Genesis of the beryllium−bearing pegmatite in Wazha W−Be deposit, Southeastern Yunnan

This paper is the result of mineral exploration engineering.

Objective Beryllium is a rare metal element, which plays an irreplaceable role in national economic construction and national defense science and technology. The Wazha W−Be deposit is located in the northeastern part of the Laojunshan granite. The two−mica granites of the Laojunshan complex, mica schist and gneiss in the second section of the Paleoproterozoic Nanyangtian Formation, and pegmatite veins are mainly exposed. The beryllium mineralization occurs in pegmatite veins which with obvious zoning. Discussion on the genesis of beryllium−bearing pegmatites is of great significance to the study on the genesis of regional tungsten−beryllium deposits and the exploration of beryllium minerals.

Methods In this paper, LA−ICP−MS zircon U−Pb dating, whole−rock major and trace elements, Sr−Nd isotopes and inclusions in beryl were studied to discuss the genesis of beryllium−bearing pegmatite.

Results The formation age of beryllium−bearing pegmatite veins in the mining area is (187.9±1.4) Ma, and the veins are characterized by high silicon, rich aluminum and rich alkali. The light rare earth elements are relatively enriched, while the heavy rare earth elements are depleted. The samples enriched in Rb, Th, U, Ta, etc, depleted in Ba, Nd, Sm and Ti. The initial ⁸⁷Sr/⁸⁶Sr ratios and ε_Nd(t) of the Wazha pegmatite are from 0.702740 to 0.732013 and from −10.3 to −10.6, respectively.

Conclusions The pegmatites formed by partial melting of continental crust, with mineralization involving amedium−temperature, moderate−salinity NaCl−H₂O−CO₂−CH₄±N₂. Fluid immiscibility occurred in the pegmatite during the mineralization process.