scholarly journals Linzizong Volcanic Rocks in Linzhou of Tibet: A Volcanic Petrologic Assemblage in Continental Collision Environment

2008 ◽  
Vol 2 (4) ◽  
pp. 128
Author(s):  
Guochen Dong ◽  
Xuanxue Mo ◽  
Zhidan Zhao ◽  
Liang Wang ◽  
Su Zhao
Keyword(s):  
Volcanic Rocks ◽  
Continental Collision ◽  
Special Issue

Himalayan Journal of Sciences Vol.2(4) Special Issue 2004 pp. 128

scholarly journals Origin of potassic postcollisional volcanic rocks in young, shallow, blueschist-rich lithosphere

2021 ◽  
Vol 7 (29) ◽  
pp. eabc0291
Author(s):  
Yu Wang ◽  
Stephen F. Foley ◽  
Stephan Buhre ◽  
Jeremie Soldner ◽  
Yigang Xu
Keyword(s):  
Temporal Trend ◽  
Volcanic Rocks ◽  
Continental Collision ◽  
Mantle Lithosphere ◽  
Source Regions ◽  
Himalayan Belt ◽  
Potassic Rocks

Potassium-rich volcanism occurring throughout the Alpine-Himalayan belt from Spain to Tibet is characterized by unusually high Th/La ratios, for which several hypotheses have brought no convincing solution. Here, we combine geochemical datasets from potassic postcollisional volcanic rocks and lawsonite blueschists to explain the high Th/La. Source regions of the volcanic melts consist of imbricated packages of blueschist facies mélanges and depleted peridotites, constituting a new mantle lithosphere formed only 20 to 50 million years earlier during the accretionary convergence of small continental blocks and oceans. This takes place entirely at shallow depths (<80 km) without any deep subduction of continental materials. High Th/La in potassic rocks may indicate shallow sources in accretionary settings even where later obscured by continental collision as in Tibet. This mechanism is consistent with a temporal trend in Th/La in potassic postcollisional magmas: The high Th/La signature first becomes prominent in the Phanerozoic, when blueschists became widespread.

Paleomagnetic study of the late Neoproterozoic Bull Arm and Crown Hill formations (Musgravetown Group) of eastern Newfoundland: implications for Avalonia and West Gondwana paleogeography1This article is one of a series of papers published in CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 308-327 ◽  
Author(s):  
Sergei A. Pisarevsky ◽  
Phil J.A. McCausland ◽  
Joseph P. Hodych ◽  
Sean J. O’Brien ◽  
Jennifer A. Tait ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Paleomagnetic Data ◽  
Special Issue ◽  
West Gondwana ◽  
Paleomagnetic Study ◽  
Late Neoproterozoic ◽  
Moderate Scale

A paleomagnetic study of subaerial volcanic rocks and associated siltstones of the Ediacaran Bull Arm Formation in the Avalon Zone of Newfoundland revealed a stable bipolar, hematite-borne primary remanence supported by positive conglomerate, contact, and fold tests. Mean remanence directions in two distal areas (Bonavista and Argentia) are similar, indicating a low paleolatitude position of Avalonia at ∼570 Ma. Redbeds of the overlying ∼550 Ma Crown Hill Formation also carry a primary bipolar hematite-borne remanence with moderate inclination, indicating that Avalonia remained at low to medium paleolatitudes through the end of the Ediacaran. Combining our results with previously published paleomagnetic data of Avalonia suggests moderate-scale drift of Avalonia through low southern paleolatitudes through the latter half of the Ediacaran, providing a paleogeographic context for the development of the first complex metazoan life.

scholarly journals A short, sharp pulse of potassium-rich volcanism during continental collision and subduction

Geology ◽  
2019 ◽  
Vol 47 (11) ◽  
pp. 1079-1082 ◽  
Author(s):  
M.R. Palmer ◽  
E.Y. Ersoy ◽  
C. Akal ◽  
İ. Uysal ◽  
Ş.C. Genç ◽  
...  
Keyword(s):  
High Pressure ◽  
Isotope Composition ◽  
Volcanic Rocks ◽  
Continental Collision ◽  
Western Anatolia ◽  
Slab Rollback ◽  
Tectonic Zones ◽  
Geochemical Indices ◽  
Partial Melts ◽  
Potassic Volcanism

Abstract Potassic volcanic rocks are characteristic of collisional tectonic zones, with recycling of continental crust playing an important role in their generation. Potassium-rich partial melts and/or fluids derived from subducted continental material initiate and/or mix with mantle-derived melts and then erupt at the surface with varying degrees of interaction with the overlying lithosphere. The details of how continental material incorporates into mantle melts are, however, uncertain. In particular, the depths from which the potassium-rich fluids and/or melts are released from the continental material and then react with the mantle-derived melts remain a subject of debate. We have measured the boron isotope composition of volcanic rocks from Western Anatolia (Turkey) that erupted between 52 and 0.1 Ma, and span the lifetime of collisional events from initial arc-type eruptions to post-collisional volcanism. These data and other geochemical indices show that ultrapotassic volcanism was mainly confined to a narrow window between ca. 20 and 15 Ma, consistent with recycling of high-pressure phengite, with the timing of the potassic volcanism coincident with slab rollback and breakoff.

