Johanna Tepsell, T. Rämö, A. Heinonen, Y. Lahaye, Pieti Haapala, T. Halkoaho, J. Heinonen, Henri Höytiä, J. Konnunaho, V. Järvinen
Archean terranes are generally poorly exposed and structurally complicated, making models of geological evolution difficult to establish. Because of pervasive metamorphism, strong deformation, and poorly exposed bedrock, the stratigraphy, geochronology, and geological evolution of the northeastern part of the Archean Western Karelia Subprovince, Finnish Lapland, is still deficient. Three new U-Pb age determinations were made using the LA-ICP-MS method on zircon in search of more profound understanding of the geochronology of the area. Data from the Pultoselkä granite yield an age of 2795±5 Ma, providing a minimum age of 2.8 Ga for the Tulppio suite. The age is coeval with widespread 2.74–2.70 Ga granitoids of the Karelia Province, likely representing the same magmatic event. The data from the Kontioselkä pegmatite define a maximum age for the pegmatite and a minimum age for mafic volcanic rocks in Kontioselkä at 1781±27 Ma. The age coincides with major deformation and metamorphism in the Karelia Province around 1.76 Ga. Zircon from the Jänesselkä mafic-ultramafic complex yields a minimum age of 2425±17 Ma, complying rather well with the 2.5–2.4 Ga mafic layered intrusions of the northern Fennoscandian Shield. Our new data show that the Archean of the northeastern part of the Western Karelia Subprovince was affected by Proterozoic thermal events more extensively than thus far perceived.
{"title":"Some new insights into the geochronology of the Western Karelia Subprovince, Finnish Lapland","authors":"Johanna Tepsell, T. Rämö, A. Heinonen, Y. Lahaye, Pieti Haapala, T. Halkoaho, J. Heinonen, Henri Höytiä, J. Konnunaho, V. Järvinen","doi":"10.17741/bgsf/92.1.001","DOIUrl":"https://doi.org/10.17741/bgsf/92.1.001","url":null,"abstract":"Archean terranes are generally poorly exposed and structurally complicated, making models of geological evolution difficult to establish. Because of pervasive metamorphism, strong deformation, and poorly exposed bedrock, the stratigraphy, geochronology, and geological evolution of the northeastern part of the Archean Western Karelia Subprovince, Finnish Lapland, is still deficient. Three new U-Pb age determinations were made using the LA-ICP-MS method on zircon in search of more profound understanding of the geochronology of the area. Data from the Pultoselkä granite yield an age of 2795±5 Ma, providing a minimum age of 2.8 Ga for the Tulppio suite. The age is coeval with widespread 2.74–2.70 Ga granitoids of the Karelia Province, likely representing the same magmatic event. The data from the Kontioselkä pegmatite define a maximum age for the pegmatite and a minimum age for mafic volcanic rocks in Kontioselkä at 1781±27 Ma. The age coincides with major deformation and metamorphism in the Karelia Province around 1.76 Ga. Zircon from the Jänesselkä mafic-ultramafic complex yields a minimum age of 2425±17 Ma, complying rather well with the 2.5–2.4 Ga mafic layered intrusions of the northern Fennoscandian Shield. Our new data show that the Archean of the northeastern part of the Western Karelia Subprovince was affected by Proterozoic thermal events more extensively than thus far perceived.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48150474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Mäkitie, H. O’Brien, O. Selonen, M. Kurhila, Turku Finland Mineralogy
{"title":"The 1.79 Ga Särkilahti leucogranite – a horizontal magma layer below granulite-grade migmatites in SE Finland","authors":"H. Mäkitie, H. O’Brien, O. Selonen, M. Kurhila, Turku Finland Mineralogy","doi":"10.17741/bgsf/91.2.003","DOIUrl":"https://doi.org/10.17741/bgsf/91.2.003","url":null,"abstract":"","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45865340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Hanski, H. Huhma, Y. Lahaye, J. Lunkka, E. Nilsson, T. Mäki, H. O’Brien, K. Strand, Mountain View Usa Atle Arctica
{"title":"Zn-Pb-Cu sulfide-bearing glacial sandstone erratics near Raahe on the western coast of Finland: Indicators of Paleozoic base metal mineralization at the bottom of the Bothnian Bay","authors":"E. Hanski, H. Huhma, Y. Lahaye, J. Lunkka, E. Nilsson, T. Mäki, H. O’Brien, K. Strand, Mountain View Usa Atle Arctica","doi":"10.17741/bgsf/91.2.001","DOIUrl":"https://doi.org/10.17741/bgsf/91.2.001","url":null,"abstract":"","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46519425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Ojala, M. Saarnisto, H. Jungner, I. Snowball, R. Muscheler
We present here radiocarbon dating results from two boreal lakes in Finland, which are permanently (meromictic) or seasonally stratified and contain continuous sequences of annually laminated sedim ...
