SEM-based automated mineralogy (SEM-AM) techniques allow fast and effective way of studying the textural settings of gold in hydrothermal deposits. Unsupervised machine learning (e.g. self-organizing maps) is an intuitive way of processing multi-dimensional geochemical datasets in order to reveal hidden patterns potentially represent different mineralization stages. We combined these two methods for studying the relationship of gold and cobalt within different prospects in a Paleoproterozoic gold-cobalt mineralized area known as Rajapalot. Gold is found as a texturally late phase, occurring in fractures of silicates and sulfides. Based on the elemental associations observed from the whole-rock geochemical dataset using self-organizing-maps, Co-only, Au-Co and Au associations can be inferred relating to either different mineralization stages or different fluid-host rock interactions. Also, the dominant mineralization-related alteration in different occurrences within the Rajapalot Au-Co prospects are reflected as elemental associations with gold in the geochemical data. Our study shows the effectiveness SEM-AM methods for studying distribution of valuable minerals. Unsupervised neural networks provide for easy and intuitive processing technique that can be validated with the mineralogical observations.
{"title":"SEM-based automated mineralogy (SEM-AM) and unsupervised machine learning studying the textural setting and elemental association of gold in the Rajapalot Au-Co area, northern Finland","authors":"J. Ranta, N. Cook, S. Gilbricht","doi":"10.17741/bgsf/93.2.003","DOIUrl":"https://doi.org/10.17741/bgsf/93.2.003","url":null,"abstract":"SEM-based automated mineralogy (SEM-AM) techniques allow fast and effective way of studying the textural settings of gold in hydrothermal deposits. Unsupervised machine learning (e.g. self-organizing maps) is an intuitive way of processing multi-dimensional geochemical datasets in order to reveal hidden patterns potentially represent different mineralization stages. We combined these two methods for studying the relationship of gold and cobalt within different prospects in a Paleoproterozoic gold-cobalt mineralized area known as Rajapalot. Gold is found as a texturally late phase, occurring in fractures of silicates and sulfides. Based on the elemental associations observed from the whole-rock geochemical dataset using self-organizing-maps, Co-only, Au-Co and Au associations can be inferred relating to either different mineralization stages or different fluid-host rock interactions. Also, the dominant mineralization-related alteration in different occurrences within the Rajapalot Au-Co prospects are reflected as elemental associations with gold in the geochemical data. Our study shows the effectiveness SEM-AM methods for studying distribution of valuable minerals. Unsupervised neural networks provide for easy and intuitive processing technique that can be validated with the mineralogical observations.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2021-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44085631","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}
P. Hölttä, I. Mänttäri, H. Huhma, M. Kurhila, T. Ruotoistenmäki, A. Kontinen
U–Pb age determinations on zircon from granitoids in the Archean of eastern Finland were conducted using the SIMS, LA-ICP-MS and TIMS techniques, with an emphasis on low-HREE granitoids. The oldest rocks in the Fennoscandian Shield are 3.4–3.5 Ga. Several samples were collected close to these rocks, but none of the samples were as old, indicating that the oldest rocks are only small, possibly allochthonous fragments in the Neoarchean bedrock. Some tonalite–trondhjemite–granodiorite (TTG) samples yielded homogeneous 2.72–2.73 Ga zircon populations, and in these samples, the initial εNd was also close to the depleted mantle (DM) values. However, several granitoid samples with a main zircon population of 2.7–2.8 Ga had 2.9–3.2 Ga grains or inherited cores, and in some samples, all grains were of 2.9–3.0 Ga. In these samples, the εNd value was also close to zero or slightly negative. These features suggest that apart from the juvenile Neoarchean magmas, the abundance of reworked 2.9 Ga material is considerable in the Archean crust, which developed during successive juvenile magmatic inputs that melted and assimilated the older sialic crust. The low- HREE geochemical character of granitoids has no correlation with their age, with the low-HREE granitoids yielding an age span of 2.72–2.98 Ga.
