Brigitte R. Gélinas, P. Hollings, Richard Friedman
The Laird Lake property, southwest Red Lake greenstone belt, straddles the contact between the Balmer (2.99–2.96 Ga) and the Confederation (2.74–2.73 Ga) assemblages. The property is 10 km along strike from the Madsen and Starrat–Olsen Au mines that are hosted near the contact. The Balmer assemblage consists of fine-grained, aphyric, locally pillowed mafic volcanic rocks, ultramafic intrusive and volcanic rocks with flow breccia textures hosting local spinifex-bearing clasts, and banded-iron formations. In contrast, the Confederation assemblage comprises porphyritic mafic volcanic rocks intercalated with intermediate to felsic volcanic rocks that include crystal lapilli tuffs, crystal tuffs, and tuffs. The Balmer assemblage is composed of tholeiitic mafic volcanic rocks with minor Al-undepleted komatiites, whereas the Confederation assemblage is calc–alkalic. Neodymium isotopes, in conjunction with trace element geochemistry, suggests that parts of the Balmer assemblage were weakly contaminated by an older intermediate basement. Both arc and back-arc volcanism occurs in the Confederation assemblage, with the arc rocks showing a stronger crustal component than the back-arc rocks. A maximum U–Pb age of 2741 ± 19 Ma for a crystal tuff and an age of 2737.68 ± 0.79 Ma for a diorite are consistent with a Confederation assemblage affinity for the intermediate calc–alkaline rocks south of the Au-bearing horizon. The Balmer assemblage represents an oceanic plateau formed by plume magmatism on the margins of the North Caribou Terrane, whereas the Confederation assemblage at Laird Lake formed in an oceanic arc setting where both arc and back-arc volcanism occurred simultaneously.
{"title":"Geochemistry, geochronology, and radiogenic isotopes of the Balmer and Confederation assemblages of the Laird Lake Area, Red Lake greenstone belt, Canada: implications for Archean tectonic evolution","authors":"Brigitte R. Gélinas, P. Hollings, Richard Friedman","doi":"10.1139/cjes-2023-0122","DOIUrl":"https://doi.org/10.1139/cjes-2023-0122","url":null,"abstract":"The Laird Lake property, southwest Red Lake greenstone belt, straddles the contact between the Balmer (2.99–2.96 Ga) and the Confederation (2.74–2.73 Ga) assemblages. The property is 10 km along strike from the Madsen and Starrat–Olsen Au mines that are hosted near the contact. The Balmer assemblage consists of fine-grained, aphyric, locally pillowed mafic volcanic rocks, ultramafic intrusive and volcanic rocks with flow breccia textures hosting local spinifex-bearing clasts, and banded-iron formations. In contrast, the Confederation assemblage comprises porphyritic mafic volcanic rocks intercalated with intermediate to felsic volcanic rocks that include crystal lapilli tuffs, crystal tuffs, and tuffs. The Balmer assemblage is composed of tholeiitic mafic volcanic rocks with minor Al-undepleted komatiites, whereas the Confederation assemblage is calc–alkalic. Neodymium isotopes, in conjunction with trace element geochemistry, suggests that parts of the Balmer assemblage were weakly contaminated by an older intermediate basement. Both arc and back-arc volcanism occurs in the Confederation assemblage, with the arc rocks showing a stronger crustal component than the back-arc rocks. A maximum U–Pb age of 2741 ± 19 Ma for a crystal tuff and an age of 2737.68 ± 0.79 Ma for a diorite are consistent with a Confederation assemblage affinity for the intermediate calc–alkaline rocks south of the Au-bearing horizon. The Balmer assemblage represents an oceanic plateau formed by plume magmatism on the margins of the North Caribou Terrane, whereas the Confederation assemblage at Laird Lake formed in an oceanic arc setting where both arc and back-arc volcanism occurred simultaneously.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141106769","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}
Correlating structurally distinctive fault zones for understanding an unknown deformation system at the regional scale remains a challenge for understanding orogenic evolution and gold endowment. The current study deals with this challenge in the southern Michipicoten greenstone belt (MGB) of the Superior craton focusing on a Neoarchean auriferous fault zone network. Three deformation events associated with episodic gold mineralization are revealed in the ca. 2745 Ma host granitoid: (1) NW‒SE shortening recorded by the subvertical Grace and Minto B fault zones and locally the inclined Jubilee and Hornblende fault zones; (2) top-to-NNE strike-slip to oblique faulting indicated primarily by the dominant structures of the Jubilee and Hornblende fault zones; and (3) top-to-NE extension demonstrated by the northeast-dipping Parkhill #4 and Cooper fault zones. Fault zone lithologies and mineral assemblages suggest that the localization of deformation for the formation of these fault zones was controlled by rheological heterogeneities and syn-deformation fluids. The first and second events are correlated with two shortening events in a gold-endowed, structurally and kinematically distinctive deformation zone of the northern MGB. This correlation based on deformation processes suggests a larger footprint of gold mineralization associated with a regional deformation in the MGB and has implications for investigating structural evolution of orogens and orogenic gold mineralization in general.