U–Pb zircon geochronology of eclogites from the Scandian Orogen, northern Western Gneiss Region, Norway: 14–20 million years between eclogite crystallization and return to amphibolite-facies conditionsThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 441-472 ◽  
Author(s):  
Thomas E. Krogh ◽  
Sandra L. Kamo ◽  
Peter Robinson ◽  
Michael P. Terry ◽  
Kim Kwok
Keyword(s):  
High Pressure ◽  
Continental Collision ◽  
Amphibolite Facies ◽  
Granitic Pegmatite ◽  
Zircon Geochronology ◽  
Plate Tectonic ◽  
Special Issue ◽  
Western Gneiss Region ◽  
Garnet Pyroxenite ◽  
Ultra High Pressure

Reconstructing tectonic histories involving continental collision, subduction, and exhumation at plate-tectonic rates of ∼1 cm/year, requires precise U–Pb zircon geochronology. The Western Gneiss Region has exceptional exposures of high-pressure (HP) and ultra-high-pressure (UHP) rocks. The strategy adopted here involved sampling eclogite and associated late unstrained pegmatites to acquire the time of eclogite crystallization and subsequent exhumation, respectively. The oldest eclogite sampled is 415 ± 1 Ma from layered, probably UHP eclogite at Tevik, Averøya, also with a garnet–hornblende assemblage at 410 ± 1 Ma. The Flem Gabbro eclogite margin, with implied UHP conditions, is 410 ± 2 Ma. Hornblende eclogite at Seth, Lepsøya, never at UHP, is 412 ± 2 Ma. These compare to Devonian ages of 401 ± 1 Ma for overgrowths on Proterozoic baddeleyite in Selnes Gabbro, 402 ± 2 Ma for coesite eclogite at Hareidlandet, 405–400 Ma for coesite eclogite at Flatraket, and 405 ± 2 Ma for near-UHP eclogite at Hjelmelandsdalen. The 415 Ma eclogite at Tevik compares to granitic pegmatite in the same outcrop at 395.2 ± 1.3 Ma and to pegmatite in eclogite at Aspøya at 395.3 ± 2 Ma. The 410 Ma age at Flem compares to nearby pegmatite in eclogite at 396 ± 4 Ma. Collectively, these results imply 14–20 million years between deep eclogite crystallization at ∼130 km and return to amphibolite-facies conditions at ∼30 km, with crystallization of locally derived granitoid melts. Nearby garnet-pyroxenite records older ages (∼430) and greater depths (∼200 km), but on similar exhumation paths at ∼0.4–0.7 cm/year.

Introduction to the special issue of Canadian Journal of Earth Sciences: The Nechako NATMAP Project of the central Canadian Cordillera

2001 ◽  
Vol 38 (4) ◽  
pp. 485-494 ◽  
Author(s):  
Lambertus C Struik ◽  
Donald G MacIntyre
Keyword(s):  
Volcanic Rocks ◽  
Mineral Deposits ◽  
Future Research ◽  
Canadian Cordillera ◽  
Special Issue ◽  
Volcanic Arc ◽  
Mountain Ranges ◽  
Crustal Thinning ◽  
Line Spacing ◽  
Central Cordillera

The Canadian Cordillera in central British Columbia has seen the Mesozoic subduction of an oceanic terrane; the amalgamation of volcanic-arc terranes; continued intermittent Mesozoic compression and magmatism; and Tertiary wrenching, extension and magmatism. Except in its northernmost mountain ranges, the area is extensively covered in glacial drift and thin veneers of Tertiary volcanic rocks. In 1994, a group of scientists and technologists believed they could understand that cover, see through it, and discover the components of that collision and extensional orogen. They would apply modern techniques of isotopic and paleontological geochronology; lake-sediment, till, and plant geochemistry; detailed gravity, magnetic, radiometric, paleomagnetic, and electromagnetic surveys; and isotopic and trace element lithochemistry, as they conducted extensive bedrock and surficial mapping. This special issue summarizes a cross-section of the scientific contributions derived from that mapping conducted under the auspices of the Nechako NATMAP Project. It demonstrates the absolute necessity of applying modern isotopic and paleontologic geochronology to understand the Phanerozoic geology of the Cordillera. It emphasizes the necessity of detailed aeromagnetic surveys (500 m or less line spacing) in looking through covered terranes at anything more than 1 : 250 000 scale. And, it shows the immense utility of applying various geochemical techniques to solve geological problems and establish baselines for future research and economic development. Bedrock and surficial mapping in the central Cordillera, using these and other techniques, have established the nature and timing of Mesozoic crustal growth, Tertiary crustal thinning, and the associated formation of mineral deposits.

