Paleoproterozoic crustal history of the southwestern Grenville Province: evidence from Nd isotopic mapping

1995 ◽  
Vol 32 (4) ◽  
pp. 472-485 ◽  
Author(s):  
C. Holmden ◽  
A. P. Dickin
Keyword(s):  
Crustal Material ◽  
Grenville Province ◽  
Detrital Zircon Geochronology ◽  
Bay Area ◽  
The North ◽  
History Of ◽  
Depositional Age ◽  
Central Gneiss Belt ◽  
Superior Craton ◽  
Common Association

Nd isotopic mapping in the North Bay area of the Central Gneiss Belt, southwestern Grenville Province, has revealed the precise trend of a TDM model age line developed between the uplifted southern margin of the Archean Superior craton (TDM = 2.7 Ga) and a Paleoproterozoic allochthon (TDM = 1.9 Ga). Separating these two crustal blocks is a narrow zone of gneisses with intermediate TDM ages. These transitional gneisses are interpreted to reflect a remnant fault or ductile shear zone, of uncertain age, along which crustal material from both blocks mechanically mixed during their juxtaposition. Accordingly, the nature of the TDM line in the North Bay area is interpreted to be tectonic. In the Temiscaming area, widespread exposures of mature metasedimentary gneisses are shown by their TDM ages to be dominantly of Paleoproterozoic provenance. These results are consistent with the existing detrital zircon geochronology, inferring a maximum depositional age of ~1.7 Ga. The anorogenic chemistry of the North Bay orthogneiss and mixed calc-alkaline–alkaline chemistry of the Temiscaming gneisses suggest a connection between Paleoproterozoic anorogenic magmatism and synsedimentary quartzite deposition, which is a common association in 1.9–1.6 Ga accretionary orogens of southern Laurentia. The relatively close correspondence between widespread 1.9 Ga TDM ages and U–Pb crystallization ages as old as 1.74 Ga implies that rocks of the Central Gneiss Belt were originally the juvenile products of Paleoproterozoic orogenesis.

scholarly journals Monazite U–Th–Pb geochronology of the Central Metasedimentary Belt Boundary Zone (CMBbz), Grenville Province, Ontario Canada

2018 ◽  
Vol 55 (9) ◽  
pp. 1063-1078 ◽  
Author(s):  
Michelle J. Markley ◽  
Steven R. Dunn ◽  
Michael J. Jercinovic ◽  
William H. Peck ◽  
Michael L. Williams
Keyword(s):  
Shear Zone ◽  
Crustal Thickening ◽  
Boundary Zone ◽  
Grenville Province ◽  
Metamorphic History ◽  
Crustal Thinning ◽  
Tectonic Significance ◽  
History Of ◽  
Central Gneiss Belt ◽  
Scale Shear

The Central Metasedimentary Belt boundary zone (CMBbz) is a crustal-scale shear zone that juxtaposes the Central Gneiss Belt and the Central Metasedimentary Belt of the Grenville Province. Geochronological work on the timing of deformation and metamorphism in the CMBbz is ambiguous, and the questions that motivate our study are: how many episodes of shear zone activity did the CMBbz experience, and what is the tectonic significance of each episode? We present electron microprobe data from monazite (the U–Th–Pb chemical method) to directly date deformation and metamorphism recorded in five garnet–biotite gneiss samples collected from three localities of the CMBbz of Ontario (West Guilford, Fishtail Lake, and Killaloe). All three localities yield youngest monazite dates ca. 1045 Ma; most of the monazite domains that yield these dates are high-Y rims. In comparison with this common late Ottawan history, the earlier history of the three CMBbz localities is less clearly shared. The West Guilford samples have monazite grain cores that show older high-Y domains and younger low-Y domains; these cores yield a prograde early Ottawan (1100–1075 Ma) history. The Killaloe samples yield a well-defined prograde, pre- to early Shawinigan history (i.e., 1220–1160 Ma) in addition to some evidence for a second early Ottawan event. In other words, the answers to our research questions are: three events; a Shawinigan event possibly associated with crustal thickening, an Ottawan event possibly associated with another round of crustal thickening, and a late Ottawan event that resists simple interpretation in terms of metamorphic history but that coincides chronologically with crustal thinning at the base of an orogenic lid.