将结构上独特的断层带关联起来，以了解区域尺度上未知的变形系统，仍然是了解造山演化和金赋存的一项挑战。目前的研究针对的是苏必利尔陨石坑南部米希皮科腾绿岩带（MGB）的这一挑战，重点是新元古代的含金断层带网络。在约 2745 Ma 的主花岗岩中，发现了三个与偶发性金矿化有关的变形事件。它们是：(1) 由俯冲的格雷斯和明托 B 断层带以及局部倾斜的朱比利和霍恩布伦德断层带记录的 NW-SE 向缩短；(2) 主要由朱比利和霍恩布伦德断层带的主要结构显示的自上而下向 NNE 的走向滑动到斜向断裂；以及 (3) 由向东北倾斜的 Parkhill #4 和 Cooper 断层带显示的自上而下向 NNE 的延伸。断层带岩性和矿物组合表明，形成这些断层带的变形定位受到流变异质性和同步变形流体的控制。第一个和第二个事件与 MGB 北部一个金赋存、结构和运动学上独特的变形带中的两个缩短事件相关联。这种基于变形过程的相关性表明，金矿化的更大足迹与 MGB 的区域变形有关，对研究造山带的结构演化和造山带金矿化具有普遍意义。
{"title":"Polyphase formation of a Neoarchean auriferous fault zone network in the Michipicoten greenstone belt, southern Superior craton","authors":"Chong Ma, Bruno Lafrance, J. Montreuil","doi":"10.1139/cjes-2023-0120","DOIUrl":"https://doi.org/10.1139/cjes-2023-0120","url":null,"abstract":"Correlating structurally distinctive fault zones for understanding an unknown deformation system at the regional scale remains a challenge for understanding orogenic evolution and gold endowment. The current study deals with this challenge in the southern Michipicoten greenstone belt (MGB) of the Superior craton focusing on a Neoarchean auriferous fault zone network. Three deformation events associated with episodic gold mineralization are revealed in the ca. 2745 Ma host granitoid: (1) NW‒SE shortening recorded by the subvertical Grace and Minto B fault zones and locally the inclined Jubilee and Hornblende fault zones; (2) top-to-NNE strike-slip to oblique faulting indicated primarily by the dominant structures of the Jubilee and Hornblende fault zones; and (3) top-to-NE extension demonstrated by the northeast-dipping Parkhill #4 and Cooper fault zones. Fault zone lithologies and mineral assemblages suggest that the localization of deformation for the formation of these fault zones was controlled by rheological heterogeneities and syn-deformation fluids. The first and second events are correlated with two shortening events in a gold-endowed, structurally and kinematically distinctive deformation zone of the northern MGB. This correlation based on deformation processes suggests a larger footprint of gold mineralization associated with a regional deformation in the MGB and has implications for investigating structural evolution of orogens and orogenic gold mineralization in general.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141114644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Antigonish sub-basin lies within the late Paleozoic Maritimes Basin of Atlantic Canada. Late Devonian to early Carboniferous basin development resulted in a basin-and-range topography, within which the clastic Horton Group was deposited in grabens and half-grabens. The overlying Visean Windsor Group contains substantial evaporite units; later basin development was accompanied by expulsion of these evaporites. In the Antigonish sub-basin a significant stratigraphic omission surface initially described as a thrust was subsequently reinterpreted as the extensional Ainslie Detachment. This surface can be examined in drill-core, where the halite-bearing interval is reduced to 3.8 m of halite-cemented breccia of sedimentary rock fragments. The halite cement is sub-horizontally foliated and lineated. At Lakevale an outcrop section of the Windsor Group is reduced in thickness to tens of metres. Above a basal limestone unit containing pseudomorphs of gypsum, most of the Windsor Group is represented by sedimentary-clast breccias which resemble those seen in core, but with the halite removed by solution in the near-surface environment. The stratigraphic record within the sub-basin implies that expulsion of lower Windsor salt was initially toward the edges of the basin where rising diapirs blocked the deposition of Middle Windsor group, but in the basin centre a second salt unit was deposited. Subsequently, during contractional inversion of basin-bounding faults, the middle Windsor salt was expelled into diapirs near the centre of the basin. The Ainslie Detachment is reinterpreted as a primary salt weld: a boundary between units formerly above and below expelled lower Windsor evaporites. The resulting stratigraphic omissions and structures match those seen above expelled evaporite layers on continental margins.
