西昆仑慕士塔格岩体的岩石地球化学特征、岩石成因及其构造意义

慕士塔格岩体是西昆仑造山带出露面积最大的侵入岩体,主要由石英二长岩、花岗闪长岩和二长花岗岩组成。岩石地球化学特征显示,该岩体具有较高的SiO2含量和碱度率,低的Al2O3、Fe2O3、MgO、P2O5,稀土元素总量较低,总体上轻重稀土元素分馏明显,富集Rb、Th、K和LREE等大离子亲石元素,亏损Nb、Ta、Sr、P、Ti和HREE等高场强元素,应为高钾钙碱性准铝质—弱过铝质岩石,属于未分异I型-分异I型花岗岩。通过对源岩性质、成因和构造环境的研究,结合区域地质资料,认为该岩体是古特提斯后碰撞伸展环境下,在高温(>839.6℃)低压(<15kbar)环境中壳源变玄武岩发生部分熔融,并伴随着幔源岩浆的参与,经历了以斜长石、磷灰石和钛铁矿为主的分离结晶作用的产物。

西昆仑慕士塔格岩体的LA-ICP-MS锆石U-Pb定年:对古特提斯碰撞时限的制约

慕士塔格岩体是西昆仑造山带出露面积最大的侵入体,主要由黑云母二长花岗岩、似斑状黑云母二长花岗岩和花岗闪长岩组成,其中发育大量的暗色微细粒包体和基性岩浆条带。根据锆石的阴极发光图像以及Th、U、REE元素等特征,所测试的锆石均为典型的岩浆结晶锆石,利用LA-ICP-MS锆石U-Pb定年,测得岩体东西部分的加权平均206Pb/238U年龄分别为229.6±0.8Ma(MSWD=0.44)、232.8±1.5Ma(MSWD=0.21),两者在误差范围内一致,综合获得该岩体年龄为231.4±0.7Ma(MSWD=1.5),属于中三叠世晚期。根据岩石学、锆石内部结构及其REE元素特征,结合前人地球化学资料,该岩体应为壳幔岩浆混合成因。结合区域地质资料,慕士塔格岩体应是从挤压的主碰撞期向伸展后碰撞期转换的产物,表明古特提斯主碰撞作用发生在中三叠世晚期之前,之后开始进入古特提斯后碰撞阶段。

慕士塔格山卡尔塔马克冰川补给径流与非冰川补给径流水化学特征及主控因素研究

2016年7～8月对慕士塔格山卡尔塔马克冰川补给径流与非冰川补给径流进行了采样分析,通过统计分析、主成分分析、Piper图、Gibbs图、正演模型等方法分析了冰川补给径流和非冰川补给径流的水化学特征及其主控因素。结果表明:冰川补给径流和非冰川补给径流两种水体均呈碱性,水化学类型皆为Ca^(2+)-SO_4^(2-)-HCO_3^-,但冰川补给径流和非冰川补给径流的pH值、EC和TDS均存在显著差异(p <0. 05),主要离子浓度间均存在极显著差异(p <0. 01)。冰川补给径流中所有离子具有同源性,而非冰川补给径流NO_3^-显示出与其它离子来源不同。正演模型结果显示,大气输入、硅酸盐风化、碳酸盐风化和蒸发岩溶解对冰川补给径流和非冰川补给径流中离子浓度的贡献率分别为10. 47%、0. 55%、65. 61%、23. 37%和1. 52%、19. 57%、60. 37%、18. 54%。在冰川补给径流中,碳酸盐风化对径流中离子浓度的贡献占主导地位,蒸发岩溶解占次要地位;在非冰川补给径流中,碳酸盐风化亦占主要支配地位,而硅酸盐风化占次要地位。两者差异的原因是硅酸盐风化相比蒸发岩溶解更难进行,冰川补给径流中水岩相互作用时间较短,故硅酸盐风化贡献率较低;而非冰川补给径流经过更充分的水岩相互作用,故硅酸盐风化贡献率较高。其成果可为西部地区水资源管理应用提供参考。

