scholarly journals Emplacement mechanism of Late Triassic granitic Dushan pluton, North China and its tectonic implications

2020 ◽  
Author(s):  
Huabiao Qiu ◽  
Wei Lin ◽  
Yan Chen ◽  
Michel Faure
Keyword(s):  
Solid State ◽  
North China ◽  
Tectonic Setting ◽  
Late Triassic ◽  
Gravity Modeling ◽  
Magnetic Fabrics ◽  
Southeastern Margin ◽  
Emplacement Mechanism ◽  
Southwestern Margin ◽  
Magnetic Lineations

<p>To better understand the Late Triassic tectonic setting in the northern North China Craton (NCC), a multidisciplinary investigation, including structural geology, geochronology, anisotropy of magnetic susceptibility (AMS) and gravity modeling, has been carried out in the Dushan pluton. The Dushan pluton consists of monzogranite and biotite-rich facies along the pluton margin without sharp contact between them. The granite varies southwestwards from isotropic texture to arcuate gneissic structures, with locally mylonitic structures. The intensity of solid-state deformation increases southwestwards across the pluton, leaving preserved magmatic fabrics in the northeastern part. The compatible outward dipping magmatic and solid-state magnetic fabrics, together with mesoscopic fabrics, define an elliptic dome-like pattern with a NE-SW oriented long axis, despite the fabrics dip inwards in the southeastern margin of the pluton. Combining gravity modeling, the Dushan pluton presents an overall tabular or tongue-like shape with a northeastern root. The magnetic lineations nearly strike NE-SW, concordant with the stretching lineations observed in the mylonitic zones. We propose the emplacement mode that the Dushan pluton emplaced southwards through the feeder zone in its northeast, beginning probably with a sill. The later successive magma batches may laterally and upwardly inflate, deform and even recrystallize the former cool-down magma. This inflation forms an arcuate, gneissic to mylonitic foliation in the southwestern margin. The Dushan pluton is considered as typically post-tectonic in emplacement, recording a Late Triassic post-tectonic setting of the northern NCC.</p>

scholarly journals Supplemental Material: Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

2021 ◽  
Author(s):  
Zhenhua Xue ◽  
Wei Lin ◽  
et al.
Keyword(s):  
North China ◽  
Stereographic Projection ◽  
Magnetic Hysteresis ◽  
Central China ◽  
Late Triassic ◽  
Adjacent Area ◽  
Yangtze Block ◽  
Data Set ◽  
Basic Principles ◽  
Magnetic Fabrics

Text: Basic principles of anisotropy of magnetic susceptibility (AMS); Figure S1: Photographs of supplementary shearing indicators of the structural kinematics; Figure S2: Complete magnetic hysteresis data set for specimen selected from 34 sites; Figure S3: Measurements of isothermal remanent magnetization of specimen selected from 34 representative sites of the Bikou Terrane; Figure S4: Thermo-magnetic experiments of specimen selected from 12 representative sites; Figure S5: Mrs/Ms versus Hcr/Hc diagram from the selected specimen of the representative sites to define the size of magnetite; Figure S6: Stereographic projection of the AMS directional fabrics and structural fabrics.

Emplacement mechanism of the Tafresh granitoids, central part of the Urumieh–Dokhtar Magmatic Arc, Iran: evidence from magnetic fabrics

2019 ◽  
Vol 156 (9) ◽  
pp. 1510-1526
Author(s):  
Davoud Raeisi ◽  
Hassan Mirnejad ◽  
Maryam Sheibi
Keyword(s):  
Tectonic Setting ◽  
Magnetic Fabric ◽  
Shape Parameters ◽  
Calc Alkaline ◽  
High Field Strength ◽  
Magmatic Arc ◽  
Arc Magmas ◽  
Magnetic Fabrics ◽  
Data Field ◽  
Emplacement Mechanism

AbstractGranitoid stocks crop out in the Ghahan and Sarbadan areas near Tafresh city, which is situated in the central part of the Urumieh–Dokhtar Magmatic Arc, Iran. The stocks, consisting of porphyritic and sub-granular diorite and granular granodiorite, intruded into Eocene volcano-sedimentary units. Normalized multi-element diagrams indicate that the analysed rocks are enriched in large-ion lithophile elements and depleted in high field strength elements. These geochemical features are typical of subduction-related calc-alkaline arc magmas. The stocks belong to the ferromagnetic and I-type granitoid series. Anisotropy of magnetic susceptibility provides information about the internal fabric of the granitoids. Susceptibility values range from 5.6 × 10−3 to more than 71.6 × 10−3, averaging 27.9 × 10−3 SI. Relatively low anisotropy values (P%) rarely exceed 10 %. Shape parameters (T) vary between −0.48 and +0.74, averaging + 0.2. Each stock is interpreted to contain a distinct feeder zone in which magnetic lineation plunges steeply (> 60°), suggesting that the magma ascended mainly in a NW–SE conduit and, to a lesser extent, in an E–W direction. Integration of magnetic fabric data, field observations and tectonic setting indicates that the shear zone that was developed between the Indes and Talkhab faults had created an opening into which the Ghahan and Sarbadan stocks were emplaced by way of creating a suitable tensional space for the ascent of magma.