{"title":"A primary evaporite weld revealed in the late Paleozoic Antigonish sub-basin of Nova Scotia","authors":"Alison K. Thomas, John W.F. Waldron","doi":"10.1139/cjes-2024-0030","DOIUrl":"https://doi.org/10.1139/cjes-2024-0030","url":null,"abstract":"The Antigonish sub-basin lies within the late Paleozoic Maritimes Basin of Atlantic Canada. Late Devonian to early Carboniferous basin development resulted in a basin-and-range topography, within which the clastic Horton Group was deposited in grabens and half-grabens. The overlying Visean Windsor Group contains substantial evaporite units; later basin development was accompanied by expulsion of these evaporites. In the Antigonish sub-basin a significant stratigraphic omission surface initially described as a thrust was subsequently reinterpreted as the extensional Ainslie Detachment. This surface can be examined in drill-core, where the halite-bearing interval is reduced to 3.8 m of halite-cemented breccia of sedimentary rock fragments. The halite cement is sub-horizontally foliated and lineated. At Lakevale an outcrop section of the Windsor Group is reduced in thickness to tens of metres. Above a basal limestone unit containing pseudomorphs of gypsum, most of the Windsor Group is represented by sedimentary-clast breccias which resemble those seen in core, but with the halite removed by solution in the near-surface environment. The stratigraphic record within the sub-basin implies that expulsion of lower Windsor salt was initially toward the edges of the basin where rising diapirs blocked the deposition of Middle Windsor group, but in the basin centre a second salt unit was deposited. Subsequently, during contractional inversion of basin-bounding faults, the middle Windsor salt was expelled into diapirs near the centre of the basin. The Ainslie Detachment is reinterpreted as a primary salt weld: a boundary between units formerly above and below expelled lower Windsor evaporites. The resulting stratigraphic omissions and structures match those seen above expelled evaporite layers on continental margins.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141002307","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. Shaw, K. Boggild, Zhen Li, Jordan Eamer, D. C. Stacey
Based on high-resolution multibeam-sonar data and low-resolution (GEBCO) data we classify the geomorphology of Canada’s Pacific margin within the four bioregions designated by Fisheries and Oceans Canada for management of biological resources. We designate fourteen units. Nine continental shelf units are: fiords, bedrock terrain, offshore banks, Haida Gwaii platform, Haida Gwaii shelf, Vancouver Island shelf, incised shelf, glacial trough, and major delta. On the continental slope we identify the canyon zone, the accretionary wedge (off Vancouver Island), and the transform (Queen Charlotte Fault) terrain. The abyssal zone is treated as a single unit with two components: seafloor spreading terrain, and abyssal plain with fans, seamounts, and channels. Hexactinellid sponge reefs of various morphologies are found in three of the continental shelf geomorphic units, and cover up to 10 % of the seafloor in the glacial trough category. Examples based on multibeam sonar imagery are used to display the chief characteristics of the fourteen units as well as the geomorphic diversity within them. Compared with Canada’s east-coast glaciated passive margin, geomorphic similarities include: 1) the panoply of glacial landforms; and 2) shelf terrain dissected by sub-glacial meltwater. Major differences include: 1) the presence of unique ‘tectonic’ terrains on the Pacific continental slopes; 2) hexactinellid sponge bioherm reefs are unique to the Pacific margin; 3) the absence of glacio-tectonic terrains on the Pacific shelves; and 4) the absence of ‘classic’ trough-mouth fans on the Pacific margin.
{"title":"Submarine geomorphology of a glaciated active margin, British Columbia, Canada","authors":"J. Shaw, K. Boggild, Zhen Li, Jordan Eamer, D. C. Stacey","doi":"10.1139/cjes-2023-0100","DOIUrl":"https://doi.org/10.1139/cjes-2023-0100","url":null,"abstract":"Based on high-resolution multibeam-sonar data and low-resolution (GEBCO) data we classify the geomorphology of Canada’s Pacific margin within the four bioregions designated by Fisheries and Oceans Canada for management of biological resources. We designate fourteen units. Nine continental shelf units are: fiords, bedrock terrain, offshore banks, Haida Gwaii platform, Haida Gwaii shelf, Vancouver Island shelf, incised shelf, glacial trough, and major delta. On the continental slope we identify the canyon zone, the accretionary wedge (off Vancouver Island), and the transform (Queen Charlotte Fault) terrain. The abyssal zone is treated as a single unit with two components: seafloor spreading terrain, and abyssal plain with fans, seamounts, and channels. Hexactinellid sponge reefs of various morphologies are found in three of the continental shelf geomorphic units, and cover up to 10 % of the seafloor in the glacial trough category. Examples based on multibeam sonar imagery are used to display the chief characteristics of the fourteen units as well as the geomorphic diversity within them. Compared with Canada’s east-coast glaciated passive margin, geomorphic similarities include: 1) the panoply of glacial landforms; and 2) shelf terrain dissected by sub-glacial meltwater. Major differences include: 1) the presence of unique ‘tectonic’ terrains on the Pacific continental slopes; 2) hexactinellid sponge bioherm reefs are unique to the Pacific margin; 3) the absence of glacio-tectonic terrains on the Pacific shelves; and 4) the absence of ‘classic’ trough-mouth fans on the Pacific margin.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141011490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The South Mountain Batholith (SMB) is a syntectonic composite batholith emplaced in the upper crust within the Meguma terrane between 380 Ma and 370 Ma during the later stages of the Neoacadian orogeny. Coeval plutons in southern Nova Scotia are surrounded by mid-crustal (~4 kbar) andalusite-staurolite aureoles and are discordant to NE-trending, regional Neoacadian folds. Detailed field studies, combined with published results, indicate emplacement within a dextral transpressional regime during the transition from distributed (D1) to focused heterogeneous strain (D2), which provided vertical conduits that facilitated magma ascent. The Port Mouton Pluton (PMP) intruded along P-orientated crustal-scale fractures as a series of subvertical granitic sheets, which were progressively rotated and folded with ongoing dextral shearing. By contrast, the Barrington Passage pluton (BPP) intruded between crustal-scale, antithetic (sinistral) P-shear fractures and spread laterally between them as pulsed increments to form a layered, subhorizontal, sill-like complex resembling the laccolithic structure of the SMB. The SMB was emplaced below the Meguma Supergroup, with magma derived from underthrust Avalon terrane and Silurian Rockville Notch Group. The lack of mantle components in the SMB suggests transpressional orogenesis facilitated conductive crustal heating without significant mantle addition, consistent with low p-wave velocities of Meguma lower crust. 400-355 Ma zircons, recorded either as inherited grains in granites or in felsic granulite xenoliths, imply the Neoacadian thermal anomaly extended for 45 Ma, but magmatism represented only ~40% of that perturbation.
