Pengcheng Jiao

The world’s earliest Aral-Sea type disaster: the decline of the Loulan Kingdom in the Tarim Basin

Remnants of cities and farmlands in China’s hyperarid Tarim Basin indicate that environmental conditions were significantly wetter two millennia ago in a region which is barren desert today. Historical documents and age data of organic remains show that the Loulan Kingdom flourished during the Han Dynasty (206 BCE–220 CE) but was abandoned between its end and 645 CE. Previous archaeological, geomorphological and geological studies suggest that deteriorating climate conditions led to the abandonment of the ancient desert cities. Based on analyses of lake sediments from Lop Nur in the eastern Tarim Basin and a review of published records, we show that the Loulan Kingdom decline resulted from a man-made environmental disaster comparable to the recent Aral Sea crisis rather than from changing climate. Lop Nur and other lakes within the Han Dynasty realm experienced rapidly declining water levels or even desiccation whilst lakes in adjacent regions recorded rising levels and relatively wet conditions during the time of the Loulan Kingdom decline. Water withdrawal for irrigation farming in the middle reaches of rivers likely caused water shortage downstream and eventually the widespread deterioration of desert oases a long time before man initiated the Aral Sea disaster in the 1960s.

Composition Determination of Single Fluid Inclusions in Salt Minerals by Laser Ablation ICP-MS

Abstract The chemistry of primary fluid inclusions in salt minerals can be used to study brine composition change and environment evolution of the salt lake. In this study, artificial fluid inclusions in quartz microcapillary tubes were used to be calibration samples. We have initially established the method of composition determination of single fluid inclusions in salt minerals by laser ablation ICP-MS, and the calibration curves of the eight common elements (K, Ca, Mg, Sr, Rb, B, Li and Br) in salt mineral inclusions. The correlative coefficient ( R 2 ) of the calibration curves was over 0.9991, and the relative standard ranged from 0.13% to 6.2% for K, Ca, Mg, Sr, Rb and Li. Whereas R 2 of the calibration curves was 0.9910 and 0.9618 for B and Br respectively, and the relative standard were 4.05% and 29.56%. The calibration curves indicated that the multi-element composition determination method of single fluid inclusion in salt minerals by laser ablation ICP-MS is feasible and accurate. This method has the advantages such as simplicity, speediness, high sensitivity, etc. It is suitable for the composition determination of single fluid inclusions in halite and gypsum from the Lop Nur playa, in Western China.

The First Halite Age Revealed by MC-ICP-MS U-series Dating in Lop Nur, Northwestern China

Quaternary saline lakes are significant for paleoclimatic reconstruction due to the high sensitivity of salt minerals to environmental changes. However, salts in these areas with great thickness such as halite or potash representing extreme environments have severely blocked the application of traditional chronological methods. This is typified by Lop Nur, since accurate age to constrain salt sequences is very limited hindering further exploration for climatic changes and genetic mechanism of potash resources. For the first time, this work used MC-ICP-MS U-series to date halite of Lop Nur. The obtained results combined with previous age data will provide new age constrains on salt sequences in this area and improve our understanding of phased evolution of saline lake and the formation of potash deposits on a time scale.

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

The homogenization temperature (Th) of primary fluid inclusions in halite can be used for paleoclimate interpretations. Lop Nur, in Central Asia, is an extremely arid zone where large amounts of glauberite were deposited from the late Middle to Late Pleistocene. This deposition was accompanied by formation of large-scale potash-bearing brines. However, quantitative paleotemperature data are still lacking, hindering reconstruction of Quaternary climate conditions and their control over potash formation. We measured the Th of inclusions in halite from the salt field and the top of Upper Pleistocene strata in Lop Nur. The maximum homogenization temperature (ThMAX) of inclusions in halite from the salt field was 41.1u2009°C, consistent with the maximum ambient temperature (43.4u2009°C) in the same period. The ThMAX of inclusions in halite from the Upper Pleistocene strata ranged from 35.6u2009°C to 43u2009°C, where maximum air temperatures may have reached 37.9u2009°C to 45.3u2009°C. The results show that a hot and arid climate prevailed in Lop Nur at the end of the Late Pleistocene. Furthermore, changes of the brine chemical composition due to supply variations instead of climate change, may have caused glauberite deposition to cease at the end of the Late Pleistocene.

The Formation Model for Marine Potash Deposits within China's Small Continental Blocks

Chinese geologists have always been expecting to find out a large scale of potash deposits in marine basins,but only one small-middle scale industrial solid potash deposit had been found at Mengyejing in Langping-Simao basin