关键词: 锗元素, 煤锗矿床, 成矿模式, 赋存状态

Abstract:

Germanium is the most researched and bestdeveloped available associated element in coal. All of coal in the nature has Ge, while a tiny minority can accumulate commercially and most has little Ge. The average mass fractions of Ge in coal in China, USA, Australia, UK and former Soviet Union are 3.6×10-6, 5.7×10-6, 2.9×10-6, 4.4×10-6, and 1.5×10-6, respectively. n×100×10-6 is high anomaly in Ge content. Two commerciallyexploited coalGe deposits have been found in China, namely, Cenozoic basin in western Yunnan Province and Mesozoic basin in Inner Mongolia Autonomous Region. But the geological factors of two basins are different. In the article, we mainly compare two basins unique features respectively.The situation of Ge in coal in Yunnan Province is abundant and in the stage of mature development. The known reserve is high to 800 tons in Bangmai Basin in Lincang County, which belongs to extralarge Ge deposit. The approximate area is 16.4 km2 of Bangmai Basin, which is a smallscale Neogene faulted basin. The Ge distributions in each coal seams are not extremely even. Ge in coal generally occurs at the bottom of coal seams in the formation and at the margins of basins in planar surface. The basement of these Neozoic basins in western Yunnan Province can supply granite which is rich in Ge. The average Ge value in binary granite distributed in western Bangmai Basin is 3.5×10-6, and biotite granite in the east is 1.7×10-6, which uneven distribution is related with the different Ge sources supplied by two types of granite. Ge, which was released from source rocks, went into the solution, and flowed into coalbearing basins through favourable palaeohydrologic geological conditions.The coalGe deposit in Shenli coalfield in Inner Mongolia is in the stage of development. Monzonitic granite and diorite outcrop in western mineral land have high Ge value above 15×10-6 after sampling and testing. A bulk of active germanium was released from these rocks by oxygenolysis and decomposition, dissolved in the form of germanium acid solution and migrated into coal basins.Ge abundance increases in upper coal seams because Ge dissolved in hydrothermal fluid in thermometamorphic process and migrated upward. And it decreases near surface because of subsurface water leaching and migration downward. The result generated by the two migrations is that the Ge enriched zone formed between lower bituminous coal and low metamorphic coal near surface (volatile separated rate is above 37%), in which the average Ge value is 15×10-6 and the maximum value is high to 450×10-6.The Ge enrichment and geological factors in Shengli and Yimin coal fields, Inner Mongolia have great difference with those in Lincang County, Yunnan Province. It may be found new mineral occurrences in further general investigation and exploration in Erlian Basin Group which has semigraben basin, graben basin, faulteddepressed basin and contains affluent coal, oil and natural gas. The geological research outcomes related with coal and petroleum are abundant, which is a perfect basis for advanced research on coalGe deposits in basin groups.

Key words: germanium, coalGe deposit, metallogenic model, occurrence