南山浴成岩（SMB）是在新奥卡迪亚造山运动后期的 380 Ma 到 370 Ma 之间，在 Meguma terrane 的上地壳中隆起的合成构造复合浴成岩。新斯科舍省南部的同时期块岩被地壳中期（约 4 千巴）的安山岩-陶粒岩金星环绕，并与 NE 走向的区域性 Neoacadian 褶皱不和谐。详细的实地研究与已公布的结果相结合，表明在从分布式应变（D1）向集中式异质应变（D2）过渡期间，岩浆是在右旋转压机制下形成的，这为岩浆的上升提供了垂直通道。穆通港岩浆岩（Port Mouton Pluton，PMP）沿 P 向地壳尺度断裂侵入，形成一系列近垂直的花岗岩片，并在持续的右旋剪切作用下逐渐旋转和褶皱。相比之下，巴林顿通道岩体（Barrington Passage pluton，BPP）则侵入地壳尺度的反向（正弦）P-剪切断裂之间，并以脉冲式的增量在断裂之间横向扩散，形成层状、亚水平、矽卡岩状的复合体，类似于深圳地铁的裂隙结构。SMB隆起于Meguma超群之下，岩浆来源于下推阿瓦隆地层和志留纪洛克维尔缺口群。SMB中缺乏地幔成分，这表明换位造山作用促进了地壳的传导加热，而没有大量地幔的加入，这与Meguma下地壳的低p波速度相一致。花岗岩中的400-355Ma锆石或花岗岩中的长英质花岗岩碎屑记录表明，Neoacadian热异常延续了45Ma，但岩浆活动仅占该扰动的约40%。
{"title":"Conjugate shear model for emplacement of midcrustal plutons during dextral transpression, southern Nova Scotia, Canada: tectonic and petrological consequences","authors":"William J. Collins, J. B. Murphy","doi":"10.1139/cjes-2024-0044","DOIUrl":"https://doi.org/10.1139/cjes-2024-0044","url":null,"abstract":"The South Mountain Batholith (SMB) is a syntectonic composite batholith emplaced in the upper crust within the Meguma terrane between 380 Ma and 370 Ma during the later stages of the Neoacadian orogeny. Coeval plutons in southern Nova Scotia are surrounded by mid-crustal (~4 kbar) andalusite-staurolite aureoles and are discordant to NE-trending, regional Neoacadian folds. Detailed field studies, combined with published results, indicate emplacement within a dextral transpressional regime during the transition from distributed (D1) to focused heterogeneous strain (D2), which provided vertical conduits that facilitated magma ascent. The Port Mouton Pluton (PMP) intruded along P-orientated crustal-scale fractures as a series of subvertical granitic sheets, which were progressively rotated and folded with ongoing dextral shearing. By contrast, the Barrington Passage pluton (BPP) intruded between crustal-scale, antithetic (sinistral) P-shear fractures and spread laterally between them as pulsed increments to form a layered, subhorizontal, sill-like complex resembling the laccolithic structure of the SMB. The SMB was emplaced below the Meguma Supergroup, with magma derived from underthrust Avalon terrane and Silurian Rockville Notch Group. The lack of mantle components in the SMB suggests transpressional orogenesis facilitated conductive crustal heating without significant mantle addition, consistent with low p-wave velocities of Meguma lower crust. 400-355 Ma zircons, recorded either as inherited grains in granites or in felsic granulite xenoliths, imply the Neoacadian thermal anomaly extended for 45 Ma, but magmatism represented only ~40% of that perturbation.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141015858","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}
Laura Termes, G. Keddie, R. Hebda, P. Trask, Victoria Arbour, Camilla Speller, L. Paskulin, C. Ramsey, Michael Richards
As part of a larger project identifying and directly radiocarbon dating Late Pleistocene megafaunal remains in British Columbia (B.C.), Canada we have confirmed the identity of many newly identified mammoth (Mammuthus sp.) specimens (n=32) from Vancouver Island in Southwestern B.C. We undertook radiocarbon dating on all specimens and were able to obtain dates (due to preservation) on 16 of these remains, including re-dating a previously dated mammoth using newer radiocarbon extraction methods. The mammoth dates span a wide range, from >47,500 to 18,000 radiocarbon years BP (uncalibrated). These later new dates support other lines of evidence for portions of Vancouver Island remaining unglaciated towards the end of Late Pleistocene.