{"title":"Growth of the Archean sialic crust as revealed by zircon in the TTGs in eastern Finland","authors":"P. Hölttä, I. Mänttäri, H. Huhma, M. Kurhila, T. Ruotoistenmäki, A. Kontinen","doi":"10.17741/bgsf/93.2.001","DOIUrl":"https://doi.org/10.17741/bgsf/93.2.001","url":null,"abstract":"U–Pb age determinations on zircon from granitoids in the Archean of eastern Finland were conducted using the SIMS, LA-ICP-MS and TIMS techniques, with an emphasis on low-HREE granitoids. The oldest rocks in the Fennoscandian Shield are 3.4–3.5 Ga. Several samples were collected close to these rocks, but none of the samples were as old, indicating that the oldest rocks are only small, possibly allochthonous fragments in the Neoarchean bedrock. Some tonalite–trondhjemite–granodiorite (TTG) samples yielded homogeneous 2.72–2.73 Ga zircon populations, and in these samples, the initial εNd was also close to the depleted mantle (DM) values. However, several granitoid samples with a main zircon population of 2.7–2.8 Ga had 2.9–3.2 Ga grains or inherited cores, and in some samples, all grains were of 2.9–3.0 Ga. In these samples, the εNd value was also close to zero or slightly negative. These features suggest that apart from the juvenile Neoarchean magmas, the abundance of reworked 2.9 Ga material is considerable in the Archean crust, which developed during successive juvenile magmatic inputs that melted and assimilated the older sialic crust. The low- HREE geochemical character of granitoids has no correlation with their age, with the low-HREE granitoids yielding an age span of 2.72–2.98 Ga.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2021-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48211751","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}
Krister Dalhem, S. Mattbäck, A. Boman, P. Österholm
Speciation of inorganic sulfur species, mainly pyrite and metastable iron sulfides by operationally defined methods, is widely used for risk assessment of acid sulfate soils by quantifying the acidity producing elements, as well as for general characterisation of marine sediments and subaqueous soils. “Traditional” sulfur speciation methods commonly use highly specialised glassware which can be cumbersome for the operator, or, require long reaction times which limit the usability of the method. We present a simplified method which has a sufficiently low limit of detection (0.002%) and quantitation (0.006%) required for the analysis of sulfidic sulfur in acid sulfate soil materials. Commercially available sulfide reagents were used for determining reproducibility and the method was assessed on natural sulfidic soil materials, including fine to coarse grained soil materials as well as sulfide bearing peat, with a large variation of metastable sulfide and pyrite content.
{"title":"A simplified distillation-based sulfur speciation method for sulfidic soil materials","authors":"Krister Dalhem, S. Mattbäck, A. Boman, P. Österholm","doi":"10.17741/BGSF/93.1.002","DOIUrl":"https://doi.org/10.17741/BGSF/93.1.002","url":null,"abstract":"Speciation of inorganic sulfur species, mainly pyrite and metastable iron sulfides by operationally defined methods, is widely used for risk assessment of acid sulfate soils by quantifying the acidity producing elements, as well as for general characterisation of marine sediments and subaqueous soils. “Traditional” sulfur speciation methods commonly use highly specialised glassware which can be cumbersome for the operator, or, require long reaction times which limit the usability of the method. We present a simplified method which has a sufficiently low limit of detection (0.002%) and quantitation (0.006%) required for the analysis of sulfidic sulfur in acid sulfate soil materials. Commercially available sulfide reagents were used for determining reproducibility and the method was assessed on natural sulfidic soil materials, including fine to coarse grained soil materials as well as sulfide bearing peat, with a large variation of metastable sulfide and pyrite content.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"93 1","pages":"19-30"},"PeriodicalIF":0.7,"publicationDate":"2021-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47521432","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}
Earthquake-induced deformations located near Murmansk City were investigated for information on the age, tectonic position and spatial occurrence of paleo-earthquakes. The main earthquake-generating zone is identified to be the system of strike slip faults and reverse-oblique faults trending NNW along the Kola River valley. We used radiocarbon analysis and paleogeographic reconstructions and revealed three episodes of increased seismic activity: from 9500 to 10 500 cal BP, from 892 to 1182 cal BP, and from 200 to 300 cal BP. Based on the peak ground velocity estimation method we suggest that an earthquakes with a maximum moment magnitude up to Mw ≈ 6.0–6.5 may have taken place in the studied area. The recorded location of seismogenic deformation near faults indicates area of strong Late Glacial and Holocene earthquakes occurring in the northern Kola Peninsula; this is also consistent with observations concerning the historical events of 1772 and 1873, which took place near the area. Combined with previous data on palaeoseismicity in Kola region, our studies indicate a longer lasting and more complex spatial and temporal history of postglacial seismicity in the Northeastern Fennoscandian Shield area. In contrast to the generally accepted opinion, strong seismic events occurred not only during the deglaciation period or immediately after it, but continued until the late Holocene and the last centuries. Glacial isostasy as a factor giving rise to stresses has become minimal by the present time, while the tectonic factor continues to be felt.
