新疆西天山卡特巴阿苏金矿床锆石U-Pb年龄、地球化学特征及其地质意义

卡特巴阿苏大型金矿床位于新疆西天山中部那拉提北缘断裂带南侧,找矿前景较好。为查明矿区容矿岩浆岩的成因及其与矿床形成的联系,对主要矿石类型含金蚀变二长花岗岩和含金石英硫化物脉进行LA-MC-ICP-MS锆石U-Pb测年和地球化学研究。结果表明,锆石稀土元素显示较陡的左倾配分模式,具有明显的正Ce异常和负Eu异常,指示岩浆锆石成因。根据锆石Ce异常值,获得含矿岩石有关岩浆岩氧逸度对数值(Log(fo_2))为-29.2～5.1,指示岩浆具有较高的氧逸度,有利于金在岩体中初步富集。同时,氧逸度具有较大的变化范围,指示岩浆演化过程中,存在明显的上地壳混染。应用锆石Ti温度计,获得含金蚀变二长花岗岩锆石结晶温度为765～975℃,反映岩浆来自下地壳缺水条件下的部分熔融。含金石英硫化物脉锆石具有较低的结晶温度(641～823℃),可能与早期角闪石的分异结晶有关。以上2种矿石类型的锆石U-Pb年龄分别为350.4±1.6Ma和348.9±1.4Ma,代表了容矿二长花岗岩的结晶年龄。岩体结晶年龄早于前人报道的矿床成矿年龄,表明岩体侵位与成矿作用无直接关系。     

大兴安岭天保工程区生态系统服务变化研究

利用Landsat和MODIS遥感数据和InVEST模型,评估了1990―2015年大兴安岭天保工程区实施前后生态系统土壤风蚀量、生境质量和碳储量的时空变化,并通过地理探测器方法对生态系统服务时空变化分布与趋势进行驱动因子探测和交互作用探测分析。结果表明：① 从空间分布来看,额尔古纳市南部、鄂温克族自治旗西北部、科尔沁右翼前旗的土壤风蚀量大,生境质量差,碳储量低。② 2000年天保工程实施之后,森林面积显著增加,土壤风蚀量减少1.14%,生境质量增加0.49%,碳储量减少幅度为0.12%,低于2000年以前的0.64%。③ 土壤风蚀量主要受植被类型、土壤类型的影响,生态系统类型、植被类型对生境质量、碳储量空间异质性的影响显著大于其他因素,海拔、坡度2种地形因子对土壤风蚀量、碳储量的解释能力很小。温度、降水2种气候因子对土壤风蚀量、生境质量和碳储量的解释能力不固定,但仍是不可或缺的因素。     

1990-2020年间念青唐古拉山中段北坡边坝地区冰川变化及气候响应

念青唐古拉山作为青藏高原东南缘重要山古冰川分布区,受季风影响,各区域冰川变化特征差异明显。论文通过Landsat TM/ETM+/OLI资料、ASRTMGDEM与气象数据,采用比值—阈值法、目视解译和VOLTA模型,结合实地考察,对1990—2020年间念青唐古拉山中段北坡边坝地区现代冰川进退状况、面积变化、冰储量变化以及冰川变化对气候变化响应特征进行研究。结果表明：① 1990—2020年5条冰川(玉贡拉冰川、玛拉波冰川、祥格拉冰川、孔嘎冰川、贡日—庚东冰川)末端高程逐渐升高,面积和冰储量分别减少30.38 km²和4.64 km³,总体缩减并呈现加速趋势。② 冰川冰储量减少0.14~1.92 km³,总体变化率为0.40%·a^-1。2020年上述5条冰川储量占1990年冰川储量的比例分别为0.70、0.99、0.98、0.91和0.82,显示出冰川规模越大,在短时间尺度的变化量越小。③ 气象数据分析显示,1990—2020年研究区冰川变化受气温升高主导,平均气温变化率为0.51 ℃。水热组合呈现温度升高—降水减少,且在最后10 a日益显著,预测未来冰川变化仍受气温控制并呈加速退缩趋势。④ 区域对比研究表明,念青唐古拉山冰川面积变化总体呈退缩状态,但各区域冰川变化特征差异明显。同时,不同研究方法对同一冰川区冰储量模拟结果相差较大,相对误差范围为34.45%~115.49%,精确的冰储量可对比研究方法仍有待进一步研究。     