scholarly journals Supplemental Material: Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

2021 ◽  
Author(s):  
Zhenhua Xue ◽  
Wei Lin ◽  
et al.
Keyword(s):  
North China ◽  
Stereographic Projection ◽  
Magnetic Hysteresis ◽  
Central China ◽  
Late Triassic ◽  
Adjacent Area ◽  
Yangtze Block ◽  
Data Set ◽  
Basic Principles ◽  
Magnetic Fabrics

Text: Basic principles of anisotropy of magnetic susceptibility (AMS); Figure S1: Photographs of supplementary shearing indicators of the structural kinematics; Figure S2: Complete magnetic hysteresis data set for specimen selected from 34 sites; Figure S3: Measurements of isothermal remanent magnetization of specimen selected from 34 representative sites of the Bikou Terrane; Figure S4: Thermo-magnetic experiments of specimen selected from 12 representative sites; Figure S5: Mrs/Ms versus Hcr/Hc diagram from the selected specimen of the representative sites to define the size of magnetite; Figure S6: Stereographic projection of the AMS directional fabrics and structural fabrics.

scholarly journals Sandstone petrography and geochemistry of the Nayband Formation (Upper Triassic, Central Iran): Implications for sediment provenance and tectonic setting

2019 ◽  
Vol 112 (1) ◽  
pp. 20-41 ◽  
Author(s):  
Asghar Etesampour ◽  
Asadollah Mahboubi ◽  
Reza Moussavi-Harami ◽  
Nasser Arzani ◽  
Mohammad Ali Salehi
Keyword(s):  
Tectonic Setting ◽  
Active Continental Margin ◽  
Source Area ◽  
Major Elements ◽  
Upper Triassic ◽  
Late Triassic ◽  
Sediment Provenance ◽  
Provenance Areas ◽  
Nayband Formation ◽  
Southwestern Margin

AbstractThe Upper Triassic (Norian–Rhaetian) Nayband Formation is situated at the southwestern margin of Central East Iranian Microcontinent and records Eo-Cimmerian events. The formation is composed of mixed carbonate-siliciclastic deposits. This study presents information on the tectonic reconstruction and palaeoclimate of the southwestern margin of Central East Iranian Microcontinent during the Late Triassic. Petrography and modal analyses of sandstones show a variety of quartz-rich petrofacies including subarkose, lithic arkose, sublitharenite, feldspathic litharenite and litharenite. The combined modal analysis and geochemical results of major and trace elements of the sandstone samples represents mixed sedimentary, intermediate, felsic igneous rocks and moderate- to high-grade metamorphic provenance areas. The major elements and modal analyses of the Nayband Formation sandstone samples suggest an active continental margin tec-tonic settings. The palaeoclimatic conditions were sub-humid to humid with relatively low to moderate weathering in the source area which is in agreement with the palaeogeography and palaeotectonic history of southwestern margin of Central East Iranian Microcontinent during the Late Triassic.

scholarly journals Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

2021 ◽  
Author(s):  
Zhenhua Xue ◽  
Wei Lin ◽  
Yang Chu ◽  
Wei Wei ◽  
Zhentian Feng ◽  
...  
Keyword(s):  
Structural Analysis ◽  
South China ◽  
North China ◽  
Late Triassic ◽  
Yangtze Block ◽  
The South ◽  
Structural Geometry ◽  
The North ◽  
Magnetic Fabrics ◽  
Multi Phase

The Bikou Terrane, located at the conjunction of the Longmenshan fold-thrust belt and the west Qinling orogenic belt in centeral China, was involved in the Late Triassic collision between the South China and North China blocks. The Bikou Terrane has preserved crucial information on structural geometry and kinematics of Triassic tectonics, and is therefore of great importance for reconstructing the Paleo-Tethyan evolutionary history. However, multi-phase tectonic events of the Bikou Terrane are unsettled. This work presents detailed structural analysis based on both the field and laboratory works, which reveals three phases of deformation events in Bikou and its adjacent areas, including top-to-the-SW shearing related to SW-ward thrusting (DI) mainly to the north of the Bikou Terrane, top-to-the-NNW shearing related to NNW-ward thrusting (DII) in the Bikou Terrane, and strike-slip faulting (DIII) locally developed in the northern Bikou Terrane. Anisotropy of magnetic susceptibility (AMS) study and related structural analysis not only support the multiphase deformation but also reveal a gradual transition from the DII-related magnetic fabrics to the DIII-related magnetic fabrics in the Bikou Terrane. Integrating published geochronological data, it is constrained that DI occurred at ca. 237−225 Ma, DII occurred at ca. 224−219 Ma, and DIII possibly occurred during the Early Cretaceous. Based on regional tectonics, the DI event corresponds to the collision between the South Qinling block and the Bikou Terrane, and the DII event reflects the intracontinental amalgamation between the Bikou Terrane and the Yangtze block, which indicates a Late Triassic successive amalgamation from the North China block to the South China block. Intracontinental adjustment represented by the strike-slip (DIII event) occurred after the final amalgamation between the North China and South China blocks. By applying AMS on deciphering structural geometry and multi-phase deformation, our study suggests that AMS is a useful tool for structural analysis.

