Publication detail

Mineralization of the Bayan Obo Rare Earth Element Deposit by Recrystallization and Decarbonation

Wei, CW. Deng, M. Xu, C. Chakhmouradian, AR. Smith, MP. Kynicky, J. Song, WL. Chen, W. Fu, B.

Original Title

Mineralization of the Bayan Obo Rare Earth Element Deposit by Recrystallization and Decarbonation

Type

journal article in Web of Science

Language

English

Original Abstract

The genesis of the Bayan Obo giant rare earth element (REE) deposit has been debated for several decades. Here, we report the isotopic effects of dynamic recrystallization in the H8 carbonatite, which is the principal ore carrier in the deposit. We studied fresh drill core to a depth of 1.78 km and documented the elemental and C-O-Sr isotope evolution of rock-forming dolomite during its deformation and reaction with fluids. The precursor dolomite and the products of its recrystallization differ in delta C-13(Vienna-PeeDee Belemnite (V-PDB)) (-1.09 to 2.37 vs. -3.59 to 0.79%, respectively) and Sr-87/Sr-86 (0.70241-0.70394 vs. 0.70288-0.71409, respectively), and show a similar delta O-18(Vienna-standard mean ocean water) ((V-SMOW)) range (10.3-16.9%). The strong negative shift in delta C-13(V-PDB) indicates that, locally, there was as much as 40% loss of CO2 from the precursor dolomite, although most of the recrystallized dolomite experienced decarbonation on a smaller scale. Clumped monazite grains associated with apatite in paragenetically similar samples yielded variable in situ Th-Pb dates (980-340 Ma), whereas those in monomineralic veinlets give a consistent age of similar to 400 Ma and consistent initial Nd isotope ratios. This indicates that the wide range of dates may not represent real REE depositional events and that the primary REE minerals deposited in the Mesoproterozoic underwent isotopic reequilibration and REE remobilization in the mid-Paleozoic. Recrystallization and decarbonation of dolomite in the H8 unit were facilitated by its reaction with subduction-derived silica- and halogen-rich fluid, genetically linked to plate-convergence processes along the northern margin of the North China craton, and did not require an influx of REEs from an external source.

Keywords

NORTH CHINA CRATON; REE-NB DEPOSIT; INNER-MONGOLIA; CARBON-ISOTOPE; STABLE-ISOTOPE; BAINAIMIAO ARC; EVOLUTION; ORIGIN; MANTLE; GEOCHEMISTRY

Authors

Wei, CW.; Deng, M.; Xu, C.; Chakhmouradian, AR.; Smith, MP.; Kynicky, J.; Song, WL.; Chen, W.; Fu, B.

Released

1. 9. 2022

Publisher

SOC ECONOMIC GEOLOGISTS, INC

Location

LITTLETON

ISBN

1554-0774

Periodical

ECONOMIC GEOLOGY

Year of study

117

Number

6

State

United States of America

Pages from

1327

Pages to

1338

Pages count

12

URL

https://pubs.geoscienceworld.org/segweb/economicgeology/article/117/6/1327/612483/Mineralization-of-the-Bayan-Obo-Rare-Earth-Element

BibTex

@article{BUT187263,
  author="Wei, CW. and Deng, M. and Xu, C. and Chakhmouradian, AR. and Smith, MP. and Kynicky, J. and Song, WL. and Chen, W. and Fu, B.",
  title="Mineralization of the Bayan Obo Rare Earth Element Deposit by Recrystallization and Decarbonation",
  journal="ECONOMIC GEOLOGY",
  year="2022",
  volume="117",
  number="6",
  pages="1327--1338",
  doi="10.5382/econgeo.4926",
  issn="1554-0774",
  url="https://pubs.geoscienceworld.org/segweb/economicgeology/article/117/6/1327/612483/Mineralization-of-the-Bayan-Obo-Rare-Earth-Element"
}