{"title":"Late Glacial and postglacial seismicity in the Northeastern Fennoscandian Shield: tectonic position and age of paleo-earthquakes near Murmansk","authors":"S. Nikolaeva, M. Rodkin, S. Shvarev","doi":"10.17741/BGSF/93.1.004","DOIUrl":"https://doi.org/10.17741/BGSF/93.1.004","url":null,"abstract":"Earthquake-induced deformations located near Murmansk City were investigated for information on the age, tectonic position and spatial occurrence of paleo-earthquakes. The main earthquake-generating zone is identified to be the system of strike slip faults and reverse-oblique faults trending NNW along the Kola River valley. We used radiocarbon analysis and paleogeographic reconstructions and revealed three episodes of increased seismic activity: from 9500 to 10 500 cal BP, from 892 to 1182 cal BP, and from 200 to 300 cal BP. Based on the peak ground velocity estimation method we suggest that an earthquakes with a maximum moment magnitude up to Mw ≈ 6.0–6.5 may have taken place in the studied area. The recorded location of seismogenic deformation near faults indicates area of strong Late Glacial and Holocene earthquakes occurring in the northern Kola Peninsula; this is also consistent with observations concerning the historical events of 1772 and 1873, which took place near the area. Combined with previous data on palaeoseismicity in Kola region, our studies indicate a longer lasting and more complex spatial and temporal history of postglacial seismicity in the Northeastern Fennoscandian Shield area. In contrast to the generally accepted opinion, strong seismic events occurred not only during the deglaciation period or immediately after it, but continued until the late Holocene and the last centuries. Glacial isostasy as a factor giving rise to stresses has become minimal by the present time, while the tectonic factor continues to be felt.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"93 1","pages":"53-72"},"PeriodicalIF":0.7,"publicationDate":"2021-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43572225","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}
Maarit Saresma, E. Kosonen, A. Ojala, A. Kaskela, L. Korkiala-Tanttu
The capital region of Finland is growing rapidly and into areas with challenging con struction conditions such as deep fine-grained sediments. In the coastal city of Espoo, present land use is mainly focused in the southern and central parts, which were submerged by the Baltic Sea during the early and mid-Holocene. These areas have experienced saline and brackish water phases during the history of the Baltic Sea Basin. The deposition environments of the presently studied onshore areas are an analogue for the present day offshore Baltic Sea sedimentation settings for fine-grained material. The results from Baltic Sea studies have demonstrated that the seabed topography has a significant role in the deposition of sediments and their properties. In this study, paleotopographic models were created for the ancient Baltic Sea Basin in the Espoo area 1) after deglaciation and 2) during the Litorina transgression and classified into bathymetric (terrain) zones and structures. Topographic classification was combined with the water depth of the Litorina stage, the thickness of fine-grained deposits and wind fetch to establish the overall characteristics of sedimentary environments in the coastal area. Fine-grained sediments can be found mainly in depressions that are classified here as broad, narrow or local. The study found the most challenging environments for construction purposes in sheltered narrow depressions that contain thick layers of fine-grained sediments deposited during the Litorina transgression. These are mainly located in the southern and central parts of Espoo. Minor deep canyons were also found in the northern parts of Espoo. This study provides new prior knowledge for urban planning and construction design in Espoo. The methodology could be applied to other Baltic Sea coastal cities and areas with fine-grained sediments.
