Yaming Sun, Bile Li, Peng Li, Chengxue Li, Zhihua Li, Yufan Shi
This study focuses on quartz monzonite and diorite plutons in Dachaigou, East Kunlun, examining their formation, age, petrogenesis, magmatic source and tectonic setting. Through comprehensive field observations, zircon geochronology, geochemistry, and Hf isotope analysis, new insights into the Paleozoic tectonic evolution of the proto-Tethys Ocean in the East Kunlun orogenic belt are provided. Zircon U-Pb dating reveals that quartz monzonite and diorite formed at 417.4 ± 2.1 Ma and 404.6 ± 1.8 Ma, respectively. Geochemical analysis shows that the A/CNK value of quartz monzonite ranges from 0.98 to 1.07, with the Pb content proportional to SiO2, which aligns with the characteristics of I-type granite. The εHf(t) values for quartz monzonite and diorite are -0.84 to 2.2 and -13.22 to 2.04, respectively. Considering the formation age, geochemical characteristics, and regional tectonic evolution, it is concluded that quartz monzonite has a crust-derived origin, whereas diorite has a crust-mantle mixing origin. Both were formed in a post-collision extensional tectonic setting resulting from slab break-off, implying the Proto-Tethys Ocean East Kunlun entered a post-collisional extension stage in the Late Silurian-Early Devonian.
{"title":"Geochronology, geochemistry and Hf isotope of the quartz monzonite and the diorite in Dachaigou, the East Kunlun Orogenic Belt, China, and their geological significance","authors":"Yaming Sun, Bile Li, Peng Li, Chengxue Li, Zhihua Li, Yufan Shi","doi":"10.1139/cjes-2023-0107","DOIUrl":"https://doi.org/10.1139/cjes-2023-0107","url":null,"abstract":"This study focuses on quartz monzonite and diorite plutons in Dachaigou, East Kunlun, examining their formation, age, petrogenesis, magmatic source and tectonic setting. Through comprehensive field observations, zircon geochronology, geochemistry, and Hf isotope analysis, new insights into the Paleozoic tectonic evolution of the proto-Tethys Ocean in the East Kunlun orogenic belt are provided. Zircon U-Pb dating reveals that quartz monzonite and diorite formed at 417.4 ± 2.1 Ma and 404.6 ± 1.8 Ma, respectively. Geochemical analysis shows that the A/CNK value of quartz monzonite ranges from 0.98 to 1.07, with the Pb content proportional to SiO2, which aligns with the characteristics of I-type granite. The εHf(t) values for quartz monzonite and diorite are -0.84 to 2.2 and -13.22 to 2.04, respectively. Considering the formation age, geochemical characteristics, and regional tectonic evolution, it is concluded that quartz monzonite has a crust-derived origin, whereas diorite has a crust-mantle mixing origin. Both were formed in a post-collision extensional tectonic setting resulting from slab break-off, implying the Proto-Tethys Ocean East Kunlun entered a post-collisional extension stage in the Late Silurian-Early Devonian.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140703452","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}
Massif-type anorthosites occur worldwide and were predominantly formed during the Paleo- to Mesoproterozoic Era, with an exceptionally large number emplaced in southeastern Laurentia, both within the Grenville Province and in the foreland of the Southeastern Churchill Province and North Atlantic Craton (Nain Province). Their secular nature infers that physical and chemical conditions necessary for their formation were optimized during that time period. A review of geochronological and ambient tectonic regimes that were operating during their emplacement suggests that they formed during four periods, ca. 1.65 Ga, ca. 1.45-1.30 Ga, ca. 1.16-1.14 Ga, and 1.08-1.02 Ga. The first two pulses overlap with continent-ocean convergence and subduction beneath the SE Laurentian margin. The last two pulses correlate with continent-continent collisional tectonics. We argue that higher mantle temperatures during the Proterozoic, as inferred in published models, were not sufficient, by themselves, to produce the necessary volume of basaltic underplate – a key factor in the generation of massif-type anorthosites – and that mantle re-fertilization through metasomatism and/or lateral accretion of oceanic lithosphere might have played a key role. High geothermal gradients acquired during the 2.0-1.2 Ga accretionary and continental arc phase may have helped sustain abnormally high temperatures during the 1.2-1.0 Ga collisional phase of the Grenville Province.
