Evaluation of gridded precipitation data in the Hindu Kush–Karakoram–Himalaya mountainous area

The accurate measurement of precipitation is crucial for hydrological studies. This is especially true for the Hindu Kush–Karakoram–Himalaya (HKKH) mountain region, which is characterized by high spatiotemporal precipitation variability. The paucity of raingauges makes it difficult to measure precipitation in this region precisely. We conducted evaluation of TMPA 3B42V7 and APHRO 1101 in the HKKH area on a daily basis at a spatial resolution of 0.25°?×?0.25°, using 27 raingauges. Statistically, the largest error in the gridded data arose mainly from elevation, followed by volumetric error and Nash–Sutcliffe efficiency. Overall, the TMPA data have a poor correlation with ground observations in the HKKH area, especially for higher altitudes. The western areas are relatively more underestimated and the Karakoram shows higher frequency of bias in the TMPA retrievals. This method could help improve the satellite precipitation estimation algorithm as it considers local physiography and climatic factors.     

新疆喀喇昆仑火烧云超大型铅锌矿床矿物学、地球化学及成因

近年来,青藏高原北缘喀喇昆仑铅锌找矿取得重大突破,新发现的火烧云超大型铅锌矿床已成为中国最大的铅锌矿床,矿石矿物以菱锌矿、白铅矿、水锌矿为主,也是世界第二大非硫化物铅锌矿床。矿体呈似层状产出,埋藏浅,主要为褐色块状矿石,Pb+Zn平均品位近30%。可分为3个成矿阶段。早期铅锌硫化物成矿阶段（方铅矿、闪锌矿、方解石）、中期铅锌非硫化物成矿阶段（菱锌矿、锰氧化物→菱锌矿、白铅矿、石膏）与晚期表生氧化阶段（水锌矿）。硫化物阶段方铅矿的δ34S为-18.9‰~-4.2‰,非硫化物阶段热液石膏的δ34S为-20.6‰~-7.5‰,继承了硫化物阶段矿物的硫同位素特征。Pb同位素组成集中,具有地壳来源特征,二叠系—白垩系可能提供了金属成矿物质。方解石的δ18CPDB为0.6‰~3.1‰,δ18OSMOW为15.3‰~24.6‰,菱锌矿的δ18CPDB为-2.7‰~4.5‰,δ18OSMOW为10.4‰~26.1‰,来源于碳酸盐岩的溶解作用;白铅矿的δ18CPDB为-7.7‰~4.3‰,δ18OSMOW为9.3‰~24.3‰,同位素发生漂移,可能是与大气降水的混入有关。硫化物成矿阶段方解石中流体包裹体的3He/4He值为0.05~0.39 R/Ra,40Ar/36Ar值为296.2~428.9,方铅矿中流体包裹体的3He/4He值为0.03 R/Ra,40Ar/36Ar值为290.0,成矿流体可能为中温、低盐度、中低密度的还原性壳源流体;非硫化物成矿阶段菱锌矿中流体包裹体的3He/4He值为0.10~0.43 R/Ra,40Ar/36Ar值为290.6~295.3;白铅矿中流体包裹体的3He/4He值为0.08 R/Ra,40Ar/36Ar值为293.5,成矿流体可能为中低温、低盐度、中密度的壳源流体与大气降水混合流体。综上所述,火烧云超大型铅锌矿床是盆地边缘褶皱逆冲+构造流体+次生交代成矿系统的产物,硫化物成矿阶段为构造热液成因,非硫化物成矿阶段为围岩交代成因,后期发生叠加氧化作用,形成大量水锌矿。     

Quaternary lacustrine deposits in a high-energy semi-arid mountain environment,Karakoram Mountains,northern Pakistan

Impressive Quaternary lacustrine deposits are present as terrace remnants throughout the Karakoram Mountains, northern Pakistan. They are mainly the result of damming of drainage systems during glacial advances or by catastrophic mass movement deposits. The longevity of most lakes is relatively short, in the order of years to tens of years, but sedimentation rates are extremely high as a consequence of the high sediment loads within the rivers. This results in deposits that frequently exceed 10 m in thickness. The sediments comprise dominantly planar bedded, massive and, less commonly, planar laminated, silts, comprising detrital quartz, feldspar, mica, calcite, chlorite and illite. A facies model for lacustrine sedimentation in a high-energy semi-arid high mountain region is presented, using case studies from a glacially dammed palaeolake (Glacial Lake Gilgit) and a debris-flow dammed palaeolake (Lake Serat). The rapid deposition and absence of organic material restricts the usefulness of these lacustrine sediments as proxies for palaeoenvironmental reconstruction, but they are helpful in reconstructing the former extent of glaciers and illustrating the importance of high-magnitude–low-frequency events, such as landsliding, as formative processes contributing to the evolution of the Karakoram landscape.     

