New geochronological data on volcanic rocks from northeast Sudan and their implication for crustal evolution

1985 ◽  
Vol 30 (3) ◽  
pp. 263-276 ◽  
Author(s):  
P.M. Klemenic
Keyword(s):  
Volcanic Rocks ◽  
Crustal Evolution ◽  
Geochronological Data

Geochronological data from TTG-type rock associations of the Arroio dos Ratos Complex and implications for crustal evolution of southernmost Brazil in Paleoproterozoic times

2015 ◽  
Vol 57 ◽  
pp. 49-60 ◽  
Author(s):  
Tiago Rafael Gregory ◽  
Maria de Fátima Bitencourt ◽  
Lauro Valentim Stoll Nardi ◽  
Luana Moreira Florisbal ◽  
Farid Chemale
Keyword(s):  
Crustal Evolution ◽  
Geochronological Data

Petrogenesis and Geochronology of the late-Archean Na-rich A Type granite from the Bundelkhand Craton, India: Implication for tectonic and crustal evolution

2020 ◽  
Author(s):  
Mohd Baqar Raza ◽  
Fernando Corfu ◽  
Pritam Nasipuri
Keyword(s):  
High Pressure ◽  
Iron Formation ◽  
Crustal Evolution ◽  
Geochronological Data ◽  
Banded Iron Formation ◽  
Emplacement Temperature ◽  
Eu Anomaly ◽  
Type Granite ◽  
High Silica ◽  
Concordia Diagram

<p>Tonalite-trondhjemite-granodiorite gneisses (TTG) are the oldest litho-units of the Bundelkhand craton. The supracrustal rocks include variable deformed mafic volcanics and Banded Iron Formation. Magmatic zircons from the TTG’s yield an upper intercept of ~ 3590 Ma. The TTG’s gradually grades to a Na-feldspar rich A type porphyric granite towards the south. In this abstract, we report mineralogical, geochemical, and geochronological information of high silica- low Ca - high Na A-type granite from Bundelkhand craton.</p><p>In the TAS diagram, the studied samples plot in the field of granite and have a metaluminous affinity with high Ga/Al and Ce + Y + Nb + Zr values typical of A-type granites. In a primitive normalized multi-element spider diagram, the studied samples exhibit negative Nb, Ti, and P anomalies characteristics of a subduction zone setting. The chondrite normalized REE’s exhibit a strong fractionated pattern with negative Eu anomaly; the LREE are enriched and the HREE depleted with moderate to high (La/Yb)<sub>CN </sub>ratios ranging from 11.12 to 26.24 ppm. The studied samples have plagioclase compositions that vary from X<sub>Ab </sub>= 0.980-0.997 and chlorite compositions varying from X<sub>Mg </sub>= 0.309-0.469.</p><p>Phase equilibria modeling yield an emplacement temperature of 700-750<sup>O</sup>C, at 1.0 GPa. Most of the zircon grains are prismatic with visible cores and rims in optical examinations. In a U-Pb concordia diagram, the grains yield an upper intercept of 2536.6 ± 1.8 Ma. The geochemical and geochronological data taken together, indicate the Na-rich A-type granite generated by the high temperature and high-pressure partial melting of Archaean supracrustal rocks.</p>

Pyroclastic rocks from Kanchanaburi and Uthai Thani Province, Inthanon Zone, Western Thailand

2020 ◽  
Author(s):  
Suwijai Jatupohnkhongchai ◽  
Sirot Salyapongse ◽  
Burapha Phajuy ◽  
Daniela Gallhofer ◽  
Christoph Hauzenberger
Keyword(s):  
Volcanic Rocks ◽  
Potassium Feldspar ◽  
Geochronological Data ◽  
Rock Composition ◽  
Pyroclastic Rocks ◽  
Eu Anomaly ◽  
Geologic Map ◽  
Ree Patterns ◽  
First Time ◽  
Strong Depletion

<p>A series of pyroclastic rocks are mapped as a Silurian-Devonian unit in the Kanchanaburi-Uthai Thani area, Western Thailand, which belongs to the Inthanon Zone. These pyroclastic rocks were discovered and described for the first time in 1977 and mentioned in the 1:250,000 Suphanburi geologic map sheet and report. Since then these rocks were poorly investigated and their formation and geotectonic setting is unclear. As a result, we report petrographic, geochemical and geochronological data of these pyroclastic rocks. Petrographically, the pyroclastic rocks can be described as a meta-quartz-K-feldspar crystal tuff, a meta-quartz crystal tuff, and a meta-lithic tuff. They are made up of mm sized clasts in a finely grained matrix. The clasts consist of potassium feldspar, rounded quartz, embayed quartz, trachytic and metasedimentary rock clasts embedded in a highly altered devitrified fine-ash matrix containing sericite.</p><p>The whole-rock composition shows enrichments in SiO<sub>2</sub> and K<sub>2</sub>O and a strong depletion in CaO and Na<sub>2</sub>O which is related to late alteration of the volcanoclastic rocks. Based on the immobile element classification plot of Pearce 1996, the tuffs can be classified as trachyandesite, trachyte, dacite and rhyolite. Their chondrite-normalized REE patterns display light REE enrichment with nearly flat heavy REE and a negative Eu anomaly, typical for calcalkaline volcanic rocks. Most samples fall in the volcanic arc granites field in the granite discrimination diagrams of Pearce 1984.</p><p>Zircons extracted from the tuffs will be used to constrain their crystallization age by U-Pb LA-MCICPMS dating. This allows us to constrain the age of formation and to place this in context with the closure of the Paleotethys.</p>