{"title":"Biases in radiocarbon dating of organic fractions in sediments from meromictic and seasonally hypoxic lakes","authors":"A. Ojala, M. Saarnisto, H. Jungner, I. Snowball, R. Muscheler","doi":"10.17741/bgsf/91.2.004","DOIUrl":"https://doi.org/10.17741/bgsf/91.2.004","url":null,"abstract":"We present here radiocarbon dating results from two boreal lakes in Finland, which are permanently (meromictic) or seasonally stratified and contain continuous sequences of annually laminated sedim ...","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42056360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Glaciofluvial ice-contact deltas were mapped and altitudes of the highest shorelines defined in the eastern arc of the Salpausselkä zone, southern Finland, using Light Detection and Ranging (LiDAR)-based digital elevation models and GIS tools. Mapping of deltas and the highest shorelines in the Salpausselkä zone were undertaken in order to calculate and define the glacio-isostatic uplift palaeo-isobases, uplift gradients and equidistant diagrams (distance diagrams) for the Salpausselkä zone. The results indicate that the glacio-isostatic uplift palaeo-isobases were orientated NE-SW (50°–230°) and the uplift gradients for both the First and the Second Salpausselkä in the eastern arc, are virtually the same, namely 0.6 mkm-1. This suggests that both Salpausselkä ridge complexes, which were originally laid down in front of the Finnish Lake District Ice Lobe (FLDIL) in relatively shallow water, were deposited within a short time period during the Late Weichselian Younger Dryas Stadial. The results also suggest that the Baltic Ice Lake water level regressed 7.5 metres from Baltic Ice Lake level B I to level B III as the ice retreated in its eastern arc from the First to the Second Salpausselkä.
{"title":"Baltic Ice Lake levels and a LiDAR/DEM-based estimate of the glacio-isostatic uplift gradient of the Salpausselkä zone, SE Finland","authors":"J. Lunkka, T. Nikarmaa, N. Putkinen","doi":"10.17741/BGSF/91.1.005","DOIUrl":"https://doi.org/10.17741/BGSF/91.1.005","url":null,"abstract":"Glaciofluvial ice-contact deltas were mapped and altitudes of the highest shorelines defined in the eastern arc of the Salpausselkä zone, southern Finland, using Light Detection and Ranging (LiDAR)-based digital elevation models and GIS tools. Mapping of deltas and the highest shorelines in the Salpausselkä zone were undertaken in order to calculate and define the glacio-isostatic uplift palaeo-isobases, uplift gradients and equidistant diagrams (distance diagrams) for the Salpausselkä zone. The results indicate that the glacio-isostatic uplift palaeo-isobases were orientated NE-SW (50°–230°) and the uplift gradients for both the First and the Second Salpausselkä in the eastern arc, are virtually the same, namely 0.6 mkm-1. This suggests that both Salpausselkä ridge complexes, which were originally laid down in front of the Finnish Lake District Ice Lobe (FLDIL) in relatively shallow water, were deposited within a short time period during the Late Weichselian Younger Dryas Stadial. The results also suggest that the Baltic Ice Lake water level regressed 7.5 metres from Baltic Ice Lake level B I to level B III as the ice retreated in its eastern arc from the First to the Second Salpausselkä.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45474246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Huhta, P. Tuisku, T. Balić-Žunić, A. Kärki, Kivitieto Oy
The Finnish soapstone industry has found through practical experience that the surface of the magnesite soapstone used in fire chambers and funnels hardens over time. We have studied a magnesite soapstone used in a fireplace continuously for 60 years. The mineralogical changes, that took place during heating and subsequent cooling of the fireplace have been investigated with electron probe microanalyzer and X-ray diffractometer to find an explanation, what kind of reactions caused the hardening. We found that ferromagnesite has been altered to pseudomorphic aggregates composed of ferropericlase and magnesioferrite in the nearest ~30 mm from the surface exposed to fire. Iron has been mobilized in the uppermost 3 mm, enriched in the rims, and depleted from the cores of the ferropericlase aggregates. Magnesioferrite occurs preferably in the fire chamber side of the aggregates in the uppermost 0.20 mm. Talc rims are altered to forsterite and/or enstatite in the reaction with ferromagnesite or its alteration products in the uppermost ~1 mm. In addition, wood combustion gases caused considerable enrichment of zinc and potassium in the chamber surface rock to the depth on 0.20 mm and 3 mm, respectively. The enrichment occurred by crystallization of Zn bearing ferropericlase and magnesioferrite and by crystallization of K bearing sheet silicates.
