Pub Date : 2017-01-01DOI: 10.1080/09853111.2017.1359773
K. S. Kavak, O. Parlak, Haluk Temiz
Abstract Number of dismembered ophiolite bodies crop out between Sivas and Malatya on the top of the Eastern Tauride platform in the central-eastern Turkey. One of which at the southern margin of the Sivas basin in the Tecer Mountain area comprises melange and the lower part of an oceanic lithospheric section on top of the Tauride platform. The mantle tectonites are characterized by variably serpentinized harzburgites and dunites, and are intruded by numerous isolated dykes. The gabbroic cumulates consist of olivine gabbro, gabbro and gabbronorite. The major and trace element geochemistry of the mafic cumulate rocks suggests that the primary magma was compositionally similar to those observed in modern island-arc tholeiitic sequences. The isolated dykes are exclusively basaltic in composition and display geochemically two distinct subgroups: Group I is represented by high TiO2 (.87–1.47 wt.%) and other incompatible elements, whereas Group II is characterized by low TiO2 (.36–.66 wt.%) and other incompatible elements. The Group I isolated diabase dykes have flat to slightly LREE-depleted profiles (La/YbN = .32–.79), whereas the Group II isolated diabase dykes are more depleted in general and have a LREE-depleted character (La/YbN = .19–.49). This suggests that the isolated dykes were derived from an island arc tholeiitic magma (Nb/Y = .02–.05) with different degrees of partial melting (Group II > Group I) and relatively high oxygen fugacity in intra-oceanic subduction zone. The ophiolitic rocks in the study area may well be compared with the Divriği ophiolite to the southeast. All the evidence suggests that the isolated dykes in the Tecer Mountain area differ from the alkaline isolated dykes cutting the Divriği ophiolite. Since the late stage dykes (~76 Ma) in the Divriği area are alkaline, the tholeiitic isolated dykes in the present study should have been emplaced prior to the alkaline dykes during Late Cretaceous SSZ-spreading (~90 Ma) within the Inner Tauride Ocean.
{"title":"Geochemical characteristics of ophiolitic rocks from the southern margin of the Sivas basin and their implications for the Inner Tauride Ocean, Central-Eastern Turkey","authors":"K. S. Kavak, O. Parlak, Haluk Temiz","doi":"10.1080/09853111.2017.1359773","DOIUrl":"https://doi.org/10.1080/09853111.2017.1359773","url":null,"abstract":"Abstract Number of dismembered ophiolite bodies crop out between Sivas and Malatya on the top of the Eastern Tauride platform in the central-eastern Turkey. One of which at the southern margin of the Sivas basin in the Tecer Mountain area comprises melange and the lower part of an oceanic lithospheric section on top of the Tauride platform. The mantle tectonites are characterized by variably serpentinized harzburgites and dunites, and are intruded by numerous isolated dykes. The gabbroic cumulates consist of olivine gabbro, gabbro and gabbronorite. The major and trace element geochemistry of the mafic cumulate rocks suggests that the primary magma was compositionally similar to those observed in modern island-arc tholeiitic sequences. The isolated dykes are exclusively basaltic in composition and display geochemically two distinct subgroups: Group I is represented by high TiO2 (.87–1.47 wt.%) and other incompatible elements, whereas Group II is characterized by low TiO2 (.36–.66 wt.%) and other incompatible elements. The Group I isolated diabase dykes have flat to slightly LREE-depleted profiles (La/YbN = .32–.79), whereas the Group II isolated diabase dykes are more depleted in general and have a LREE-depleted character (La/YbN = .19–.49). This suggests that the isolated dykes were derived from an island arc tholeiitic magma (Nb/Y = .02–.05) with different degrees of partial melting (Group II > Group I) and relatively high oxygen fugacity in intra-oceanic subduction zone. The ophiolitic rocks in the study area may well be compared with the Divriği ophiolite to the southeast. All the evidence suggests that the isolated dykes in the Tecer Mountain area differ from the alkaline isolated dykes cutting the Divriği ophiolite. Since the late stage dykes (~76 Ma) in the Divriği area are alkaline, the tholeiitic isolated dykes in the present study should have been emplaced prior to the alkaline dykes during Late Cretaceous SSZ-spreading (~90 Ma) within the Inner Tauride Ocean.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"29 1","pages":"160 - 180"},"PeriodicalIF":1.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2017.1359773","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42228795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/09853111.2017.1294013
A. Kürçer, V. Özaksoy, S. Özalp, Ç. U. Güldoǧan, E. Özdemir, T. Duman
The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.