scholarly journals New U-Pb geochronological data on the age of volcanic-plutonic assemblage of Oloy belt, Alazey-Oloy fold system (West Chukotka)

2019 ◽  
Vol 487 (6) ◽  
pp. 653-658
Author(s):  
T. V. Kara ◽  
M. V. Luchitskaya ◽  
S. M. Katkov ◽  
E. A. Belousova
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Geochronological Data ◽  
Fold System ◽  
Hypabyssal Intrusions ◽  
Icp Ms ◽  
Age Limits ◽  
Felsic Volcanic

New U-Pb (SIMS and LA-ICP-MS) geochronological data for rocks of Egdygkych complex of hypabyssal intrusions, Nichan and Vukney plutons, and felsic volcanic rocks and tuffs from host strata of Oloy volcanic belt of Alasey-Oloy fold system are obtained. Concordant ages of Egdygkych complex rocks correspond to Early Cretaceous (Berriasian-Valanginian), those for host strata, to the end of Late Jurassic (Tithonian) - beginning of Early Cretaceous (Berriasian). New U-Pb geochronological data allow confidently to distinguish uniform volcanic-plutonic assemblage of Late Jurassic (Tithonian) - Early Cretaceous (Berriasian-Valanginian) age of Oloy volcanic belt. Obtained data more definitely determine age limits of Au-Mo-Cu mineralization, associated with contacts between rocks of Egdydkych complex and host volcanic-sedimentary rocks or contacts of separated intrusive phases.

scholarly journals Zircon U-Pb dating of Mesozoic volcanic and tectonic events in north-west Palmer Land and south-west Graham Land, Antarctica

2009 ◽  
Vol 21 (6) ◽  
pp. 633-641 ◽  
Author(s):  
P.T. Leat ◽  
M.J. Flowerdew ◽  
T.R. Riley ◽  
M.J. Whitehouse ◽  
J.H. Scarrow ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Geochronological Data ◽  
Zircon Age ◽  
North West ◽  
Magmatic Arc ◽  
Tectonic Events ◽  
South West ◽  
Silicic Volcanic ◽  
The Antarctic

AbstractNew whole rock Rb-Sr and zircon U-Pb geochronological data and Sm-Nd isotopic data are presented from the central magmatic arc domain of the Antarctic Peninsula in the area of north-west Palmer Land and south-west Graham Land, Rb-Sr isochrons indicate an age of 169 ± 6 Ma for basement orthogneisses and 132 ± 9 to 71 ± 9 Ma for plutons. A U-Pb age of 183 ± 2.1 Ma, with no detectable inheritance, on zircons from an orthogneiss from Cape Berteaux provides the first reliable age for the orthogneisses, which are interpreted as metamorphosed silicic volcanic rocks, and Sm-Nd data indicate derivation in a mature volcanic arc. The age indicates they may be correlatives of the Jurassic ‘Chon Aike’ volcanism of the eastern Antarctic Peninsula. A U-Pb zircon age of 107 ± 1.7 Ma on a terrestrial volcanic sequence overlying an uncomformity strongly suggests a mid-Cretaceous age for the extensive volcanic cover of north-west Palmer Land that was previously thought to be Jurassic. The unconformity is interpreted to have been a result of compressional uplift related to the Palmer Land event. This is the first date for the event in the western part of the central magmatic arc terrane of the Antarctic Peninsula.

Geochronology and radiogenic isotope geochemistry of plutonic rocks from the central Abitibi subprovince: significance to the internal subdivision and plutono-tectonic evolution of the Abitibi belt

2000 ◽  
Vol 37 (2-3) ◽  
pp. 117-133 ◽  
Author(s):  
W J Davis ◽  
S Lacroix ◽  
C Gariépy ◽  
N Machado
Keyword(s):  
Tectonic Evolution ◽  
Isotope Geochemistry ◽  
Volcanic Rocks ◽  
Granite Gneiss ◽  
Magmatic Evolution ◽  
Geochronological Data ◽  
Two Samples ◽  
Plutonic Complex ◽  
Abitibi Subprovince ◽  
Northern Zone

