The Himalayan cryosphere: A critical assessment and evaluation of glacial melt fraction in the Bhagirathi basin

The cryosphere constitutes an important subset of the hydrosphere.The Himalayan cryosphere is a significant contributor to the hydrological budget of a large river system such as the Ganges.Basic data on the cryosphere in the Himalaya is inadequate and also has large uncertainties.The data on glacial melt component in the Himalayan rivers of India also shows high variability.The Gangotri glacier which constitutes nearly a fifth of the glacierized area of the Bhagirathi basin represents one of the fastest receding,large valley glaciers in the region which has been surveyed and monitored for over sixty years.The availability of measurement over a long period and relatively small glacier-fed basin for the Bhagirathi river provides suitable constraints for the measurement of the glacial melt fraction in a Himalayan river.Pre- and post-monsoon samples reveal a decreasing trend Of depletion of δ~(18)O in the river water from glacier snout(Gaumukh) to the confluence of the Bhagirathi river with the Alaknanda river near Devprayag.Calculations of existing glacial melt fraction(~ 30%at Rishikesh) are not consistent with the reported glacial thinning rates.It is contended that the choice of unsuitable end-members in the three component mixing model causes the overestimation of glacial melt component in the river discharge.Careful selection of end members provides results(~11%at Devprayag) that are consistent with the expected thinning rates.     

山东胶西北矿集区和焦家金矿田成矿构造系统

胶西北矿集区金矿床主要受三山岛断裂、龙莱断裂和招平断裂3条主干断裂及其次级断裂控制,构成胶西北3条金矿带和一系列金矿田。断裂总体呈NNE走向,平面形态呈S形,多期活动特征明显,自主裂面向外依次出现黄铁绢英岩质碎裂岩、黄铁绢英岩化花岗质碎裂岩、黄铁绢英岩化花岗岩等矿化蚀变带。焦家金矿田受焦家断裂的控制,金矿床在平面上主要产于焦家断裂分枝复合、膨胀转折的部位;焦家断裂在剖面上呈上陡下缓的铲式特征,金矿床主要产于断裂倾角由陡变缓的转折点下部,主要矿体沿焦家断裂下盘分布,赋存于主裂面和与主裂面平行的一组缓倾斜裂隙中,远离主裂面逐渐出现一组陡倾的控矿裂隙。胶西北3条主要金矿控矿断裂构成了一条沿玲珑花岗岩与早前寒武纪地质体边界分布的大型伸展构造带。     

Molybdenite Mineralization and Re‐Os Geochronology of the Escondida and Escondida Norte Porphyry Deposits,Northern Chile

Molybdenum is an economically important subproduct of North Chilean porphyry‐type deposits, and thus spatial and temporal distribution of molybdenite as the primary Mo‐bearing mineral in the Escondida and Escondida Norte deposits were characterized using several mineralogical and chemical techniques and the Re‐Os dating method. Molybdenum is distributed extensively in the two deposits, and high molybdenum concentrations (>500 ppm) are recognized particularly in the chlorite‐sericite transitional zone between the potassic and sericitic zones. Two modes of occurrence of molybdenite are observed in the Escondida deposit: aggregates with Cu‐Fe‐sulfide minerals in fine veinlets (sulfide‐veinlet type), and monomineralic microveinlets associated with NE‐trending faults. The former and the latter yielded ages of 36.1 ± 0.2 Ma and 35.2 ± 0.2 Ma, respectively. Re‐Os dating of Escondida Norte molybdenites also show two distinct episodes, at 37.7 ± 0.3 Ma and a younger episode at 36.6 ± 0.2 Ma. These data indicate that the Escondida Norte is older than the main Escondida deposit. The Re‐Os age data combined with those of the porphyry emplacement suggest that the molybdenite mineralization in the Escondida district occurred as several short episodic pulses during the late‐magmatic to hydrothermal transition, and that the Cu‐Mo deposits were formed in a variable overall period spanning 1 to 5 m.y.     

特提斯成矿域中新世斑岩铜矿岩石成因、源区、构造演化及其成矿作用过程

作为全球三大成矿域之一,特提斯成矿域发育众多的世界级成矿带(矿床),例如,旁地德斯、萨汉德-巴兹曼、贾盖、玉龙、冈底斯成矿带等。为了进一步了解特提斯成矿域中新世斑岩铜矿的成因及成矿作用,本文对萨汉德-巴兹曼、贾盖和冈底斯铜矿带典型矿床的地质、地球化学、Sr-Nd-Pb数据进行对比分析,探讨含矿斑岩岩石成因、源区特征和构造环境,归纳其构造演化与其成矿作用过程。地球化学数据显示,这三个铜矿带中新世斑岩体总体显示钙碱性I型花岗岩的特征,具有埃达克岩亲和性。与冈底斯铜矿带相比较,萨汉德-巴兹曼铜矿带和贾盖铜矿带斑岩体显示出弧岩浆岩与埃达克岩过渡的地球化学特征,暗示其岩浆源区MORB质角闪榴辉岩或榴辉岩可能发生的较大程度的部分熔融。Sr-Nd-Pb同位素数据显示,这些含矿斑岩主要来源于受岩浆作用控制的壳幔混合物质,显示DUPAL异常。综合研究分析,认为这些含矿斑岩可能形成于岛弧造山带演化过程中,是洋壳俯冲消减和大陆碰撞过程中增厚下地壳部分熔融的结果。     

