Paleomagnetism of dykes from the Groundhog River Block, northern Ontario: implications for the uplift history of the Kapuskasing Structural Zone

1991 ◽  
Vol 28 (9) ◽  
pp. 1424-1428 ◽  
Author(s):  
M. P. Bates ◽  
H. C. Halls
Keyword(s):  
Superior Province ◽  
High Grade ◽  
Northern Ontario ◽  
Central Segment ◽  
History Of ◽  
Crustal Uplift ◽  
Uplift History ◽  
Host Rocks

The groundhog River Block (GB) forms the central segment of the Kapuskasing Structural Zone a fault-bounded belt of Proterozoic crustal uplift in the southern Superior Province. Dykes adjacent to the GB carry a magnetization (D = 11°, I = 26°, α95 = 27°, N = 3) that is characteristic of 2.45 Ga Matachewan dykes. However, within the GB, dykes and high-grade gneissic host rocks carry a steep positive magnetization (D = 295°, I = 83°, α95 = 12°, N = 9) that also partially overprints the dykes immediately outside the GB. The boundaries between the contrasting paleomagnetic signatures coincide with boundary faults and changes in paleopressure that define the GB. The steep magnetization in the GB was acquired during uplift and cooling close to the time at about 1.95 Ga when a virtually antiparallel remanence of similar origin was being formed in the Chapleau Block, the southern segment of the Kapuskasing Structural Zone.

The Pikwitonei Granulite Domain, Manitoba: a giant Neoarchean high-grade terrane in the northwest Superior ProvinceThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.N. Machado, T.E. Krogh, and W. Weber are deceased.

2011 ◽  
Vol 48 (2) ◽  
pp. 205-245 ◽  
Author(s):  
L. M. Heaman ◽  
Ch. O. Böhm ◽  
N. Machado ◽  
T. E. Krogh ◽  
W. Weber ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Superior Province ◽  
High Grade ◽  
Metamorphic Zircon ◽  
Special Issue ◽  
Metamorphic History ◽  
Zircon Growth ◽  
The World ◽  
Northwestern Margin ◽  
History Of

The Pikwitonei Granulite Domain located at the northwestern margin of the Superior Province is one of the largest Neoarchean high-grade terranes in the world, with well-preserved granulite metamorphic assemblages preserved in a variety of lithologies, including enderbite, opdalite, charnockite, and mafic granulite. U–Pb geochronology has been attempted to unravel the protolith ages and metamorphic history of numerous lithologies at three main localities; Natawahunan Lake, Sipiwesk Lake, and Cauchon Lake. The U–Pb age results indicate that some of the layered enderbite gneisses are Mesoarchean (3.4–3.0 Ga) and the more massive enderbites are Neoarchean. The high-grade metamorphic history of the Pikwitonei Granulite Domain is complex and multistage with at least four episodes of metamorphic zircon growth identified: (1) 2716.1 ± 3.8 Ma, (2) 2694.6 ± 0.6 Ma, (3) 2679.6 ± 0.9 Ma, and (4) 2642.5 ± 0.9 Ma. Metamorphic zircon growth during episodes 2 and 3 are interpreted to be regional in extent, corresponding to M1 amphibolite- and M2 granulite-facies events, respectively, consistent with previous field observations. The youngest metamorphic episode at 2642.5 Ma is only recognized at southern Cauchon Lake, where it coincides with granite melt production and possible development of a major northeast-trending deformation zone. The timing and multistage metamorphic history recorded in the Pikwitonei Granulite Domain is similar to most Superior Province high-grade terranes and marks a fundamental break in Archean crustal evolution worldwide at the termination of prolific global Neoarchean greenstone belt formation.

Archean crustal evolution of the northwestern Superior craton margin: U-Pb zircon results from the Split Lake Block

1999 ◽  
Vol 36 (12) ◽  
pp. 1973-1987 ◽  
Author(s):  
Christian O Böhm ◽  
Larry M Heaman ◽  
M Timothy Corkery
Keyword(s):  
Superior Province ◽  
High Grade ◽  
Grade Metamorphism ◽  
Metamorphic History ◽  
Zircon Growth ◽  
Growth History ◽  
Northwestern Margin ◽  
History Of ◽  
High Grade Metamorphism ◽  
Superior Craton

The Split Lake Block forms a partly retrogressed, granulite-grade basement segment located at the northwestern margin of the Superior Province in Manitoba. Unlike other segments along the craton margin, the effects of Proterozoic tectonism are relatively minor in the Split Lake Block, making it amenable to establishing firm temporal constraints for the Archean magmatic and metamorphic history of the northwestern Superior Province margin. Consequently, samples from the main lithological units within the Split Lake Block were selected for precise single-grain U-Pb zircon geochronology. Heterogeneous zircon populations isolated from representative enderbite, tonalite, and granodiorite samples reveal a complex growth history with pre-2.8 Ga protolith ages (e.g., 2841 ± 2 Ma tonalite), possibly as old as 3.35 Ga as indicated in a granodiorite sample. The youngest Archean granitic magmatism identified in the eastern Split Lake Block is represented by the 2708 ± 3 Ma Gull Lake granite. A U-Pb zircon age of 2695+4-1 Ma obtained for leucosome in mafic granulite is interpreted to reflect the timing of granulite-grade metamorphism in the Split Lake Block, supported by polyphase zircon growth and (or) lead loss at ca. 2.7 Ga in the enderbite sample. A younger phase of metamorphic zircon growth at ca. 2.62 Ga is documented in the tonalite and granodiorite zircon populations. The 2.70-2.71 Ga crust formation, the occurrence of ca. 2695 Ma high-grade metamorphism, and broadly contemporaneous Paleoproterozoic mafic dykes in both the Split Lake Block and Pikwitonei Granulite Domain imply a common evolution of these high-grade terrains along the northwestern Superior craton margin since the late Archean.