慕士塔格地区大气水汽氢氧稳定同位素季节内变化特征及影响因素分析

慕士塔格地区位于青藏高原西北部,常年受西风影响。为了更清楚地认识西风水汽来源和局地蒸发过程对区域水循环过程的影响,利用2017年7月26日—2017年11月6日和2018年7月30日—2018年12月10日在慕士塔格西风带环境综合观测研究站的监测数据,分析了地表大气水汽氢氧稳定同位素组成和相关局地气象要素的变化特征及其相关关系。研究发现:慕士塔格地区水汽中δ^(18)O、d-excess与局地温度和比湿呈现明显的小时变化、日变化和季节变化;水汽δ^(18)O值与温度的显著正相关关系在不同时间尺度稳定存在;在小时和日尺度上,水汽δ^(18)O值与比湿呈现对数关系;后向轨迹追踪表明,西风将西伯利亚和北大西洋及慕士塔格周围地区的水汽传输至观测站点;当水汽自地中海和北大西洋长距离传输至慕士塔格时,水汽δ^(18)O显著降低可达约7‰,d-excess会显著增大;该地区水汽稳定同位素组成的季节变化特征与降水稳定同位素组成的季节变化特征一致。研究内容初步揭示了青藏高原西风传输水汽稳定同位素变化的主要影响因素,可为区域水循环研究提供必要数据和关键认知,有助于理解西风控制区冰芯稳定同位素记录的气候意义。

青藏高原定日——木孜塔格峰地区重力场特征与断裂构造

为研究青藏高原的地下地质结构和断裂,陕西省地质调查院于2003年～2006年在定日—木孜塔格峰区进行了1∶100万区域重力调查。作者等对获得的重力资料进行了处理和分析,结合地质及其他地球物理资料,将该区布格重力场分成七个区域,描述了其主要特征并分析了其地质意义。进行了定日—木孜塔格峰剖面的重力曲线拟合计算及地质解释,获得了该区地壳结构的定量模型。识别出30条断裂,对它们进行了分类,对其中的重要断裂进行了详细解释。结果表明:重力场分区特征与地质构造分区特征对应得较好;高原边缘及内部各块体间重要的边界断裂都在重力场上有明显的显示;断裂按走向分为近东西向、北东向、近南北向等3组,其中近东西向断裂为主干断裂。

青藏高原定日—木孜塔格峰地区重力场小波分析

目的探究青藏高原的深部结构。方法对定日—木孜塔格峰地区的重力场资料进行小波分析,重点对比分析四阶、五阶的小波逼近异常和细节异常。结果拉轨岗日—康马变质核杂岩带在四、五阶小波细节异常图上表现为近东西向重力低,在四、五阶小波逼近异常图上均表现为梯级带;雅鲁藏布江缝合带在四、五阶小波细节异常图及四阶小波逼近异常图上主要表现为重力高,在五阶小波逼近异常图上表现为梯级带;冈底斯岩基花岗岩带在四阶、五阶小波逼近异常和细节异常图上均表现为重力低;班公湖—怒江缝合带在四、五阶小波细节异常图及四阶小波逼近图上主要表现为近东西向重力高,在五阶小波逼近图上为梯级带;龙木错—双湖缝合带在布格异常图,四、五阶小波逼近异常图及五阶小波细节异常图上均表现为重力异常分界。结论拉轨岗日—康马变质核杂岩带只存在于浅层;雅鲁藏布江缝合带重力高带的场源存在于中深度层次及以上;冈底斯重力低除了反映浅部大规模的花岗岩带外,还可能反映了深部存在的热熔融体;班公湖—怒江缝合带重力高带的场源存在于中深度层次及以上;龙木错—双湖缝合带是重要的构造分界线。

试论塔吉克文化中的四大象征

在古老的中国塔吉克文化中,慕士塔格阿塔山被尊为神。鹰在塔吉克文化中占有极为重要的地位。鲁斯塔木是位民族英雄形象。马在塔吉克族文化中的地位更为突出。文章对此从文化历史渊源上进行了阐释。

Variations of near-surface atmospheric CO_(2)and H_(2)O concentrations during summer on Muztagata

