| 云南勐野井钾盐矿床特征,微量元素地球化学及成因探讨 |
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| POTASH DEPOSITS IN MENGYEJING, YUNNAN——A STUDY OF CERTAIN CHARACTERISTICS, GEOCHEMISTRY OF TRACE ELEMENTS AND GENESIS OF THE DEPOSITS |
| The Mengyejing potash deposits, found in the "red" Mengyejing Formation of Upper Cretaceous to Paleogene ages, are located in the southof the Lanping-Simao depression zone between the Ailaoshan and Lancangjiang faults. The salt sequence consists of mixed (sedimentary rocks characterizedby repeated occurrence of chemical evaporites and clastic sediments. Thetypical section may be subdivided into nine rhythmical layers which fallinto three compositional units, i.e., the upper and lower halite beds andmiddle potash member. Trace elements of the deposits have been studied rather systematically. The average content of Br in halite is 127 ppm, in grey sylvite, 2060ppm, and in carnallite, 1399 ppm, with the exception of low Br contentin carnallite, that of the other two falls within the respective theoretical value. The average amounts of Rb in sylvite and carnallite are respectively 50 ppm and 60 ppm. Although Rb in the sylvite is more than thatof the theoretical value from sea water, however, that in the carnallitefalls within the theoretical value. This shows that the parent brine wasof marine and deep-level water source. The red sylvite associated with carnallite has abnormally low Br(1229 ppm) and abnormally high Rb (67 ppm) as compared with primarygrey sylvite. These facts can be explained satisfactorily if it is a secondary leaching product from carnallite. Br in the halite profile increases upward slightly. But there is evident rising of the Br curve at the points where the lower or the upperhalite bed passes into the middle potash member with saw-like variationin between, indicating that the brine giving rise to the potash precipitation has reached the "dry-lake" stage. Strontium and boron have substituted respectively for Ca++ and SO_4in anhydrite, thus denoting the diluting of the brine, while celestite, boracite and the presence of boron in absorption form are related closelyto the potash layers and may indicate its concentration in related salts. |
| XU Xiao-song,WU Jia-ling.1983.POTASH DEPOSITS IN MENGYEJING, YUNNAN——A STUDY OF CERTAIN CHARACTERISTICS, GEOCHEMISTRY OF TRACE ELEMENTS AND GENESIS OF THE DEPOSITS[J].Acta Geoscientica Sinica,5(1):17-36. |
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