The abundances of ultraheavy elements in the cosmic radiation

Analysis of the data from the Heavy Nuclei Experiment on the HEAO-3 spacecraft has yielded the cosmic ray abundances of odd-even element pairs with atomic number, Z, in the range 33 ≤ Z ≤60, and the abundances of broad element groups in the range 62 ≤ Z ≤83, relative to iron. These data show that the cosmic ray source composition in this charge range is quite similar to that of the solar system provided an allowance is made for a source fractionation based on first ionization potential. The observations are inconsistent with a source composition which is dominated by either r-process or s-process material, whether or not an allowance is made for first ionization potential. Although the observations do not exclude a source containing the same mixture of r- and s-process material as in the solar system. the data are best fit by a source having an r- to s-process ratio of 1.22^(+0.25)_(0.21), relative to the solar system The abundances of secondary elements are consistent with the leaky box model of galactic propagation, implying a pathlength distribution similar to that which explains the abundances of nuclei with Z<29.

The energy spectra of the even elements in the range 38 ≤ Z ≤ 60 are found to have a deficiency of particles in the range ~1.5 to 3 GeV/amu, compared to iron. This deficiency may result from ionization energy loss in the interstellar medium, and is not predicted by propagation models which ignore such losses. ln addition, the energy spectra of secondary elements are found to be different to those of the primary elements. Such effects are consistent with observations of lighter nuclei, and are in qualitative agreement with galactic propagation models using a rigidity dependent escape length. The energy spectra of secondaries arising from the platinum group are found to be much steeper than those of lower Z. This effect may result from energy dependent fragmentation cross sections.

A novel hybrid based on carbon nanotubes and heteropolyanions as effective catalyst for hydrogen evolution

Heteropolyanions of tungstophosphoric acid (PWA) have been successfully hybridized with carbon nanotubes (CNTs) by a severe mechanical milling. The obtained hybrid is electroactive for hydrogen evolution (HE) at potentials as positive as -0.16 V vs. Ag/AgCl in 0.2 M HClO4 aqueous solution and its electrocatalysis is up to the level of Pt/CNTs (20 wt% Pt) for HE, indicating a vigorous alternative to Pt group metals. The HE mechanism of the hybrid was also studied and it was found that the tungsten oxycarbides are the electroactive components for HE.

东天山后碰撞镁铁-超镁铁岩镍铜硫化物矿床PGE地球化学示踪与富集规律研究

Eastern Tianshan area, a Paleozoic complex trench-arc-basin system, experienced multi-period sudbuction and collision in geological history. A large number of Early Permian mafic-ultramafic intrusions emplaced along deep faults in post-collision extension tectonic stage and hosted a series of magmatic Cu-Ni sulfide deposits. This paper sets newly-discovered Tianyu magmatic Cu-Ni sulfide deposit related to small intrusion as an example. On basis of the study of ore-forming mechanism of Cu-Ni deposit, we compared PGE content and discussed enrichment mechanism and regularity of mafic-ultramafic rocks and ores in Jueluotage tectonic belt and Central Tianshan Massif. PGE and Cu, Ni, S contents correlate with each other. PGE is mainly controlled by S content.Samilar PGE distribution patterns of mafic-ultramafic show that complex originated from the same parental magma; Pd/Ir and Ni/Cu ratios indicate that high-Mg basaltic magma and deep sulfide segregation happened during magma evolution process. PGE and Cu-Ni ores are enriched in liquid sulfide and only individual samples completely control by monosulfide solid solution. Comparison of all control factors, early segregation of sulfide and quality of supply of magma may be the key factors leading to the Eastern Tianshan magmatic copper-nickel sulfide deposits don’t reach PGE grade, but we do not rule out the possibility of occurrence continuous mafic-ultramafic rocks and PGE-rich layer in deep.