Expeditions during the summers of 2002 and 2003 implemented continuous monitoring of near-surface (2 m height) atmospheric CO2 and H2O concentrations at the 4500 m elevation on Muztagata. The resultant data sets reveal a slight decrease of CO2 concentrations (of about 5 μmol·mol?1) and changes in the diurnal variations from the end of June to the middle August. The daily maximum CO2 concentrations occur between 02:30―05:30 AM (local time) and the minimum levels occur between 12:00―15:30 PM. The atmospheric CO2 concentrations in the summer of 2002 were around 5 μmol·mol?1 lower than those during the same period of 2003, whereas the diurnal amplitude was higher. In contrast, we found that the daily mean atmospheric H2O content in 2003 was much lower than that in 2002 and there exists a striking negative correlation between CO2 and H2O con-centrations. We therefore suggest that the near-surface atmospheric CO2 concentration is affected not only by photosynthesis and respiration, but also by the air H2O content in the glaciated region around Muztagata.

Relationships between δ ^(18)O in summer precipitation and temperature and moisture trajectories at Muztagata, western China

Based on summer observations of stable isotope of precipitation at Muztagata, western China, during 2002―2003, this paper presents the relationship between δ 18O in precipitation and air temperature, and discusses the effect of moisture transport on δ 18O in precipitation. Results show that air temperature correlates positively with δ 18O in precipitation, and the temperature effect controls the δ 18O of precipitation in this area. The Muztagata region exhibits high δ 18O values in summer precipi-tation, similar to those shown at stations in adjacent regions. According to the results of our model set up to trace the moisture trajectories, the westerlies and local moisture circulation contribute to varia-tions of oxygen isotopes in precipitation. In addition, the impacts of the moisture transport distance, the moisture transport level, and the incursion of the polar air mass also influence the variations of δ 18O in precipitation. The moisture origins and transport mechanisms also contribute to the variation of δ 18O in precipitation at Muztagata.

Variations of δ^(18)O in precipitation from the Muztagata Glacier, East Pamirs

Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of2002 and 2003 collected precipitation samples and measured their oxygen isotopes. The δ^(18)O inprecipitation displays a wide range, varying from -17.40per thousand to +1.33per thousand inJune—September 2002 and from -22.31per thousand to +4.59per thousand in May—August 2003. Theδ^(18)O in precipitation correlates with the initial temperature of precipitation during theobserving periods. The positive correlation between δ^(18)O and temperature suggests that δ^(18)Ocan be used as an indicator of temperature in this region. The δ^(18)O values in fresh-snow samplescollected from two snow events at different elevations on the Muztagata Glacier show a strong''altitude effect'', with a ratio of nearly -0.40per thousand per 100 m from 5500 m to 7450 m.

Atmospheric Pb variations in Central Asia since 1955 from Muztagata ice core record, eastern Pamirs

A Muztagata ice core recovered at 7010 m altitude in East Pamirs provides a Pb concentration record from 1955 to 2000. The result reveals in- creasing Pb concentrations from 1955 to 1993, with two Pb concentration peaks in 1980 and 1993. After 1993, Pb concentrations in ice core show an obvi- ously declining trend. Analysis shows that the lead in the Muztagata ice core mainly came from anthropo- genic emissions from countries in Central Asia, while the local emission had little contribution.

Grain size record of microparticles in the Muztagata ice core

The dust transport and sediment characteristics are discussed based onanalysis of mi-croparticle size and size distribution in the Muztagata ice core at 6350 m a.s.I. Thefiner particles with diameter of 1—5 μm are the dominant fraction in number, while middle andcoarse particles mainly contribute to the total volume. The lognormal distribution characteristicscan be seen for some high concentration samples, showing that model size and standard variation aregreater than that in the Greenland ice cores. However, size-volume distribution of some lowconcentration samples is abnormal. Those distributions reflect the dust deposit process in highmountain glaciers at mid-low latitudes and show differences from those in polar ice sheet.

