Browsing by Subject "geokemia"

Sort by: Order: Results:

Now showing items 1-13 of 13
  • Hekkala, Toni (Helsingin yliopisto, 2019)
    Arsenic (As) is a metalloid naturally present in the environment. Arsenic species vary in toxicity. Metal mining has contributed to the anthropogenic input of arsenic to groundwaters and surface waters. In this study, water samples were collected from 20 sample points in three mining-impacted study areas in Finland: the former Ylöjärvi Cu–W–As and Haveri Au–Cu mines, and the active Pyhäsalmi Zn–Cu mine. Six groundwater well samples, eleven surface water samples and three tailings seepage collection ditch samples were analyzed for dissolved arsenic speciation by HPLC-ICP-MS and for geochemical composition by ICP-MS, titration, and ion chromatography. Dissolved arsenic concentrations ranged from 14.2 to 6649 µg L-1 in samples collected at the Ylöjärvi study area, from 0.5 to 6.2 µg L-1 in samples collected at the Haveri study area, and from 0.2 to 9.4 µg L-1 in samples collected at the Pyhäsalmi study area. In all study areas, measured dissolved arsenic concentrations showed a general decrease from the tailings to the surroundings. Speciation analysis showed that two of the samples collected at the Ylöjärvi study area had arsenite [As(III)] as the dominant form of dissolved inorganic arsenic (iAs), three had arsenate [As(V)] as the dominant form of dissolved iAs, and four had a mixture of both. In the water samples collected at the Haveri and Pyhäsalmi study areas, all concentrations of dissolved arsenic species were below method detection limits. Also, none of the 22 water samples analyzed for arsenic speciation had dissolved MMA or DMA concentrations above method detection limits. Identification of dissolved arsenic species in the sampled waters in Haveri and Pyhäsalmi, and of MMA and DMA in all sampled waters requires more detailed study. A significant 2-tailed Pearson correlation between dissolved arsenic and dissolved molybdenum (Mo) (r=0.80**, n=20), and dissolved arsenic and dissolved potassium (K) (0.68**, n=19) suggests that in these three study areas the distributions of dissolved arsenic and Mo, as well as dissolved arsenic and K may be controlled by the same environmental variables. Anomalously high maximum concentrations of dissolved Al, Ca, Co, Cu, Fe, Ni, and SO4 were measured in surface water samples collected at the Ylöjärvi and Haveri study areas, and in a seepage collection ditch sample collected at the Pyhäsalmi study area.
  • Eranti, Olli (Helsingin yliopisto, 2020)
    Geochemistry of stone tools and sources remains largely unknown in Finnish archaeology, but the potential is promising. Most formal Finnish stone tools beside quartz are made from ground metamorphic stone, which often has a specific source of collection. Geochemistry can reveal compositional and trace element links between the sources and tools found in various Stone Age settlement sites. Discoveries about technological properties of the stone types can be a helpful comparison, since many geochemical methods can produce data that has inconsistencies. In this thesis both geochemical and technological aspects of two lithic material sources are examined. Samples were collected from two lithic material sources: Rakkaviita and Rieskapaikka in Tervola, Southern Lapland. The 62 collected samples were measured with a Bruker S1 Titan portable x-ray fluorescence device as a preliminary method. Three samples from Rakkaviita and two samples from Rieskapaikka were chosen for the primary method, which was the PANalytical Axios mAX 4 kW, Wavelength Dispersive X-Ray fluorescence spectrometer in the Department of Geosciences in the University of Helsinki. The data from these measurements is evaluated and plotted to reveal geochemical properties of the stone. In this study, the properties of these stone materials are documented for the first time, so it can also be considered as a mapping study. The measurements revealed differentiation between methods, especially on the SiO2 percentages. The WD-XRF measurements are done without sample specific calibration, which obscures the quantitative proportions of some elements. The content of the stone revealed various components in different proportions. The result of major components was a coarsely qualitative definition of stone from both sources, which can be used in further material studies of stone tools. The trace element comparison between yttrium (Y) and strontium (Sr) revealed clear similarity between sources, excluding one sample that had significantly different tool production properties than others. According to this study, methods that handle trace elements well like ICP-MS are best suited for provenance studies on this type of stone. With trace elements it’s likely that these types of stones can be successfully sourced by geological region. The technological properties of the material are studied to find out the potential of the raw material as a stone to make and use tools with. Differences in the technological properties of the two sources is reflected in the composition and formation differences. Rieskapaikka included more mafic, porphyritic and fine-grained samples while Rakkaviita stones were more foliated and deteriorated.
