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Ma S.-Q.,China University of Geosciences | Chen J.,Qinghai Geological Survey Institute
Geology in China | Year: 2012

The recently-discovered Lumin molybdenum deposit is located in the southern section of the Yichun-Yanshou polymetallic ore-forming belt. The ore-forming rocks mainly include adamellite -granite porphyry, and the LA -ICP - MS micro- situ isotopic analysis shows that their ages arel95.4±1.4 Ma and 197.6±1.3 Ma, suggesting products of the late Indosinian - Early Yanshanian period. Geochemical studies indicate that SiO2 (wt%) values vary in the range of 3.36%∼5.78%,whereas K2O and Na 2O vary in the range of 3.36%∼5.78% and 2.60%∼3.78% respectively. Rittmann indexes vary between 0.9 and 3.1. Analysis shows that the intrusions belong to high-K calc-alkaline-shoshonitic series. The 2REE values are low with a strong fractionation between light and heavy rare earth elements (LaN/YbN=7.76∼26.47) and obvious Eu negative anomaly (Eu/Eu*=0.34∼0.62). Trace elements display enrichment of Rb, Th, U, K and depletion of Nb, Ta, Ti, Y, Yb, suggesting that the source might have been a relatively water-rich magma, or the magma might have suffered from metasomatism by subduction zone fluid. Combined with results of previous studies, it is concluded that the formation of the deposit was probably controlled by the subduction of Pacific plate in early Mesozoic. Source

Yu L.,CAS Qinghai Institute of Salt Lakes | Yu L.,Qinghai Geological Survey Institute | Yu L.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Lai Z.,CAS Qinghai Institute of Salt Lakes | And 2 more authors.
Quaternary Research (United States) | Year: 2014

Paleoclimatic reconstruction based on aeolian sediments in the eastern Qaidam Basin (QB) has been hindered by the limited chronological data. Here we present 61 Optically Stimulated Luminescence (OSL) ages. On the basis of these OSL ages and the lithologic stratigraphy, we propose the 'effective moisture index (EMI)' for aeolian sediments to reconstruct the effective moisture change. Based on the EMI from twelve sections, the effective moisture change, moisture sources and relevant mechanisms for paleoclimatic change in the eastern QB are discussed. The results indicate that (1) aeolian deposition started at least before 12.4 ± 0.7. ka during the deglaciation, the paleosols developed at the early and mid-Holocene, and aeolian sand and loess accumulated at mid- and late Holocene (2) effective moisture history was: hyper-arid at 12.8-11.6. ka, humid and variable at 11.6-8.3. ka, moderately humid and stable at 8.3-3.5. ka, and increasingly arid at 3.5-0. ka; (3) the effective moisture change was mainly controlled by the Asian summer monsoon (ASM), which mainly followed the change of Northern Hemispheric summer insolation, and the westerlies strengthened and increased the aridity in the QB when the ASM shrank. © 2013 University of Washington. Source

Han W.,CAS Qinghai Institute of Salt Lakes | Han W.,CAS Institute of Earth Environment | Ma Z.,CAS Institute of Geology and Geophysics | Lai Z.,CAS Qinghai Institute of Salt Lakes | And 5 more authors.
Earth Surface Processes and Landforms | Year: 2014

The arid Qaidam Basin is the largest (~3.88×104km2) basin on the north-eastern Tibetan Plateau. Wind erosion in the area has been regarded as an important trigger for intra-basin tectonic balance upheaval, geomorphologic development and as a major supplier of dust to the Chinese Loess Plateau downwind. An initial estimate of the rate of wind erosion (Kapp et al., 2011) based on geological cross-sections has suggested up to 3.2×104km3 of sediments has been deflated over the past 2.8Ma, lowering the landscape by an average of 0.29mm/yr. In this paper we re-evaluate this estimate by dating surface crusts present on three playas within the basin. Understanding the development of these playas is crucial to assessing the overall role of the wind in shaping the regional landscape because they are typically capped with a thick salt crust which effectively protects them from wind erosion. Optically stimulated luminescence (OSL) and U-series dating from a pit section and from the top of a deep drill core, together with results from magnetostratigraphy and a climate proxy record correlated to the marine oxygen isotope record, are used here to determine the age of the playa plains and suggest that the salt crusts have an age of c. 0.1Ma. This young age and the wide distribution of resistant thick salt crusts of the playa plains indicate a much lower degree of wind erosion than previously suggested. The crusts protect the surface from significant surface erosion (including sediment exhumation and unloading) and whilst some wind erosion does occur, it is unlikely to be sufficient to trigger tectonic uplift of the basin or to be a major dust source for the Loess Plateau as previously suggested. © 2013 John Wiley & Sons, Ltd. Source