铂族元素分析方法研究及其在有关地质问题中的应用

Characterization of Platinum Group Elements (PGE) has been applied to earth, space and environmental sciences. However, all these applications are based on a basic prerequisite, i.e. their concentration or ratio in the research objects can be accurately and precisely determined. In fact, development in these related studies is a great challenge to the analytical chemistry of the PGE because their content in the geological sample (non-mineralized) is often extremely low, range from ppt (10~(-12)g/g) to ppt (10~(-9)g/g). Their distribution is highly heterogeneous, usually concentrating in single particle or phase. Therefore, the accurate determination of these elements remains a problem in analytical chemistry and it obstructs the research on geochemistry of PGE. A great effort has been made in scientific community to reliable determining of very low amounts of PGE, which has been focused on to reduce the level of background in used reagents and to solve probable heterogeneity of PGE in samples. Undoubtedly, the fire-assay method is one of the best ways for solving the heterogeneity, as a large amount of sample weight (10-50g) can be hold. This page is mainly aimed at development of the methodology on separation, concentration and determination of the ultra-trace PGE in the rock and peat samples, and then they are applied to study the trace of PGE in ophiolite suite, in Kudi, West Kunlun and Tunguska explosion in 1908. The achievements of the study are summarized as follows: 1. A PGE lab is established in the Laboratory of Lithosphere Tectonic Evolution, IGG, CAS. 2. A modified method of determination of PGE in geological samples using NiS Fire-Assay with inductively coupled plasma-mass spectrometry (ICP-MS) is set up. The technical improvements are made as following: (1) investigating the level of background in used reagents, and finding the contents of Au, Pt and Pd in carbonyl nickel powder are 30, 0.6 and 0.6ng/g, respectively and 0.35, 7.5 and 6.4ng, respectively in other flux, and the contents of Ru, Rh, Os in whole reagents used are very low (below or near the detection limits of ICP-MS); (2) measuring the recoveries of PGE using different collector (Ni+S) and finding 1.5g of carbonyl nickel is effective for recovering the PGE for 15g samples (recoveries are more than 90%), reducing the inherent blank value due to impurities reagents; (3) direct dissolving nickel button in Teflon bomb and using Te-precipitation, so reducing the loss of PGE during preconcentration process and improving the recoveries of PGE (above 60% for Os and 93.6-106.3% for other PGE, using 2g carbonyl nickel); (4) simplifying the procedure of analyzing Osmium; (5)method detection limits are 8.6, 4.8, 43, 2.4, 82pg/g for 15g sample size ofRu, Rh, Pd, Ir, Pt, respectively. 3. An analytical method is set up to determine the content of ultra-trace PGE in peat samples. The method detection limits are 0.06, 0.1, 0.001, 0.001 and 0.002ng/mL for Ru, Rh, Pd, Ir and Pt, respectively. 4. Distinct anomaly of Pd and Os are firstly found in the peat sampling near the Tunguska explosion site, using the analytical method. 5. Applying the method to the study on the origin of Tunguska explosion and making the following conclusions: (1) these excess elements were likely resulted from the Tunguska Cosmic Body (TCB) explosion of 1908. (2) The Tunguska explosive body was composed of materials (solid components) similar to C1 chondrite, and, most probably, a cometary object, which weighed more than 10~7 tons and had a radius of more than 126 m. 6. The analysis method about ultra-trace PGE in rock samples is successfully used in the study on the characteristic of PGE in Kudi ophiolite suite and the following conclusions are made: (1) The difference of the mantle normalization of PGE patterns between dunite, harzburgite and lherzolite in Kudi indicates that they are residual of multi-stage partial melt of the mantle. Their depletion of Ir at a similar degree probably indicates the existence of an upper mantle depleted Ir. (2) With the evolution of the magma produced by the partial melt of the mantle, strong differentiation has been shown between IPGE and PPGE; and the differentiation from pyroxenite to basalt would have been more and more distinct. (3) The magma forming ophiolite in Kudi probably suffered S-saturation process.