  • Heinonen, Jussi S. (Unigrafia, 2011)
    Department of Geosciences and Geography
    This study provides insights into the composition and origin of ferropicrite dikes (FeOtot = 13–17 wt. %; MgO = 13–19 wt. %) and associated meimechite, picrite, picrobasalt, and basalt dikes found at Vestfjella, western Dronning Maud Land, Antarctica. The dikes crosscut Jurassic Karoo continental flood basalts (CFB) that were emplaced during the early stages of the breakup of the Gondwana supercontinent ~180 Ma ago. Selected samples (31 overall from at least eleven dikes) were analyzed for their mineral chemical, major element, trace element, and Sr, Nd, Pb, and Os isotopic compositions. The studied samples can be divided into two geochemically distinct types: (1) The depleted type (24 samples from at least nine dikes) is relatively depleted in the most incompatible elements and exhibits isotopic characteristics (e.g., initial εNd of +4.8 to +8.3 and initial 187Os/188Os of 0.1256–0.1277 at 180 Ma) similar to those of mid-ocean ridge basalts (MORB); (2) The enriched type (7 samples from at least two dikes) exhibits relatively enriched incompatible element and isotopic characteristics (e.g., initial εNd of +1.8 to +3.6 and initial 187Os/188Os of 0.1401–0.1425 at 180 Ma) similar to those of oceanic island basalts. Both magma types have escaped significant contamination by the continental crust. The depleted type is related to the main phase of Karoo magmatism and originated as highly magnesian (MgO up to 25 wt. %) partial melts at high temperatures (mantle potential temperature >1600 °C) and pressures (~5–6 GPa) from a sublithospheric, water-bearing, depleted peridotite mantle source. The enriched type sampled pyroxene-bearing heterogeneities that can be traced down to either recycled oceanic crust or melt-metasomatized portions of the sublithospheric or lithospheric mantle. The source of the depleted type represents a sublithospheric end-member source for many Karoo lavas and has subsequently been sampled by the MORBs of the Indian Ocean. These observations, together with the purported high temperatures, indicate that the Karoo CFBs were formed in an extensive melting episode caused mainly by internal heating of the upper mantle beneath the Gondwana supercontinent. My research supports the view that ferropicritic melts can be generated in several ways: the relative Fe-enrichment of mantle partial melts is most readily achieved by (1) relatively low degree of partial melting, (2) high pressure of partial melting, and (3) melting of enriched source components (e.g., pyroxenite and metasomatized peridotite). Ferropicritic whole-rock compositions could also result from accumulation, secondary alteration, and fractional crystallization, however, and caution is required when addressing the parental magma composition.
