Minerogenic Theory of the Superlarge Lop Nur Potash Deposit, Xinjiang, China

Abstract

Located in the eastern part of the Tarim basin, Xinjiang, the Lop Nur was an ultimate water catchment area of the Tarim basin during the Quaternary. Through nearly ten years of investigation and research, the authors have found a superlarge brine potash deposit in the Luobei s u b b a s i w secondary basin of the Lop Nur depression. The deposit has been mined now. On that basis, the authors propose new theories on the genesis of the potash rock deposit, In the tectonic and geomorphologic contexts, the Tarim basin lies in a "high mountain-deep basin'' environment. At the beginning of the Quaternary, influenced by the neotectonk movement, the Lop Nur evolved into a "deep basin" in the Tarim basin. At the end of the middle Pleistocene, neotectonic migration began to take place in the intenor of the Lop Nur and a new secondary deep basi-e Luobei subbasin4onned gradually. Despite its small area, it is actually the deepest subbasin in the Lop N u depression, where brines of the Lop Nur Salt Lake gather and evaporate, thus providing materials for the formation of a superlarge brine potash rock deposit. With respect to the phenomenon of brine concentration and change with deepening of the lake, the authors propose a model of "high mountain-deep basin" tectonic migration for potash concentration. In the sedimentological context, the honeycomb-shaped voids developed in glauberite rock in the subbasin are good space for potash-fich brine accumulation. Study indicates that the deposition of glauberite requires recharge of calcium-rich water.In the Tarim area the calcium-rich water might come from deep formation water or oilfield water, and the river water recharging the Lop Nur Salt Lake was rich in sulfate radicals and other components; in addition, the climate in the area was very and the brine evaporated steadily, thus resulting in deposition of substantial amount of glauberite, potash accumulation in intercrystal brine and final formation of the potash deposit. Generally, potash formation in a salt lake undergoes a three-stage process of "carbonates+sulfates (gypsum and glaubente)+chlorides (halite etc.)", but in the study area there only occurred a two-stage process of "carbonates-mlfates (gypsum and glauberite)". The authors call this new geological phenomenon the "two-stage potash formation" model. In conclusion, the superlarge Lop Nor potash deposit is the result of combined "high mountain-deep basin" tectonism and "two-stage potash formation".Superscripts alalluvial sedimcats; chchemical sediments (the numbers 1.2 and 3 followhg it means the early, middle and late stages); didiluvial sediments; eoleolian sediments; Ilacushe sediments; I + chadinary lacustrine sediments occurring alternatively with chemical sediments.Boreholes ZK95-I. ZK95-2 and ZK95-3 w~t diiUed in 1995. and Z K W and ZKlzoO were drilled in 19961997 by the Third Geological Pa@ of Xinjiang.Vol. 79 No.

Research on Process Mineralogy of Potassium-Rich Shale

“…There existed endothermal effect in the range of 1000~1200°C due to derly adjusting crystal trellis of muscovite in rupture to form speculate mullite and other amorphous scraps. It was proved that in the system of quartz and potassium feldspar, eutectic temperature of them was 990°C and quartz played a supportive role in the skeleton because potassium feldspar was changed into liquid at about 1150°C [6] . Fig.…”

Paleoclimatic information recorded in fluid inclusions in halites from Lop Nur, Western China

“…The region has an average annual rainfall of approximately 20 mm and average annual evaporation of approximately 3,000 mm 7 . Over the past 20 years, many studies have investigated sedimentary characteristics 12–14 , salt lake evolutionary history 9,15 , the formation mechanism of potassium-rich brine 10,16–19 , and paleoclimate and environmental evolution 20–31 in Lop Nur. However, minimal research has been conducted on quantitative reconstructions of paleotemperature and its effect on potassium formation in Lop Nur.…”