{"title":"Survival of mammoths (Mammuthus sp.) into the Late Pleistocene in Southwestern British Columbia (Vancouver Island), Canada","authors":"Laura Termes, G. Keddie, R. Hebda, P. Trask, Victoria Arbour, Camilla Speller, L. Paskulin, C. Ramsey, Michael Richards","doi":"10.1139/cjes-2023-0102","DOIUrl":"https://doi.org/10.1139/cjes-2023-0102","url":null,"abstract":"As part of a larger project identifying and directly radiocarbon dating Late Pleistocene megafaunal remains in British Columbia (B.C.), Canada we have confirmed the identity of many newly identified mammoth (Mammuthus sp.) specimens (n=32) from Vancouver Island in Southwestern B.C. We undertook radiocarbon dating on all specimens and were able to obtain dates (due to preservation) on 16 of these remains, including re-dating a previously dated mammoth using newer radiocarbon extraction methods. The mammoth dates span a wide range, from >47,500 to 18,000 radiocarbon years BP (uncalibrated). These later new dates support other lines of evidence for portions of Vancouver Island remaining unglaciated towards the end of Late Pleistocene.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141021743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Mesoproterozoic Frontenac terrane in the southern Grenville Province of Ontario is separated by shear zones from the Composite Arc Belt to the west and the Adirondack Lowlands to the east. The majority of the terrane is made up of granulite-facies metasedimentary rocks that are the oldest lithologies recognized in the terrane. Five samples were selected for U-Pb geochronology to constrain (1) metamorphic age, (2) depositional age of sedimentary protoliths, and (3) source regions of detrital zircon. Two pelitic gneisses and a marble are dominated by metamorphic zircon, whereas two quartzites contain a diverse population of detrital zircon that are surrounded by metamorphic rims. Metamorphic zircon have 206Pb/207Pb ages of 1.19–1.16 Ga, and a small population is 1.22 Ga. These ages correspond to the Shawinigan and Elzevirian orogenies, and provide minimum ages for deposition. The youngest detrital grains with ages of 1.25–1.24 Ga provide maximum depositional ages. Quartzites (and pelitic gneisses) have a wide range of detrital zircon ages that reflect local Mesoproterozoic Grenville sources and Paleoproterzoic and Archean sources in the northern Grenville Province and elsewhere in Laurentia. Most notable is a large population of 1.9–1.8 Ga zircon which point towards derivation from the Penokean orogen in the Midcontinent or Makkovikian–Ketilidian orogen of Labrador and Greenland; indicating long sedimentary transport distances. The similarities in depositional ages and detrital zircon ages between Frontenac terrane and Adirondack metasedimentary rocks suggest a shared sedimentary history which we interpret as deposition in the same Trans-Adirondack backarc basin at ca. 1.25 Ga.
位于安大略省格勒维尔省南部的中新生代福朗特纳克（Frontenac）陆相被剪切带隔开，西面是复合弧带，东面是阿迪朗达克低地。陆相的大部分由花岗岩成因的变质岩组成，是陆相中公认的最古老的岩性。选取了五个样本进行铀-铅地质年代测定，以确定：（1）变质年龄；（2）沉积原岩的沉积年龄；（3）锆英石的来源地区。两块辉长片麻岩和一块大理岩中主要是变质锆石，而两块石英岩中则含有多种被变质边缘包围的碎屑锆石。变质锆石的 206Pb/207Pb 年龄为 1.19-1.16 Ga，一小部分为 1.22 Ga。这些年龄与沙维尼根（Shawinigan）和埃尔泽维（Elzevirian）造山运动相对应，并提供了沉积的最小年龄。年龄在 1.25-1.24 Ga 之间的最年轻的碎屑岩提供了最大沉积年龄。石英岩（和角闪岩片麻岩）的锆石碎片年龄范围很广，反映了当地中新生代格勒维尔源以及格勒维尔省北部和劳伦西亚其他地区的古生代和阿契安源。最值得注意的是，大量 1.9-1.8 Ga 锆石表明，这些锆石来源于中大陆的佩诺肯造山带或拉布拉多和格陵兰的马科维基-凯蒂里德造山带；这表明沉积运移距离很长。福龙特纳克岩系和阿迪朗达克变质岩的沉积年龄和锆英石碎片年龄相似，这表明它们有着共同的沉积历史，我们将其解释为在大约 1.25 Ga 时沉积于同一个跨阿迪朗达克弧后盆地。1.25 Ga.