  • Karvinen, Seppo (Helsingin yliopisto, 2019)
    The Central Finland Granitoid Complex (CFGC) is a large (44,000 km2) plutonic core of a Svecofennian (Paleoproterozoic, 1.91–1.82 Ga) arc complex, formed from collisions of several volcanic arcs and their accretion over the Karelian craton. The CFGC consists mostly of granitic to granodioritic rock types. Mafic-ultramafic plutonic rock types are not common, and they consist of mostly small gabbro-diorite intrusions, which may have ultramafic parts. There are two distinct belts around the CFGC, where Ni-Cu potential mafic-ultramafic intrusions are situated – Vammala and Kotalahti. The intrusions within these belts were formed during the height of magmatism within the CFGC (1.89–1.87 Ga). They host Ni-Cu mineralizations, some of which have been economically exploited. The mineralizations are hosted by olivine-rich ultramafic cumulates. The intrusions formed from hydrous tholeiitic basalts (10–12 wt-% MgO) with arc-type trace element chemistry. The difference between Vammala and Kotalahti type intrusions (clinopyroxene and orthopyroxene-dominated, respectively) are attributed to the rock type of the assimilated country rock. In this thesis, three previously unknown or poorly studied mafic-ultramafic intrusions (Matokulma, Palojärvi, and Hongonniittu) within the CFGC are studied in detail. The petrology, similarity to Vammala-Kotalahti type intrusions, parental magma compositions, ore potential, and petrogenesis of the intrusions are described. Rock samples and field observations were gathered during the summer of 2017. Whole-rock geochemistry, mineral geochemistry, isotope geochemistry, and geophysics are used to describe the petrology of the intrusions. Matokulma and Palojärvi intrusions are studied in detail, compared to Hongonniittu intrusion, which was not studied as intricately. The Matokulma intrusion is the least evolved (whole-rock median Mg#=72) of the studied intrusions and consists of tholeiitic melagabbros where clinopyroxene±orthopyroxene and plagioclase are the main cumulus phases within interstitial, magmatic amphibole (magnesiohastingsite to pargasite in composition). Orthopyroxene and plagioclase are intercumulus phases in some samples. There are also mafic dikes that intrude the tonalitic country rock that surrounds the gabbro. The dikes are similar to the gabbros in geochemistry although they are generally more evolved. Trace element geochemistry suggests that the gabbros and dikes are genetically connected, and the dikes possibly represent the residual magmas of the gabbros. The Palojärvi intrusion is noticeably more evolved than the Matokulma intrusion (median Mg#=49), which is apparent in the iron and titanium rich mineral and whole-rock geochemistry. The strongly tholeiitic melagabbros are composed of both orthopyroxene and clinopyroxene as cumulus phases with plagioclase and common Fe-Ti oxide, often within interstitial magmatic amphibole (magnesio-hastingsite to magnesioferri-hornblende in composition). The Fe-Ti oxides are mostly ilmenomagnetite but both magnetite and ilmenite grains are present in same samples. Based on a few mineral analyzes, the ilmenomagnetite contains up to 1.4 wt-% V2O3. U-Pb age determination samples from a leucogabbro dike within the intrusion and granite that crosscuts the intrusion yielded weighted average 206Pb/207Pb ages of 1883.4±4.8 Ma and 1893.8±7.1 Ma, respectively. The age results are in contrast to the intrusive relationship observed in the field. However, considering the margin of error of the results, the granite can be younger than the gabbro, 1887 Ma and 1888 Ma, respectively. The age of ca. 1.89 Ga is at the early stage of the most voluminous mafic-ultramafic magmatism in the Svecofennian terrane. The parental magmas of the Matokulma and Palojärvi intrusions were evolved and contained approximately 5 wt-% and 2 wt-% MgO, respectively. The presence of magmatic amphiboles in most samples indicate that the parental magmas were hydrous. Samples from all intrusions plot similarly in primitive mantle normalized Rare Earth Element (REE) and Normal-Mid-Ocean Ridge Basalt (NMORB) normalized spider diagrams. Similar patterns indicate a similar source for the parental magmas. The trace element geochemistry has signatures of subduction related fluid metasomatism. The rocks are enriched in large ion lithophile elements (LILE) and depleted in High Field Strength Elements (HFSE). These geochemical characteristics indicate that the studied intrusions crystallized from a hydrous, NMORB-like evolved basaltic magma, which has experienced fluid metasomatism. The studied intrusions differ from olivine-rich ultramafic cumulates of Vammala and Kotalahti type intrusions based on their more evolved, gabbroic composition and because of this, they are not Ni-Cu ore potential. Palojärvi may host a Fe-Ti-V mineralization, if there are magnetite rich layers within the intrusion.
