LA-MC-ICP-MS dating of zircon from chromitite of the Archean Bangur Gabbro Complex, Orissa, India – Ambiguities and constraints

Authors

  • P. V. SUNDER-RAJU National Geophysical Research Institute (CSIR). Uppal Road, Hyderabad, Telangana, India.
  • E. HANSKI Oulu Mining School. P.O. Box 3000, 90014 University of Oulu, Finland.
  • Y. LAHAYE Geological Survey of Finland. P.O. Box 96, 02151 Espoo, Finland.

Keywords:

Chromitite, Zircon, Galena, U-Pb isotopes, Pb-Pb isotopes, Archean, Orissa (India)

Abstract

The Mesoarchean chromitites in the Singhbhum craton provide the main source of chromium in India. We report here results of dating zircon grains that were found in the chromitite of ultramafic rocks belonging to the southern part of the Archean Baula Complex. The chromite-bearing ultramafic rocks are cut by a gabbronorite intrusion, which had earlier been dated by SHRIMP at 3.12Ga. We have performed isotopic analysis of the zircon grains by Laser Ablation Multicollector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) and obtained an age of 2.84Ga, which is inconsistent with the previous age reported for the gabbronorite. We have also determined the Pb isotopic composition of galena found in the chromitite and found out it was highly radiogenic given the Archean age of its host rock. We discuss the potential reasons for these results, such as later Neoarchean or even Proterozoic tectono-magmatic/hydrothermal events, and stress the importance of future detailed petrographic, mineralogical and isotopic studies to solve the dilemmas.

Author Biographies

E. HANSKI, Oulu Mining School. P.O. Box 3000, 90014 University of Oulu, Finland.

Professor

Y. LAHAYE, Geological Survey of Finland. P.O. Box 96, 02151 Espoo, Finland.

LA-MC-ICPMS Lab

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Published

2015-10-26

Issue

Vol. 13 No. 4 (2015)

Section

Articles

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