An application of Nd isotope mapping in structural geology: delineating an allochthonous Grenvillian terrane at North Bay, Ontario

2003 ◽  
Vol 140 (5) ◽  
pp. 539-548 ◽  
Author(s):  
A. P. DICKIN ◽  
R. H. MCNUTT
Keyword(s):  
Structural Geology ◽  
Amphibolite Facies ◽  
High Grade ◽  
Grenville Province ◽  
Nd Isotope ◽  
Bay Area ◽  
The North ◽  
Depleted Mantle ◽  
Different Types ◽  
Isotope Analyses

Fifty new Nd isotope analyses are presented from the North Bay area of the Grenville Province in Ontario. These data are used to map the extent of an allochthonous Grenvillian terrane which is an outlier of the Allochthonous Polycyclic Belt of the Grenville Province. Amphibolite facies orthogneisses from the allochthonous terrane have depleted mantle Nd model ages (TDM) below 1.8 Ga, whereas the gneisses of the structurally underlying parautochthon almost invariably have model ages above 1.8 Ga. The distribution of model ages is consistent with the distribution of distinct types of metabasic rock, used by other researchers as the criterion for recognizing rocks of the allochthonous and parautochthonous belts of the Grenville Province. The agreement between these different types of evidence demonstrates that Nd isotope mapping is a reliable and powerful tool for mapping terrane boundaries in high-grade metamorphic belts.

Crustal architecture and tectonic assembly of the Central Gneiss Belt, southwestern Grenville Province, Canada: a new interpretation

2000 ◽  
Vol 37 (2-3) ◽  
pp. 217-234 ◽  
Author(s):  
J WF Ketchum ◽  
A Davidson
Keyword(s):  
Structural Model ◽  
Hanging Wall ◽  
Mafic Rock ◽  
Grenville Province ◽  
The North ◽  
Rock Types ◽  
Structural Barrier ◽  
New Interpretation ◽  
Central Gneiss Belt ◽  
Tectonic Boundary

The Central Gneiss Belt, southwestern Grenville Province, is characterized by parautochthonous crust in the north and allochthonous lithotectonic domains in the south. Despite nearly two decades of study, the basal décollement to allochthonous domains transported from the southeast, known as the allochthon boundary thrust, has not been precisely located throughout much of the belt. Between Lake Nipissing and Georgian Bay where its surface trace is known, it separates 1.24 Ga Sudbury metadiabase in the footwall from eclogite remnants and 1.17-1.15 Ga coronitic olivine metagabbro confined to its hanging wall. On the premise that this relationship can be used to trace the allochthon boundary thrust elsewhere in the Central Gneiss Belt, we have sought to extend the known distribution of these mafic rock types, making use of field, petrographic, and geochemical criteria to identify them. New occurrences of all three mafic types are identified in a region extending from south of Lake Nipissing to western Quebec, and the mutually exclusive pattern of occurrence is maintained within this region. Structural trends and reconnaissance mapping of high-strain zones that appear to represent a structural barrier to the mafic suites suggest that the allochthon boundary thrust lies well to the north of its previously suggested location. Our preferred surface trace for it passes around the southern end of the Powassan batholith and through the town of North Bay before turning east to join up with the Lac Watson shear zone in western Quebec. This suggests that a large segment of "parautochthonous" crust lying north of, and including, the Algonquin domain is in fact allochthonous. The mutually exclusive distribution of the mafic suites points to significant separation of allochthonous and parautochthonous components prior to the Grenvillian orogeny, in accord with models of pre-Grenvillian continental rifting proposed by others. Despite a relative abundance of geological and geochronological data for the Central Gneiss Belt and a mafic rock distribution that appears to successfully locate a major tectonic boundary, we emphasize the need for additional field and laboratory work aimed at testing our structural model.

Post-convergent structures in lower parts of the 1090–1050 Ma (early-Ottawan) thrust-sheet stack, Grenville Province of Ontario, southern Canadian Shield

2014 ◽  
Vol 51 (3) ◽  
pp. 243-265 ◽  
Author(s):  
W.M. Schwerdtner ◽  
Toby Rivers ◽  
Brant Zeeman ◽  
C.C. Wang ◽  
Jason Tsolas ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Lateral Extension ◽  
Significant Component ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Granite Pegmatite ◽  
Horizontal Length ◽  
History Of ◽  
Central Gneiss Belt ◽  
Highly Strained