Shen H.,Linyi Normal University | Yu L.,Linyi Normal University | Yu L.,Qinghai Geological Survey Institute | Zhang H.,Linyi Normal University | And 3 more authors.
Quaternary Geochronology | Year: 2015

Flood is a kind of serious nature disaster, so studies on the palaeofloods are the keys to understand the mechanisms and their relationships with climatic change, geomorphologic evolution and civilization evolution are of great importance. The floods happened frequently in the Yihe-Shuhe River Basin in history, forming the alluvial plain and affecting the evolution of the ancient civilization. However, the complex sediment sources and depositional processes make the flood deposits difficult to be dated and consequently hinder our understanding to the palaeofloods. In this study, we present twelve Optically Stimulated Luminescence (OSL) ages and four AMS 14C ages of flood deposits to study the palaeoflood activities in the Yihe River Basin and its palaeoclimatic and archaeological implications. The youngest OSL age of 0.19±0.02 ka at the depth of 0.5m shows that the residual OSL age, if any, must be much smaller than this amount, and the well comparison between OSL ages and AMS 14C ages further confirm that the flood deposits could be well bleached before buried and consequently the OSL ages are not overestimated. The source of sediments from ground surface in the mountain regions in the upper stream and the special characteristic of quartz might have contributed to the sufficiently bleaching. Consequently, OSL dating has the potential to offer reliable chronology for the flood deposits. The extraordinary floods happened at 4.1-3.8 ka, 3.3-3.0 ka and 0.9-0.1 ka correspond to the global abrupt climatic events, demonstrating that the extreme floods might be caused by or be parts of these climatic instabilities in monsoonal China. The flood happened at 4.1-3.8 ka might have directly caused the decline of the highly developed late Neolithic civilization (Longshan Culture) in the Yihe-Shuhe River Basin. © 2015 Elsevier B.V. Source

Yu L.,Linyi Normal University | Yu L.,Qinghai Geological Survey Institute | Yu L.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Lai Z.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | And 5 more authors.
Quaternary International | Year: 2015

Aeolian sediments are widely distributed in the eastern Qaidam Basin (QB), the main habitats for human in the hyper-arid basin during the Holocene, especially since 3 ka. The evolution of aeolian sediments is an important factor for the environmental change, and influence human activities and migration. However, many questions, e.g., when the aeolian sediments start to accumulate, what controls their initiation and how their evolution responds to climate change and human activities, still need further studies. In this study, we present a detailed Optically Stimulated Luminescence (OSL) chronology for both aeolian and underlying fluvial sediments from the Tiekui Desert in the eastern QB to discuss aeolian and fluvial processes, climatic changes, desert evolution, and human activities. Dating results show that: (1) underlying fluvial sediments were formed during ~23.9-12.1 ka, and the erosion caused by the fluvial process may provide an explanation for the absence of aeolian sediments during and before this period; (2) aeolian sediments accumulated from ca. 9-8 ka to modern times, with loess development from 9-8 ka to 1.6 ka and 1.4-0.7 ka, and dune sand accumulation at 1.6-1.4 ka and 0.7-0 ka. Through the comparison with the local and global palaeoclimatic records, we suggest that desert evolution in this region was sensitive to climatic changes induced by the Asian summer monsoon. Detailed local historical records of the past 2000 years suggest that desert evolution was also influenced by human activities. © 2014 Elsevier Ltd and INQUA. Source

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