{"title":"Magnesite soapstone in use of fire chamber constructions: composition and structure adaptation","authors":"A. Huhta, P. Tuisku, T. Balić-Žunić, A. Kärki, Kivitieto Oy","doi":"10.17741/BGSF/91.1.004","DOIUrl":"https://doi.org/10.17741/BGSF/91.1.004","url":null,"abstract":"The Finnish soapstone industry has found through practical experience that the surface of the magnesite soapstone used in fire chambers and funnels hardens over time. We have studied a magnesite soapstone used in a fireplace continuously for 60 years. The mineralogical changes, that took place during heating and subsequent cooling of the fireplace have been investigated with electron probe microanalyzer and X-ray diffractometer to find an explanation, what kind of reactions caused the hardening. We found that ferromagnesite has been altered to pseudomorphic aggregates composed of ferropericlase and magnesioferrite in the nearest ~30 mm from the surface exposed to fire. Iron has been mobilized in the uppermost 3 mm, enriched in the rims, and depleted from the cores of the ferropericlase aggregates. Magnesioferrite occurs preferably in the fire chamber side of the aggregates in the uppermost 0.20 mm. Talc rims are altered to forsterite and/or enstatite in the reaction with ferromagnesite or its alteration products in the uppermost ~1 mm. In addition, wood combustion gases caused considerable enrichment of zinc and potassium in the chamber surface rock to the depth on 0.20 mm and 3 mm, respectively. The enrichment occurred by crystallization of Zn bearing ferropericlase and magnesioferrite and by crystallization of K bearing sheet silicates.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41364504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The 2.05 Ga Otanmäki suite represents a globally rare occurrence of Paleoproterozoic non-orogenic A1-type magmatism. It consists of a broad variety of A-type felsic and intermediate igneous rocks including monzodiorites, monzonites, syenites and peralkaline to peraluminous granites, containing both plutonic and subvolcanic members. The suite has chemical characteristics similar to those of A1-type suites formed in intraplate hotspots or continental rifts by differentiation of variably crustally contaminated, mafic mantle-derived magmas. However, compared to the Otanmäki rocks, most A1-type suites are considerably younger. original geologic because the suite deformed metamorphosed under amphibolite facies C, kbar) orogeny i.e., initial emplacement. result, Otanmäki pervasively foliated rocks within two nappe units sandwiched between Archean granitoid gneiss of 1950 Ma ocean-continent-transition ophiolitic rocks in the same thrust belt and the proximity of the Otanmäki suite to the Karelia-Svecofennia margin suggest that the suite records an early stage of a slow, ca. 100-Ma-long extension-rifting process which, at ca. 1950 Ma, eventually led to the final break-up of the Karelia craton and formation of the nascent ocean basin witnessed by the Jormua ophiolite complex.