Remnants of the early-Ottawan thrust-sheet stack are exposed in the Central Gneiss Belt (CGB, lower portion of stack) and the Composite Arc Belt (upper portion of stack). Post-collisional vertical thinning and associated horizontal extension of the stack produced structures ranging over eight orders of magnitude in horizontal length, and both orogen-parallel and orogen-perpendicular in orientation. At the 100 km scale, the fold-induced constriction in the northern Parry Sound domain appears to have been enhanced, and lineation trend lines in its footwall locally deflected, by a component of NW–SE (i.e., orogen-perpendicular) flattening and a component of NE–SW (i.e., orogen-parallel) ductile extension. At the 10 km scale, four non-cylindrical lenticular bodies of gabbro–anorthosite gneiss within the domain, inferred to be triaxial mega-boudins or heterogeneously strained plutons, are separated by large extensional bending folds, the complementary structures attesting to a component of NW–SE flattening and a component of NE–SW extension. Non-cylindrical lenticular structures in other domains of the CGB, interpreted as triaxial foliation mega-boudins, exceed 30 km in length. Their moderately strained granulite-facies interiors give way to highly strained amphibolite-facies margins, thus documenting subvertical ductile flattening and multi-lateral extension during retrogression. Well-layered, highly strained gneiss is commonly deformed by steep NE–SW-trending extensional faults and associated monoclinal fault-propagation folds (FPFs). The short limbs of the FPFs bend the regional elongation lineation and host a set of fault-parallel, unstrained to slightly deformed, granite–pegmatite dikes. Dilation vectors of most dikes are oblique to the granite–pegmatite contacts, and the sense of their tangential components attests to orogen-perpendicular extension. The fault-parallel dikes and associated FPFs are cut by a set of unstrained dikes. Collectively these observations document a prolonged history of post-collisional extension of the mid crust, from ductile structures indicative of a significant component of orogen-parallel extension shortly after the metamorphic peak at mid-crustal depths, to brittle–ductile structures indicative of a component of orogen-perpendicular extension and associated magmatic dilation following its exhumation and cooling in the upper crust.

scholarly journals Exhumation history of the Variscan suture: Constrains on the detrital zircon geochronology from Carboniferous–Permian sandstones (Northern Gemericum; Western Carpathians)

2019 ◽  
Vol 70 (6) ◽  
pp. 512-530
Author(s):  
Anna Vozárová ◽  
Katarína Šarinová ◽  
Dušan Laurinc ◽  
Elena Lepekhina ◽  
Jozef Vozár ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Tectonic Setting ◽  
Age Distribution ◽  
Foreland Basin ◽  
Sedimentary Basins ◽  
Distribution Patterns ◽  
Magmatic Zircon ◽  
Detrital Zircon Geochronology ◽  
History Of ◽  
Depositional Age

Abstract The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and space within the collisional tectonic regime of the Western Carpathian Variscan orogenic belt. The detrital zircon age spectra, obtained from the Mississippian, Pennsylvanian and Permian metasediments, have distinctive age distribution patterns that reflect the tectonic setting of the host sediments. An expressive unimodal zircon distribution, with an age peak at 352 Ma, is shown by the basal Mississippian metasediments. These represent a relic of the convergent trench-slope sedimentary basin fill. In comparison, the Pennsylvanian detrital zircon populations display distinct multimodal distributions, with the main age peaks at 351, 450, 565 Ma and smaller peaks at ~2.0 and ~2.7 Ga. This is consistent with derivation of clastic detritus from the collisional suture into the foreland basin. Similarly, the Permian sedimentary formations exhibit the multimodal distribution of zircon ages, with main peaks at 300, 355 and 475 Ma. The main difference, in comparison with the Pennsylvanian detrital zircon assemblages, is the sporadic occurrence of the Kasimovian– Asselian (306–294 Ma), as well as the Artinskian–Kungurian (280–276 Ma) igneous zircons. The youngest magmatic zircon ages nearly correspond to the syn-sedimentary volcanic activity with the depositional age of the Permian host sediments and clearly indicate the extensional, rift-related setting.

scholarly journals Revised Maximum Depositional Age for the Ediacaran Browns Hole Formation: Implications for Western Laurentia Neoproterozoic Stratigraphy

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Ashley W. Provow ◽  
Dennis L. Newell ◽  
Carol M. Dehler ◽  
Alexis K. Ault ◽  
W. Adolph Yonkee ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Hole Formation ◽  
Deep Time ◽  
Inductively Coupled ◽  
The North ◽  
Global Connections ◽  
History Of ◽  
Absolute Age ◽  
Depositional Age ◽  
Cordilleran Margin

Abstract Constraining the depositional age of Neoproterozoic stratigraphy in the North American Cordilleran margin informs global connections of major climatic and tectonic events in deep time. Making these correlations is challenging due to a paucity of existing geochronological data and adequate material for absolute age control in key stratigraphic sequences. The late Ediacaran Browns Hole Formation in the Brigham Group of northern Utah, USA, provides a key chronological benchmark on Neoproterozoic stratigraphy. This unit locally comprises <140 m of volcaniclastic rocks with interbedded mafic-volcanic flows that lie within a 3500 m thick package of strata preserving the Cryogenian, Ediacaran, and the lowermost Cambrian history of this area. Prior efforts to constrain the age of the Browns Hole Formation yielded uncertain and conflicting results. Here, we report new laser-ablation-inductively-coupled-mass-spectrometry U-Pb geochronologic data from detrital apatite grains to refine the maximum depositional age of the volcanic member of the Browns Hole Formation to 613±12 Ma (2σ). Apatite crystals are euhedral and pristine and define a single date population, indicating they are likely proximally sourced. These data place new constraints on the timing and tempo of deposition of underlying and overlying units. Owing to unresolved interpretations for the age of underlying Cryogenian stratigraphy, our new date brackets two potential Brigham Group accumulation rate scenarios for ~1400 m of preserved strata: ~38 mm/kyr over ~37 Myr or ~64 mm/kyr over ~22 Myr. These results suggest that the origins of regional unconformities at the base of the Inkom Formation, previously attributed to either the Marinoan or Gaskiers global glaciation events, should be revisited. Our paired sedimentological and geochronology data inform the timing of rift-related magmatism and sedimentation near the western margin of Laurentia.