滇中砂岩铜矿成矿过程中水－岩反应的证据与机理

从野外地质产状、岩石化学、有机岩石学、元素地球化学、有机地球化学等方面详细分析了滇中砂岩铜矿成矿过程中的水－岩反应证据，阐明了成矿过程中水－岩反应的机理，其中包括渗滤作用、扩散作用、混染作用、交代作用、交代溶蚀作用、氧化还原作用和沸腾作用     

新疆东准噶尔地区玉希喀拉多金属异常特征及评述

通过总结玉希喀拉综合异常区特征，分析异常地质背景，探讨了异常区找锡的前景，指出玉希喀拉花岗财为非含锡矿花岗岩，锡成矿可能性小。认为该异常是由于岩体多次侵入引起Ａｕ，Ｃｕ，Ｓｎ等元素三次活化，迁移，聚集的结果。     

Timing of mineralization and source of fluids in a slate-belt auriferous vein system, Hill End goldfield, NSW, Australia: Evidence from Ar/Ar dating and O- and H-isotopes

⁴⁰Ar/³⁹Ar dating of metamorphic biotite and alteration muscovite from the auriferous veins and host rocks at the Hill End goldfield, N.S.W., Australia, has distinguished four major geological events, including the timing of gold mineralization. The earliest hydrothermal event occurred during the Middle Devonian Tabberabberan Orogeny (370–380 Ma) and resulted in the formation of quartz veins barren of Au. A second and major episode of vein emplacement occurred in the Early Carboniferous during the principal phase of metamorphism and deformation at 359–363 Ma. This was followed by Au accumulation in two stages: (1) after the major phases of quartz deposition, and (2) during and after the development of conspicuous internal vein laminations (˜ 357 Ma and ˜ 343 Ma, respectively). Two sources of fluid are proposed for vein and ore formation. The first is a local metamorphic fluid characterized by δ¹⁸O_H2O values of 8.9 to 12.5 per mil and δD_H2O values of −87 to −90 per mil. The second is a mixed ore fluid with δ¹⁸O and δD values in the range of δ¹⁸O_H2O 8.4 to 11 per mil and δD_H2O of −49 to −36 per mil. Progressive entry of this second fluid, sourced from trough-fill or deeper crustal rocks, is linked closely to cycles of gold precipitation at Hill End.     

浙江中生代热液矿床的分形研究

根据浙江293个有开采价值的中生代热液萤石、金、银和铅锌矿床数据,在矿床地质研究基础上探讨了这些矿床的空间和储量分形问题。研究表明,在两个尺度范围内,矿床在空间上呈分形分布,其中群集分布的分维数D分别为0.1405-0.3778(1-20km)和0.7168-1.1851(20-750km);密度分布的分维数D分别为0.294-1.1242(1-40km)和0.135-0.252(40-750km)。研究还发现矿床的频度-大小分布也是分形的,其储量分形分布的分维数为萤石(浙江)D=2.34萤石(中国)D=2.13:铅锌(浙江)D=2.27;银(浙江)D=1.63:金(浙江)D=1.09。     

南蒙古欧玉陶勒盖斑岩型矿床研究进展

南蒙古欧玉陶勒盖矿床是世界上已知最大的斑岩型铜金矿床之一,处在中古生代哈萨克-蒙古岩浆弧内,是中国"一带一路"项目中中国企业"走出去"的重要方向之一。铜金储量高、矿床品位好、矿化范围广、矿体规模巨大,属世界级超大型斑岩型铜(金)矿床,开发潜力巨大。在收集大量资料的基础上,通过整理和分析,建立成因模型,并划分出北Heruga区域、Javkhlant区域、西Hugo深部区域、西Hugo深部区域、Ulaan Khud北部矿点5个找矿远景区。欧玉陶勒盖矿床所在成矿带沿哈萨克-蒙古岩浆弧向两端延伸,向西经新疆土屋铜矿延伸至哈萨克斯坦境内的科翁腊德和阿克脱盖斑岩铜矿,向东延伸至中国境内多宝山、铜山地区。     

北祁连西段钨矿床成矿地质特征对比与研究

北祁连西段达到大型规模的钨矿床有3处,分别是塔儿沟钨矿、小柳沟钨矿和西柳沟钨矿,空间上自西向东展布;其地质特征各有特点,成矿条件也不尽相同。通过对3个矿床地质特征的对比和成矿条件的分析,认为北祁连西段钨矿是加里东期的产物,初始矿源来自元古界古老地层,构造控制矿体数量、产状和规模,酸性花岗质岩体侵入热液作用使W元素富集最终成矿,成矿期从中奥陶世延续到晚志留世。塔儿沟钨矿和小柳沟钨矿成矿在"板块俯冲"时形成,西柳沟钨矿在"陆-陆碰撞"时形成。北祁连西段具有良好的钨矿成矿背景和有利的成矿条件,矿床外围地质工作程度低,在其外围和深部开展工作,找矿会有重大突破,勘查方法以钻探为主。