{"title":"Provenance and depositional age of metasedimentary rocks in the Frontenac terrane (Grenville Province, Ontario)","authors":"William H. Peck, Henry Y. Lin","doi":"10.1139/cjes-2024-0029","DOIUrl":"https://doi.org/10.1139/cjes-2024-0029","url":null,"abstract":"The Mesoproterozoic Frontenac terrane in the southern Grenville Province of Ontario is separated by shear zones from the Composite Arc Belt to the west and the Adirondack Lowlands to the east. The majority of the terrane is made up of granulite-facies metasedimentary rocks that are the oldest lithologies recognized in the terrane. Five samples were selected for U-Pb geochronology to constrain (1) metamorphic age, (2) depositional age of sedimentary protoliths, and (3) source regions of detrital zircon. Two pelitic gneisses and a marble are dominated by metamorphic zircon, whereas two quartzites contain a diverse population of detrital zircon that are surrounded by metamorphic rims. Metamorphic zircon have 206Pb/207Pb ages of 1.19–1.16 Ga, and a small population is 1.22 Ga. These ages correspond to the Shawinigan and Elzevirian orogenies, and provide minimum ages for deposition. The youngest detrital grains with ages of 1.25–1.24 Ga provide maximum depositional ages. Quartzites (and pelitic gneisses) have a wide range of detrital zircon ages that reflect local Mesoproterozoic Grenville sources and Paleoproterzoic and Archean sources in the northern Grenville Province and elsewhere in Laurentia. Most notable is a large population of 1.9–1.8 Ga zircon which point towards derivation from the Penokean orogen in the Midcontinent or Makkovikian–Ketilidian orogen of Labrador and Greenland; indicating long sedimentary transport distances. The similarities in depositional ages and detrital zircon ages between Frontenac terrane and Adirondack metasedimentary rocks suggest a shared sedimentary history which we interpret as deposition in the same Trans-Adirondack backarc basin at ca. 1.25 Ga.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140654934","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}
There are numerous Neoarchean metasedimentary rock packages in the Slave craton, and they serve as important archives of tectonic processes. Little is documented on the Neoarchean sedimentary packages of the Winter Lake greenstone belt of the central Slave craton, however, and their interpretation can aid in the understanding of the final stages of Slave craton amalgamation. This project investigates the depositional environments and tectonic settings of the Itchen Formation and Sherpa Formation of the Winter Lake greenstone belt. Our study provides constraints for reconstructing the Neoarchean evolution of the central Slave craton through bedrock mapping and facies analysis. The Itchen Formation consists of submature mudstone, siltstone, and sandstone, with preserved graded bedding, planar bedding, and flame structures. Unconformably overlying the Itchen Formation is the Sherpa Formation, which is dominated by polymictic conglomerates and coarse-grained sandstones with preserved cross-bedding, imbricated clasts, and scour surfaces. The Itchen Formation is interpreted to have been deposited in a convergent basin (i.e., retro-arc foreland basin), where two facies associations outline turbidite and suspension sedimentation consistent with submarine fan deposition on a continental slope and a basin floor environment. By contrast, the Sherpa Formation has three facies associations representing dominantly alluvial–fluvial environments in terrestrial–marine–lacustrine settings deposited in pull-apart basins resulting from transtensional forces associated with the Beniah fault zone.