{"title":"Characterization of sedimentary depositional environments for land use and urban planning in Espoo, Finland","authors":"Maarit Saresma, E. Kosonen, A. Ojala, A. Kaskela, L. Korkiala-Tanttu","doi":"10.17741/BGSF/93.1.003","DOIUrl":"https://doi.org/10.17741/BGSF/93.1.003","url":null,"abstract":"The capital region of Finland is growing rapidly and into areas with challenging con struction conditions such as deep fine-grained sediments. In the coastal city of Espoo, present land use is mainly focused in the southern and central parts, which were submerged by the Baltic Sea during the early and mid-Holocene. These areas have experienced saline and brackish water phases during the history of the Baltic Sea Basin. The deposition environments of the presently studied onshore areas are an analogue for the present day offshore Baltic Sea sedimentation settings for fine-grained material. The results from Baltic Sea studies have demonstrated that the seabed topography has a significant role in the deposition of sediments and their properties. In this study, paleotopographic models were created for the ancient Baltic Sea Basin in the Espoo area 1) after deglaciation and 2) during the Litorina transgression and classified into bathymetric (terrain) zones and structures. Topographic classification was combined with the water depth of the Litorina stage, the thickness of fine-grained deposits and wind fetch to establish the overall characteristics of sedimentary environments in the coastal area. Fine-grained sediments can be found mainly in depressions that are classified here as broad, narrow or local. The study found the most challenging environments for construction purposes in sheltered narrow depressions that contain thick layers of fine-grained sediments deposited during the Litorina transgression. These are mainly located in the southern and central parts of Espoo. Minor deep canyons were also found in the northern parts of Espoo. This study provides new prior knowledge for urban planning and construction design in Espoo. The methodology could be applied to other Baltic Sea coastal cities and areas with fine-grained sediments.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"93 1","pages":"31-51"},"PeriodicalIF":0.7,"publicationDate":"2021-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44660319","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}
Pollen analysis is a commonly used method to interpret vegetation and environmental change. The standard pollen preparation technique in minerogenic sediments involves the use of hydrofluoric acid (HF) which is highly toxic. Currently the European legislation requires that hazardous chemicals should be substituted with less hazardous or nontoxic chemicals if possible. In the present paper the authors introduce a safer pollen preparation method, based on the use of low-toxic heavy liquid lithium hetero polytungstate (LST Fastfloat) and provide instructions for pollen preparation with the LST Fastflow method. Furthermore, five paired samples were processed from clayey and silty sediments with LST Fastfloat and conventional HF methods and the pollen and spore counting results obtained from these two methods were compared to test if there is statistically significant differences between the taxa. Calculation of the 95 % confidence interval revealed statistical agreement in all studied taxa except one taxon in one sample pair. However, the study revealed systematic differences within two taxa, Betula and Pinus. Thus caution is needed when comparing results obtained by HF and heavy liquid (LST Fastfloat) methods.
