yann Lahaye

This article presents the results of the first-ever lead isotope (LI) analysis of copper-based archaeological artefacts found in the region of Finland. Eight metal objects recovered from the Iron Age water burial site of Levänluhta in western Finland were analysed via multi collector inductively coupled plasma mass spectrometry (MC-ICP-MS) and portable X-ray fluorescence spectrometry (pXRF) in order to attain geochemical and LI data. The majority of the objects are Merovingian period (ca. 550-800 CE) jewellery, displaying domestic Iron Age artefact styles, and were probably cast by local workshops in Finland. Until recently, the copper exploited in Bronze and Iron Age metallurgy in Finland had been linked to Scandinavian ores. However, this provenance scenario seems implausible in the light of recent LI studies demonstrating that Scandinavian Bronze Age artisans in fact relied on long-distance metal transport. Comparisons between the LI data of the analysed objects and published ore databases exclude the possibility of a domestic or Scandinavian copper source for the metals. Instead, it appears likely that the copper originated from southern European ores. The low arsenic and antimony levels in the copper alloys provide indication of long recycling patterns of the metals used in the Iron Age workshops in Finland. It is possible that the Iron Age artefacts contain recycled copper-alloys already acquired in the Bronze Age. The metals were transported for long distances, and it appears that the pan-European metal circulation network also crossed the Baltic Sea to reach coastal Finland.

New mineralogical and geochemical methods for till sampling-based exploration were developed at the Geological Survey of Finland (GTK) during the TEKESfunded project “Novel technologies for greenfield exploration (NovTecEx)”. The techniques are based on recently installed analytical instruments at the Finnish Geosciences Research Laboratory (SGL), a high-resolution single collector inductively coupled mass spectrometer for trace element analysis (HR-SC-ICPMS) and field emission SEM for automated electron optics (FE-SEM-EDS). The sample material comprised till samples collected in the Savukoski-Pelkossenniemi study area in eastern Lapland during another NovTecEx subproject in which different drilling techniques were tested for sampling. The heavy mineral concentrates of the till samples were produced by optimizing conventional processing methods to meet the requirements of modern research instruments. The fully digested concentrates were analysed by HR-SC-ICPMS to detect interesting ...

We have determined Pd, Ni, and Fe solubilities in silicate melts of anorthite-diopside eutectic composition with variable TiO 2 concentrations, from TiO 2 -free melts to melts with up to 26 wt% TiO 2 . The experiments were conducted with metal loops at 1300 °C, one atm total ...

Whole-rock and isotope geochemistry of six ∼1.8 Ga post-kinematic intrusions, emplaced along the ∼1.9 Ga Southern Svecofennian Arc Complex (SSAC) and in the SW part of the Karelian Domain in Finland, was studied. The intrusive age [U–Pb secondary ion mass spectrometer (SIMS)] of one of these, the Petravaara Pluton, was determined as 1811 ± 6 Ma.
Basic-intermediate rocks are alkali-rich (K2O + Na2O > 4 wt.%) and typically shoshonitic, strongly enriched in large ion lithophile elements and light rare earth elements, but relatively depleted in high field strength elements and heavy rare earth lements.
The enrichment is much higher than can be accounted for by crustal contamination and
requires previously melt-depleted mantle sources, subjected to variable metasomatism
by carbonate-rich fluids and sediment-derived melts. These sources are inferred to consist
of phlogopite ± amphibole-bearing peridotites from depths below the spinel–garnet
transition, as shown by the high Ce/Yb ratios. 87Sr/86Sr(1.8 Ga) ratios in the range
0.7027–0.7031 and ‘mildly depleted’ eNd(1.8 Ga) values (+0.1 to +1.4), with TDM values
<2.1 Ga, suggest that mantle enrichment was associated with the previous Svecofennian
subduction–accretion process, when enriched sub-Svecofennian mantle sections
developed, dominantly characterized by 147Sm/144Nd ratios of 0.14–0.17.
The associated granitoids are diversified. One group is marginally peraluminous,
transitional between I (volcanic-arc) and S (syn-collisional) types, and was derived
from mixed igneous and sedimentary, but juvenile Svecofennian source rocks, as supported
by near-chondritic eNd(1.8 Ga) and somewhat elevated 87Sr/86Sr(1.8 Ga). The
other group is transitional between I and A (within-plate) types in character and had
dominantly igneous protoliths. The whole-rock geochemistry and isotopes suggest that
the compositional variation between ∼50 and 70 wt.% SiO2 may be explained by
hybridization between strongly enriched mantle-derived magmas and anatectic granitic
magmas from the juvenile Svecofennian crust. One intrusion in the east contains a significant
portion of Archaean, mostly igneous protolithic material (eNd(1.8 Ga) = –2.8
and eHf(t) for zircons between +2.8 and −11.9, with an average of −4.9).
The ∼1.8 Ga post-kinematic intrusions were emplaced within the SSAC subsequent
to the continental collision with the Volgo-Sarmatia craton from the SE, during a shift
from contraction to extension, that is, in a post-collisional setting.

Coronet is a small komatiite-hosted Ni-Cu-(PGE) ore deposit within the northwestern part of the Kambalda dome. Coronet is unusual in that it is concealed beneath a faulted wedge of Lunnon Basalt, which also forms the footwall of the deposit. The orebody consists of four ...