{"title":"Facies analysis for the Neoarchean Itchen and Sherpa formations of the Winter Lake greenstone belt, Slave craton, Northwest Territories, Canada","authors":"E.J. MacMillan, B. Knox, Y. M. DeWolfe, C. Partin","doi":"10.1139/cjes-2023-0054","DOIUrl":"https://doi.org/10.1139/cjes-2023-0054","url":null,"abstract":"There are numerous Neoarchean metasedimentary rock packages in the Slave craton, and they serve as important archives of tectonic processes. Little is documented on the Neoarchean sedimentary packages of the Winter Lake greenstone belt of the central Slave craton, however, and their interpretation can aid in the understanding of the final stages of Slave craton amalgamation. This project investigates the depositional environments and tectonic settings of the Itchen Formation and Sherpa Formation of the Winter Lake greenstone belt. Our study provides constraints for reconstructing the Neoarchean evolution of the central Slave craton through bedrock mapping and facies analysis. The Itchen Formation consists of submature mudstone, siltstone, and sandstone, with preserved graded bedding, planar bedding, and flame structures. Unconformably overlying the Itchen Formation is the Sherpa Formation, which is dominated by polymictic conglomerates and coarse-grained sandstones with preserved cross-bedding, imbricated clasts, and scour surfaces. The Itchen Formation is interpreted to have been deposited in a convergent basin (i.e., retro-arc foreland basin), where two facies associations outline turbidite and suspension sedimentation consistent with submarine fan deposition on a continental slope and a basin floor environment. By contrast, the Sherpa Formation has three facies associations representing dominantly alluvial–fluvial environments in terrestrial–marine–lacustrine settings deposited in pull-apart basins resulting from transtensional forces associated with the Beniah fault zone.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140682938","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}
T. Slagstad, Michael R.M. Easton, Magdalena H. Huyskens, N. Culshaw
Combined U–Pb and Hf isotopic analysis of detrital and igneous zircon provides information about variations in crustal addition vs. reworking through time. However, whereas detrital zircon data from only a few samples can provide information about extended periods of orogenic activity, this approach lacks the geological context that comes with studying igneous zircon and may not record mid- and deep-crustal sources or sources isolated from sites of deposition. Conversely, igneous zircon is likely to miss sources that were removed by later tectonic activity, but which may be preserved in the detrital record. The Central Gneiss Belt of the SW Grenville Province in Ontario has a relatively well-understood orogenic architecture and records active-margin growth and reworking between ca. 1900–1200 Ma. We present U–Pb and Hf isotope data of zircon from 30 orthogneiss samples ranging in age from ca. 1750 to 1250 Ma, covering all tectonostratigraphic levels of the Central Gneiss Belt. As expected, the detrital and igneous datasets display many of the same overall features, such as crustal growth along the SW Laurentian active margin; however, there are also some distinct differences. In particular, sedimentation appears to have taken place near the active margin, with little or no input from distal inboard sources, thus missing this significant component of reworked crust. This study highlights the need for a combination of detrital and igneous samples in order to provide the most complete picture of long-lived accretionary orogenic systems.
对碎屑岩锆石和火成岩锆石进行 U-Pb 和 Hf 同位素综合分析，可提供有关地壳增生与再加工随时间变化的信息。然而，仅从少量样本中获得的碎屑锆石数据可以提供有关造山活动长时期的信息，但这种方法缺乏研究火成岩锆石所需的地质背景，可能无法记录中、深地壳来源或与沉积地点隔离的来源。相反，火成岩锆石很可能会遗漏被后来的构造活动移走的矿源，但这些矿源可能保留在碎屑记录中。安大略省西南格勒维尔省的中央片麻岩带具有相对完善的造山构造，记录了约 1900-1200 Ma 之间的活动边缘增长和再加工。我们展示了来自 30 个正长片麻岩样本的锆石的 U-Pb 和 Hf 同位素数据，这些样本的年龄从大约 1750 到 1250 Ma 不等，涵盖了中央片麻岩带的所有构造地层层位。正如预期的那样，碎屑岩数据集和火成岩数据集显示出许多相同的总体特征，例如沿劳伦伦西南部活动边缘的地壳增长；但是，也存在一些明显的差异。特别是，沉积似乎是在活动边缘附近进行的，很少或根本没有来自远端内侧来源的沉积，因此缺少了再造地壳的这一重要组成部分。这项研究突出表明，需要将碎屑岩样本和火成岩样本结合起来，才能最全面地了解长寿命增生造山系统。
{"title":"Complementarity of Hf isotopes from detrital and igneous zircon: an example from the Central Gneiss Belt, Grenville Province, Ontario","authors":"T. Slagstad, Michael R.M. Easton, Magdalena H. Huyskens, N. Culshaw","doi":"10.1139/cjes-2024-0017","DOIUrl":"https://doi.org/10.1139/cjes-2024-0017","url":null,"abstract":"Combined U–Pb and Hf isotopic analysis of detrital and igneous zircon provides information about variations in crustal addition vs. reworking through time. However, whereas detrital zircon data from only a few samples can provide information about extended periods of orogenic activity, this approach lacks the geological context that comes with studying igneous zircon and may not record mid- and deep-crustal sources or sources isolated from sites of deposition. Conversely, igneous zircon is likely to miss sources that were removed by later tectonic activity, but which may be preserved in the detrital record. The Central Gneiss Belt of the SW Grenville Province in Ontario has a relatively well-understood orogenic architecture and records active-margin growth and reworking