Editorial of the special issue “Subduction and continental collision processes: Petrologic, geochemical and structural perspectives”

Lithos ◽  
2020 ◽  
Vol 360-361 ◽  
pp. 105430
Author(s):  
Hafiz Ur Rehman ◽  
Tatsuki Tsujimori ◽  
Chin-Ho Tsai ◽  
Sun-Lin Chung
Keyword(s):  
Continental Collision ◽  
Special Issue ◽  
Collision Processes

Insights from geodynamical modeling on possible fates of continental mantle lithosphere: collision, removal, and overturnThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.

2010 ◽  
Vol 47 (4) ◽  
pp. 541-563 ◽  
Author(s):  
Russell N. Pysklywec ◽  
Oguz Gogus ◽  
J. Percival ◽  
A. R. Cruden ◽  
C. Beaumont
Keyword(s):  
Late Stage ◽  
Continental Collision ◽  
Density Stratification ◽  
Mantle Lithosphere ◽  
Special Issue ◽  
Tectonically Active ◽  
Tectonic Environments

Geodynamic modeling demonstrates various modes of behaviour of the tectonically active continental mantle lithosphere. At continental collision, mantle lithosphere below thickening crust can be accommodated by mixed subduction-like consumption and viscous drip-like instability, depending on the material rheology, temperature, and convergence velocity. Late-stage slab steepening, dual-sided and ablative consumption, and breakoff can occur as the buoyant crust resists subduction. Removal of accreted crust by erosion can modify how even the deepest portions of the mantle lithosphere evolves during contraction. When gravitational forcing rather than plate shortening dominates, mantle lithosphere may be removed through viscous dripping-like instability or delamination. The removal induces crustal heating, modified topography, and deformation, but distinctive styles of these develop depending on whether mantle lithosphere delaminates or drips. With a modified density stratification postulated for the Archean, relatively buoyant mantle lithosphere may undergo an in-situ overturn when triggered by unstable dense eclogite and basal traction. This causes a pulse of rapid crustal heating as hot lowermost lithosphere is brought into contact with the base of the crust. As an interpretive tool, the geodynamic experiments illustrate some of the dynamically feasible modes of behaviour and controlling parameters for the continental mantle lithosphere in ancient to modern tectonic environments.

Structure and stratigraphy of the south flank of the Kisseynew Domain in the Trans-Hudson Orogen, Manitoba: implications for 1.845-1.77 Ga collision tectonics

1999 ◽  
Vol 36 (11) ◽  
pp. 1859-1880 ◽  
Author(s):  
Herman V Zwanzig
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Continental Collision ◽  
High Grade ◽  
The South ◽  
Collision Tectonics ◽  
High Grade Metamorphism ◽  
Thrust System ◽  
Flin Flon ◽  
Superior Craton

On the south flank of the Kisseynew Domain, orthogneisses derived from 1.92-1.85 Ga volcano-plutonic rocks are overlain by paragneisses (Burntwood and Missi groups) derived from 1.855-1.84 Ga marine turbidite and 1.845-1.83 Ga terrestrial clastic and volcanic rocks. The sediments in these groups are interpreted as having been shed into the Kisseynew paleobasin from an active margin bordering the Flin Flon Belt. The sedimentation apparently followed early microcontinental collision and accompanied the last arc magmatism in the Trans-Hudson Orogen. The sedimentary rocks and their basement were deformed into a complexly refolded stack of large recumbent folds. Premetamorphic F1 structures represent a fold and thrust system initiated during the sedimentation. These structures are interpreted as transported toward the Kisseynew Domain in the northeast and the hinterland in the southwest. F2 structures (~1.82 Ga) comprise westerly transported nappes. During 1.82-1.80 Ga high-grade metamorphism, the early structures were overturned, amplified, and refolded. Basement-cored culminations and sheet-like synforms of paragneiss were horizontally attenuated and transported south and southwest. North- and northeast-trending F4 folds and F5 faults formed after 1.79 Ga. The whole cycle of deformation is related to stages of continental collision between the internal (juvenile) zone of the Trans-Hudson Orogen and the three surrounding Archean cratons (Sask, Superior, and Hearne). The F4 upright folds and steep F5 faults are interpreted as the record of intracontinental transpression, strongly controlled by the Superior Craton boundary.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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