{"title":"Comparison between modified LST Fastfloat and conventional HF methods for pollen preparation in highly minerogenic sediments","authors":"Tiina Eskola, Riitta Kontio, J. Lunkka","doi":"10.17741/BGSF/93.1.001","DOIUrl":"https://doi.org/10.17741/BGSF/93.1.001","url":null,"abstract":"Pollen analysis is a commonly used method to interpret vegetation and environmental change. The standard pollen preparation technique in minerogenic sediments involves the use of hydrofluoric acid (HF) which is highly toxic. Currently the European legislation requires that hazardous chemicals should be substituted with less hazardous or nontoxic chemicals if possible. In the present paper the authors introduce a safer pollen preparation method, based on the use of low-toxic heavy liquid lithium hetero polytungstate (LST Fastfloat) and provide instructions for pollen preparation with the LST Fastflow method. Furthermore, five paired samples were processed from clayey and silty sediments with LST Fastfloat and conventional HF methods and the pollen and spore counting results obtained from these two methods were compared to test if there is statistically significant differences between the taxa. Calculation of the 95 % confidence interval revealed statistical agreement in all studied taxa except one taxon in one sample pair. However, the study revealed systematic differences within two taxa, Betula and Pinus. Thus caution is needed when comparing results obtained by HF and heavy liquid (LST Fastfloat) methods.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"93 1","pages":"5-18"},"PeriodicalIF":0.7,"publicationDate":"2021-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43823565","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}
J. Ranta, E. Hanski, H. Stein, Matthew Goode, T. Mäki, Atte Taivalkoski, Ballinteer Dublin D Hk Ireland Ballinteer Park, Tampere Finland Näsilinnankatu D
The Kivilompolo molybdenite occurrence is located in the northern part of the Perä poh ja belt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The mineralization occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.
Kivilompolo辉钼矿产状位于Peräpoh ja带的北部，在岩性Ylitornio推覆杂岩内。它位于造山前1.99 Ga Kierovaara岩套的变形斑状花岗岩中。矿化主要以粗粒辉钼矿薄片的形式出现在粗石英脉中，含少量黄铜矿、黄铁矿、磁铁矿和钛铁矿。在本研究中，我们报道了来自主岩花岗岩的新的地球化学数据和来自矿化的辉钼矿的Re-Os定年结果。就全岩地球化学而言，矿化花岗岩与先前研究中分析的Kierovaara套花岗岩相似。此外，辉钼矿的约2.0 Ga-Re-Os年龄在误差范围内等于Kierovaara套花岗岩的U-Pb锆石年龄。此外，据报道，位于Kivilompolo东北30公里处的Rompas Rajapalot Au Co矿点的辉钼矿和铀矿年龄相似。我们提出，大约2.0 Ga前的岩浆作用启动了热液循环，这是Kivilompolo辉钼矿矿化和与Rompas Rajapalot Au Co产状相关的原生铀矿化的原因，或者至少，岩浆提供了加热，此外，冷却岩浆热液系统。
{"title":"Kivilompolo Mo mineralization in the Peräpohja belt revisited: Trace element geochemistry and Re-Os dating of molybdenite","authors":"J. Ranta, E. Hanski, H. Stein, Matthew Goode, T. Mäki, Atte Taivalkoski, Ballinteer Dublin D Hk Ireland Ballinteer Park, Tampere Finland Näsilinnankatu D","doi":"10.17741/bgsf/92.2.004","DOIUrl":"https://doi.org/10.17741/bgsf/92.2.004","url":null,"abstract":"The Kivilompolo molybdenite occurrence is located in the northern part of the Perä poh ja belt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The mineralization occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"92 1","pages":"131-150"},"PeriodicalIF":0.7,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42421730","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}
This study examines the effect of poly-aluminium chloride (PACl) pre-treatment on the biological purification process taking place during managed aquifer recharge (MAR). PACl treatment is used in waste and surface water treatment to remove organic material. PACl can decrease the organic carbon contents of water significantly. However, aluminium is toxic to microbes, which may be detrimental when the PACl treatment is followed by infiltration into an aquifer (MAR). In this study the effect of pre-treatment with PACl on the water purification process in MAR was examined, by using sediment from a MAR site in four test columns. Two columns were filled with PACl-treated water, and the remaining ones with river water without PACl. The residence time of water in the columns was raised from direct sampling gradually to 64 days. Among the parameters monitored were the pH of the water, microbial activity and the decomposition of dissolved organic carbon (DOC). The results showed active decomposition in all columns. Decomposition of organic matter, and the amount of living/active microbial cells, was marginally higher in the untreated water, which could imply a better functioning MAR system. However, this may also be due to higher DOC starting concentration.