  • Rönkä, Esa; Uusinoka, Raimo; Vuorinen, Antti (Vesihallitus. National Board of Waters, 1980)
    Vesientutkimuslaitoksen julkaisuja 38, 41-53.
  • Karhu, Noora (Helsingin yliopisto, 2020)
    Geochemical ore exploration with geogases is based, like the MMI method, on the movement of mobile metal ions. The assumption is that the buried mineralization is possible to locate using the samples collected from the surface sediment. In this study, the detection of gold-copper anomalies by geogases was tested in three different regions of the West Lapland ice divide zone. Geogas samples were collected using an active gas collector at 25 cm below the lowest visible soil horizon. The samples were bubbled into nitric acid and analysed with ICP-MS. The elements studied were As, Co, Cr, Cu, Fe, Hg, Ni, Pb, U and Zn. Only few elevated levels of arsenic, cobalt, mercury and nickel were found in the gas samples In the Hannukainen mining area, geogases were collected at known ore settlement, in which gas concentrations showed a clear anomaly in soil directly above the outcropping ore. At Kelontekemä, the concentrations of geogases were compared with MMI results from soil samples collected nearby. There appears to be a connection between concentrations of gases and soil samples, but the concentrations of soil samples are often a thousandfold higher. In this study, the Jolhikko region served as a background area, which allowed to conduct a comparison between the area containing mineralization and the background area of precious metals. In light of this research, geogases are a working tool for geochemical ore exploration. However, and in order to understand the complexity of this phenomenon, it is necessary to conduct further studies. The use of geogases also requires special care from samplers to minimize contamination risks.
  • Lindholm, Tanja (Helsingin yliopisto, 2010)
    Object of this reseach is geochemical characterization of Häme diabase dyke swarm. The analysed dyke (n=42) samples were collected using a hammer. The chemical analysis were performed at Helsinki University for major and some trace elements using XRF analyser and at GeoLab, Washington University for lanthanides and trace elements using ICPMS analyser. The reseach area is situated in the east 35 km north from Tampere and in the west the area of Heinola city. The age of Häme dike swarm is ~1.6 Ga, which is also the age of nearby rapakivi inturions in the area. The Häme dike swarm cuts sharply 1.9 Ga svecofennian bedrock. The Häme swarm has been divided into two sets of dykes based on different strikes, compositional features and in age. One of the sets strikes WNW and the other one NW. Häme dyke swarm resembles continental flood basalts. They are relatively alkaline ironrich continental quartz and olivine tholeiites. Main minerals are olivine, pyroxenes and plagioclase. Their TiO2 (1,4–3,3 p. %), P2O5 (0,4–1,1 p. %), Fe2O3 (12,3–16,6 p. %) and Al2O3 (12,9–18,6 p. %) contents are relatively high and MgO (3,4–5,9 p. %) and CaO (6,2–8,7 p. %) contents are relatively low. The abundances of incompatible trace elements are high and they show LREEenriched REEpatterns, also their Ni and Cr contents are relatively low. In Spider diagram you can see negative Eu, Nb and Ti anomalies in and positive Pb anomaly. Geochemical data doesn’t correlate with two different strike sets and dykes have no correlation with their geographical settings.