Seasonal variations of dust record in the Muztagata ice cores

Based on the oxygen isotope ratio and microparticle record in ice cores recovered at Mt. Muztagata, Eastern Pamirs, the seasonal variations of atmospheric dust have been reconstructed for the past four decades. High dust concentrations and coarser particle grains have the similar trend with oxygen iso- tope value. Our statistical results indicate that 50%―60% high dust concentration samples occur dur- ing the season with high oxygen isotope values (summer), while low dust storm frequency during spring and winter. Back-trajectory analysis shows that the air mass hitting Muztagata predominately came from West Asia (such as Iran-Afghanistan Plateau) and Central Asia, which are the main dust source area for Muztagata. Dust storms in those source areas most frequently occur during summer (from May to August), while frequent dust storm events in northern China mainly occur during spring (March to May). Regions in the path of Asian dust transport, such as in Japan, the North Pacific, and Greenland, also show high dust concentrations during spring (from March to May). Our results indicate that dust storms have different seasonality in different regions within Asia.

Chernobyl nuclear accident revealed from the 7010 m Muztagata ice core record

The total activity variation with depth from a 41.6 m Muztagata ice core drilled at 7010 m, recorded not only the 1963 radioactive layer due to the thermonuclear test, but also clearly the radioactive peak released by the Chernobyl accident in 1986. This finding indicates that the Chernobyl nuclear accident was clearly recorded in alpine glaciers in the Pamirs of west China, and the layer can be potentially used for ice core dating in other high alpine glaciers in the surrounding regions.

Ammonium record over the last 96 years from the Muztagata glacier in Central Asia

As a major alkaline gas in the atmosphere, ammonia (NH3) plays an important role in atmospheric chemistry. However, there is little knowledge about NH3 variations in the Central Asia. Here we ana- lyzed the ammonium (NH+4) history recorded in an ice core from the East Pamir in Central Asia, which was drilled on the Mt. Muztagata at the elevation of 7010 m a.s.l. in 2003. The core was carefully dated and NH4+ concentration history during 1907―2002 was reconstructed. The result shows that NH4+ con- centration remained approximately constant until the 1930s after a sudden decrease at the very begin- ning of the 20th century, followed by a minimum in 1940 before increasing steadily to the peak at the end of 1990s. It is found that the annual mean NH4+ concentration was strongly associated with the Northern Hemisphere temperature, suggesting the impact of temperature on NH3 emissions in the Central Asia. Moreover, an increase of NH+4 concentration after 1940 also reflects the enhancement of NH3 emissions from anthropogenic sources such as fertilizer applications and livestock wastes in the 20th century.

Formate and acetate records in the Muztagata ice core,Northwest Tibetan Plateau

Formate and acetate concentrations are meas- ured in a 22.56 m-depth ice core recovered in Mt. Muztagata Glacier, northwest Tibetan Plateau. The mean concentrations for formate and acetate in this ice core are 186.6±160.1 and 136.4±133.9 ng/g, respectively. Study shows that there is a positive correlation between formate and nitrate, suggesting both continental origins. However, no significant relationship has been found between formate and acetate, though they both have obvious periodical variations. Because Mt. Muz- tagata lies in the mid-latitude and is correlative to the nearby human activities, formate and acetate concentrations are higher than those in Greenland and Antarctica. During re- cent decades, the increase of formate concentration in the Muztagata ice core and formaldehyde production shows a close correlation. We preliminarily presume that the high formate concentration in the Muztagata ice core is concerned with the thriving of house decoration in which excess for- maldehyde was used.

慕士塔格冰芯中近百年来细菌数量与气候环境变化的关系

应用流式细胞技术分析了取自青藏高原西部慕士塔格冰川73m冰芯上部56.27m中细菌的数量变化,在1907～2000年的93年中,细菌年平均数在0.66×10~3ml(1982年)至6.91×10~3个/ml(1912年)之间变化,平均2.59x10^3个/ml。细菌数量的变化可分为10个不同的阶段,其中6个高峰期和4个低峰期,分别与氧同位素所反映的高温和低温期有较好的对应。冰芯中细菌数量除温度影响外,还受人类活动和陆源粉尘的影响。慕士塔格冰芯中细菌的数量远低于位于高原中部的各拉丹冬冰芯中细菌的数量,且慕士塔格冰芯中细菌数量受陆源粉尘的影响也小于各拉丹冬冰芯,可能是因为慕士塔格冰芯所处荒漠带植物稀少和土壤中细菌数量少所致,慕士塔格和各拉丹冬冰芯中细菌数量的不同反映了冰芯细菌对所处的不同生态环境的响应。