2.05 Ga Otanmäki套代表了全球罕见的古元古代非造山a1型岩浆活动。它由种类繁多的a型长英质和中间火成岩组成，包括二长岩、二长岩、正长岩和过碱性至过铝质花岗岩，包括深成岩和次火山岩。该套具有类似于a1型套的化学特征，这些a1型套形成于板块内热点或大陆裂谷，是由受不同地壳污染的基性幔源岩浆分异形成的。然而，与Otanmäki岩石相比，大多数a1型套相当年轻。原始地质由于套体变形变质，在角闪岩相C、kbar造山作用下形成，即初始侵位。结果，夹在同一冲断带上的1950 Ma洋陆过渡蛇绿岩之间的两个推覆体单元内的Otanmäki普遍片理岩石，以及Otanmäki套件与Karelia-Svecofennia边缘的接近表明，该套件记录了一个大约100 Ma长的缓慢伸展-裂陷过程的早期阶段，该过程大约在1950 Ma左右。最终导致了卡累利阿克拉通的最终分裂，形成了由Jormua蛇绿岩复合体见证的新生海洋盆地。
{"title":"Geology, geochronology and geochemistry of the 2.05 Ga gneissic A1-type granites and related intermediate rocks in central Finland: implication for the tectonic evolution of the Karelia craton margin","authors":"K. Kärenlampi, A. Kontinen, H. Huhma, E. Hanski","doi":"10.17741/BGSF/91.1.002","DOIUrl":"https://doi.org/10.17741/BGSF/91.1.002","url":null,"abstract":"The 2.05 Ga Otanmäki suite represents a globally rare occurrence of Paleoproterozoic non-orogenic A1-type magmatism. It consists of a broad variety of A-type felsic and intermediate igneous rocks including monzodiorites, monzonites, syenites and peralkaline to peraluminous granites, containing both plutonic and subvolcanic members. The suite has chemical characteristics similar to those of A1-type suites formed in intraplate hotspots or continental rifts by differentiation of variably crustally contaminated, mafic mantle-derived magmas. However, compared to the Otanmäki rocks, most A1-type suites are considerably younger. original geologic because the suite deformed metamorphosed under amphibolite facies C, kbar) orogeny i.e., initial emplacement. result, Otanmäki pervasively foliated rocks within two nappe units sandwiched between Archean granitoid gneiss of 1950 Ma ocean-continent-transition ophiolitic rocks in the same thrust belt and the proximity of the Otanmäki suite to the Karelia-Svecofennia margin suggest that the suite records an early stage of a slow, ca. 100-Ma-long extension-rifting process which, at ca. 1950 Ma, eventually led to the final break-up of the Karelia craton and formation of the nascent ocean basin witnessed by the Jormua ophiolite complex.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41754264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The 1.64 Ga Ahvenisto complex, southeastern Finland, is an anorthosite-mangeritecharnokite-granite (AMCG) suite in which diverse interaction styles of coeval mafic and felsic magmas are observed. Commingling, resulting in mafic pillows and net-veined granite dykes, and chemical mixing producing hybrid rocks, are the most common interaction types. Detailed description of the factors that controlled the interaction styles and relationships between involved rock types are provided using targeted mapping, petrography, and geochemical analyses complemented by chemical mixing and melt viscosity modeling. Interaction occurred at intermediate stages in the magmatic evolution of the complex: when the last fractions of mafic (monzodioritic) melts and the earliest fractions of felsic (hornblende granitic) melts existed simultaneously. Differentiation of mafic magma has produced three monzodioritic rock types: 1) olivine monzodiorite (most mafic, Mg# 49–40), 2) ferrodiorite (Mg# 42–33), and 3) massive monzodiorite (most evolved, Mg# 28–27). The types form an evolutionary trend, and each exhibits different style of interaction with coeval hbl-granite resulting from contrasting conditions and properties (temperature, viscosity, composition). The variation in these properties due to magma evolution and relative proportions of interacting magmas dictated the interaction style: interaction between olivine monzodiorites and granite was almost negligible; ferrodiorites intermingled forming pillows with granitic veins intruding them; and chemical mixing of massive monzodiorite and hbl-granite produced hybrid rocks.
