Skip Navigation

This Article
Right arrow Full Text Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Veena, K.
Right arrow Articles by Gupta, J. N.
Right arrow Search for Related Content
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Journal of Petrology | Volume 39 | Number 11-12 | Pages 1875-1884 | 1998
© Oxford University Press 1998

Pb, Sr and Nd Isotopic Systematics of the Carbonatites of Sung Valley, Meghalaya, Northeast India: Implications for Contemporary Plume-Related Mantle Source Characteristics

K. Veena*, B. K. Pandey, P. Krishnamurthy and J. N. Gupta

Atomic Minerals Division, Department of Atomic Energy Hyderabad —500 016, India

Received September 30, 1997; Revised typescript accepted June 8, 1998


  Abstract

A 206Pb/204Pb–207Pb/204Pb age of 134 ± 20 Ma with a model µ1 of 8.19 ± 0.02 has been obtained for the carbonatites from Sung Valley, Meghalaya, placing their time of emplacement very close to the time assigned for the break-up of Gondwana. Initial {varepsilon}Sr (+5.3 to +7.8), {varepsilon}Nd (+1.7 to +2.3), 206Pb/204Pb (19.02), 207Pb/204Pb (15.67) and 208Pb/204Pb (39.0) indicate a mantle source region with a somewhat higher Rb/Sr ratio than Bulk Earth, minor light rare earth element (LREE) depletion, and a time-integrated enhancement of U/Pb. The isotopic characteristics of the Sung Valley carbonatites, however, differ significantly from those of basalts from Rajmahal and the Ninetyeast Ridge, which have a relatively more depleted upper-mantle source component, indicating involvement of different mantle sources. The mantle source region of the carbonatites is characterized by an EM2–HIMU signature, similar to that observed for Ambadongar, western India, but different from the carbonatites of East Africa, which have an EM1–HIMU signature. It is speculated that the Sung Valley carbonatites were derived from a parental magma generated by partial melting of the sub-continental lithosphere, which was previously metasomatized by fluids derived from an EM2-HIMU type mantle plume. The data suggest that the pre-130 Ma sub-continental mantle exhibited preferentially an EM2 type signature.

KEY WORDS: carbonatites; isotopic systematics; mantle sources; Sung Valley India

* Corresponding author. Present address: 1–10–153, Sardar Patel Road,Geochronology Laboratory, Atomic Minerals Division, Department of Atomic Energy, Begumpet, Hyderabad—500 016, India. Telephone: 0091-40-7767101, ext. 265. Fax: 0091-40-7762940. e-mail: amdhyd{at}ap.nic.in


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 J PetrologyHome page
J. S. Ray
Radiogenic Isotopic Ratio Variations in Carbonatites and Associated Alkaline Silicate Rocks: Role of Crustal Assimilation
J. Petrology, October 1, 2009; 50(10): 1955 - 1971.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.