{"title":"The Manyas fault zone (southern Marmara region, NW Turkey): active tectonics and paleoseismology","authors":"A. Kürçer, V. Özaksoy, S. Özalp, Ç. U. Güldoǧan, E. Özdemir, T. Duman","doi":"10.1080/09853111.2017.1294013","DOIUrl":"https://doi.org/10.1080/09853111.2017.1294013","url":null,"abstract":"The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"29 1","pages":"42 - 61"},"PeriodicalIF":1.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2017.1294013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42753417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-20DOI: 10.1080/09853111.2016.1208525
Alican Kop, Selim Özalp, Hasan Elmacı, Meryem Kara, T. Duman
The Mustafakemalpaşa Fault (MF), located among Manyas, Ulubat and Orhaneli faults, is a right lateral strike-slip and 47 km in length. The MF begins with a pressure ridge at the west and exhibits complex jog terminations at east ends in restraining left stepovers. The western section of the fault bounds Miocene and Quaternary units and continues towards İlyasçılar. The central segment of the fault, starts with approximately 750-m leftward stepover, exhibits a sinusoidal geometry between Kapaklıoluk and Kabulbaba. In this section, MF traverses mountainous terrain and cuts Ophiolite, Jurassic limestones and Miocene detritals, forming dextral faulting features and gaining reverse component. The eastern section exhibits left stepping en-echelon pattern and consists 2.5-km offset on the Orhaneli River. In this study, palaeoseismological findings related to the Holocene activity and active tectonic properties of the MF are presented. The trenches exposed mismatched stratigraphy, demonstrating evidence of events across the fault. We identified three events (before BC 2190, later AD 1425 and 1850) that have occurred during the past 4000 years. We suggest a long non-characteristic recurrence interval and ~0.7 mm/y slip-rate for MF, based on trench data and offset of the Late Pliocene drainage of Orhaneli River.
{"title":"Active tectonic and palaeoseismological features of the western section of Mustafakemalpaşa Fault; Bursa, NW Anatolia","authors":"Alican Kop, Selim Özalp, Hasan Elmacı, Meryem Kara, T. Duman","doi":"10.1080/09853111.2016.1208525","DOIUrl":"https://doi.org/10.1080/09853111.2016.1208525","url":null,"abstract":"The Mustafakemalpaşa Fault (MF), located among Manyas, Ulubat and Orhaneli faults, is a right lateral strike-slip and 47 km in length. The MF begins with a pressure ridge at the west and exhibits complex jog terminations at east ends in restraining left stepovers. The western section of the fault bounds Miocene and Quaternary units and continues towards İlyasçılar. The central segment of the fault, starts with approximately 750-m leftward stepover, exhibits a sinusoidal geometry between Kapaklıoluk and Kabulbaba. In this section, MF traverses mountainous terrain and cuts Ophiolite, Jurassic limestones and Miocene detritals, forming dextral faulting features and gaining reverse component. The eastern section exhibits left stepping en-echelon pattern and consists 2.5-km offset on the Orhaneli River. In this study, palaeoseismological findings related to the Holocene activity and active tectonic properties of the MF are presented. The trenches exposed mismatched stratigraphy, demonstrating evidence of events across the fault. We identified three events (before BC 2190, later AD 1425 and 1850) that have occurred during the past 4000 years. We suggest a long non-characteristic recurrence interval and ~0.7 mm/y slip-rate for MF, based on trench data and offset of the Late Pliocene drainage of Orhaneli River.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"363 - 378"},"PeriodicalIF":1.5,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2016.1208525","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59555734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-18DOI: 10.1080/09853111.2016.1208526