芬兰东南部的1.64 Ga Ahvenisto杂岩是一个斜长岩-镁铁质-长英质花岗岩（AMCG）岩套，其中观察到同时代镁铁质和长英质岩浆的不同相互作用样式。混合作用是最常见的相互作用类型，产生镁铁质枕和网状脉花岗岩脉，以及化学混合产生混合岩石。通过有针对性的绘图、岩石学和地球化学分析以及化学混合和熔体粘度建模，对控制相互作用风格和相关岩石类型之间关系的因素进行了详细描述。相互作用发生在杂岩岩浆演化的中间阶段：镁铁质（二闪长质）熔体的最后部分和长英质（角闪花岗岩）熔体的最早部分同时存在。镁铁质岩浆的分化产生了三种二长闪长岩类型：1）橄榄石二长闪岩（大部分镁铁质，Mg#49-40），2）铁闪长岩（Mg#42-33），3）块状二长闪岩体（大部分演化，Mg#28-27）。这些类型形成了一种进化趋势，由于不同的条件和性质（温度、粘度、成分），每种类型都表现出与同时代hbl花岗岩不同的相互作用风格。由于岩浆演化和相互作用岩浆的相对比例，这些性质的变化决定了相互作用的风格：橄榄石二长闪长岩和花岗岩之间的相互作用几乎可以忽略不计；铁闪长岩混杂在一起形成枕状物，花岗岩脉侵入其中；块状二长闪长岩和hbl花岗岩的化学混合产生了混合岩。
{"title":"Tracing the styles of mafic-felsic magma interaction: A case study from the Ahvenisto igneous complex, Finland","authors":"Riikka Fred, A. Heinonen, Pasi Heikkilä","doi":"10.17741/BGSF/91.1.001","DOIUrl":"https://doi.org/10.17741/BGSF/91.1.001","url":null,"abstract":"The 1.64 Ga Ahvenisto complex, southeastern Finland, is an anorthosite-mangeritecharnokite-granite (AMCG) suite in which diverse interaction styles of coeval mafic and felsic magmas are observed. Commingling, resulting in mafic pillows and net-veined granite dykes, and chemical mixing producing hybrid rocks, are the most common interaction types. Detailed description of the factors that controlled the interaction styles and relationships between involved rock types are provided using targeted mapping, petrography, and geochemical analyses complemented by chemical mixing and melt viscosity modeling. Interaction occurred at intermediate stages in the magmatic evolution of the complex: when the last fractions of mafic (monzodioritic) melts and the earliest fractions of felsic (hornblende granitic) melts existed simultaneously. Differentiation of mafic magma has produced three monzodioritic rock types: 1) olivine monzodiorite (most mafic, Mg# 49–40), 2) ferrodiorite (Mg# 42–33), and 3) massive monzodiorite (most evolved, Mg# 28–27). The types form an evolutionary trend, and each exhibits different style of interaction with coeval hbl-granite resulting from contrasting conditions and properties (temperature, viscosity, composition). The variation in these properties due to magma evolution and relative proportions of interacting magmas dictated the interaction style: interaction between olivine monzodiorites and granite was almost negligible; ferrodiorites intermingled forming pillows with granitic veins intruding them; and chemical mixing of massive monzodiorite and hbl-granite produced hybrid rocks.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41925578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Ylitornio area in northern Finland is a typical example of a poorly outcropping, multiply deformed, complex Precambrian terrain. U–Pb, Sm-Nd and geochemical data from metavolcanic, metasedimentary and plutonic rocks combined with structural data define the lithodemic units and tectonostratigraphy of the area. The Mellajoki, Martimo, Hosiojoki, Kierovaara and Uusivirka suites form the Ylitornio nappe complex. Although main thrust stacking had occurred between 1.92– 1.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Väystäjä bimodal volcanic rocks (2.09–2.05 Ga) from the Martimo suite are plume-related EMORB-OIB rocks formed during a continent breakup. The Kaskimaa greywacke of the Martimo suite is inferred to represent sedimentation in a deepening rift basin in the continental margin. The coeval Hosiojoki felsic rocks with A-type affinity and the Kierovaara suite granites (2.00–1.98 Ga) represent dry melting of a dominantly 2.1–2.05 Ga contaminated mafic underplate, and hydrous melting of both the mafic underplate and a refractory lower crust of Archean age, respectively. The older rocks of the Uusivirka suite are early-collisional (1.92–1.91 Ga) and derived from poorly mixed local sources, whereas younger psammite-pelite associations (Ristivuoma) are syn-collisional (1.91– 1.89 Ga) and derive from multiply recycled and thoroughly mixed sources. These rocks were deformed during continued collision with the development of foreland foldand