between ca. 1900–1200 Ma. We present U–Pb and Hf isotope data of zircon from 30 orthogneiss samples ranging in age from ca. 1750 to 1250 Ma, covering all tectonostratigraphic levels of the Central Gneiss Belt. As expected, the detrital and igneous datasets display many of the same overall features, such as crustal growth along the SW Laurentian active margin; however, there are also some distinct differences. In particular, sedimentation appears to have taken place near the active margin, with little or no input from distal inboard sources, thus missing this significant component of reworked crust. This study highlights the need for a combination of detrital and igneous samples in order to provide the most complete picture of long-lived accretionary orogenic systems.","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":"140699469","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}
Pavel Kabanov, Keith Dewing, E.A. Atkinson, R. D. VandenBerg
The Devonian clastic wedge (DCW) and underlying carbonate platforms and basinal mudrocks of the study area are re-examined using legacy seismic data and XRF surveys of borehole chip samples. The Ordovician-Devonian basinal succession of Melville Island is consolidated under the name Ibbett Bay Group within the Northwest Territories, whereas equivalent strata in Nunavut are grouped into the Cape Phillips Formation. The Kitson Formation black shale is correlative with the upper Ibbett Bay Group. Six horizons with high TOC and high gamma response are traced in the Ordovician-Devonian, with the fourth (4a) approximating the Silurian/Devonian boundary; the upper two (4b, 5) are Emsian and Eifelian. In the direction of progradation, the base of Kitson Formation rises stratigraphically from gamma horizon 4a to 5. The upper Kitson represents basinal toes of westward prograding DCW clinoforms. The Blackley and Cape de Bray formations of Embry and Klovan (1976) are not traceable enough to warrant their formation rank. We revert to the original usage of Tozer and Thorsteinsson (1964) where these units are members within the Weatherall Formation. The distinctive seismic character of the Cape de Bray in western and central Melville Island warrants its recognition as a formal member; elsewhere it is informal as it cannot be consistently traced. The Blackey is treated as a formal member in an outcrop area of ⁓2000 km2 where it was defined; it is not recognized in the subsurface. Onset of the DCW is tentatively linked to flexural subsidence and crustal thickening caused by the Romanzof Orogeny in the hinterland.
利用遗留的地震数据和钻孔芯片样本的 XRF 勘测，对研究区域的泥盆纪碎屑楔（DCW）和下伏碳酸盐平台及基底泥岩进行了重新研究。梅尔维尔岛的奥陶纪-泥盆纪基底演替在西北地区被整合为伊贝特湾组，而努纳武特地区的相应地层则被整合为菲利普斯角地层。Kitson Formation 黑色页岩与上伊贝特湾组相关。在奥陶系-德文系地层中，有六个具有高总有机碳和高伽马响应的地层，其中第四个地层（4a）接近志留纪/德文系边界；上面两个地层（4b、5）分别是埃姆西亚和埃菲尔西亚地层。在渐变方向上，Kitson 地层的基底从伽马层 4a 向 5 层上升。Kitson地层上部代表了DCW地块向西递变的基底趾部。Embry和Klovan（1976年）的Blackley地层和Cape de Bray地层没有足够的可追溯性来证明其地层等级。我们恢复了 Tozer 和 Thorsteinsson（1964 年）最初的用法，将这些单元归入 Weatherall 地层。梅尔维尔岛西部和中部的德布雷角（Cape de Bray）具有独特的地震特征，因此被认定为正式岩层；而其他地区的德布雷角（Cape de Bray）则因无法持续追踪而被认定为非正式岩层。布拉克基（Blackey）在其被界定的⁓2000 平方公里的露头区域内被视为正式岩层；在地下则不被承认。DCW的形成与腹地罗曼佐夫造山运动造成的挠曲下沉和地壳增厚有初步联系。
{"title":"The Devonian clastic wedge and underlying strata of SW Canadian Arctic Archipelago: stratigraphic revisions","authors":"Pavel Kabanov, Keith Dewing, E.A. Atkinson, R. D. VandenBerg","doi":"10.1139/cjes-2023-0144","DOIUrl":"https://doi.org/10.1139/cjes-2023-0144","url":null,"abstract":"The Devonian clastic wedge (DCW) and underlying carbonate platforms and basinal mudrocks of the study area are re-examined using legacy seismic data and XRF surveys of borehole chip samples. The Ordovician-Devonian basinal succession of Melville Island is consolidated under the name Ibbett Bay Group within the Northwest Territories, whereas equivalent strata in Nunavut are grouped into the Cape Phillips Formation. The Kitson Formation black shale is correlative with the upper Ibbett Bay Group. Six horizons with high TOC and high gamma response are traced in the Ordovician-Devonian, with the fourth (4a) approximating the Silurian/Devonian boundary; the upper two (4b, 5) are Emsian and Eifelian. In the direction of progradation, the base of Kitson Formation rises stratigraphically from gamma horizon 4a to 5. The upper Kitson represents basinal toes of westward prograding DCW clinoforms. The Blackley and Cape de Bray formations of Embry and Klovan (1976) are not traceable enough to warrant their formation rank. We revert to the original usage of Tozer and Thorsteinsson (1964) where these units are members within the Weatherall Formation. The distinctive seismic character of the Cape de Bray in western and central Melville Island warrants its recognition as a formal member; elsewhere it is informal as it cannot be consistently traced. The Blackey is treated as a formal member in an outcrop area of ⁓2000 km2 where it was defined; it is not recognized in the subsurface. Onset of the DCW is tentatively linked to flexural subsidence and crustal thickening caused by the Romanzof Orogeny in the hinterland.","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":"140702594","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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