scholarly journals Timing of magmatism of the Ditrău Alkaline Massif, Romania – A review based on new U–Pb and K/Ar data

2021 ◽  
Author(s):  
Elemér Pál-Molnár ◽  
Luca Kiri ◽  
Réka Lukács ◽  
István Dunkl ◽  
Anikó Batki ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Late Triassic ◽  
East European ◽  
Eastern Carpathians ◽  
Extensional Tectonic ◽  
Southwestern Margin ◽  
Tectonic Framework ◽  
Back Arc ◽  
Alkaline Massif ◽  
Shed Light

AbstractThe timing of Triassic magmatism of the Ditrău Alkaline Massif (Eastern Carpathians, Romania) is important for constraining the tectonic framework and emplacement context of this igneous suite during the closure of Paleotethys and coeval continental rifting, as well as formation of back-arc basins.Our latest geochronological data refine the previously reported ages ranging between 237.4 ± 9.1 and 81.3 ± 3.1 Ma. New K/Ar and U–Pb age data combined with all recently (post-1990) published ages indicate a relatively short magmatic span (between 238.6 ± 8.9 Ma and 225.3 ± 2.7 Ma; adding that the most relevant U–Pb ages scatter around ∼230 Ma) of the Ditrău Alkaline Massif. The age data complemented by corresponding palinspastic reconstructions shed light on the paleogeographic environment wherein the investigated igneous suite was formed.The magmatism of the Ditrău Alkaline Massif could be associated with an intra-plate, rift-related extensional tectonic setting at the southwestern margin of the East European Craton during the Middle–Late Triassic (Ladinian–Norian) period.

Lithospheric modification at the onset of the destruction of the North China Craton: Evidence from Late Triassic mafic dykes

2021 ◽  
Vol 566 ◽  
pp. 120105
Author(s):  
Chao Wang ◽  
Shuguang Song ◽  
Li Su ◽  
Mark B. Allen ◽  
Jinlong Dong
Keyword(s):  
North China Craton ◽  
North China ◽  
Late Triassic ◽  
Mafic Dykes ◽  
The North

Mineral ages and zircon Hf isotopic composition of the Andong ultramafic complex: implications for the evolution of Mesozoic subduction system and subcontinental lithospheric mantle beneath SE Korea

2013 ◽  
Vol 151 (5) ◽  
pp. 765-776 ◽  
Author(s):  
GI YOUNG JEONG ◽  
CHANG-SIK CHEONG ◽  
KEEWOOK YI ◽  
JEONGMIN KIM ◽  
NAMHOON KIM ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Tectonic Setting ◽  
Eastern China ◽  
Mantle Xenoliths ◽  
Late Triassic ◽  
Magmatic Differentiation ◽  
Suprasubduction Zone ◽  
Ultramafic Complex ◽  
Yeongnam Massif ◽  
Subduction System

AbstractThe Phanerozoic subduction system of the Korean peninsula is considered to have been activated by at least Middle Permian time. The geochemically arc-like Andong ultramafic complex (AUC) occurring along the border between the Precambrian Yeongnam massif and the Cretaceous Gyeongsang back-arc basin provides a rare opportunity for direct study of the pre-Cretaceous mantle wedge lying above the subduction zone. The tightly constrained SHRIMP U–Pb age of zircons extracted from orthopyroxenite specimens (222.1±1.0 Ma) is indistinguishable from the Ar/Ar age of coexisting phlogopite (220±6 Ma). These ages represent the timing of suprasubduction zone magmatism likely in response to the sinking of cold and dense oceanic lithosphere and the resultant extensional strain regime in a nascent arc environment. The nearly coeval occurrence of a syenite-gabbro-monzonite suite in the SW Yeongnam massif also suggests an extensional tectonic setting along the continental margin side during Late Triassic time. The relatively enriched ɛHf range of dated zircons (+6.2 to −0.6 at 222 Ma) is in contrast to previously reported primitive Sr–Nd–Hf isotopic features of Cenozoic mantle xenoliths from Korea and eastern China. This enrichment is not ascribed to contamination by the hypothetical Palaeozoic crust beneath SE Korea, but is instead attributable to metasomatism of the lithospheric mantle during the earlier subduction of the palaeo-Pacific plate. Most AUC zircons show a restricted core-to-rim spread of ɛHf values, but some grains testify to the operation of open-system processes during magmatic differentiation.

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