块状正长岩出现在世界各地，主要形成于古生代至中新生代，在劳伦西亚东南部格勒维尔省以及东南丘吉尔省和北大西洋克拉通（纳恩省）的前缘有大量的块状正长岩。它们的世俗性推断出，它们形成所需的物理和化学条件在这一时期得到了优化。对它们形成期间所处的地质年代和环境构造体系的研究表明，它们形成于四个时期，即大约 1.65 Ga、大约 1.45-1.30 Ga、大约 1.16-1.14 Ga 和 1.08-1.02 Ga。前两个时期与大陆-海洋辐合和劳伦大陆东南边缘下的俯冲相重叠。后两个脉冲与大陆-大陆碰撞构造相关。我们认为，根据已发表的模型推断，原生代期间较高的地幔温度本身不足以产生必要的玄武岩底板体积--这是产生块状正长岩的关键因素--地幔通过变质作用和/或大洋岩石圈的横向增生而重新肥沃，可能起到了关键作用。在 2.0-1.2 Ga 的增生和大陆弧阶段获得的高地热梯度可能有助于维持格伦维尔省 1.2-1.0 Ga 碰撞阶段的异常高温。
{"title":"Geodynamic setting of Proterozoic Massif-type Anorthosites in the Eastern Canadian Shield","authors":"David Corrigan","doi":"10.1139/cjes-2024-0021","DOIUrl":"https://doi.org/10.1139/cjes-2024-0021","url":null,"abstract":"Massif-type anorthosites occur worldwide and were predominantly formed during the Paleo- to Mesoproterozoic Era, with an exceptionally large number emplaced in southeastern Laurentia, both within the Grenville Province and in the foreland of the Southeastern Churchill Province and North Atlantic Craton (Nain Province). Their secular nature infers that physical and chemical conditions necessary for their formation were optimized during that time period. A review of geochronological and ambient tectonic regimes that were operating during their emplacement suggests that they formed during four periods, ca. 1.65 Ga, ca. 1.45-1.30 Ga, ca. 1.16-1.14 Ga, and 1.08-1.02 Ga. The first two pulses overlap with continent-ocean convergence and subduction beneath the SE Laurentian margin. The last two pulses correlate with continent-continent collisional tectonics. We argue that higher mantle temperatures during the Proterozoic, as inferred in published models, were not sufficient, by themselves, to produce the necessary volume of basaltic underplate – a key factor in the generation of massif-type anorthosites – and that mantle re-fertilization through metasomatism and/or lateral accretion of oceanic lithosphere might have played a key role. High geothermal gradients acquired during the 2.0-1.2 Ga accretionary and continental arc phase may have helped sustain abnormally high temperatures during the 1.2-1.0 Ga collisional phase of the Grenville Province.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140724047","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}
Louis-Philippe Bateman, Richard Cloutier, Hans C.E. Larsson
The Bonaventure Formation is an early Carboniferous fossil-bearing rock unit that crops out in northern New Brunswick and eastern Quebec, eastern Canada. Here, we describe CMNFV 10013, a tetrapod trackway found in Bonaventure Formation outcrops on Heron Island, New Brunswick, by Robert Wheelock Ells in 1879. The specimen shows at least seven prints including two pes-manus couples, one of which is sufficiently well preserved to be attributable to Hylopus isp. Several underprints significantly depart from typical Hylopus tracks and emphasise the importance of considering taphonomy when identifying fossil trackways. CMNFV 10013 is the first described fossil reported from the Bonaventure Formation. It extends the Carboniferous Maritimes Basin tetrapod trackway record northwards and represents one of the oldest tetrapod trackways from Canada. Reviewing the global record of Hylopus isp. reveals CMNFV 10013 is also one of the earliest Hylopus found. This global record also reveals that Hylopus occurrences are clustered around the paleotropics, possibly suggesting a biogeographical preference. This specimen highlights the importance of describing forgotten museum specimens. Future research should focus on undescribed museum specimens and contributing to existing collections through fieldwork in the promising rocks of Heron Island.