{"title":"The effect of water pre-treatment with poly-aluminiumchloride on the decomposition of dissolved organic matter in managed aquifer recharge","authors":"Paula Niinikoski-Fusswinkel, L. Purkamo, J. Karhu","doi":"10.17741/bgsf/92.2.002","DOIUrl":"https://doi.org/10.17741/bgsf/92.2.002","url":null,"abstract":"This study examines the effect of poly-aluminium chloride (PACl) pre-treatment on the biological purification process taking place during managed aquifer recharge (MAR). PACl treatment is used in waste and surface water treatment to remove organic material. PACl can decrease the organic carbon contents of water significantly. However, aluminium is toxic to microbes, which may be detrimental when the PACl treatment is followed by infiltration into an aquifer (MAR). In this study the effect of pre-treatment with PACl on the water purification process in MAR was examined, by using sediment from a MAR site in four test columns. Two columns were filled with PACl-treated water, and the remaining ones with river water without PACl. The residence time of water in the columns was raised from direct sampling gradually to 64 days. Among the parameters monitored were the pH of the water, microbial activity and the decomposition of dissolved organic carbon (DOC). The results showed active decomposition in all columns. Decomposition of organic matter, and the amount of living/active microbial cells, was marginally higher in the untreated water, which could imply a better functioning MAR system. However, this may also be due to higher DOC starting concentration.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"92 1","pages":"99-110"},"PeriodicalIF":0.7,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46847392","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}
Several Ni-Cu deposits occur within the Kotalahti area, central Finland, in proximity to an Archaean gneiss dome surrounded by a Palaeoproterozoic craton-margin supracrustal sequence comprising quartzites, limestones, calc-silicate rocks, black schists and banded diopside amphibolites. The geology of the area and age of the Ni-bearing intrusions (1.88 Ga) are similar to the Thompson Ni belt in the Canadian Trans-Hudson Orogen. The small mafic-ultramafic and Ni-Cu -bearing Särkiniemi intrusion, closely associated with the Archaean basement core of the Kotalahti Dome, is composed of a western peridotite and eastern gabbro body, both of which are mineralized. The eastern gabbro has a contact aureole several meters thick, consisting of orthopyroxene +/- cordierite bearing hornfels between the intrusion and the migmatites. Geochemically, the Särkiniemi intrusion shares many features in common with other Svecofennian mafic-ultramafic intrusions, including crustal contamination and nickel depletion. The related Ni-Cu deposit has a low Ni/Co value (15) and low nickel content in the sulphide fraction (2.8 wt.%), together with a low estimated magma/sulphide ratio of around 170. Svecofennian 1.88 Ga mafic-ultramafic intrusions occur in terrains of variable metamorphic grade (from low-amphibolite to granulite facies) and are likely to represent emplacement at different crustal depths. Multi-equilibrium thermobarometry indicates that the contact aureole at Särkiniemi reached equilibrium at pressures of 4.5–6 kbar (15–20 km depth) and temperatures of 600–670 °C. Combined with the results of earlier research on the Svecofennian intrusions, this study indicates that a depth of 15–20 km crustal level was favourable, along with other critical factors, for nickel sulfide deposition at 1.88 Ga.