Emre Aydınçakır
Mineral chemistry, major and trace elements, 40Ar/39Ar age and Sr–Nd–Pb isotopic data are presented for the Late Cretaceous Hamsilos volcanic rocks in the Central Pontides, Turkey. The Hamsilos volcanic rocks mainly consist of basalt, andesite and associated pyroclastics (volcanic breccia, vitric tuff and crystal tuff). They display shoshonitic and high-K calc-alkaline affinities. The shoshonitic rocks contain plagioclase, clinopyroxene, alkali feldspar, phlogopite, analcime, sanidine, olivine, apatite and titanomagnetite, whereas the high-K calc-alkaline rocks contain plagioclase, clinopyroxene, orthopyroxene, magnetite / titanomagnetite in microgranular porphyritic, hyalo-microlitic porphyritic and glomeroporphyritic matrix. Mineral chemistry data reveal that the pressure condition of the clinopyroxene crystallisation for the shoshonitic rocks are between 1.4 and 6.3 kbar corresponds to 6–18-km depth and the high-K calc-alkaline rocks are between 5 and 12 km. 40Ar/39Ar age data changing between 72 ± .5 Ma and 79.0 ± .3 Ma (Campanian) were determined for the Late Cretaceous Hamsilos volcanic rocks, contemporaneous with the subduction of the Neo-Tethyan Ocean beneath the Pontides. The studied volcanic rocks were enriched in the large-ion lithophile and light rare earth element contents, with pronounced depletion in the contents of high-field-strength elements. Chondrite-normalised rare earth element patterns (LaN/LuN = 6–17) show low to medium enrichment, indicating similar sources of the rock suite. Initial 87Sr/86Sr values vary between .70615 and .70796, whereas initial 143Nd/144Nd values change between .51228 and .51249. Initial 206Pb/204Pb values vary between 18.001 and 18.349, 207Pb/204Pb values between 15.611 and 15.629 and 208Pb/204Pb values between 37.839 and 38.427. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallisation, with minor amounts of crustal contamination ± magma mixing. According to geochemical evidence, the shoshonitic melts in the Hamsilos volcanic rocks were possibly derived from the low degree of partial melting of a subcontinental lithospheric mantle (SCLM), while the high-K calc-alkaline melts were derived from relatively high degree of partial melting of SCLM that was enriched by fluids and/or sediments from a subduction of oceanic crust.
{"title":"Subduction-related Late Cretaceous high-K volcanism in the Central Pontides orogenic belt: constraints on geodynamic implications","authors":"Emre Aydınçakır","doi":"10.1080/09853111.2016.1208526","DOIUrl":"https://doi.org/10.1080/09853111.2016.1208526","url":null,"abstract":"Mineral chemistry, major and trace elements, 40Ar/39Ar age and Sr–Nd–Pb isotopic data are presented for the Late Cretaceous Hamsilos volcanic rocks in the Central Pontides, Turkey. The Hamsilos volcanic rocks mainly consist of basalt, andesite and associated pyroclastics (volcanic breccia, vitric tuff and crystal tuff). They display shoshonitic and high-K calc-alkaline affinities. The shoshonitic rocks contain plagioclase, clinopyroxene, alkali feldspar, phlogopite, analcime, sanidine, olivine, apatite