{"title":"Description of a tetrapod trackway from the early Carboniferous Bonaventure Formation of New Brunswick, Canada","authors":"Louis-Philippe Bateman, Richard Cloutier, Hans C.E. Larsson","doi":"10.1139/cjes-2023-0119","DOIUrl":"https://doi.org/10.1139/cjes-2023-0119","url":null,"abstract":"The Bonaventure Formation is an early Carboniferous fossil-bearing rock unit that crops out in northern New Brunswick and eastern Quebec, eastern Canada. Here, we describe CMNFV 10013, a tetrapod trackway found in Bonaventure Formation outcrops on Heron Island, New Brunswick, by Robert Wheelock Ells in 1879. The specimen shows at least seven prints including two pes-manus couples, one of which is sufficiently well preserved to be attributable to Hylopus isp. Several underprints significantly depart from typical Hylopus tracks and emphasise the importance of considering taphonomy when identifying fossil trackways. CMNFV 10013 is the first described fossil reported from the Bonaventure Formation. It extends the Carboniferous Maritimes Basin tetrapod trackway record northwards and represents one of the oldest tetrapod trackways from Canada. Reviewing the global record of Hylopus isp. reveals CMNFV 10013 is also one of the earliest Hylopus found. This global record also reveals that Hylopus occurrences are clustered around the paleotropics, possibly suggesting a biogeographical preference. This specimen highlights the importance of describing forgotten museum specimens. Future research should focus on undescribed museum specimens and contributing to existing collections through fieldwork in the promising rocks of Heron Island.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140373193","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}
We assessed 28 Canadian volcanoes in terms of their relative threats to people, aviation, and infrastructure. The methodology we used was developed by the United States Geological Survey for the 2005 National Volcano Early Warning System. Each volcano is scored on multiple hazard and exposure factors, producing an overall threat score. The scored volcanoes are assigned to five threat categories, ranging from Very Low to Very High. We developed a knowledge uncertainty score to provide additional information about assessed threat levels; this does not affect the threat scoring. Two Canadian volcanoes are in the Very High threat category (Mt. Garibaldi and Mt. Meager). Three Canadian volcanoes are in the High threat category (Mt. Cayley, Mt. Price, and Mt. Edziza) and one volcano is in the Moderate threat category (Mt. Silverthrone). We compare the ranked Canadian volcanoes to volcanoes in the USA and assess current levels of monitoring against internationally recognized monitoring strategies. We find that even one of the best-studied volcanoes in Canada (Mt. Meager) falls significantly short of the recommended monitoring level and is currently monitored at a level commensurate with a Very Low threat edifice. All other Canadian volcanoes are unmonitored (apart from falling within a regional seismic network). This threat ranking has been used to prioritize hazard and risk assessment targets and to help select monitoring activities that will most effectively address the undermonitoring of Canadian volcanoes.