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on the P–T evolution from igneous, metasomatic and metamorphic amphiboles

2020 ◽  
Vol 84 (5) ◽  
pp. 662-690 ◽  
Author(s):  
Emil Aarestrup ◽  
Taus R. C. Jørgensen ◽  
Paul E.B. Armitage ◽  
Allen P. Nutman ◽  
Ole Christiansen ◽  
...  
Keyword(s):  
High Strain ◽  
High Grade ◽  
Field Observations ◽  
Metamorphic History ◽  
Minimum Age ◽  
History Of ◽  
Mineral Data ◽  
Host Rocks ◽  
Layered Complex ◽  
Representative Samples

AbstractThe metamorphic history of the Mesoarchean Amikoq Layered Complex within the Akia terrane of SW Greenland was characterised by electron microprobe mineral data and detailed petrography on 12 representative samples, integrated with zircon U–Pb geochronology and petrology. The complex intruded into a >3004 Ma supracrustal association now consisting of granoblastic metabasites with subordinate quartz-rich gneiss. Supracrustal host rocks contain a relict high-temperature assemblage of orthopyroxene–clinopyroxene (± pigeonite exsolution lamellae, exsolved at ~975–1010°C), which is interpreted to pre-date the Amikoq intrusion. Cumulate to granoblastic-textured rocks of the main Amikoq Layered Complex range modally from leuconorite to melanorite, orthopyroxenite to harzburgite/dunite and rare hornblende melagabbro. Observed mineralogy of main complex noritic lithologies is essentially relict igneous with orthopyroxene–biotite and hornblende–plagioclase thermometers yielding temperatures of ~800–1070°C. An anatectic zircon megacryst from a patchy quartzo–feldspathic leucosome hosted in an orthopyroxene-dominated Amikoq rock reflects local anatexis at peak metamorphic P–T conditions and yields an intrusion minimum age of 3004 ± 9 Ma. Field observations indicate local anatexis of orthopyroxene-dominated lithologies, possibly indicating a post-intrusion peak temperature of >900°C. The last preserved stages of retrogression are recorded in paragneiss plagioclase–garnet, biotite–garnet and host rock ilmenite–magnetite pairs (≤3 kbar and ~380–560°C).The Amikoq Complex intruded a MORB-like crustal section and the former remained relatively undisturbed in terms of modal mineralogy. Preservation of igneous textures and mineralogy are related to an anhydrous, high-grade metamorphic history that essentially mimics igneous crystallisation conditions, whereas local high-strain zones acted as fluid pathways resulting in hydrous breakdown of igneous minerals. There is no evidence of equilibration of the intrusion at sub-amphibolite-facies conditions.

scholarly journals Uplift history of the Sila Massif, southern Italy, deciphered from cosmogenic10Be erosion rates and river longitudinal profile analysis

Tectonics ◽  
2012 ◽  
Vol 31 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Valerio Olivetti ◽  
Andrew J. Cyr ◽  
Paola Molin ◽  
Claudio Faccenna ◽  
Darryl E. Granger
Keyword(s):  
Southern Italy ◽  
Profile Analysis ◽  
Longitudinal Profile ◽  
Erosion Rates ◽  
History Of ◽  
Uplift History

Natural history of high grade pin in prostate biopsies

2002 ◽  
Vol 1 (1) ◽  
pp. 119
Author(s):  
Hubert Volgger ◽  
Wolfgang Horninger ◽  
Hannes Steiner ◽  
Hermann Rogatsch ◽  
Georg Bartsch
Keyword(s):  
Natural History ◽  
High Grade ◽  
Prostate Biopsies ◽  
History Of

A rare case of high-grade chondroblastic osteosarcoma post-radiotherapy for a right frontal oligodendroglioma

2021 ◽  
Vol 2 (2) ◽  
Author(s):  
Sinead Horan ◽  
◽  
Oscar Breathnach ◽  
Liam Grogan ◽  
David Fitzpatrick ◽  
...  
Keyword(s):  
Radiation Exposure ◽  
Brain Tumour ◽  
Radiation Field ◽  
Rare Case ◽  
Previous History ◽  
High Grade ◽  
History Of ◽  
Rare Malignancy ◽  
Chondroblastic Osteosarcoma

This is the fourteenth case of an intracranial and dural-based osteosarcoma in the literature to date. The case involves a forty-year old woman with a previous history of a brain tumour, which was treated with surgery, chemotherapy and radiotherapy six years previously. The hypothesis is that this rare malignancy is secondary to the radiation exposure given the growth of the lesion in the previous radiation field

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