and titanomagnetite, whereas the high-K calc-alkaline rocks contain plagioclase, clinopyroxene, orthopyroxene, magnetite / titanomagnetite in microgranular porphyritic, hyalo-microlitic porphyritic and glomeroporphyritic matrix. Mineral chemistry data reveal that the pressure condition of the clinopyroxene crystallisation for the shoshonitic rocks are between 1.4 and 6.3 kbar corresponds to 6–18-km depth and the high-K calc-alkaline rocks are between 5 and 12 km. 40Ar/39Ar age data changing between 72 ± .5 Ma and 79.0 ± .3 Ma (Campanian) were determined for the Late Cretaceous Hamsilos volcanic rocks, contemporaneous with the subduction of the Neo-Tethyan Ocean beneath the Pontides. The studied volcanic rocks were enriched in the large-ion lithophile and light rare earth element contents, with pronounced depletion in the contents of high-field-strength elements. Chondrite-normalised rare earth element patterns (LaN/LuN = 6–17) show low to medium enrichment, indicating similar sources of the rock suite. Initial 87Sr/86Sr values vary between .70615 and .70796, whereas initial 143Nd/144Nd values change between .51228 and .51249. Initial 206Pb/204Pb values vary between 18.001 and 18.349, 207Pb/204Pb values between 15.611 and 15.629 and 208Pb/204Pb values between 37.839 and 38.427. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallisation, with minor amounts of crustal contamination ± magma mixing. According to geochemical evidence, the shoshonitic melts in the Hamsilos volcanic rocks were possibly derived from the low degree of partial melting of a subcontinental lithospheric mantle (SCLM), while the high-K calc-alkaline melts were derived from relatively high degree of partial melting of SCLM that was enriched by fluids and/or sediments from a subduction of oceanic crust.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"379 - 411"},"PeriodicalIF":1.5,"publicationDate":"2016-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2016.1208526","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59555633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-14DOI: 10.1080/09853111.2016.1208524
Selim Özalp, A. Kürçer, E. Özdemir, T. Duman
The Bekten Fault is 20-km long N55°E trending and oblique-slip fault in the dextral strike-slip fault zone. The fault is extending sub-parallel between Yenice-Gönen and Sarıköy faults, which forms the southern branch of North Anatolian Fault Zone in Southern Marmara Region. Tectonomorphological structures indicative of the recent fault displacements such as elongated ridges and offset creeks observed along the fault. In this study, we investigated palaeoseismic activities of the Bekten Fault by trenching surveys, which were carried out over a topographic saddle. The trench exposed the fault and the trench stratigraphy revealed repeated earthquake surface rupture events which resulted in displacements of late Pleistocene and Holocene deposits. According to radiocarbon ages obtained from samples taken from the event horizons in the stratigraphy, it was determined that at least three earthquakes resulting in surface rupture generated from the Bekten Fault within last ~1300 years. Based on the palaeoseismological data, the Bekten Fault displays non-characteristic earthquake behaviour and has not produced any earthquake associated with surface rupture for about the last 400 years. Additionally, the data will provide information for the role of small fault segments play except for the major structures in strike-slip fault systems.
