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Zuun Mod is a porphyry-type Mo-Cu deposit located in the Edren terrane in Southwest Mongolia. The deposit has estimated resources of 218 Mt with an average Mo grade of 0.057% and Cu grade of 0.069%, and significant amounts of Re. The deposit is characterized by multiple pulses of magmatism and exsolution of magmatic ore fluids and associated alteration and mineralization. The timing of these events and the tectonic environment were unconstrained, and the deposit’s origin remains controversial. Based on drill core and field examinations, four lithological units of the Bayanbulag intrusive complex are identified in the deposit area including quartz syenite, quartz monzonite, granodiorite, and granite. The majority of Mo mineralization at Zuun Mod occurs in sheeted and stockwork quartz veins that crosscut units of the Bayanbulag complex as well as disseminations within altered granitoids wherein the mineralized quartz veins occur with potassic and phyllic alteration selvages. Zircon U-Pb age dating for quartz monzonite and granodiorite defined the timing of magmatic events at 305.3 ± 3.6 Ma and 301.8 ± 2.7 Ma, respectively. Molybdenite Re-Os geochronology on grains from a quartz vein with potassic alteration selvage determined the age of Mo mineralization at 297 ± 4.8 Ma. Lithogeochemical data of intrusive units suggest the granitoid rocks show calc-alkaline to high-K calc-alkaline, I-type, and metaluminous to slightly peraluminous affinities that formed in a post-collisional setting and were likely sourced from subduction-modified lithosphere. Lithogeochemical signatures and the tectonic environment classify Zuun Mod into neither Climax nor Endako-types, but as a Mo-rich porphyry Cu deposit.
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This content will become publicly available on June 1, 2026
Genesis and geochronology of the Bayanteeg Li-mineralized pegmatite in the Idermeg terrane, central Mongolia
We present the first petrographic, lithogeochemical, and geochronological study of the Bayanteeg LCT pegmatite located in Idermeg terrane, central Mongolia, and interpret the findings within the geodynamic setting. The pegmatite extends over 140 m with a width of 1.3 m and unknown depth within Neoproterozoic gneiss. The pegmatite contains plagioclase, quartz, and lepidolite with minor K-feldspar, spodumene, muscovite, and topaz, and accessory amounts of cassiterite, amblygonite, columbite-tantalite, monazite, zircon, apatite, and fluorite. Locally, minor secondary quartz and lepidolite occur interstitially between plagioclase and quartz and along the edges of primary lepidolite, respectively, implying late-stage hydrothermal influence. Lithogeochemical data show that the pegmatite contains 0.3–1.12 wt% Li, 256–1285 ppm Cs, and 59–522 ppm Ta. Monazite U-Th-Pb geochronology yielded an age of 144.9 ± 2.8 Ma while cassiterite yielded a U-Pb age of 134.8 ± 1.4 Ma. Lepidolite yielded 40Ar/39Ar plateau age of 131.25 ± 0.3 Ma. These age results fall during the geodynamic evolution of an intracontinental extension accompanied by the exhumation of metamorphic core complexes and extensive magmatism in the eastern Central Asian Orogenic Belt. These events occurred due to a combination of gravitational collapse resulting from lithospheric delamination and asthenospheric upwelling. The geodynamic setting during the pegmatite emplacement implies abnormally hot conditions, ruling out the possibility of anatectic origin. The pegmatite dike with elevated concentrations of Be, Ga, Rb, Nb, Sn, Cs, Ta, and Tl supports a granitic origin with a hidden parental granite at depth. The fact that the Idermeg terrane contains several LCT pegmatites implies an important exploration target for Li exploration.
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- PAR ID:
- 10588548
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Asian Earth Sciences
- Volume:
- 287
- Issue:
- C
- ISSN:
- 1367-9120
- Page Range / eLocation ID:
- 106615
- Subject(s) / Keyword(s):
- LCT pegmatite, Bayanteeg, Monazite, Cassiterite, Lepidolite, Geochronology
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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