喀喇昆仑甜水海—火烧云一带铅锌矿成矿条件及找矿潜力

甜水海—火烧云处于青藏高原西北部喀喇昆仑山主脊北侧新疆和田县境内。近年来,该区开展了大量的地质找矿工作,发现了火烧云超大型铅锌矿,乔尔天山大断裂以南一带除火烧云以外还发现了一大批铅锌矿找矿线索。通过对区内成矿地质背景、地球化学特征及已发现的矿床特征的综合研究,认为区内成矿地球化学条件优越,地质背景有利于铅锌成矿,与中侏罗统龙山组碳酸盐岩有关的喷流沉积型(SEDEX)铅锌矿、产于中侏罗统龙山组和白垩系铁隆滩组的碎屑岩-碳酸盐岩及三叠系碎屑岩的密西西比河谷型(MVT)铅锌矿找矿潜力较大,指出了研究区找矿方向,可作为今后该区铅锌矿找矿及矿产勘查工作的参考。     

新疆白龙山伟晶岩型锂矿床研究进展

大红柳滩-白龙山一带是西昆仑-喀喇昆仑山花岗伟晶岩分布最为集中、稀有金属矿化最好的地区。项目组2017年通过多次野外勘查、系统取样与室内化验分析,确认在新疆和田县喀喇昆仑腹地白龙山新发现了一处超大型锂铷多金属矿床,该矿床为花岗伟晶岩型。同时在大红柳滩-白龙山发现了雪凤岭、雪盆、双牙、冰舟、白龙山南、大红柳滩东(496北沟)等多处花岗伟晶岩型锂多金属矿床。通过对白龙山锂多金属矿床研究,目前已确定含矿伟晶岩脉群带长度>8250 m,宽度46～165 m,在白龙山锂多金属矿区划分出5个含矿伟晶岩脉群带,共发现含矿伟晶岩脉166条,对其中52条主要矿体进行了研究,含矿伟晶岩脉长度50～1230 m,宽1.5～157 m不等,Li₂O平均品位0.93%～3.44%, BeO平均品位0.54%～0.63%,Rb₂O平均品位0.11%～0.18%, Nb₂O₅平均品位0.011%～0.018%, Ta₂O₅平均品位0.003%～0.009%。新疆昆仑蓝钻矿业开发有...     

Combined thermobarometry and geochronology of peraluminous metapelites from the Karakoram metamorphic complex,North Pakistan; New insight into the tectonothermal evolution of the Baltoro and Hunza Valley regions

Petrographic analysis of peraluminous metapelites from two separate regions of the Karakoram metamorphic complex, North Pakistan, has produced new insights into the P–T–t evolution of the deep crust along the south Asian margin before and after the India‐Asia collision. Average P–T estimates and pseudosection construction in the MnO–Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–Fe₂O₃ (MnNCKFMASHTO) system using THERMOCALC have provided prograde and peak metamorphic conditions and U–Pb geochronology of metamorphic monazite has provided age constraints. Two new events in the tectonothermal evolution of the Hunza Valley have been documented; an andalusite‐grade contact metamorphic event at 105.5 ± 0.8 Ma, at unknown P–T conditions, associated with the widespread subduction‐related granite magmatism before the India‐Asia collision, and a kyanite‐grade overprint of sillimanite‐grade rocks with peak P–T conditions of ～7.8 kbar, 645 °C at 28.2 ± 0.8 Ma associated with the ongoing India‐Asia collision. A kyanite‐grade event observed in the Baltoro region with similar peak P–T conditions (～7.4–8.0 kbar, ～640–660 °C) is interpreted to have occurred sometime after 21.8 ± 0.6 Ma, however, previous studies have suggested that this event commenced in the Baltoro as early as c. 28 Ma. A calculated prograde P–T path for this kyanite‐grade event in the Baltoro indicates that garnet first nucleated on an initially high geothermal gradient (～30 °C km^?1) and grew during a significant increase in pressure of ～2.6 kbar over a temperature increase of ～100 °C. This event is thought to represent evidence for conductive heating of the middle crust during early stages of intrusion and lateral migration of the Baltoro batholith, with thermal conditions comparable with tectonic models of magmatic over‐accretion.     

