THE TECTONIC AND METAMORPHIC HISTORY OF THE PRE-CAMBRIAN ROCKS OF THE MBEYA REGION, SOUTH-WEST TANGANYIKA

1962 ◽  
Vol 118 (1-4) ◽  
pp. 295-314 ◽  
Author(s):  
P. E. BROWN
Keyword(s):  
Metamorphic History ◽  
South West ◽  
History Of

Re-investigating the Barrovian metamorphic rocks of the Isbjørnhamna Group, Svalbard Caledonides

2021 ◽  
Author(s):  
Margot Patry ◽  
Iwona Klonowska ◽  
Karolina Kośmińska ◽  
Jarosław Majka
Keyword(s):  
High Arctic ◽  
Metamorphic Rocks ◽  
Metamorphic History ◽  
South West ◽  
Science Centre ◽  
National Science ◽  
History Of ◽  
Orogenic Events ◽  
Preliminary Phase

<p>The Isbjørnhamna Group, which crops out in the south-west of Svalbard in the High Arctic, is crucial for understanding Svalbard’s regional geology. It can be traced in southern Wedel Jarlsberg Land and Sørkapp Land, and it consists of a Barrovian-type series of metapelites that were metamorphosed during the Torellian (c. 640Ma; Majka et al. 2008) and overprinted during the Caledonian orogenesis (Majka & Kośmińska, 2017). Although relatively recent petrological study exists, there are certain gaps in it. In order to fill these gaps, we decided to re-investigate these rocks using the most up-to-date petrochronological approach. Hence, we aim to determine the metamorphic history of these rocks in detail, test the hypothesis if there are indeed several orogenic events registered by these rocks and what was a possible exhumation mechanism responsible for uplift of this sequence.</p><p>The studied garnet-bearing mica schists preserve four different parageneses, ranging from chloritoid to kyanite metamorphic zones. Here we report on the samples containing chlorite and chloritoid, kyanite, staurolite and both staurolite and kyanite. The studied samples are the same exact rocks that have been previously studied by Majka et al. (2008, 2010) using both geothermobarometry and petrogenetic grids in the KFMASH system. According to those authors the estimated pressure-temperature conditions (P-T) were c. 655°C at 11kbar for the kyanite-bearing shist, c. 624°C at 6.6 to 8.7kbar for the staurolite + kyanite pelite and c. 580°C at 8-9kbar for the staurolite-bearing rock. The chloritoid schist has not been studied previously.</p><p>Our preliminary phase equilibrium modelling in the MnNCKFMASHTO system using the Theriak-Domino software indicates P-T conditions of c. 660°C at 7 kbar for the kyanite-schist and c. 575°C at 8 to 9.5kbar for the staurolite-schist, respectively. The chloritoid schist yielded conditions of c. 560°C at 7.5kbar. Further P-T modelling coupled with in-situ Ar-Ar and U-Pb geochronology should allow for much better understanding of the complex geological history of these rocks as well as potential flaws in the previous studies.</p><p> </p><p>Research funded by National Science Centre (Poland) project no. 2019/33/B/ST10/01728.</p><p> </p><p>References:</p><p>Majka & Kośmińska (2017): Arktos, 3:5, 1.17.</p><p>Majka et al. (2008): Geological Magazine, 145, 822-830.</p><p>Majka et al. (2010): Polar Research, 29, 250-264.        </p>

“The Fumes of Polonism and the Stench of Herzenism”: “Vestnik Zapadnoy Rossii” Against Class Revolution and Clas Reaction

2020 ◽  
Vol 58 ◽  
pp. 118-134
Author(s):  
Aleksandr E. Kotov
Keyword(s):  
Short History ◽  
South West ◽  
The People ◽  
History Of ◽  
Stereotypical Image

The journal of Ksenofont A. Govorsky “Vestnik Yugo-Zapadnoy I Zapadnoy Rossii” (“South-West and West Russia Herald”) is known in the history of pubic thought as odious and reactionary. However, this stereotypical image needs some revision: the anti-Polish discourse on the pages of the magazine was not so much nationalistic as anti-aristocratic in nature. Considering the “Poles” primarily as carriers of the aristocratic principles, the editorial board of the magazine claimed to protect the broad masses of the people. Throughout its short history, the magazine consistently opposed both revolutionary and aristocratic propaganda. However, the regional limitations of the problems covered in the magazine did not give it the opportunity to reflect on the essential closeness of the revolutionary and reactionary principles. Yu.F. Samarin and I.S. Aksakov – whose conservative-democratic views, on the whole, were close to “Western Russianism”, promoted by the authors of “Vestnik Yugo-Zapadnoy I Zapadnoy Rossii”, managed to reach that goal.

A Study in the History of Clare, Suffolk; with Special Reference to its Development as a Borough (Alexander Prize Essay, 1928)

1928 ◽  
Vol 11 ◽  
pp. 83-115
Author(s):  
Gladys A. Thornton
Keyword(s):  
Special Reference ◽  
Middle Ages ◽  
Subsequent Development ◽  
Considerable Importance ◽  
Medieval Period ◽  
South West ◽  
Full Development ◽  
History Of ◽  
The Town ◽  
Prize Essay

Clare is situated in the south-west corner of Suffolk, in the valley of the Stour River. At the present day it is only a village, for its market is no longer held; yet its history shows that in earlier times it was of considerable importance, especially during the medieval period, when it was a favourite residence of the Clare lords. The town then had a busy market and a flourishing cloth-making industry; and at one time it seemed possible that Clare might attain full development as a borough, possessing as it did some burghal characteristics. In the following pages it is proposed to study in detail the history of Clare as a seignorial borough during the Middle Ages, and its subsequent development.

Tectono-metamorphic history of the ophiolitic Lento unit (northern Corsica): evidences for the complexity of accretion-exhumation processes in a fossil subduction system

2007 ◽  
Vol 20 (1-2) ◽  
pp. 99-118 ◽  
Author(s):  
Nicola Levi ◽  
Alessandro Malasoma ◽  
Michele Marroni ◽  
Luca Pandolfi ◽  
Matteo Paperini
Keyword(s):  
Metamorphic History ◽  
History Of ◽  
Subduction System

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.

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.

scholarly journals Formation age and metamorphic history of the Nuvvuagittuq Greenstone Belt

2012 ◽  
Vol 220-221 ◽  
pp. 23-44 ◽  
Author(s):  
Jonathan O’Neil ◽  
Richard W. Carlson ◽  
Jean-Louis Paquette ◽  
Don Francis
Keyword(s):  
Greenstone Belt ◽  
Metamorphic History ◽  
History Of
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