New Research Reveals Formation of Crystalline Graphite Deposits in the Aobaoshan Crystalline Graphite Ore Cluster

Strategic Insights -

Researchers from Lanzhou University have made a significant discovery in the field of ore geology, shedding light on the formation of crystalline graphite deposits in the Aobaoshan Crystalline Graphite Ore Cluster in the Dunhuang block, Gansu, NW China. The study, published in the journal Ore Geology Reviews, reveals that the formation of these deposits was controlled by at least two tectonic-thermal events, including Paleoproterozoic high-grade metamorphism and a Silurian-Devonian magmatic-tectonic-thermal event.

Key Takeaways:

  • The Aobaoshan Crystalline Graphite Ore Cluster is located in the southwest of the Central Asian Orogenic Belt (CAOB) and is characterized by two-mica quartz schist of Dunhuang group.
  • The research team conducted a comprehensive study of the petrography, major and trace elements, zircon U-Pb ages, and carbon isotopes of the mineralized two-mica quartz schist from the ACGOC.
  • The results suggest that the ages of 2442 +/- 15 Ma and 2462 +/- 20 Ma are interpreted as the maximum depositional ages of the sedimentary protoliths, while those of 1756 +/- 10 Ma and 1821 +/- 20 Ma reflect high-grade metamorphism in the Aobaoshan (ABS) and Hongliuxia (HLX) crystalline graphite deposits.
  • The study also revealed that the whole-rock samples are enriched in silicon and exhibit low total rare-earth element abundances, with (La/Yb)(N) ratios varying widely (0.48-7.35) and consistently negative Eu anomalies.
  • The primitive mantle-normalized trace element patterns indicates a marine sedimentary environment for the ACGOC rocks, with depictions in Nb, Ta, Zr, and Hf, coupled with enrichments in Rb, Ba, and Sr.
  • The study concluded that the formation of crystalline graphite deposits in the ACGOC was controlled by at least two tectonic-thermal events, including Paleoproterozoic high-grade metamorphism and a Silurian-Devonian magmatic-tectonic-thermal event.

Statistics:

  • 2442 +/- 15 Ma: age of maximum depositional ages of sedimentary protoliths
  • 2462 +/- 20 Ma: age of maximum depositional ages of sedimentary protoliths
  • 1756 +/- 10 Ma: age of high-grade metamorphism in Aobaoshan (ABS) deposit
  • 1821 +/- 20 Ma: age of high-grade metamorphism in Hongliuxia (HLX) deposit
  • 407 +/- 11 Ma: age of Silurian-Devonian magmatic-tectonic-thermal event
  • & sum;REE = 50.9-164.9 ppm: total rare-earth element abundances in whole-rock samples
  • (La/Yb)(N) ratios: 0.48-7.35

Sources:

  • Geochronology and Geochemistry of the Aobaoshan Crystalline Graphite Ore Cluster In the Dunhuang Block, Gansu, Nw China. Ore Geology Reviews, 2025;186.
  • NewsRx. Reports Outline Ore Geology Study Results from Lanzhou University (Geochronology and Geochemistry of the Aobaoshan Crystalline Graphite Ore Cluster In the Dunhuang Block, Gansu, Nw China). China Weekly News. November 4, 2025; p 294.