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Age and isotope geochemistry of magmatic rocks of the Lohit Plutonic Complex, eastern Himalaya; implications for the evolution of Transhimalayan arc magmatism

R. K. Bikramaditya, Sun-Lin Chung, A. Krishnakanta Singh, Hao-Yang Lee, Te-Hsien Lin and Yoshiyuki Iizuka
Age and isotope geochemistry of magmatic rocks of the Lohit Plutonic Complex, eastern Himalaya; implications for the evolution of Transhimalayan arc magmatism
Journal of the Geological Society of London (October 2019) Pre-Issue Publication

Abstract

We present integrated in situ zircon U-Pb and Hf isotope data, along with whole-rock Sr-Nd isotope and geochemical data for plutonic rocks of the Lohit Plutonic Complex of eastern Himalaya to understand the age distribution and petrogenetic-tectonic evolution of the Transhimalayan batholiths in the eastern Himalaya. The plutonic rocks are gabbro, diorite and quartz-diorite in composition, have calc-alkaline signatures with metaluminous character and have an affinity with Gangdese I-type granitoids of southern Tibet. The enrichment of large ion lithophile elements with highly depleted negative Nb anomalies is consistent with their origin in a subduction-related environment. Our laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb ages suggest that two major stages of magmatic emplacement took place at c. 145 Ma (Early Cretaceous) for gabbro and c. 100-90 Ma (early Late Cretaceous) for diorite and quartz-diorite. The zircon Hf isotopes in both the gabbro and diorite samples show high positive epsilon Hf(t) values between +11 and +20, suggesting crystallization from juvenile crust or depleted mantle derived melts, as also constrained by the low initial (super 87) Sr/ (super 86) Sr ratios (0.7038-0.7045) and high positive epsilon (sub Nd) (t) values (+2.9 to +5.9). Results of REE modelling indicate that the source of these rocks is garnet lherzolite. Field observations and mineralogical and geochemical characteristics in conjunction with the isotopic database suggest that the Transhimalayan magmatic rocks in eastern Himalaya were generated by partial melting of the lithospheric mantle wedge and emplaced into the lower crust (c. 25-30 km) during at least two major magmatic events that took place in the Cretaceous period. Supplementary material: LA-ICP-MS zircon U-Pb and Hf isotope data are available at https://doi.org/10.6084/m9.figshare.c.4665305


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: Pre-Issue Publication
Title: Age and isotope geochemistry of magmatic rocks of the Lohit Plutonic Complex, eastern Himalaya; implications for the evolution of Transhimalayan arc magmatism
Affiliation: Banaras Hindu University, Department of Geology, Varnasi, India
Published: 20191030
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 95
Accession Number: 2019-093050
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
N28°00'00" - N29°00'00", E95°00'00" - E96°00'00"
Secondary Affiliation: Academia Sinica, Institute of Earth Sciences, TWN, TaiwanWadia Institute of Himalayan Geology, IND, IndiaNational Taiwan University, TWN, Taiwan
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 2019
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