大别（超）包产到户铁岩和阜新火山岩铂族元素斌存规律研究

The platinum-group elements (PGE), including Os, Ir, Ru, Rh, Pt and Pd, axe strongly siderophile and chalcophile. On the basis of melting temperature, the PGE may be divided into two groups: the Ir group (IPGE, >2000°C) consisting of Os, Ir and Ru, and the Pd group (PPGE, <20GO°C) consisting of Rh, Pt and Pd. Because of their unique geochemical properties, PGE provide critical information on global-scale differentiation processes, such as core-mantle segregation, late accretionary history, and core-mantle exchange. In addition, they may be used to identify magma source regions and unravel complex petrogenetic processes including partial melting, melt percolation and metasomatism in the mantle, magma mixing and crustal contamination in magma chambers and melt crystallization.Compared with other rocks, (ultra)mafic rocks have lower REE content but higher PGE content, so PGE have advantages in studying the petrogeneses and evolution of them. In this study, we selected (ultra)mafic rocks collected in Dabie Orogen and volcanic rocks from Fuxin Region. Based on the distribution and behaviour of platinum-group elements, combined with other elements, we speculate the magma evolution and source mantle of these (ultra)mafic rocks and volcanic rocks.Many (ultra)mafic rocks are widely distributed in Dabie Region. According to their deformation and metamorphism, we classed them into three types. One is intrusive (ultra)mafic rocks, which are generally undeformed and show no or little sign of metamorphism, such as (ultra)mafic intrusions in Shacun, zhujiapu, Banzhufan, qingshan, Xiaohekou, Jiaoziyan, Renjiawan and Daoshichong. The other one is ultrahigh pressure metamorphic (ultra)mafic rocks, some of them appeared as eelogites, such as complex in Bixiling and adjacent Maowu. Another one is intense deformed and metamorphic, termed as tectonic slice, alpine-type (ultra)mafic rocks. The most representative is Raobazhai and Dahuapin. However, there are many controversies about the formation of those (ultra)mafic rocks. Here, we select typical rocks of the three types. The PGE were determined by inductively coupled plasma mass spectrometry (ICP-MS) ater NiS fire-assay and tellurium co-precipitation.The PGE tracing shows that three components are needed in the source of the cretaceous (uitra)mafic intrusions. They could be old enriched sub-continental lithospheric mantle, lower crust and depleted asthenospheric mantle. The pattern of PGE also shows the primitive magma of these intrusions underwent S saturation. According to palladium, we can conclude that the mantle enrich in PGE. Distribution of PGE in Bixiiing and Maowu (ultra)mafic rocks display they are products of magmas fractional crystallization. The (ultra)mafic rocks in Bixiiing and Maowu are controlled by various magmatic processes and the source mantle is depleted in PGE. Of interest is that the mantle produced UHP (ultra)mafic rocks are PGE-depleted, whereas the mantle of cretaceous (ultra)mafic intrusions are enrich in PGE. This couldindicate that the mantle change from PGE-enriched to PGE-depleted during120-OOMa, which in accord with the time of tectonic system change in the East China. At the same time, (ultra)mafic intrusions in cretaceous took information of deep mantle, which means the processes in deep mantle arose structural movement in the crust The character of PGE in alpine-type (ultra)mafic rocks declared that the rocks had experienced two types of metasomatic processes - hydrous melt derived from slab and silicate melt. In addition, we analyze the platinum-group elements in volcanic rocks on the northern margin of the North China Craton, Fuxin. The volcanic rocks characterized by negative anomalies of platinum. This indicates that platinum alloys, which may host some Pt resided in the mantle. The PGE patterns also show that Jianguo alkali basalts derived from asthenospheric mantle source, but wulahada high-Mg andesites derived from lithospheric mantle.

An investigation of catalysts for the on board synthesis of NH3. A possible route to low temperature NOx reduction for lean-burn engines

Platinum group metal catalysts have been investigated for the formation of NH3 from NO + H-2 at low temperatures in the absence and presence of CO. Although CO inhibits the formation of NH3, substantial amounts are still observed with a Pt catalyst. By combining Pt with a support (ceria-zirconia) that has low temperature NOx storage characteristics it has been shown in transient experiments that NH3 can be formed and stored in situ under rich conditions, and may then be used to reduce NOx under lean burn conditions.