{"title":"The Bekten Fault: the palaeoseismic behaviour and kinematic characteristics of an intervening segment of the North Anatolian Fault Zone, Southern Marmara Region, Turkey","authors":"Selim Özalp, A. Kürçer, E. Özdemir, T. Duman","doi":"10.1080/09853111.2016.1208524","DOIUrl":"https://doi.org/10.1080/09853111.2016.1208524","url":null,"abstract":"The Bekten Fault is 20-km long N55°E trending and oblique-slip fault in the dextral strike-slip fault zone. The fault is extending sub-parallel between Yenice-Gönen and Sarıköy faults, which forms the southern branch of North Anatolian Fault Zone in Southern Marmara Region. Tectonomorphological structures indicative of the recent fault displacements such as elongated ridges and offset creeks observed along the fault. In this study, we investigated palaeoseismic activities of the Bekten Fault by trenching surveys, which were carried out over a topographic saddle. The trench exposed the fault and the trench stratigraphy revealed repeated earthquake surface rupture events which resulted in displacements of late Pleistocene and Holocene deposits. According to radiocarbon ages obtained from samples taken from the event horizons in the stratigraphy, it was determined that at least three earthquakes resulting in surface rupture generated from the Bekten Fault within last ~1300 years. Based on the palaeoseismological data, the Bekten Fault displays non-characteristic earthquake behaviour and has not produced any earthquake associated with surface rupture for about the last 400 years. Additionally, the data will provide information for the role of small fault segments play except for the major structures in strike-slip fault systems.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"347 - 362"},"PeriodicalIF":1.5,"publicationDate":"2016-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2016.1208524","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59555376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-02DOI: 10.1080/09853111.2015.1047195
J. Turowski, J. Bloem
Fluvial bedrock erosion rates due to impacting sediment particles are thought to be proportional to the energy delivered to the bedrock. When sediment particles cover the bed, they reduce the energy transmitted to the bed by an impacting particle. We measured the decline of energy transferred through sediment cover of increasing thickness in laboratory experiments. The energy arriving at the bed is a function both of the cover thickness and the grain size of the covering sediment. Using a simple stochastic model of cover distribution, the experimental results were upscaled to the reach scale. Although cover thickness influences energy delivery heavily at a given point, when averaging over the whole bed, cover-free areas dominate total energy delivery, making partial energy transfer through the cover negligible when a small or intermediate fraction of the bed is covered by sediment. Partial energy delivery through the bed cover is not negligible when a large fraction or the complete bed is already covered, but in this situation, an erosion threshold may become important. On grounds of the presented data, we expect that the areal distribution of sediment in a bedrock channel dominates total energy delivery and that partial energy delivery to the bed through a sediment layer can be neglected for most modelling purposes.
{"title":"The influence of sediment thickness on energy delivery to the bed by bedload impacts","authors":"J. Turowski, J. Bloem","doi":"10.1080/09853111.2015.1047195","DOIUrl":"https://doi.org/10.1080/09853111.2015.1047195","url":null,"abstract":"Fluvial bedrock erosion rates due to impacting sediment particles are thought to be proportional to the energy delivered to the bedrock. When sediment particles cover the bed, they reduce the energy transmitted to the bed by an impacting particle. We measured the decline of energy transferred through sediment cover of increasing thickness in laboratory experiments. The energy arriving at the bed is a function both of the cover thickness and the grain size of the covering sediment. Using a simple stochastic model of cover distribution, the experimental results were upscaled to the reach scale. Although cover thickness influences energy delivery heavily at a given point, when averaging over the whole bed, cover-free areas dominate total energy delivery, making partial energy transfer through the cover negligible when a small or intermediate fraction of the bed is covered by sediment. Partial energy delivery through the bed cover is not negligible when a large fraction or the complete bed is already covered, but in this situation, an erosion threshold may become important. On grounds of the presented data, we expect that the areal distribution of sediment in a bedrock channel dominates total energy delivery and that partial energy delivery to the bed through a sediment layer can be neglected for most modelling purposes.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"199 - 208"},"PeriodicalIF":1.5,"publicationDate":"2016-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2015.1047195","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59554317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-02DOI: 10.1080/09853111.2015.1113024
Youjun Zhang, T. Kusky, Lu Wang, Jian-wei Li, P. Feng, Y. Huang, R. Giddens
The Taupo Volcanic Zone (TVZ) on the North Island of New Zealand is located above the subducting Pacific slab and hosts hydrothermal systems related to subduction, arc magmatism and crustal extension. In these systems, gold is transported primarily as sulphide complexes, with gold being deposited in response to boiling and mixing of the deep geothermal fluids. Conglomerate cobbles and hydrothermal fumaroles from the upper Retaruke River in the western TVZ are mineralised deposits that have been eroded from the nearby Miocene alluvial sedimentary plateau. Abundant gold-bearing pyrite was precipitated in the conglomerates and fumaroles by late hydrothermal process, primarily occurring as veinlets, disseminations and fine-grained aggregates which consists discrete euhedral microcrystals. Scanning electron microscopy combined with X-ray energy disperses spectroscopy shows that pyrites are commendably affected by late hydrothermal fluids, possibly by the carbonate fluid. Electron probe microanalysis revealed that the pyrite contains 20–120 ppm Au (averaging 60 ppm). Wavelength dispersive spectral elemental mapping suggests that gold is distributed uniformly in pyrite, indicating structurally bound gold (solid solution) in pyrite. Gold mineralisation recognised in the conglomerates and fumaroles demonstrates that the upper Retaruke River is a promising target for future gold exploration.
