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 Tilton, G. R.
Right arrow Articles by Mateen, A.
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 1865-1874 | 1998
© Oxford University Press 1998

Pb–Sr–Nd Isotope Data from 30 and 300 Ma Collision Zone Carbonatites in Northwest Pakistan

G. R. Tilton1,*, J. G. Bryce1 and A. Mateen2

1 Department of Geological Sciences, University of California, Santa Barbara Santa Barbara, CA 93106-9630, USA
2 Pakistan Institute of Engineering and Applied Sciences P.O. Nilore, Islamabad, Pakistan

Received September 30, 1997; Revised typescript accepted May 21, 1998


  Abstract

We present isotope data for the synorogenic Sillai Patti and Loe Shilman (30 Ma) and the pre-orogenic Koga and Jhambil (300 Ma) carbonatites, of the Indus Suture Zone. The younger carbonatites are foliated–banded sheet-like bodies in the metamorphosed belts of the Higher and Lesser Himalaya, within the Indus Suture Zone. They appear to be collision related and have no relationship to the silicate rocks in the complex. The initial isotope ratios are: {varepsilon}Nd –3.1 to –3.8; 87Sr/86Sr 0.70463–0.70486 ({varepsilon}Sr +2.4 to+5.6); 206Pb/204Pb 19.01–21.35; 207Pb/204Pb 15.54–15.67; 208Pb/204Pb 38.29–40.63. The pattern is atypical given that carbonatites generally yield positive {varepsilon}Nd and negative {varepsilon}Sr. The Nd, Sr, and least radiogenic Pb isotope ratios also fit the pattern of carbonatites from the East African Rift, suggesting derivation from similar sources. In that case a lithospheric source for the 30 Ma Pakistan carbonatites was probably transported with the Indian plate during migration from East Africa to the collision with the Asian continent. Intrusion of the carbonatites into rocks of the Himalayan orogenic zone apparently affected only the Pb isotopes in some of the plutons. Nd, Sr and Pb isotope patterns for the 300 Ma Pakistan plutons fit those for most intra-plate carbonatites, with positive {varepsilon}Nd and negative {varepsilon}Sr, showing that neither transport nor collision noticeably disturbed their isotope patterns.

KEY WORDS: carbonatite; isotope tracers; mantle; Pakistan; petrogenesis

* Corresponding author. Fax: 805-893-2314. e-mail: tilton{at}magic.geol.ucsb.edu


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
K. BELL and G. R. TILTON
Nd, Pb and Sr Isotopic Compositions of East African Carbonatites: Evidence for Mantle Mixing and Plume Inhomogeneity
J. Petrology, October 1, 2001; 42(10): 1927 - 1945.
[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.