New methods in Biomass Depolymerisation: Catalytic Hydrogenolysis of Barks

Hydrogenolysis of bark from three different species of tree using heterogeneous platinum group metal catalysts produces two major product streams. Aromatic substituted guaiacols are produced from lignin and the lignin-like regions of suberin and a range of saturated fatty acids and alcohols, including a,?-functionalised species, are produced from the polyester regions of suberin. Control experiments demonstrate clear advantages of catalytic hydrogenolysis over base hydrolysis, both in terms of conversion and product selectivity.

Integration of geochemical and biological modifications in mining areas: waters, sediments and diatoms

The development of mining activities over thousands of years in the region of Aljustrel is nowadays visible as a vast area of ore tailings, slag and host rocks of sulphides mineralization. The generation of acidic waters by the alteration of pyritic minerals - Acid Mine Drainage (AMD) - causes a significant impact on the river system both in the south of the village (Rib ª. Água Forte) and in the north of it (Rib ª. Água Azeda and Barranco do Farrobo), which is reflected in extremely low pH values (< 3) and high concentrations of As, Cd, Cu, Fe, Mn, Pb, Zn and sulphates. This study aimed to assess the environmental impacts extent, integrating geochemical (surface waters and stream sediments) and biological (diatoms) parameters. Three groups of sites were defined, based on sediments and water analysis, which integration with diatom data showed the same association of groups: Group 1- impacted, with acidic pH (1.9-5.1), high metal contents (0.4-1975 mg L-1) and Fe-Mg-sulphate waters, being metals more bioavailable in waters in cationic form (Me2+); mineralogically the sediments were characterized by phyllosilicates and sulphates/oxy-hydroxysulphate phases, easily solubilized, retaining a high amount of metals when precipitated; dominant taxon was Pinnularia aljustrelica (a new species); Group 2- slightly impacted, weak acid to neutral pH (5.0-6.8), metal contents not so high (0.2-25 mg L-1) and Fe-Mg-sulphate to Mg-chloride waters; dominant taxa were Brachysira neglectissima and Achnanthidium minutissimum; Group 3- unimpacted, alkaline pH (7.0-8.4), low metal contents (0-7 mg L-1) with Mg-chloride waters. In this group, metals were associated to the primary phases (e.g. sulphides), not so easily available; the existence of high chloride contents explained the presence of typical taxa of brackish/marine (e.g. Entomoneis paludosa) waters. Taxonomical aspects of the diatoms were studied (discovery of a new species: Pinnularia aljustrelica Luis, Almeida et Ector sp. nov.), as well as morphometric (size decrease of diatoms valves, as well as the appearance of deformed valves of Eunotia exigua in Group 1 and A. minutissimum in Group 2) and physiological (effective to assess the effects of metals/acidity in the photosynthetic efficiency through PAM Fluorometry) aspects. A study was carried out in an artificial river system (microcosm) that aimed to mimic Aljustrel’s extreme conditions in controlled laboratory conditions. The chronic effects of Fe, SO42- and acidity in field biofilms, inoculated in the artificial rivers, were evaluated as well as their contribution to the communities’ tolerance to metal toxicity, through acute tests with two metals (Cu and Zn). In general, the effects caused by low pH values and high concentrations of Fe and SO42- were reflected at the community level by the decrease in diversity, the predominance of acidophilic species, the decrease in photosynthetic efficiency and the increase of enzymatic (e.g. catalase, superoxide dismutase) and non-enzymatic activities (e.g. total glutathione and total phytochelatins). However, it was possible to verify that acidity performed a protective effect in the communities, upon Cu and Zn addition. A comparative study between Aljustrel mining area and New Brunswick mining area was carried out, both with similar mining and geological conditions, reflected in similar diatom communities in both mines, but in very different geographic and climatic areas.