{"title":"Occurrence of gold in hydrothermal pyrite, western Taupo Volcanic Zone, New Zealand","authors":"Youjun Zhang, T. Kusky, Lu Wang, Jian-wei Li, P. Feng, Y. Huang, R. Giddens","doi":"10.1080/09853111.2015.1113024","DOIUrl":"https://doi.org/10.1080/09853111.2015.1113024","url":null,"abstract":"The Taupo Volcanic Zone (TVZ) on the North Island of New Zealand is located above the subducting Pacific slab and hosts hydrothermal systems related to subduction, arc magmatism and crustal extension. In these systems, gold is transported primarily as sulphide complexes, with gold being deposited in response to boiling and mixing of the deep geothermal fluids. Conglomerate cobbles and hydrothermal fumaroles from the upper Retaruke River in the western TVZ are mineralised deposits that have been eroded from the nearby Miocene alluvial sedimentary plateau. Abundant gold-bearing pyrite was precipitated in the conglomerates and fumaroles by late hydrothermal process, primarily occurring as veinlets, disseminations and fine-grained aggregates which consists discrete euhedral microcrystals. Scanning electron microscopy combined with X-ray energy disperses spectroscopy shows that pyrites are commendably affected by late hydrothermal fluids, possibly by the carbonate fluid. Electron probe microanalysis revealed that the pyrite contains 20–120 ppm Au (averaging 60 ppm). Wavelength dispersive spectral elemental mapping suggests that gold is distributed uniformly in pyrite, indicating structurally bound gold (solid solution) in pyrite. Gold mineralisation recognised in the conglomerates and fumaroles demonstrates that the upper Retaruke River is a promising target for future gold exploration.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"185 - 198"},"PeriodicalIF":1.5,"publicationDate":"2016-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2015.1113024","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59554878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-02DOI: 10.1080/09853111.2015.1065308
U. Tarı, O. Tüysüz
North-western Anatolia has been actively deformed since Pliocene by the right-lateral North Anatolian Fault (NAF). This transform fault, which has a transtensional character in its western end due to effects from the Aegean extensional system, is a major control on the regional geomorphologic evolution. This study applied some geomorphic analyses, such as stream longitudinal profiles, stream length-gradient index, ratio of valley floor width and valley height, mountain front sinuosity, hypsometry and asymmetry factor analyses, to an area just east of the Sea of Marmara in order to understand the tectonic effects on the area’s geomorphological evolution. The active and fastest northern branch of the NAF lies within a topographic depression connecting Sea of Marmara in the east to the Adapazarı Basin in the west. This depression filled with early Pleistocene and younger sediment after a series of pull-apart basins opened along the NAF. North of this depression lies the Kocaeli Peneplain, whose southern edge the NAF uplifted. Meandering streams on the central peneplain were incised possibly due to baselevel changes in the Black Sea. South of the depression, an E-trending mountainous area has a rugged morphology. Based on geomorphic analyses, uplifted Pliocene sediment, marine terraces, and recent earthquake activity, this area between northern and southern branches of the NAF is actively uplifting. The geomorphic indices used in this study are sensitive to vertical movements rather than lateral ones. The bedrock lithology that played an important role on the area’s geomorphologic evolution also affects the geomorphic indices used here.