Nine new U-Pb ages are reported for plutons of the central granite-gneiss zone of the Abitibi belt in Quebec. The large plutonic complex along Lithoprobe seismic reflection line 28 formed by multiple intrusion over at least 40 million years, synchronous with and postdating formation of adjacent volcanic sequences. Ages for the four principal plutons within the complex are: Mistaouac at 2726 ± 2 Ma, Boivin at 2713 ± 2 Ma, Rousseau at 2703 ± 2 Ma, and Paradis at 2686 ± 2 Ma. The latter also constrains deformation within the Laberge deformation zone to be at least in part younger than 2686 Ma. Inherited zircons in the Mistaouac pluton indicate that the oldest pluton formed in significantly older crust (>2.75 Ga), not presently exposed in the area. The La Reine and Waswanapi plutons have ages of ca. 2695 Ma similar to other tonalitic plutons in the area and elsewhere in the Abitibi belt. A syenite pluton deformed within the Douay fault zone, a late fault associated with the Casa Berardi zone, has an age of 2676+6-5 Ma, similar to alkalic plutons associated with the Destor-Porcupine and Cadillac-Larder Lake deformation zones of the southern Abitibi belt. Two samples from the Lac Case pluton yielded monazite ages of 2676 ± 3 and 2660 ± 3 Ma. Nd, Pb, and Sr isotopic compositions for central Abitibi belt plutons show dominantly juvenile sources with minor contributions of older crust in the Lac Case pluton. Although geochronological data for volcanic rocks has been used to suggest that the northern zone is older and magmatic activity youngs to the south, consideration of the ages for plutonic and volcanic rocks does not support such hypothesis. The available data indicate that magmatism occurred throughout the Abitibi subprovince from 2730 to 2685 Ma, permissive of a linked tectono-magmatic evolution for the northern and southern zones.

scholarly journals Permian A-type rhyolites of the Muráň Nappe, Inner Western Carpathians, Slovakia: in-situ zircon U–Pb SIMS ages and tectonic setting

2018 ◽  
Vol 69 (2) ◽  
pp. 187-198 ◽  
Author(s):  
Martin Ondrejka ◽  
Xian-Hua Li ◽  
Rastislav Vojtko ◽  
Marian Putis ◽  
Pavel Uher ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Western Carpathians ◽  
Magmatic Activity ◽  
Extensional Tectonics ◽  
Geochronological Data ◽  
Pb Isotope ◽  
Isotope Technique ◽  
Rhyolitic Rock

AbstractThree representative A-type rhyolitic rock samples from the Muráň Nappe of the inferred Silicic Unit of the Inner Western Carpathians (Slovakia) were dated using the high-precision SIMS U–Pb isotope technique on zircons. The geochronological data presented in this paper is the first in-situ isotopic dating of these volcanic rocks. Oscillatory zoned zircon crystals mostly revealed concordant Permian (Guadalupian) ages: 266.6 ± 2.4 Ma in Tisovec-Rejkovo (TIS-1), 263.3 ± 1.9 Ma in Telgárt-Gregová Hill (TEL-1) and 269.5 ± 1.8 Ma in Veľká Stožka-Dudlavka (SD-2) rhyolites. The results indicate that the formation of A-type rhyolites and their plutonic equivalents are connected to magmatic activity during the Permian extensional tectonics and most likely related to the Pangea supercontinent break-up.

Petrogenesis of the Despen Volcanic Rocks of the Middle–Late Ordovician Volcanoplutonic Association of the Tannu-Ola Terrane (Southwestern Tuva)

2021 ◽  
Vol 62 (6) ◽  
pp. 633-647
Author(s):  
E.V. Vetrov ◽  
A.N. Uvarov ◽  
N.I. Vetrova ◽  
F.A. Letnikov ◽  
I.A. Vishnevskaya ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Explosive Volcanism ◽  
Late Ordovician ◽  
Upper Crust ◽  
Southern Slope ◽  
Geochronological Data ◽  
Eu Anomaly ◽  
Sayan Region ◽  
Ree Patterns ◽  
Southwestern Tuva

Abstract ––We have studied the structure and composition of a volcanic unit in the valley of the Despen River, on the southern slope of the East Tannu-Ola Ridge. The unit was earlier assigned to the Lower Devonian Kendei Formation. The new geological and geochronological data show that it resulted from explosive volcanism at 460–450 Ma. The Despen volcanic rocks formed in association with granitoids of the Argolik complex at the end of the accretion–collision stage of evolution of the Altai–Sayan region, in particular, the Tannu-Ola terrane. These are predominantly felsic ferroan metaluminous and weakly peraluminous nappe volcanic rocks resulted from the differentiation of tholeiitic basalts. Their REE patterns, like those of the Argolik granitoids, are flat in the HREE, show a distinct Eu anomaly, and suggest magma generation at shallow depths in the upper crust. The magmatic source was of subduction origin, as evidenced by the negative Ta–Nb anomalies in the multielement patterns and by εNd(T) = +3.1 to +5.6, and has a Neoproterozoic model age, TNd(DM-2st) = 0.94–0.69 Ga.

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