{"title":"Geochemical and U-Pb and Sm-Nd isotopic constraints on the evolution of the Paleoproterozoic Ylitornio nappe complex, northern Fennoscandia","authors":"R. Lahtinen, H. Huhma, L. Lauri, M. Sayab","doi":"10.17741/BGSF/91.1.003","DOIUrl":"https://doi.org/10.17741/BGSF/91.1.003","url":null,"abstract":"The Ylitornio area in northern Finland is a typical example of a poorly outcropping, multiply deformed, complex Precambrian terrain. U–Pb, Sm-Nd and geochemical data from metavolcanic, metasedimentary and plutonic rocks combined with structural data define the lithodemic units and tectonostratigraphy of the area. The Mellajoki, Martimo, Hosiojoki, Kierovaara and Uusivirka suites form the Ylitornio nappe complex. Although main thrust stacking had occurred between 1.92– 1.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Väystäjä bimodal volcanic rocks (2.09–2.05 Ga) from the Martimo suite are plume-related EMORB-OIB rocks formed during a continent breakup. The Kaskimaa greywacke of the Martimo suite is inferred to represent sedimentation in a deepening rift basin in the continental margin. The coeval Hosiojoki felsic rocks with A-type affinity and the Kierovaara suite granites (2.00–1.98 Ga) represent dry melting of a dominantly 2.1–2.05 Ga contaminated mafic underplate, and hydrous melting of both the mafic underplate and a refractory lower crust of Archean age, respectively. The older rocks of the Uusivirka suite are early-collisional (1.92–1.91 Ga) and derived from poorly mixed local sources, whereas younger psammite-pelite associations (Ristivuoma) are syn-collisional (1.91– 1.89 Ga) and derive from multiply recycled and thoroughly mixed sources. These rocks were deformed during continued collision with the development of foreland foldand","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2019-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49001368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Joanna Rychel, B. Woronko, M. Błaszkiewicz, T. Karasiewicz
Formation of dunes in the Płock Basin of the Vistula River valley in Central Poland is connected with the aeolian processes that occurred within the European Sand Belt during the Late Pleistocene. Changes in sedimentation conditions, from fluvial (unit G1), to fluvio–aeolian (unit G2) then to aeolian (unit G3), were respectively recorded in the fluvioglacial terrace sand dune profiles in the village of Goreń Duży (the Płock Basin, Central Poland). Both fluvial and aeolian processes occurred in the periglacial zone of the last glaciation, the northern limit of which is defined by the Last Glacial Maximum (LGM), being 18.4 ka in the Płock Basin. River and ice-marginal valley terrace sand sediments, in association with glacial deposits, could be the source material for the studied aeolian bedforms. The results of morphoscopic analysis of dunal sand quartz grains indicate that rapid deposition occurred more often than did long-term longrange grain transport. Grain transport genesis begins during the Older Dryas, which is confirmed by optically stimulated luminescence (OSL) dating performed for unit G2: 13.06±0.76 ka and 13.54±0.84 ka. During dune formation, dead-ice blocks remained intact in a subglacial channel until the Allerød, which suggests that aeolian processes continued after block melting, throughout the Younger Dryas. Successional aeolian processes have resulted in the extensive dune fields of the Płock Basin.
{"title":"Aeolian processes records within last glacial limit are as based on the Płock Basin case (Central Poland)","authors":"Joanna Rychel, B. Woronko, M. Błaszkiewicz, T. Karasiewicz","doi":"10.17741/BGSF/90.2.007","DOIUrl":"https://doi.org/10.17741/BGSF/90.2.007","url":null,"abstract":"Formation of dunes in the Płock Basin of the Vistula River valley in Central Poland is connected with the aeolian processes that occurred within the European Sand Belt during the Late Pleistocene. Changes in sedimentation conditions, from fluvial (unit G1), to fluvio–aeolian (unit G2) then to aeolian (unit G3), were respectively recorded in the fluvioglacial terrace sand dune profiles in the village of Goreń Duży (the Płock Basin, Central Poland). Both fluvial and aeolian processes occurred in the periglacial zone of the last glaciation, the northern limit of which is defined by the Last Glacial Maximum (LGM), being 18.4 ka in the Płock Basin. River and ice-marginal valley terrace sand sediments, in association with glacial deposits, could be the source material for the studied aeolian bedforms. The results of morphoscopic analysis of dunal sand quartz grains indicate that rapid deposition occurred more often than did long-term longrange grain transport. Grain transport genesis begins during the Older Dryas, which is confirmed by optically stimulated luminescence (OSL) dating performed for unit G2: 13.06±0.76 ka and 13.54±0.84 ka. During dune formation, dead-ice blocks remained intact in a subglacial channel until the Allerød, which suggests that aeolian processes continued after block melting, throughout the Younger Dryas. Successional aeolian processes have resulted in the extensive dune fields of the Płock Basin.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42922240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：