Zircon geochronology of the Koraput alkaline complex: Insights from combined geochemical and U–Pb–Hf isotope analyses, and implications for the timing of alkaline magmatism in the Eastern Ghats Belt, India

2016 ◽  
Vol 34 ◽  
pp. 205-220 ◽  
Author(s):  
K. Hippe ◽  
A. Möller ◽  
A. von Quadt ◽  
I. Peytcheva ◽  
K. Hammerschmidt
Keyword(s):  
Hf Isotope ◽  
Eastern Ghats ◽  
Alkaline Magmatism ◽  
Zircon Geochronology ◽  
Alkaline Complex ◽  
Eastern Ghats Belt ◽  
Isotope Analyses

Eocene post-collisional magmatism in Himalaya orogenic belt: evidence from petrography, zircon U-Pb age and Sr-Nd-Hf isotope of the Mayum alkaline complex, southern Lhasa subterrane

2020 ◽  
Author(s):  
Xiaoshuang Chen ◽  
Haijin Xu
Keyword(s):  
Oceanic Lithosphere ◽  
Hf Isotope ◽  
Alkaline Magmatism ◽  
Early Eocene ◽  
Alkaline Complex ◽  
Southern Tibet ◽  
Quartz Syenite ◽  
Alkaline Rocks ◽  
Slab Breakoff ◽  
T Values

<p>Alkaline magmatism is commonly generated in extensional settings, playing an important role in constraining the timing of slab breakoff. Eocene post-collisional magmatism is widely distributed along the Gangdese belt of southern Tibet. However, few Eocene post-collisional alkaline magmatism has been identified. Here, we present a comprehensive study of whole-rock geochemistry, zircon U-Pb ages and Sr-Nd-Hf isotopes of the Mayum alkaline complex from the Southern Lhasa Subterrane, providing an insight into the timing of breakoff of the Neo-Tethyan slab. The alkaline complex is composed of amphibolite syenite, quartz syenite and alkaline granite. The mafic microgranular enclaves are ubiquitous in the syenites. Zircon U-Pb analyses indicates that the alkaline rocks were generated in Early Eocene (ca. 53-50 Ma). These ages suggest that the alkaline rocks emplaced shortly (10-15Ma) after the continental collision between the Indian and Eurasian plates. The alkaline rocks have high SiO<sub>2 </sub>(64.32-77.36 wt.%), Na<sub>2</sub>O + K<sub>2</sub>O (6.63-9.03 wt.%) contents, low MgO (0.14-2.52 wt.%) contents. These rocks show obvious arc-like geochemical features in trace elements, i.e., enrichment in LILEs (e.g., Rb, K), LREEs, Th and U, and depletion in HFSEs (e.g., Nb, Ta, Ti), HREEs with strongly to moderately negative Eu anomalies (δEu=0.28–0.72). These features together with high FeO<sup>T</sup>/MgO, Ga/Al, Ce/Nb and Y/Nb values, and low Ba, Sr contents, suggesting that the Mayum alkaline rocks belong to an A2-type granitoids. Besides, the alkaline rocks have homogeneous initial <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.7052-0.7059) and negative ε<sub>Nd</sub>(t) values (-2.1 to -0.9) for whole-rock, and positive zircon ε<sub>Hf</sub>(t) values (+0.73 to +11.16). Nd-Hf isotope decoupling suggests that the alkaline was likely produced by mixing of mantle- and crust-derived magmas under a post-collisional extensional setting. Combined with previous published results, we propose that the slab breakoff of the subducting Neo-Tethyan oceanic lithosphere at least prior to Early Eocene (ca. 53Ma). The Eocene Mayum alkaline complex might be related to asthenosphere upwelling trigged by the slab breakoff.</p>

Zircon geochronology of deformed alkaline rocks along the Eastern Ghats Belt margin: India–Antarctica connection and the Enderbia continent

2018 ◽  
Vol 310 ◽  
pp. 407-424 ◽  
Author(s):  
Sameer Ranjan ◽  
Dewashish Upadhyay ◽  
Kumar Abhinay ◽  
Kamal L. Pruseth ◽  
Jayanta K. Nanda
Keyword(s):  
Eastern Ghats ◽  
Zircon Geochronology ◽  
Alkaline Rocks ◽  
Eastern Ghats Belt

scholarly journals The U-Pb Zircon Geochronology (LA-ICP-MS) of Geological Processes in Granulites of Middle Bouh Area. Article 3. Rock association in the lower reaches of the Yatran river

2021 ◽  
Vol 43 (1) ◽  
pp. 34-50
Author(s):  
L.M. STEPANYUK ◽  
L.V. SHUMLYANSKYY ◽  
S.I. KURYLO ◽  
V.O. SYOMKA ◽  
S.M. BONDARENKO ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Hf Isotope ◽  
Zircon Geochronology ◽  
Pb Isotope ◽  
Isotope Data ◽  
Geological Processes ◽  
Icp Ms ◽  
Isotope Systematics ◽  
Isotope Analyses ◽  
Rock Association

LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charnockitic gneiss and biotite-garnet-hypersthene enderbite that occur in the lower reaches of the Yatran river (Yatran block of the Bouh river area). According to the obtained isotope data, charnockitic gneiss hosts three zircon populations. The oldest one is represented by three crystals that have isotope age between 3125 and 3300 Ma, and εHf values between –2.3 and –7.5. The next population is well-defined, it has an age of 2038±25 Ma and large variations of Hf isotope composition: 176Hf/177Hf — from 0.28122 to 0.28261, εHf — from –9.3 до 4.6. However, the ages of most of the analyzed zircons spread along the concordia between 2300 and 2800 Ma. All zircons in this population have a similar Hf isotope composition 176Hf/177Hf = 0.28072 to 0.28092, which does not depend on the age. It is characteristic that the oldest (with preserved U-Pb isotope systematics) crystals have positive or slightly negative εHf values. Most of the U-Pb isotope analyses of zircons from enderbite fall on the discordia line that has an upper interception age of 2029 ± 18 Ma. A small number of discordant grains have 207Pb/206Pb ages up to 2500 Ma. Hafnium isotope composition in zircons from enderbite varies widely: 176Hf/177Hf = 0.28131 to 0.28151, and εHf from –6.2 to 1.8.

Crustal geodynamics from the Archaean Bundelkhand Craton, India: constraints from zircon U–Pb–Hf isotope studies

2015 ◽  
Vol 153 (1) ◽  
pp. 179-192 ◽  
Author(s):  
L. SAHA ◽  
D. FREI ◽  
A. GERDES ◽  
J. K. PATI ◽  
S. SARKAR ◽  
...  
Keyword(s):  
Time Frame ◽  
Hf Isotope ◽  
Alkaline Magmatism ◽  
Similar Time ◽  
Tectonic Zone ◽  
The North ◽  
Isotope Studies ◽  
Tectonothermal Event ◽  
Isotope Analyses ◽  
Comprehensive Study

AbstractA comprehensive study based on U–Pb and Hf isotope analyses of zircons from gneisses has been conducted along the western part (Babina area) of the E–W-trending Bundelkhand Tectonic Zone in the central part of the Archaean Bundelkhand Craton. 207Pb–206Pb zircon ages and Hf isotopic data indicate the existence of a felsic crust at ~ 3.59 Ga, followed by a second tectonothermal event at ~ 3.44 Ga, leading to calc-alkaline magmatism and subsequent crustal growth. The study hence suggests that crust formation in the Bundelkhand Craton occurred in a similar time-frame to that recorded from the Singhbhum and Bastar cratons of the North Indian Shield.

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