Ag dopedWO(3)-based powder sensor for the detection of NO gas in air

WO3-based materials as sensors for the monitor of environmental gases such as NO2 (NO + NO2) have been rapidly developed for various potential applications (stationary and mobile uses). It has been reported that these materials are highly sensitive to NOx with the sensitivity further enhanced by adding precious group metals (PGM such as Pt, Pd, Au, etc.). However, there has been limited work in revealing the sensing mechanism for these gases over the WO3-based sensors. In particular, the role of promoter is not yet clear though speculations on their catalytic, electronic and structural effects have been made in the past. In parallel to these PGM promoters here we report,for the first time, that Ag promotion can also enhance WO3 sensitivity significantly. In addition, this promotion decreases the optimum sensor temperature of 300 degreesC for Most WO3-based sensors, to below 200 degreesC. Characterizations (XRD, TEM, and impedance measurement) reveal that there is no significant bulk structure change nor particle size alteration in the WO3 phases during the NO exposure. However, it is found that the Ag doping creates a high concentration of oxygen vacancies in form of coordinated crystallographic shear (CS) planes onto the underneath WO3. It is thus proposed that the Ag particle facilitates the oxidative conversion of NO to NO2 followed by a subsequent NO2 adsorption on the defective WO, sites created at the Ag-WO3 interface; hence, accounting for the high molecular sensitivity. (C) 2002 Elsevier Science B.V. All rights reserved.

Environmental effects of Deccan volcanism across the Cretaceous-Tertiary transition in Meghalaya, India

The Um Sohryngkew section of Meghalaya, NE India, located 800–1000 km from the Deccan volcanic province, is one of the most complete Cretaceous–Tertiary boundary (KTB) transitions worldwide with all defining and supporting criteria present: mass extinction of planktic foraminifera, first appearance of Danian species, δ13C shift, Ir anomaly (12 ppb) and KTB red layer. The geochemical signature of the KTB layer indicates not only an extraterrestrial signal (Ni and all Platinum Group Elements (PGEs)) of a second impact that postdates Chicxulub, but also a significant component resulting from condensed sedimentation (P), redox fluctuations (As, Co, Fe, Pb, Zn, and to a lesser extent Ni and Cu) and volcanism. From the late Maastrichtian C29r into the early Danian, a humid climate prevailed (kaolinite: 40–60%, detrital minerals: 50–80%). During the latest Maastrichtian, periodic acid rains (carbonate dissolution; CIA index: 70–80) associated with pulsed Deccan eruptions and strong continental weathering resulted in mesotrophic waters. The resulting super-stressed environmental conditions led to the demise of nearly all planktic foraminiferal species and blooms (> 95%) of the disaster opportunist Guembelitria cretacea. These data reveal that detrimental marine conditions prevailed surrounding the Deccan volcanic province during the main phase of eruptions in C29r below the KTB. Ultimately these environmental conditions led to regionally early extinctions followed by global extinctions at the KTB.

Gênese dos corpos de sulfeto maciço hidrotermal e platinóides associados no depósito de Fortaleza de Minas (MG)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New constraints on the genesis and long-term stability of Os-rich alloys in the Earth's mantle

A variety of seemingly unrelated processes, such as core-mantle interaction, desulfurization, and direct precipitation from a silicate melt have been proposed to explain the formation of Ru-Os-Ir alloys (here referred to as osmiridiums) found in terrestrial mantle rocks. However, no consensus has yet been reached on how these important micrometer-sized phases form. In this paper we report the results of an experimental study on the solubilities of Ru, Os and Ir in sulfide melts (or mattes) as a function of alloy composition at 1300 degrees C. Considering the low solubilities of Ru, Os, and Ir in silicate melts, coupled with their high matte/silicate-melt partition coefficients, our results indicate that these elements concentrate initially at the ppm level in a matte phase in the mantle source region. During partial melting, the extraction of sulfur into silicate melt leads to a decrease in fS(2) that triggers the exsolution of osmiridiums from the refractory matte in the residue. The newly formed osmiridiums may persist in the terrestrial mantle for periods exceeding billions of years. (C) 2012 Elsevier Ltd. All rights reserved.