{"title":"Assessing the relative threats from Canadian volcanoes","authors":"Melanie C. Kelman, Alexander M. Wilson","doi":"10.1139/cjes-2023-0074","DOIUrl":"https://doi.org/10.1139/cjes-2023-0074","url":null,"abstract":"We assessed 28 Canadian volcanoes in terms of their relative threats to people, aviation, and infrastructure. The methodology we used was developed by the United States Geological Survey for the 2005 National Volcano Early Warning System. Each volcano is scored on multiple hazard and exposure factors, producing an overall threat score. The scored volcanoes are assigned to five threat categories, ranging from Very Low to Very High. We developed a knowledge uncertainty score to provide additional information about assessed threat levels; this does not affect the threat scoring. Two Canadian volcanoes are in the Very High threat category (Mt. Garibaldi and Mt. Meager). Three Canadian volcanoes are in the High threat category (Mt. Cayley, Mt. Price, and Mt. Edziza) and one volcano is in the Moderate threat category (Mt. Silverthrone). We compare the ranked Canadian volcanoes to volcanoes in the USA and assess current levels of monitoring against internationally recognized monitoring strategies. We find that even one of the best-studied volcanoes in Canada (Mt. Meager) falls significantly short of the recommended monitoring level and is currently monitored at a level commensurate with a Very Low threat edifice. All other Canadian volcanoes are unmonitored (apart from falling within a regional seismic network). This threat ranking has been used to prioritize hazard and risk assessment targets and to help select monitoring activities that will most effectively address the undermonitoring of Canadian volcanoes.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140431886","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}
Dinosaur skeletal material from the mid Cretaceous of Canada is rare, however, the Cenomanian-aged Dunvegan Formation of northeastern British Columbia and northwestern Alberta is rich with ichnofossils attributed to nodosaurid ankylosaurs. A long bone (Hudson’s Hope Museum specimen HH 2017.010.002) collected in 1993 from the Murray River of northeastern British Columbia is identified here as an ankylosaur femur. Femoral measurements of the bone plotted against femoral measurements of major dinosaur clades, combined with observations on femoral features, indicate the bone belongs to an ankylosaur. The specimen is too damaged to assign to Nodosauridae or Ankylosauridae. HH 2017.010.002 represents the first limb bone material recovered from the Dunvegan Formation; previous ankylosaur material described from the Dunvegan Formation includes associated vertebrae and ribs from British Columbia and osteoderms from Alberta, as well as the presumed nodosaurid footprints Tetrapodosaurus borealis. The Cenomanian is a time of great ecological change in North America, including the possible extirpation of ankylosaurid ankylosaurs. Fossils from the Dunvegan Formation can thus yield important insight into the responses of fauna to this major transition.
{"title":"An ankylosaur femur from the mid-Cretaceous of the Peace Region of northeastern British Columbia","authors":"Emily Grace Cross, Victoria Arbour","doi":"10.1139/cjes-2023-0118","DOIUrl":"https://doi.org/10.1139/cjes-2023-0118","url":null,"abstract":"Dinosaur skeletal material from the mid Cretaceous of Canada is rare, however, the Cenomanian-aged Dunvegan Formation of northeastern British Columbia and northwestern Alberta is rich with ichnofossils attributed to nodosaurid ankylosaurs. A long bone (Hudson’s Hope Museum specimen HH 2017.010.002) collected in 1993 from the Murray River of northeastern British Columbia is identified here as an ankylosaur femur. Femoral measurements of the bone plotted against femoral measurements of major dinosaur clades, combined with observations on femoral features, indicate the bone belongs to an ankylosaur. The specimen is too damaged to assign to Nodosauridae or Ankylosauridae. HH 2017.010.002 represents the first limb bone material recovered from the Dunvegan Formation; previous ankylosaur material described from the Dunvegan Formation includes associated vertebrae and ribs from British Columbia and osteoderms from Alberta, as well as the presumed nodosaurid footprints Tetrapodosaurus borealis. The Cenomanian is a time of great ecological change in North America, including the possible extirpation of ankylosaurid ankylosaurs. Fossils from the Dunvegan Formation can thus yield important insight into the responses of fauna to this major transition.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140445604","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}
Detrital chromite is currently accumulating in the modern, wave-influenced and gravel-dominated shoreface environment of eastern Port au Port Bay in western Newfoundland adjacent to the mouth of Fox Island River. Chromium (Cr) concentrations of up to 7485 ppm occur in modern, cross-bedded shallow marine gravel and pebbly sand facies derived by erosion of coastal cliffs cut in a lateglacial and early postglacial fan delta and lateglacial raised beach/nearshore deposits. The fan delta fills a broad coastal embayment and was constructed by a glacially influenced Fox Island River system during a lateglacial phase of rapid crustal rebound and low relative sea-level that lasted until approximately 9,500 years before present (ybp) following final deglaciation of the Newfoundland Ice Cap approximately 13,700 ybp. Geochemical analysis of 1149 samples across the Fox Island River watershed identifies relatively low Cr concentrations (maximum 1860 ppm) in glacial and fluvial sediments, including those areas adjacent to chromite-bearing rocks of the Bay of Islands Ophiolite Complex. Conversely, uplifted lateglacial shallow marine gravels of the lateglacial fan delta and associated raised beach/nearshore deposits show elevated Cr concentrations up to 5400 ppm, highlighting the importance of marine concentration. Since approximately 9,500 ybp, coastal outcrops of the fan delta have undergone rapid erosion in response to ongoing postglacial sea level rise outpacing the rate of crustal recovery. Chromite-bearing lateglacial sediment is being reworked and transported southwards by shore-parallel littoral currents resulting in secondary and higher Cr concentrations within a nearshore placer chromite deposit about 8 km long and 2 km wide.