{"title":"The effects of the North Anatolian Fault on the geomorphology in the Eastern Marmara Region, Northwestern Turkey","authors":"U. Tarı, O. Tüysüz","doi":"10.1080/09853111.2015.1065308","DOIUrl":"https://doi.org/10.1080/09853111.2015.1065308","url":null,"abstract":"North-western Anatolia has been actively deformed since Pliocene by the right-lateral North Anatolian Fault (NAF). This transform fault, which has a transtensional character in its western end due to effects from the Aegean extensional system, is a major control on the regional geomorphologic evolution. This study applied some geomorphic analyses, such as stream longitudinal profiles, stream length-gradient index, ratio of valley floor width and valley height, mountain front sinuosity, hypsometry and asymmetry factor analyses, to an area just east of the Sea of Marmara in order to understand the tectonic effects on the area’s geomorphological evolution. The active and fastest northern branch of the NAF lies within a topographic depression connecting Sea of Marmara in the east to the Adapazarı Basin in the west. This depression filled with early Pleistocene and younger sediment after a series of pull-apart basins opened along the NAF. North of this depression lies the Kocaeli Peneplain, whose southern edge the NAF uplifted. Meandering streams on the central peneplain were incised possibly due to baselevel changes in the Black Sea. South of the depression, an E-trending mountainous area has a rugged morphology. Based on geomorphic analyses, uplifted Pliocene sediment, marine terraces, and recent earthquake activity, this area between northern and southern branches of the NAF is actively uplifting. The geomorphic indices used in this study are sensitive to vertical movements rather than lateral ones. The bedrock lithology that played an important role on the area’s geomorphologic evolution also affects the geomorphic indices used here.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"139 - 159"},"PeriodicalIF":1.5,"publicationDate":"2016-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2015.1065308","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59554016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-02DOI: 10.1080/09853111.2015.1107437
E. Özcan, I. Abbasi, K. Drobne, A. Govindan, L. Jovane, K. Boukhalfa
The upper member of the Jafnayn Formation in Wadi Rusayl and Al Khoud, Seeb Area in north Oman contains Nemkovella stockari Less & Özcan, 2007, an Early Eocene orthophragminid recorded here for the first time from the Arabian Peninsula. N. stockari, the only orthophragminid identified in Jafnayn Formation, is quite distinct from any other species from Tethys in having spiral and orbitoidiform chambers around the isolepidine embryon developed before the onset of annular chambers. The Oman specimens exhibit equal-sized principal auxiliary chambers and symmetrical spirals and are assigned to N. stockari bejaensis Özcan, Boukhalfa & Scheibner, 2014, an advanced form of the N. stockari lineage. The associated alveolinids, revised in this study, rotaliids and other age-diagnostic foraminiferal taxa in the transgressive basal part of the upper member have enabled us to revise the age as middle Ilerdian (Early Eocene), assignable to SBZ 7/8 and 8; OZ 3/4. Integrating a new record of this species from Arabian Plate margin in Belen, S Turkey, and previous records from north Africa, N. stockari appears to be a diagnostic marker for the Early Eocene along the southern peri-Tethys platforms, facilitating the Tethyan correlation by orthophragminids. The palaeobiogeographic distribution of N. stockari is discussed.