Holocene megaflood history and provenance of the upper Indus-River. Implication for human migration along the ancient Silk Road at Ladakh.

2020 ◽  
Author(s):  
Choudhurimayum Pankaj Sharma ◽  
Poonam Chahal ◽  
Anil Kumar ◽  
Pradeep Srivastava ◽  
Saurabh Singhal ◽  
...  
Keyword(s):  
Silk Road ◽  
Human Migration ◽  
Provenance Analysis ◽  
Indus River ◽  
Detrital Zircon Geochronology ◽  
The North ◽  
Average Annual Temperature ◽  
History Of ◽  
Ancient Silk Road ◽  
Flooding Events

<p>          The Indus River originating from the Manasarovar Lake runs along the Indus Tsangpo Suture Zone at Ladakh separating the Tethyan Himalaya in the south from the Karakoram Zone in the north. Due to the barrier created by the Pir Panjal Ranges and the Higher Himalaya, Ladakh falls in the rain shadow zone of ISM (Indian Summer Monsoon) with an average annual temperature of ~7.3°C. Random catastrophic hydrological events are known to endanger lives and properties of people residing here. So, determination of frequency, recurrence and forcing mechanism of past extreme floods are crucial in this highly vulnerable area.</p><p>          Here we studied Holocene mega flood history of the Upper Indus River at Ladakh using slack water deposits (SWDs). SWDs are composed of stacks of sand-silt couplets deposited during high flooding events. They are deposited instantly from suspension associated with sharp reduction of flow velocity due to local obstructions. Each couplet represent a flooding event. These events are dated employing Optically Stimulated Luminescence (OSL) using sand and AMS <sup>14</sup>C using charcoal specks and hearth layers. The frequency of these events suggest higher occurrence of mega floods during pronounced northward penetration of ISM. Recurrence Interval (RI) analysis of these events suggest spatial variation in forcing mechanism between the trunk and the main tributary channel (Zanskar). Sedimentary provenance of these events are also analyzed using detrital zircon geochronology. The provenance analysis indicate more efficient sediment transportation along the Zanskar River as compared to the main Indus channel. Post LGM (Last Glacial Maximum) human migration along the channel is revealed from hearths found within these SWDs which generally occurs during post flooding episodes. Materials found within the hearths, chronology and the fashion of occurrence imply migration and cultural connectivity between the Indian sub-continent and the Central Asia along the ancient Silk Road at Ladakh as old as ~14 ka.</p>

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

Sequencing Analysis and Phylogenetic Tree of HPV Isolated from Breast Cancer Patients at Thi-Qar Province/Iraq

2020 ◽  
pp. 37-40
Keyword(s):  
Nucleotide Sequence ◽  
Phylogenetic Tree ◽  
Evolutionary Relationship ◽  
Nucleotide Sequencing ◽  
Sequencing Analysis ◽  
Breast Cancer Patients ◽  
The North ◽  
Formalin Fixed Paraffin ◽  
Formalin Fixed Paraffin Embedded ◽  
History Of

Genetic variety examination has demonstrated fundamental to the understanding of the epidemiological and developmental history of Papillomavirus (HPV), for the development of accurate diagnostic tests and for efficient vaccine design. The HPV nucleotide diversity has been investigated widely among high-risk HPV types. To make the nucleotide sequence of HPV and do the virus database in Thi-Qar province, and compare sequences of our isolates with previously described isolates from around the world and then draw its phylogenetic tree, this study done. A total of 6 breast formalin-fixed paraffin-embedded (FFPE) of the female patients were included in the study, divided as 4 FFPE malignant tumor and 2 FFPE of benign tumor. The PCR technique was implemented to detect the presence of HPV in breast tissue, and the real-time PCR used to determinant HPV genotypes, then determined a complete nucleotide sequence of HPV of L1 capsid gene, and draw its phylogenetic tree. The nucleotide sequencing finding detects a number of substitution mutation (SNPs) in (L1) gene, which have not been designated before, were identified once in this study population, and revealed that the HPV16 strains have the evolutionary relationship with the South African race, while, the HPV33 and HPV6 showing the evolutionary association with the North American and East Asian race, respectively.

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