Entwicklung eines Verfahrens zur Ultraspurenbestimmung der Platingruppenelemente in Umwelt- und geologischen Proben mit einem ICP-QMS unter Verwendung der Isotopenverdünnungsanalyse sowie geeigneter Separationstechniken

ZusammenfassungSchwerpunkt dieser Arbeit war die Verfahrensentwicklung zur Ultraspurenbestimmung der Platingruppenelemente (PGE) in Umwelt- und geologischen Proben unter Verwendung der massenspektrometrischen Isotopenverdünnungsanalyse mit anschließender Bestimmung an einem Quadrupol ICP-MS (ICP-QMSIVA). Geeignete Separationstechniken in der Probenaufbereitung, um die PGE von der Matrix der untersuchten Proben zu trennen, stellten eine richtige und präzise Bestimmung der Ultraspuren an einem Quadrupol ICP-MS sicher.Das Verfahren konnte anhand von geologischen Referenzmaterialien aus Kanada sichergestellt werden. Gerade die Wiederholungsbestimmungen der verschiedenen Referenzmaterialien unter Verwendung des ICP-QMSIVA Verfahrens sind beispiellos und in dieser Form noch nicht in der Literatur beschrieben. Durch systematische Messungen konnten Richtigkeit und Präzision des Verfahrens bestätigt werden und die Inhomogenität des Referenzmaterials UMT-1 bezüglich Pt bewiesen werden. Das in dieser Arbeit entwickelte Verfahren zur Ultraspurenbestimmung der PGE mit ICP-QMSIVA wurde im Rahmen des Projektes 'Production and certification of a road dust reference material for platinum, palladium and rhodium (PGEs) in automative catalytic converters (PACEPAC)' der Europäischen Union zur Zertifizierung von zwei Referenzmaterialien für Umweltproben eingesetzt. Hierbei wurde bei der Zertifizierung ('intercomparison round') eine sehr gute Übereinstimmung der Ergebnisse mit dem gewichteten Mittelwert der Ergebnisse für Pd und Pt mit den übrigen teilnehmenden Laboratorien festgestellt. Die mit der hier entwickelten Methode erhaltenen Ergebnisse wurden ohne Ausnahme für alle gemessenen Elemente zur Zertifizierung herangezogen. Damit leistete die vorliegende Arbeit einen erheblichen Beitrag zum erfolgreichen Abschluß dieses Projekts. Den Erwartungen hinsichtlich Richtigkeit und Reproduzierbarkeit des entwickelten Verfahrens wurde somit voll entsprochen. Erneut konnte die große Bedeutung der Isotopenverdünnungstechnik für die Zertifizierung von Referenzmaterialien aufgezeigt werden, da mit dieser Technik bei sachgerechtem Einsatz Ergebnisse hoher Richtigkeit erzielt werden. Durch vergleichende Messungen mit der NiS-Dokimasie und NAA, die in einer Kooperation mit dem Kernchemischen Institut der Universität Mainz durchgeführt wurden, und dem hier verwendeten Verfahren, konnten übereinstimmende Daten, hinsichtlich der Abnahme der Konzentrationen von Pd und Pt in Abhängigkeit von der Entfernung zu einer Autobahn, erzielt werden. Diese Arbeit und die Forschungsergebnisse, die mit der anerkannten NAA erzielt wurden, zeigen, daß die PGE durch Katalysatoren von Automobilen überwiegend metallisch emittiert werden. Der anthropogene Eintrag der PGE in die Umwelt kann mit dem ICP-QMSIVA Verfahren weiterhin sehr gut verfolgt werden.