Exploitation of Landsat data for snow zonation mapping in the Hindukush,Karakoram and Himalaya (HKH) region of Pakistan

Abstract

In the Hindukush, Karakoram and Himalaya (HKH) region of Pakistan, many glaciological variables are still not known due to the remoteness and harsh weather conditions of the area. A remote sensing technique is therefore applied to map the snow zonation in the HKH region. Landsat 7 ETM+ data for the year 2003 are used in this study. Image classification and image processing techniques are applied to map, for the first time, the major snow zones in the HKH region. Six classes are identified: the results show that the area covered by the highest-altitude snow (Snow I), lower-altitude snow (Snow II), bare ice, debris-covered ice, wet snow and shadow is 21 529.42, 22 472.58, 8696.41, 8038.75, 12 159.37 and 7322.30 km², respectively. The study also indicates that the equilibrium line altitude (ELA) lies between 5000 and 5500 m above sea level, with an accumulation area ratio (AAR) of 0.60.

Citation Butt, M.J., 2013. Exploitation of Landsat data for snow zonation mapping in the Hindukush, Karakoram and Himalaya (HKH) region of Pakistan. Hydrological Sciences Journal, 58 (5), 1088–1096.     

1993-2016年喀喇昆仑山什约克流域冰川变化遥感监测

基于1993、2000、2016年的多景Landsat TM/ETM+/OLI影像,通过目视解译法提取冰川边界,从规模、朝向、高程带和前进冰川等多个方面分析了近20年来喀喇昆仑山什约克流域冰川面积变化特征。结果表明：近20年来研究区冰川呈微弱退缩态势,年均退缩率仅为0.05%±0.20%,其中1993-2000年退缩速率为（0.03%±0.64%）·a^-1,2000-2016年退缩速率为（0.06%±0.27%）·a^-1。1993-2016年什约克流域291条冰川的末端发生了前进现象,在一定程度上减小了冰川总面积退缩的幅度。此外,近20年来研究区冰川前进现象呈减弱态势。近35年来什约克流域气温显著上升,降水量亦呈增加趋势,气温的显著上升是冰川退缩的主要原因,而降水量的增加则是冰川退缩速率相对较低的主要原因。     

Tectonics induced switching of provenance during the Late Quaternary aggradation of the Indus River Valley,Ladakh, India

The Indus River flows through Ladakh, one of the driest and coldest places on earth, in a tectonically active domain. Fluvial, glaciofluvial, lacustrine and debris dominated sequences represent the Late Quaternary sedimentary record along the river course. Karakoram Fault, a major crustal scaled feature reported to be active during the Quaternary, is associated with the Indus River drainage. Linkages between a major, active fault and deposits formed during the activity period of the fault are explored using heavy mineral deduced provenance and Optically Stimulated Luminescence(OSL) chronology.Five deposits in a ~200 km long stretch of the Indus River have been examined for a ~80 ka period to decipher the climate linked aggradation history. Damming of the Indus River at ~79 ka and existence of the Spituk Lake for >30 ka is demonstrated. Using geology of the provenance in relation to the mineralogical attributes of the Quaternary deposits, the major drainage reorganization when the connection of the Tangtse Valley to the Indus was blocked, is inferred at ~73 ka. It is supported by the geologicalgeomorphological evidence. The study demonstrates the application of provenance linked mineralogy in terrestrial aggradation in a tectonically active region.     

Quaternary glaciation in the Nubra and Shyok valley confluence, northernmost Ladakh, India

Three glacial stages (Deshkit 1, Deshkit 2 and Dishkit 3 glacial stages) are identified in the Nubra and Shyok valleys in northernmost Ladakh, northwest India, on the basis of geomorphic field mapping, remote sensing, and ¹⁰Be terrestrial cosmogenic nuclide surface exposure dating. The glacial stages date to ∼ 45 ka (Deshkit 1 glacial stage), ∼ 81 ka (Deshkit 2 glacial stage) and ∼ 144 ka (Deshkit 3 glacial stage). A mean equilibrium line altitude depression of ∼ 290 m for the Deshkit 1 glacial stage was calculated using the area accumulation ratio, toe-to-headwall ratio, area-altitude, and area-altitude balance ratio methods. Comparison of glaciation in the Nubra and Shyok valleys with glaciations in the adjacent Central Karakoram of northern Pakistan and northern side of the Ladakh Range of northern India indicates that glaciation was synchronous on Milankovitch timescales across the region during MIS-6, but differed greatly in extent, with more extensive glaciation in the Karakoram than the morphostratigraphically equivalent glaciation on the northern slopes of the Ladakh Range. This highlights the strong contrast in the extent of glaciation across ranges in the Himalaya-Tibetan orogen, necessitating caution when correlating glacial successions within and between mountain ranges.