{"title":"Origin of a glacially-influenced shallow marine chromite placer, Port au Port Bay, western Newfoundland, Canada","authors":"Mehmet Duyan, N. Eyles","doi":"10.1139/cjes-2023-0095","DOIUrl":"https://doi.org/10.1139/cjes-2023-0095","url":null,"abstract":"Detrital chromite is currently accumulating in the modern, wave-influenced and gravel-dominated shoreface environment of eastern Port au Port Bay in western Newfoundland adjacent to the mouth of Fox Island River. Chromium (Cr) concentrations of up to 7485 ppm occur in modern, cross-bedded shallow marine gravel and pebbly sand facies derived by erosion of coastal cliffs cut in a lateglacial and early postglacial fan delta and lateglacial raised beach/nearshore deposits. The fan delta fills a broad coastal embayment and was constructed by a glacially influenced Fox Island River system during a lateglacial phase of rapid crustal rebound and low relative sea-level that lasted until approximately 9,500 years before present (ybp) following final deglaciation of the Newfoundland Ice Cap approximately 13,700 ybp. Geochemical analysis of 1149 samples across the Fox Island River watershed identifies relatively low Cr concentrations (maximum 1860 ppm) in glacial and fluvial sediments, including those areas adjacent to chromite-bearing rocks of the Bay of Islands Ophiolite Complex. Conversely, uplifted lateglacial shallow marine gravels of the lateglacial fan delta and associated raised beach/nearshore deposits show elevated Cr concentrations up to 5400 ppm, highlighting the importance of marine concentration. Since approximately 9,500 ybp, coastal outcrops of the fan delta have undergone rapid erosion in response to ongoing postglacial sea level rise outpacing the rate of crustal recovery. Chromite-bearing lateglacial sediment is being reworked and transported southwards by shore-parallel littoral currents resulting in secondary and higher Cr concentrations within a nearshore placer chromite deposit about 8 km long and 2 km wide.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140487107","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}
Emma J Scanlan, Matthew Leybourne, D. Layton-Matthews, N. Van wagoner, Suzanne Paradis, S. Piercey, James L Crowley
Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil District, Keno Hill, and the Misty Creek Embayment). Volcanic rocks from the Anvil District and the Misty Creek Embayment are dominated by alkalic basalts with LREE-enriched geochemical signatures whereas metavolcanic and dike samples from Keno Hill comprise subalkaline basalts with E-MORB signatures. The Early Ordovician Menzie Creek volcanic rocks of the Anvil District display trace element geochemical signatures intermediate between OIB and E-MORB, whereas the Middle-Late Ordovician volcanic rocks from the Misty Creek Embayment have OIB signatures. Differences in the trace element geochemistry of the sample suites are attributed to the degree of partial melting. The Menzie Creek volcanic rocks formed from large volume melts of enriched mantle that diluted incompatible element signatures in the Early Ordovician. Late Ordovician magmatism produced the Misty Creek Embayment samples, where restricted melt volumes of an enriched mantle source resulted in the most enriched samples geochemically. The Keno Hill samples represent the shallowest melting of the analysed samples and may have resulted from melting of heterogenous subcontinental lithospheric mantle. Magmatic zircons from a Keno Hill metavolcanic sample analysed by CA-TIMS resulted in a primary deposition age of c. 296 ± 0.36 Ma (Early Permian), during a period with little magmatism in the Selwyn Basin and representing a previously unknown unit in the area.
