Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä
Five granulite xenoliths entrained in the ~600 Ma Lahtojoki kimberlite pipe in eastern Finland represent the lower crust below the suture zone between the Archaean Karelian craton and the Paleoproterozoic Svecofennian terranes. They provide direct information on the petrology of the lower cratonic c...
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Helsingfors universitet
2015
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Online Access: | http://hdl.handle.net/10138/154269 |
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/154269 2023-08-20T04:07:42+02:00 Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä Järvinen, Ville Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta, Geotieteiden ja maantieteen laitos University of Helsinki, Faculty of Science, Department of Geosciences and Geography Helsingfors universitet, Matematisk-naturvetenskapliga fakulteten, Institutionen för geovetenskaper och geografi 2015 application/pdf http://hdl.handle.net/10138/154269 fin fin Helsingfors universitet University of Helsinki Helsingin yliopisto URN:NBN:fi-fe2017112251548 http://hdl.handle.net/10138/154269 Geology Geologia Geologi pro gradu-avhandlingar pro gradu -tutkielmat master's thesis 2015 ftunivhelsihelda 2023-07-28T06:31:14Z Five granulite xenoliths entrained in the ~600 Ma Lahtojoki kimberlite pipe in eastern Finland represent the lower crust below the suture zone between the Archaean Karelian craton and the Paleoproterozoic Svecofennian terranes. They provide direct information on the petrology of the lower cratonic crust, and the processes that controlled its evolution. Studied xenoliths comprise a dry intermediate garnet granulite, three mafic garnet granulites with amphibole contents ranging from 3–50 vol–%, and a peraluminous micaceous garnet gneiss. Granulites have granoblastic fabrics with mineral assemblage Grt – Cpx – Plg ± Amb ± Qtz ± Ilm ± Rt ± Bt, with pink garnet and green clinopyroxene. Gneiss is coarse grained with a heavily deformed and strained fabric with mineral assemblage Qzt – Bt – Grt – Sil. Mineral chemistry based TWEEQU–thermobarometry indicates equilibration of mafic granulites at ca. 800 °C and 9.5–10.5 kbar and intermediate granulite at ca 800 °C and 17.5 kbar. The pressure estimates correspond to crustal depths of 38–55 km. Equilibration temperature for garnet gneiss is ca. 700 °C – TWEEQU based pressure estimate was not possible, but based on Grt–Sil stability equilibration pressure can be constrained to ca. 4–8.5 kbar. Mineral zonation indicates slight post peak cooling and decompression of some samples. Whole-rock geochemical composition (major and trace elements) implies derivation of dry (<10 vol–% Amb) mafic granulite from a Ni-Cr fractionated basaltic melt. Enrichment in LREE and other trace elements suggests a low to moderate degree of melting of a primitive mantle source. The sample could represent a mafic underplate crystallized in situ. Amphibole and enrichment in K and Rb could indicate a later metasomatic enrichment event. The intermediate granulite is anomalous in composition compared to other Kaavi-Kuopio lower crustal xenoliths. REE composition, depletion in K, Rb, Zr, Hf, Nb, Ta, and strong enrichment in Sr and a prominent positive Eu anomaly imply that the sample represents a ... Master Thesis karelia* karelian Helsingfors Universitet: HELDA – Helsingin yliopiston digitaalinen arkisto |
institution |
Open Polar |
collection |
Helsingfors Universitet: HELDA – Helsingin yliopiston digitaalinen arkisto |
op_collection_id |
ftunivhelsihelda |
language |
Finnish |
topic |
Geology Geologia Geologi |
spellingShingle |
Geology Geologia Geologi Järvinen, Ville Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
topic_facet |
Geology Geologia Geologi |
description |
Five granulite xenoliths entrained in the ~600 Ma Lahtojoki kimberlite pipe in eastern Finland represent the lower crust below the suture zone between the Archaean Karelian craton and the Paleoproterozoic Svecofennian terranes. They provide direct information on the petrology of the lower cratonic crust, and the processes that controlled its evolution. Studied xenoliths comprise a dry intermediate garnet granulite, three mafic garnet granulites with amphibole contents ranging from 3–50 vol–%, and a peraluminous micaceous garnet gneiss. Granulites have granoblastic fabrics with mineral assemblage Grt – Cpx – Plg ± Amb ± Qtz ± Ilm ± Rt ± Bt, with pink garnet and green clinopyroxene. Gneiss is coarse grained with a heavily deformed and strained fabric with mineral assemblage Qzt – Bt – Grt – Sil. Mineral chemistry based TWEEQU–thermobarometry indicates equilibration of mafic granulites at ca. 800 °C and 9.5–10.5 kbar and intermediate granulite at ca 800 °C and 17.5 kbar. The pressure estimates correspond to crustal depths of 38–55 km. Equilibration temperature for garnet gneiss is ca. 700 °C – TWEEQU based pressure estimate was not possible, but based on Grt–Sil stability equilibration pressure can be constrained to ca. 4–8.5 kbar. Mineral zonation indicates slight post peak cooling and decompression of some samples. Whole-rock geochemical composition (major and trace elements) implies derivation of dry (<10 vol–% Amb) mafic granulite from a Ni-Cr fractionated basaltic melt. Enrichment in LREE and other trace elements suggests a low to moderate degree of melting of a primitive mantle source. The sample could represent a mafic underplate crystallized in situ. Amphibole and enrichment in K and Rb could indicate a later metasomatic enrichment event. The intermediate granulite is anomalous in composition compared to other Kaavi-Kuopio lower crustal xenoliths. REE composition, depletion in K, Rb, Zr, Hf, Nb, Ta, and strong enrichment in Sr and a prominent positive Eu anomaly imply that the sample represents a ... |
author2 |
Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta, Geotieteiden ja maantieteen laitos University of Helsinki, Faculty of Science, Department of Geosciences and Geography Helsingfors universitet, Matematisk-naturvetenskapliga fakulteten, Institutionen för geovetenskaper och geografi |
format |
Master Thesis |
author |
Järvinen, Ville |
author_facet |
Järvinen, Ville |
author_sort |
Järvinen, Ville |
title |
Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
title_short |
Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
title_full |
Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
title_fullStr |
Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
title_full_unstemmed |
Alakuoren ksenoliitit Kaavi-Kuopio-alueen Lahtojoen kimberliitissä |
title_sort |
alakuoren ksenoliitit kaavi-kuopio-alueen lahtojoen kimberliitissä |
publisher |
Helsingfors universitet |
publishDate |
2015 |
url |
http://hdl.handle.net/10138/154269 |
genre |
karelia* karelian |
genre_facet |
karelia* karelian |
op_relation |
URN:NBN:fi-fe2017112251548 http://hdl.handle.net/10138/154269 |
_version_ |
1774719523356672000 |