{"title":"Geology and crystallization conditions of the Särkiniemiintrusion and related nickel-copper ore, central Finland – implications for depth of emplacement of 1.88 Ga nickel-bearing intrusions","authors":"H. Makkonen, P. Tuisku","doi":"10.17741/bgsf/92.2.003","DOIUrl":"https://doi.org/10.17741/bgsf/92.2.003","url":null,"abstract":"Several Ni-Cu deposits occur within the Kotalahti area, central Finland, in proximity to an Archaean gneiss dome surrounded by a Palaeoproterozoic craton-margin supracrustal sequence comprising quartzites, limestones, calc-silicate rocks, black schists and banded diopside amphibolites. The geology of the area and age of the Ni-bearing intrusions (1.88 Ga) are similar to the Thompson Ni belt in the Canadian Trans-Hudson Orogen. The small mafic-ultramafic and Ni-Cu -bearing Särkiniemi intrusion, closely associated with the Archaean basement core of the Kotalahti Dome, is composed of a western peridotite and eastern gabbro body, both of which are mineralized. The eastern gabbro has a contact aureole several meters thick, consisting of orthopyroxene +/- cordierite bearing hornfels between the intrusion and the migmatites. Geochemically, the Särkiniemi intrusion shares many features in common with other Svecofennian mafic-ultramafic intrusions, including crustal contamination and nickel depletion. The related Ni-Cu deposit has a low Ni/Co value (15) and low nickel content in the sulphide fraction (2.8 wt.%), together with a low estimated magma/sulphide ratio of around 170. Svecofennian 1.88 Ga mafic-ultramafic intrusions occur in terrains of variable metamorphic grade (from low-amphibolite to granulite facies) and are likely to represent emplacement at different crustal depths. Multi-equilibrium thermobarometry indicates that the contact aureole at Särkiniemi reached equilibrium at pressures of 4.5–6 kbar (15–20 km depth) and temperatures of 600–670 °C. Combined with the results of earlier research on the Svecofennian intrusions, this study indicates that a depth of 15–20 km crustal level was favourable, along with other critical factors, for nickel sulfide deposition at 1.88 Ga.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43696967","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. Åberg, S. Kultti, A. Kaakinen, K. Eskola, V. Salonen
Three different till units separated by interstadial fluvial deposits were observed in the Sodankylä area in the River Kitinen valley, northern Finland. The interbedded glaciofluvial sediments and palaeosol were dated by OSL to the Early (79±12 to 67±13 ka) and Middle (41±9 ka) Weichselian. A LiDAR DEM, glacial lineations, the flow direction of till fabrics, esker chains and striations were applied to investigate the glacial flow patterns of the Sodankylä, Kittilä and Salla areas. The analysis revealed that the youngest movement of the Scandinavian Ice Sheet is not visible as DEM lineations within the studied areas. The modern morphology in Kittilä and Salla shows streamlined landforms of various dimensions mainly oriented from the NW and NNW, respectively, corresponding to the Early/Middle Weichselian ice-flow directions inferred from till fabrics. The Late Weichselian ice flow has produced an insignificant imprint on the landforms. This study suggests a northern location for the ice-divide zone during the Early/Middle Weichselian, and a more western–southwestern position during the Late Weichselian. The OSL ages of 14±3.3 ka from the aeolian deposits may indicate ice-free areas during the Bølling–Allerod warm period in the vicinity of the River Kitinen.
{"title":"Weichselian sedimentary record and ice-flow patterns in the Sodankylä area, central Finnish Lapland","authors":"A. Åberg, S. Kultti, A. Kaakinen, K. Eskola, V. Salonen","doi":"10.17741/bgsf/92.2.001","DOIUrl":"https://doi.org/10.17741/bgsf/92.2.001","url":null,"abstract":"Three different till units separated by interstadial fluvial deposits were observed in the Sodankylä area in the River Kitinen valley, northern Finland. The interbedded glaciofluvial sediments and palaeosol were dated by OSL to the Early (79±12 to 67±13 ka) and Middle (41±9 ka) Weichselian. A LiDAR DEM, glacial lineations, the flow direction of till fabrics, esker chains and striations were applied to investigate the glacial flow patterns of the Sodankylä, Kittilä and Salla areas. The analysis revealed that the youngest movement of the Scandinavian Ice Sheet is not visible as DEM lineations within the studied areas. The modern morphology in Kittilä and Salla shows streamlined landforms of various dimensions mainly oriented from the NW and NNW, respectively, corresponding to the Early/Middle Weichselian ice-flow directions inferred from till fabrics. The Late Weichselian ice flow has produced an insignificant imprint on the landforms. This study suggests a northern location for the ice-divide zone during the Early/Middle Weichselian, and a more western–southwestern position during the Late Weichselian. The OSL ages of 14±3.3 ka from the aeolian deposits may indicate ice-free areas during the Bølling–Allerod warm period in the vicinity of the River Kitinen.","PeriodicalId":55302,"journal":{"name":"Bulletin of the Geological Society of Finland","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49645827","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}
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