{"title":"Early Eocene orthophragminids and alveolinids from the Jafnayn Formation, N Oman: significance of Nemkovella stockari Less & Özcan, 2007 in Tethys","authors":"E. Özcan, I. Abbasi, K. Drobne, A. Govindan, L. Jovane, K. Boukhalfa","doi":"10.1080/09853111.2015.1107437","DOIUrl":"https://doi.org/10.1080/09853111.2015.1107437","url":null,"abstract":"The upper member of the Jafnayn Formation in Wadi Rusayl and Al Khoud, Seeb Area in north Oman contains Nemkovella stockari Less & Özcan, 2007, an Early Eocene orthophragminid recorded here for the first time from the Arabian Peninsula. N. stockari, the only orthophragminid identified in Jafnayn Formation, is quite distinct from any other species from Tethys in having spiral and orbitoidiform chambers around the isolepidine embryon developed before the onset of annular chambers. The Oman specimens exhibit equal-sized principal auxiliary chambers and symmetrical spirals and are assigned to N. stockari bejaensis Özcan, Boukhalfa & Scheibner, 2014, an advanced form of the N. stockari lineage. The associated alveolinids, revised in this study, rotaliids and other age-diagnostic foraminiferal taxa in the transgressive basal part of the upper member have enabled us to revise the age as middle Ilerdian (Early Eocene), assignable to SBZ 7/8 and 8; OZ 3/4. Integrating a new record of this species from Arabian Plate margin in Belen, S Turkey, and previous records from north Africa, N. stockari appears to be a diagnostic marker for the Early Eocene along the southern peri-Tethys platforms, facilitating the Tethyan correlation by orthophragminids. The palaeobiogeographic distribution of N. stockari is discussed.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"160 - 184"},"PeriodicalIF":1.5,"publicationDate":"2016-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2015.1107437","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59554661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-13DOI: 10.1080/09853111.2016.1183445
S. Okay, S. Aydemir
Detailed reviews of multichannel seismic reflection, sparker, chirp and multibeam data that were collected on the southern Marmara Sea shelf revealed various shallow gas indicators and related sedimentary structures, including enhanced reflections, seismic chimneys, acoustic blanking, bright spots, pockmarks, mound-like features and seeps. Seismic attribute analyses were applied to characterise the existence of gas-bearing sediments. The distribution of shallow gas indicators provides important insights into their origin and the geological factors that control them. Prominent gas accumulations and seeps are observed along the profiles that cross the branches of the central segment of the North Anatolian Fault Zone, which indicates that the gas seeps are controlled by active faulting. This indicates that the faults act as conduits through the sedimentary column. The dense occurrences of gas directly off the river mouths along the shallow bays provide clues about the organic-rich carbon content of the sediments and biogenic methane generation. In some areas, the gas-related acoustic anomalies are mostly located in the upper sediments below the marine unit, which indicates that the gas emissions in these areas were terminated as a result of the increased overburden pressure after the Holocene sea level rise and the deposition of the marine unit.
{"title":"Control of active faults and sea level changes on the distribution of shallow gas accumulations and gas-related seismic structures along the central branch of the North Anatolian Fault, southern Marmara shelf, Turkey","authors":"S. Okay, S. Aydemir","doi":"10.1080/09853111.2016.1183445","DOIUrl":"https://doi.org/10.1080/09853111.2016.1183445","url":null,"abstract":"Detailed reviews of multichannel seismic reflection, sparker, chirp and multibeam data that were collected on the southern Marmara Sea shelf revealed various shallow gas indicators and related sedimentary structures, including enhanced reflections, seismic chimneys, acoustic blanking, bright spots, pockmarks, mound-like features and seeps. Seismic attribute analyses were applied to characterise the existence of gas-bearing sediments. The distribution of shallow gas indicators provides important insights into their origin and the geological factors that control them. Prominent gas accumulations and seeps are observed along the profiles that cross the branches of the central segment of the North Anatolian Fault Zone, which indicates that the gas seeps are controlled by active faulting. This indicates that the faults act as conduits through the sedimentary column. The dense occurrences of gas directly off the river mouths along the shallow bays provide clues about the organic-rich carbon content of the sediments and biogenic methane generation. In some areas, the gas-related acoustic anomalies are mostly located in the upper sediments below the marine unit, which indicates that the gas emissions in these areas were terminated as a result of the increased overburden pressure after the Holocene sea level rise and the deposition of the marine unit.","PeriodicalId":50420,"journal":{"name":"Geodinamica Acta","volume":"28 1","pages":"328 - 346"},"PeriodicalIF":1.5,"publicationDate":"2016-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09853111.2016.1183445","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59555370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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