  • Myllymaa, Urpo (Vesihallitus. National Board of Waters, 1985)
    Vesientutkimuslaitoksen julkaisuja 62, 54-92
    Valuma-aluetekijöiden vaikutus Koutajoen vesistöalueen pienten järvien vedenlaatuun, erityisesti metalleihin
  • Kailamäki, Uine (Helsingin yliopisto, 2020)
    Tutkielmassa perehdytään esihistoriallista kalliotaidetta suojaavien silikasilausten uraanisarja-ajoittamiseen. Esihistoriallista taidetta on ajoitettu uraanisarjamenetelmillä aikaisemmin kalsiittisaostumista, mutta opaaliset silikasilaukset ovat Suomen olosuhteissa paljon niitä yleisempi epäorgaaninen kivisilaustyyppi. Uraanisarjat ovat luonnossa esiintyviä radioaktiivisia hajoamissarjoja, joiden jäsenten erilaisen geokemiallisen käyttäytymisen ja eripituisten puoliintumisaikojen vuoksi niitä voidaan käyttää monipuolisesti erilaisten geologisten ja arkeologisten ilmiöiden ajoittamiseen. Kalliomaalausten ajoituksiin käytetään usein uraanin 234U ja toriumin 230Th-isotooppeja niiden sopivan puoliintumisajan vuoksi, ja koska uraanilla on vesiliukoisena taipumus kertyä selektiivisesti nuoriin saostumiin, jollaisia myös kalliomaalauksia peittävät silaukset ovat. Näytteessä oleva 230Th on siis tällaisessa näytteessä syntynyt oletettavasti uraanin radioaktiivisen hajoamisen seurauksena. Amorfisesta silikasta on saatu lupaavia tuloksia geokronometrinä, mutta ohuista (n. 100 μm) ja kovista silauksista näytteenotto on vaikeampaa kuin pehmeästä ja nopeakasvuisesta kalsiitista. Silikasaostumien suora laserablaatio massapektrometrillä analysoitavaksi onkin nostanut suosiotaan jo geologisten opaalisaostumien ajoittamisessa opaalin ohuiden, eri-ikäisten kerrosten sekoittumisen ehkäisemiseksi. Tapausesimerkkeinä tutkimuksessa käsitellään Suomussalmen Värikallion ja Puumalan Syrjäsalmen kalliomaalauksia, sekä niitä peittäviä silikasilauksia. Kohteiden silaukset osoittautuivat yllättävän erilaisiksi keskenään. Värikallion silaus on massamainen ja sisältää vain vähän detritaalisuutta. Syrjäsalmen silaus sitä vastoin on fragmentaarinen, erilaisten litobionttien peittämä, ja vaikuttaa köyhtyneen uraanista sekä keränneen itseensä epäpuhtauksia. Värikallion silaus vaikuttaa alustavan tutkimuksen perusteella lupaavalta uraanisarja-ajoittamisen kohteelta. Jos siitä saadaan myöhemmin tehtyä onnistunut ajoitus, on se todennäköisesti ensimmäinen laatuaan – niin Suomessa, kuin koko maailmassakin – tämäntyyppisestä kohteesta tehtynä.
  • Piispanen, Risto; Myllymaa, Urpo (Vesihallitus. National Board of Waters, 1982)
    Vesientutkimuslaitoksen julkaisuja 49, 64-75
    Kahden geologialtaan erilaisen alueen järvien geokemiasta Kuusamossa Koillis-Suomessa
  • Markkanen, Minna (Helsingin yliopisto, 2021)
    The orbicular quartz monzonite from Kuohenmaa, Southwest Finland, is one of the most beautiful and well-known orbicular rocks in the world. The cores of the orbicules are peraluminous in composition, most likely of xenolithic metasedimentary origin. The cores are surrounded by orbicule mantles, which consist of several alternating biotite- and plagioclase-rich shells. There are three types of orbicules in Kuohenmaa orbicular rock: proto-, small-, and large-orbicular types. Proto-orbicules have only a few shells, small orbicules ~ 50 shells in average, and large orbicules over 250 distinct shells. In addition to shells, one sample was observed to be associated with comb layering in the contact of proto-orbicular and large orbicular types. Structures and textures of the comb layer resembles those of the outer shells of large orbicules. The orbicules are embedded in interstitial coarse-grained groundmass that forms locally almost pegmatitic patches. The petrographic observations were acquired from eight samples or sample photographs gathered from different