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Geoscience ›› 2019, Vol. 33 ›› Issue (01): 73-84.DOI: 10.19657/j.geoscience.1000-8527.2019.01.08

• Petrology • Previous Articles     Next Articles

Zircon U-Pb Age, Geochemical Characteristics and Significance of the Linzizong Group Volcanic Rocks in the Luobuzhen Orefield,Tibet,China

ZHAO Yayun1(), YANG Chunsi2, LÜ Jinliang1, LIU Xiaofeng1, LIU Bo1, ZHENG Changyun1, LIU Yuanchao1, LI Li3, FU Hailong1   

  1. 1. No. 2 Geological Team, Tibet Autonomous Region Geological Mining Exploration and Development Bureau, Lhasa, Tibet 850003, China
    2. Key Laboratory of Mineralogy and Metallogeny, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China
    3. Tibet Autonomous Region Geological Mining Exploration and Development Bureau, Lhasa, Tibet 850000, China
  • Received:2018-02-13 Revised:2018-11-05 Online:2019-02-26 Published:2019-02-28

Abstract:

The Luobuzhen Pb-Zn polymetallic deposit is located in the middle-southern part of the Gangdese magmatic belt. The Linzizong Group (Gp.) volcanic rocks are widely distributed in the mining area, and contain mainly dacite and rhyolitic crystal tuff. LA-ICP-MS zircon U-Pb dating reveals that the dacite was formed at (49.14±0.86) Ma, which was coeval with the Pana Formation volcanic sequence but not the Dianzhong Formation. The rocks are characterized by high K but low Ti contents and are high-K calc-alkaline. The elements of Rb, Th, U, K, Zr, Hf and LREEs are enriched, while Nb, Ta, P, Ti, Sr and HREEs are depleted, and clear LREE/HREE fractionation is present. The volcanic rocks also have negative Eu-anomalies (δEu=0.50 to 0.65). The Neo-Tethys oceanic slab likely subducted beneath Eurasia during the incipient India-Asia collision. Extensive volcanism-plutonism occurred and mineralization reached a peak at ~50 Ma. The dacite volcanism was coeval with the regional magmatism, which suggests that the dacite was formed in an intraplate tectonic environment. This work re-determined the age of the Linzizong Gp. volcanic rocks and implied that the Pana Formation volcanic rocks in the Gangdese belt are potentially ore-bearing. Our finding also provides significant implication and prospecting guidance to understand the relationship between the Linzizong Gp. magmatism and the hydrothermal vein-type Pb-Zn polymetallic mineralization.

Key words: LA-ICP-MS zircon U-Pb age, Linzizong Group, Pana Formation, Luobuzhen, Tibet, China

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