{"title":"Petrology and lithogeochemistry of Paleozoic alkalic magmatism in the Selwyn Basin, Yukon, Canada","authors":"Emma J Scanlan, Matthew Leybourne, D. Layton-Matthews, N. Van wagoner, Suzanne Paradis, S. Piercey, James L Crowley","doi":"10.1139/cjes-2023-0081","DOIUrl":"https://doi.org/10.1139/cjes-2023-0081","url":null,"abstract":"Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil District, Keno Hill, and the Misty Creek Embayment). Volcanic rocks from the Anvil District and the Misty Creek Embayment are dominated by alkalic basalts with LREE-enriched geochemical signatures whereas metavolcanic and dike samples from Keno Hill comprise subalkaline basalts with E-MORB signatures. The Early Ordovician Menzie Creek volcanic rocks of the Anvil District display trace element geochemical signatures intermediate between OIB and E-MORB, whereas the Middle-Late Ordovician volcanic rocks from the Misty Creek Embayment have OIB signatures. Differences in the trace element geochemistry of the sample suites are attributed to the degree of partial melting. The Menzie Creek volcanic rocks formed from large volume melts of enriched mantle that diluted incompatible element signatures in the Early Ordovician. Late Ordovician magmatism produced the Misty Creek Embayment samples, where restricted melt volumes of an enriched mantle source resulted in the most enriched samples geochemically. The Keno Hill samples represent the shallowest melting of the analysed samples and may have resulted from melting of heterogenous subcontinental lithospheric mantle. Magmatic zircons from a Keno Hill metavolcanic sample analysed by CA-TIMS resulted in a primary deposition age of c. 296 ± 0.36 Ma (Early Permian), during a period with little magmatism in the Selwyn Basin and representing a previously unknown unit in the area.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139600863","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}
Khalid Lakhouidsi, Abdelali Fadil, A. Tahayt, A. Soulaimani
The GNSS has emerged as a practical and effective technique for studying slow and steady geodynamic movements, enabling continuous monitoring and precise quantification of deformation over different timescales. In Morocco, a network of GNSS stations has been established, offering valuable insights into tectonic processes. This paper focuses on investigating the geodynamic motion of the NW Moroccan Atlantic Margin (MAM). By utilizing GNSS data, subsidence rates and horizontal velocity fields were determined for the first time, providing valuable information for oil and gas exploration activities. The study reveals an active uplift rate of 1 mm/yr and a westward horizontal motion of 2.04 mm/yr in the Essaouira segment. The paper presents a case study of the Essaouira-Agadir basin (EAB) onshore segment and investigates the anomalous displacement observed in this region compared to other coastal GNSS stations. Possible explanations for the observed movements include local processes such as salt tectonics and regional NW-SE compression related to Africa-Eurasia convergence. We suggest that the anomalous movement detected in this work is due to the regional NW-SE compression related to Africa-Eurasia convergence imparting an extrusion of the Essaouira-Agadir basin to the West. This research contributes to a better understanding of the geodynamics in the NW Moroccan Atlantic margin, thereby providing valuable insights for ongoing efforts in oil and gas exploration. Furthermore, indicate the continued activity of the Agadir fault, which would exhibit a sinistral wrench movement, thus posing a threat to the city of Agadir and its inhabitants.