collections. A mineral chemistry dataset was measured from a single large orbicule from the University of Helsinki collections. The main minerals of the Kuohenmaa orbicular rock are plagioclase, biotite, microcline, muscovite, and chlorite. The shell textures vary from branching plagioclase-rich shells to fine-grained plagioclase- or biotite-rich shells. Branching shells are mainly oligoclase, but a few granular andesine crystals were detected in the core. Peculiar interstitial fibrous allanite masses were found in the inner branching plagioclase-rich shells. The plagioclase compositions generally follow a regular fractional crystallization trend from core to groundmass, but some changes towards more primary compositions are observed in the orbicule mantle. Plagioclase crystals display only minor compositional zoning, suggesting rather quick crystallization. Biotite is very aluminous (Al2O3 17.63–18.53) in composition, and the compositional changes seem to have somewhat positive correlation with plagioclase compositions, suggesting changes in their crystallization conditions. Injections of primary melt from a deeper source most likely caused the observed changes to more primitive composition in plagioclase and biotite composition. Through the detailed petrographic and geochemical studies, a model of undercooling caused by decompression driven fluid saturation is proposed as a mechanism for orbicule formation in the Kuohenmaa orbicular rock. Branching plagioclase with interstitial fibrous allanite masses and several fluid inclusions in plagioclase indicates separate aqueous REE-enriched melt and rapid crystallization. Further studies of fluid inclusions and REE-enriched phases could provide information of the fluid origin and crystallization conditions.
  • Heikkinen, Marja-Leena; Väisänen, Tero (Pohjois-Pohjanmaan ympäristökeskus, 2007)
    PPOra 7/2007
    Pyhäjärven Junttiselkää ovat vaivanneet keväiset, kalakuolemia aiheuttaneet happamuuspiikit. Keväällä 2004 Junttiselän vesimassa happamoitui äkillisesti ja samantyyppinen happamuuspiikki esiintyi myös keväällä 2006. Happamuuspiikkien taustalla on todettu olevan järven pohjan hapettomuudesta johtuva raudan ja rikkiyhdisteiden kertyminen alusveteen ja sitä seuraava kevään täyskierron yhteydessä tapahtuva hapettumisreaktio. Hapettuminen tuottaa happoa, joka laskee nopeasti koko Junttiselän pH:n alhaisiin lukemiin. Rikkiyhdisteiden lähteenä on järven pohjan noin 14–20 cm:n paksuinen, lähinnä kaivoksen jätevesipäästöstä lähtöisin oleva rikkipitoinen kerros, jossa osa rikistä on sulfi deina. Raudan lähteenä on lähinnä järven pohjasedimentti ja vedessä oleva rautapitoinen kiintoaines. Runsaasti rautaa sisältäviä vesiä laskee Junttiselkään valuma-alueelta. Vuosikymmenien kuormituksen aiheuttamasta monimutkaisesta kokonaisuudesta yksinkertaista ja nopeaa ratkaisua Junttiselän tilan parantamiseksi on vaikeaa löytää. Ulkoisen sulfaatti- ja metallikuormituksen vähentäminen on ensisijainen toimenpide järven kunnostusta suunniteltaessa. Vasta tämän jälkeen toimenpiteitä voidaan kohdentaa tarvittaessa järvialtaaseen. Junttiselän rehevyystilan vähentämisellä parannetaan järven pohjan talviaikaista happitilannetta sekä järven virkistyskäyttöarvoa. Ilman kunnostustoimenpiteitä Junttiselällä esiintyy todennäköisesti tulevaisuudessakin ajoittaisia happamuuspiikkejä. Junttiselän happamoitumista on tutkittu vuosina 2006–2007 Pohjois-Pohjanmaan ympäristökeskuksen, GTK:n Itä- Suomen yksikön sekä Kuopion ja Oulun yliopistojen yhteistyönä. Tässä selvityksessä on koottu yhteen Junttiselän happamuutta koskevien tutkimusten keskeiset tulokset. Tämän pohjalta on esitetty Junttiselän kunnostussuositukset ensisijaisesti happamuuspiikkien poistamiseksi sekä rehevyyden vähentämiseksi.