2014. Besides these elements verified by lithogeochemistry, Ag, Bi, Mo, Se, Te, W and Ni exhibited anomalous spatial patterns over the mineralization. Based on the Mann-Whitney-Wilcoxon test, the Au concentrations in twigs/stems of crowberry, bilberry, Labrador tea and common juniper over the mineralization were found to be higher than the background, but the evergreen species gave the most consistent response to the mineralization. This also applied to U, W and Mo, as well as Nd and several other rare earth elements. Using unsupervised clustering with self-organizing maps and k-means, the location of the underlying mineralized zones could be determined with high overall accuracy (70–90%). This indicates that the biogeochemical anomaly patterns over the Juomasuo sulphidic lodes are strong, and the deposit would have been detected from the biogeochemical data even without prior knowledge gained from a diamond drilling campaign. The sampled vascular species are widely distributed over the pan-Arctic and circumboreal terrains, thus demonstrating their considerable significance to mineral exploration for hydrothermal Au ores at northern latitudes

Spins and Shapes of Potentially Hazardous Asteroids

Asteroids whose orbits lie close to that of the Earth (called near-Earth objects) are a threat to our planet. Though none of the known asteroids are currently on a collision course with the Earth, there is a class called potentially hazardous asteroids (PHA's) whose orbits may in a few tens of years be perturbed to make a collision possible. In such case, we should have thorough knowledge of the physical properties of these objects because, unlike most other natural disasters, such a hazard is in principle avoidable. Thus in the fall of 2003, a group of asteroid and comet researchers from the Nordic countries have set started an observing program called Nordic NEON (Nordic Near-Earth Object Network). Both photometric and astrometric observations of PHA's have been carried out since April 2004. Photometry is used for determining the spin state and shape of PHA's and astrometry for computing more accurate orbits. In this DPS meeting we will concentrate on the photometric part of the program. We use methods developed in the University of Helsinki for analysing both kinds of data. Spin state and convex shape solution are obtained using the convex inversion method described in [1] and information of the nonconvex shape features are obtained with the spherical harmonics method (Muinonen and Torppa, in preparation). For initial period estimation only a few nights of observations is usually enough, while pole and shape determination requires more abundant data. Previously observed photometric data exists for about 35 PHA's, but only an approximate period is known for most of these. Properties of well over 500 PHA's are totally unknown. So far we have obtained period estimates for 4 new PHA's, and improved spin and shape solution for 3 targets. A number of foundations and universities from all the participating countries have taken part in funding this project

Physical and Dynamical Characterization of Near-Earth Objects by the NEON Program

In order to accrue knowledge on the physical and dynamical properties of near-Earth objects (NEOs), the recently established Nordic Near-Earth-Object Network (NEON) carries out a long-term photometric and astrometric NEO observing program at the 2.56-m Nordic Optical Telescope on La Palma (http://www.astro.helsinki.fi/~psr/NEO/not_obs.html). The spin vector, shape, and surface properties of an individual NEO are estimated from photometric observations at varying observation and illumination geometries. Improved orbits---including potential collision orbits with the Earth---can be derived from sky-plane positions available from the dedicated astrometry or the photometric observations. We have developed novel algorithms for statistical inversion of an object's shape from lightcurves and/or sparsely distributed photometric observations. The algorithms allow the computation of shapes starting from a single observed lightcurve and yield a complete error analysis of the spins and shapes obtained. Note that when only small numbers of observations are available the spectrum of potential spins and shapes is wide. As to the astrometric component of the program, we concentrate on potentially hazardous NEOs in need of a few additional observations to secure their recovery in the subsequent apparition. As one goal of the astrometric component, we aim at obtaining R-band photometry for each observed object. In the long run, this will provide us information of the true NEO absolute magnitude and size distributions greatly improving the impact risk estimation. As of 2004 Sept. 1, NEON has made photometric observations of seven NEOs: (1917) Cuyo, (2061) Anza, 2001 US16, (68950) 2002 GF15, 2003 RX7, 2004 LJ1, and 2004 HW. Making use of the new observations, we show up-to-date models for the spins and shapes of these objects. NEON has made astrometric observations of more than 30 NEOs in urgent need of additional positions---these observations have culminated in the recovery of 1998 VN (MPEC 2004-M30)