Petrogenetic evolution of Uralian-Alaskan-type mafic-ultramafic complexes in the southern and middle Urals, Russia

The PhD thesis at hand consists of three parts and describes the petrogenetic evolution of Uralian-Alaskan-type mafic ultramafic complexes in the Ural Mountains, Russia. Uralian-Alaskan-type mafic-ultramafic complexes are recognized as a distinct class of intrusions. Characteristic petrologic features are the concentric zonation of a central dunite body grading outward into wehrlite, clinopyroxenite and gabbro, the absence of orthopyroxene and frequently occurring platinum group element (PGE) mineralization. In addition, the presence of ferric iron-rich spinel discriminates Uralian-Alaskan-type complexes from most other mafic ultramafic rock assemblages. The studied Uralian-Alaskan-type complexes (Nizhnii Tagil, Kytlym and Svetley Bor) belong to the southern part of a 900 km long, N–S-trending chain of similar intrusions between the Main Uralian Fault to the west and the Serov-Mauk Fault to the east. The first chapter of this thesis studies the evolution of the ultramafic rocks tracing the compositional variations of rock forming and accessory minerals. The comparison of the chemical composition of olivine, clinopyroxene and chromian spinel from the Urals with data from other localities indicates that they are unique intrusions having a characteristic spinel and clinopyroxene chemistry. Laser ablation-ICPMS (LA-ICPMS ) analyses of trace element concentrations in clinopyroxene are used to calculate the composition of their parental melt which is characterized by enriched LREE (0.5-5.2 prim. mantle) and other highly incompatible elements (U, Th, Ba, Rb) relative to the HREE (0.25-2.0 prim. mantle). A subduction-related geotectonic setting is indicated by a positive anomaly for Sr and negative anomalies for Ti, Zr and Hf. The mineral compositions monitor the evolution of the parental magmas and decipher differences between the studied complexes. In addition, the observed variation in LREE/HREE (for example La/Lu = 2-24) can be best explained with the model of an episodically replenished and erupted open magma chamber system with the extensive fractionation of olivine, spinel and clinopyroxene. The data also show that ankaramites in a subduction-related geotectonic setting could represent parental magmas of Uralian-Alaskan-type complexes. The second chapter of the thesis discusses the chemical variation of major and trace elements in rock-forming minerals of the mafic rocks. Electron microprobe and LA-ICPMS analyses are used to quantitatively describe the petrogenetic relationship between the different gabbroic lithologies and their genetic link to the ultramafic rocks. The composition of clinopyroxene identifies the presence of melts with different trace element abundances on the scale of a thin section and suggests the presence of open system crustal magma chambers. Even on a regional scale the large variation of trace element concentrations and ratios in clinopyroxene (e.g. La/Lu = 3-55) is best explained by the interaction of at least two fundamentally different magma types at various stages of fractionation. This requires the existence of a complex magma chamber system fed with multiple pulses of magmas from at least two different coeval sources in a subduction-related environment. One source produces silica saturated Island arc tholeiitic melts. The second source produces silica undersaturated, ultra-calcic, alkaline melts. Taken these data collectively, the mixing of the two different parental magmas is the dominant petrogenetic process explaining the observed chemical variations. The results further imply that this is an intrinsic feature of Uralian-Alaskan-type complexes and probably of many similar mafic-ultramafic complexes world-wide. In the third chapter of this thesis the major element composition of homogeneous and exsolved spinel is used as a petrogenetic indicator. Homogeneous chromian spinel in dunites and wehrlites monitors the fractionation during the early stages of the magma chamber and the onset of clinopyroxene fractionation as well as the reaction of spinel with interstitial liquid. Exsolved spinel is present in mafic and ultramafic rocks from all three studied complexes. Its composition lies along a solvus curve which defines an equilibrium temperature of 600°C, given that spinel coexists with olivine. This temperature is considered to be close to the temperature of the host rocks into which the studied Uralian-Alaskan-type complexes intruded. The similarity of the exsolution temperatures in the different complexes over a distance of several hundred kilometres implies a regional tectonic event that terminated the exsolution process. This event is potentially associated with the final exhumation of the Uralian-Alaskan-type complexes along the Main Uralian Fault and the Serov-Mauk Fault in the Uralian fold belt.