{"title":"Present-day kinematics of the NW Moroccan Atlantic Margin from GNSS data: WSW extrusion at the western end of the High Atlas","authors":"Khalid Lakhouidsi, Abdelali Fadil, A. Tahayt, A. Soulaimani","doi":"10.1139/cjes-2023-0104","DOIUrl":"https://doi.org/10.1139/cjes-2023-0104","url":null,"abstract":"The GNSS has emerged as a practical and effective technique for studying slow and steady geodynamic movements, enabling continuous monitoring and precise quantification of deformation over different timescales. In Morocco, a network of GNSS stations has been established, offering valuable insights into tectonic processes. This paper focuses on investigating the geodynamic motion of the NW Moroccan Atlantic Margin (MAM). By utilizing GNSS data, subsidence rates and horizontal velocity fields were determined for the first time, providing valuable information for oil and gas exploration activities. The study reveals an active uplift rate of 1 mm/yr and a westward horizontal motion of 2.04 mm/yr in the Essaouira segment. The paper presents a case study of the Essaouira-Agadir basin (EAB) onshore segment and investigates the anomalous displacement observed in this region compared to other coastal GNSS stations. Possible explanations for the observed movements include local processes such as salt tectonics and regional NW-SE compression related to Africa-Eurasia convergence. We suggest that the anomalous movement detected in this work is due to the regional NW-SE compression related to Africa-Eurasia convergence imparting an extrusion of the Essaouira-Agadir basin to the West. This research contributes to a better understanding of the geodynamics in the NW Moroccan Atlantic margin, thereby providing valuable insights for ongoing efforts in oil and gas exploration. Furthermore, indicate the continued activity of the Agadir fault, which would exhibit a sinistral wrench movement, thus posing a threat to the city of Agadir and its inhabitants.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139602410","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}
Tianyu Ji, Wei Yang, Xueqiong Wu, Dejiang Li, Mancang Liu, Cheng-peng Song, Xi Chen
The Cambrian pre-salt dolomite sequence in the Tarim Basin is a target zone of great strategic significance for hydrocarbon exploration in the basin. Using the results of the interpretation of 3D seismic data from Lunnan and 2D seismic data covering the whole basin and based on a synthesis of outcrop data, drilling data, well logs, core data, and thin-section data and the findings from previous studies, this paper studies the characteristics of the facies of the Middle-Lower Cambrian in the platform area in the Tarim Basin, the formation and evolution of platform margins, and the sedimentary characteristics, lithofacies and paleogeographic characteristics of the middle-lower Cambrian series. Based on the types of lithofacies, and the seismic facies analysis, the sedimentary facies of the Middle-Lower Cambrian strata can be classified into the five types. From bottom to top, the Middle-Lower Cambrian have experienced several development stages, including the deposition of continental shelf sediments of the Yuertusi Formation, gently sloping non-rimmed platform margin sediments of the Xiaoerbulake Formation, weakly-rimmed platform margin sediments of the Wusongger and Shayilike formations, and strongly-rimmed platform margin sediments of the Awatage Formation. In each stage, the platform margin shifted further east relative to its location in the previous stage. Based on these results and previous studies, the lithofacies and paleogeography maps of the middle-lower Cambrian in the Tarim Basin are modified, and the implications for hydrocarbon exploration in this area are discussed.
{"title":"Sedimentary characteristics, lithofacies and paleogeography of the middle-lower Cambrian in the Tarim Basin, NW China","authors":"Tianyu Ji, Wei Yang, Xueqiong Wu, Dejiang Li, Mancang Liu, Cheng-peng Song, Xi Chen","doi":"10.1139/cjes-2023-0085","DOIUrl":"https://doi.org/10.1139/cjes-2023-0085","url":null,"abstract":"The Cambrian pre-salt dolomite sequence in the Tarim Basin is a target zone of great strategic significance for hydrocarbon exploration in the basin. Using the results of the interpretation of 3D seismic data from Lunnan and 2D seismic data covering the whole basin and based on a synthesis of outcrop data, drilling data, well logs, core data, and thin-section data and the findings from previous studies, this paper studies the characteristics of the facies of the Middle-Lower Cambrian in the platform area in the Tarim Basin, the formation and evolution of platform margins, and the sedimentary characteristics, lithofacies and paleogeographic characteristics of the middle-lower Cambrian series. Based on the types of lithofacies, and the seismic facies analysis, the sedimentary facies of the Middle-Lower Cambrian strata can be classified into the five types. From bottom to top, the Middle-Lower Cambrian have experienced several development stages, including the deposition of continental shelf sediments of the Yuertusi Formation, gently sloping non-rimmed platform margin sediments of the Xiaoerbulake Formation, weakly-rimmed platform margin sediments of the Wusongger and Shayilike formations, and strongly-rimmed platform margin sediments of the Awatage Formation. In each stage, the platform margin shifted further east relative to its location in the previous stage. Based on these results and previous studies, the lithofacies and paleogeography maps of the middle-lower Cambrian in the Tarim Basin are modified, and the implications for hydrocarbon exploration in this area are discussed.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139532201","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}
C. Dusel-Bacon, J. Aleinikoff, Suzanne Paradis, John F. Slack
The Sheep Creek prospect is a stratabound Zn-Pb-Ag-Sn massive sulphide occurrence in the Bonnifield mining district, northern Alaska Range. The prospect is within a quartz-sericite-graphite-chlorite schist unit associated with Devonian carbonaceous and siliceous metasedimentary rocks. Volcanogenic massive sulphide (VMS) deposits in the district are hosted in felsic metavolcanic rocks (362 ± 2 Ma) associated with siliciclastic and carbonaceous sedimentary rocks that overlie the stratigraphic sequence hosting the Sheep Creek prospect. Felsic metaigneous rocks in underlying units are 372 ± 4 Ma to 366 ± 4 Ma. Sheep Creek is atypical of the other sulphide deposits in the district in (1) having Sn grades up to 1.2 %; (2) being contained in fine-grained, quartz-rich rocks and quartz-pebble conglomerate that likely originated as chert and chert-clast sediment, respectively; and (3) showing minimal evidence of volcanic components in the host rocks. Comparison of immobile trace-element proportions for graphitic and siliceous rocks from the Sheep Creek area with those for argillite associated with the Bonnifield VMS deposits indicates a continental volcanic-arc provenance for the former and a within-plate and passive margin provenance for the latter. In contrast to previously published interpretations, our data analysis supports a clastic-dominated (CD) rather than a VMS affinity for the Sheep Creek prospect. In our model, Zn-Pb-Ag-Sn mineralization formed by syngenetic or early diagenetic processes on or beneath the seafloor, possibly in the shallow-water environment of an outer continental shelf setting. Potential analogues are the Paleozoic CD deposits in the Canadian Selwyn Basin outboard of the Laurentian continental margin.
{"title":"Sulphide petrology and ore genesis of the stratabound Sheep Creek sediment-hosted Zn-Pb-Ag-Sn prospect, and U–Pb zircon constraints on the timing of magmatism in the northern Alaska Range","authors":"C. Dusel-Bacon, J. Aleinikoff, Suzanne Paradis, John F. Slack","doi":"10.1139/cjes-2023-0089","DOIUrl":"https://doi.org/10.1139/cjes-2023-0089","url":null,"abstract":"The Sheep Creek prospect is a stratabound Zn-Pb-Ag-Sn massive sulphide occurrence in the Bonnifield mining district, northern Alaska Range. The prospect is within a quartz-sericite-graphite-chlorite schist unit associated with Devonian carbonaceous and siliceous metasedimentary rocks. Volcanogenic massive sulphide (VMS) deposits in the district are hosted in felsic metavolcanic rocks (362 ± 2 Ma) associated with siliciclastic and carbonaceous sedimentary rocks that overlie the stratigraphic sequence hosting the Sheep Creek prospect. Felsic metaigneous rocks in underlying units are 372 ± 4 Ma to 366 ± 4 Ma. Sheep Creek is atypical of the other sulphide deposits in the district in (1) having Sn grades up to 1.2 %; (2) being contained in fine-grained, quartz-rich rocks and quartz-pebble conglomerate that likely originated as chert and chert-clast sediment, respectively; and (3) showing minimal evidence of volcanic components in the host rocks. Comparison of immobile trace-element proportions for graphitic and siliceous rocks from the Sheep Creek area with those for argillite associated with the Bonnifield VMS deposits indicates a continental volcanic-arc provenance for the former and a within-plate and passive margin provenance for the latter. In contrast to previously published interpretations, our data analysis supports a clastic-dominated (CD) rather than a VMS affinity for the Sheep Creek prospect. In our model, Zn-Pb-Ag-Sn mineralization formed by syngenetic or early diagenetic processes on or beneath the seafloor, possibly in the shallow-water environment of an outer continental shelf setting. Potential analogues are the Paleozoic CD deposits in the Canadian Selwyn Basin outboard of the Laurentian continental margin.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138958914","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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