基于Ka波段云雷达观测的中国西天山降雨云宏微观物理特征研究

利用Ka毫米波云雷达与自动气象站降雨资料,研究了西天山地区2019年和2020年5～8月的降雨云宏微观特性。结果表明：(1)降雨主要发生在夜间,累积降雨量集中在21:00(北京时间,下同)至次日07:00,降雨频次和累积降雨量相关系数为0.71。大雨强频次虽最少,但对总累积降雨量贡献较显著。(2)小雨强、中雨强、大雨强平均反射率因子最大值分别为30 dBZ、35.8 dBZ和39.5 dBZ,最大平均液态水含量分别为1.5 g m^-3、4.2 g m^-3和7.3 g m^-3。(3)不同降雨强度对应的反射率因子都有两个集中区域,2.0～4.4 km反射率因子集中在15～26 dBZ,地面附近的小雨强、中雨强、大雨强对应的反射率因子分别集中在24～32 dBZ、29～38 dBZ和31～42 dBZ。1.75 km以下中雨强和大雨强液态含水量小于1gm^-3的频率明显少于小雨强,降雨强度的越大降雨粒子径向速度越集中。     

A mineral magnetic and scaled-chrysophyte paleolimnological study of two northeastern Pennsylvania lakes: records of fly ash deposition, land-use change, and paleorainfall variation

A combined mineral magnetic and scaled chrysophyte study of lake sediments from Lake Lacawac and Lake Giles in northeastern Pennsylvania was conducted to determine the effects of land-use and sediment source changes on the variation of pH, conductivity, and alkalinity inferred from biotic changes. Ten 30–40 cm long gravity cores were collected from Lake Lacawac and three from Lake Giles. Isothermal remanent magnetizations (IRMs) were given to the lake sediments in a 1.3 T magnetic field to measure magnetic mineral concentration variations. IRM acquisition experiments were conducted to identify magnetic mineralogy. The bedrock, soils and a peat bog on the shores of Lake Lacawac were also sampled for magnetic analysis to determine possible lake sediment sources. The top 10 cm of sediment collected from Lakes Lacawac and Giles was two to four times more magnetic than deeper sediment. ²¹⁰Pb dating suggests that this intensity increase commenced circa 1900. SEM images of magnetic extracts from the highly magnetic sediments indicates the presence of magnetic fly ash microspheres from fossil fuel burning electric power generation plants. The similarity in magnetic coercivity in the top 8 cm lake sediments and in the peat bog supports an atmospheric source for some of the magnetic minerals in the youngest lake sediments. The highly magnetic sediments also contain an antiferromagnetic mineral in two cores closest to Lake Lacawacs southeastern shore. This magnetic mineral is only present deep in the soil profile and would suggest erosion and significant land-use changes in the Lacawac watershed as another cause for the high magnetic intensities (concentrations) in the top 10 cm of the lake sediments. The most significant changes in the scaled chrysophyte flora occurred immediately above the 10 cm level and were used to infer a doubling of the specific conductivity between circa 1910 and 1929. These variations also support land-use changes in the Lacawac catchment at this time. A similar shift in the scaled chrysophte flora was not observed in the top of Lake Giles, however, distinct changes were found in the deeper sections of the core coupled with a smaller peak in magnetic concentration. Fourier analysis of the ²¹⁰Pb-dated lake sediment magnetics indicates the presence of a 50 year period, low amplitude variation in the Lake Lacawac, Lake Giles, and Lake Waynewood (Lott et al., 1994) magnetic concentration records. After removal of the land-use/fly ash magnetic concentration peak by Gaussian filtering, the 50 year variation correlates strongly from lake to lake even though the lakes are in different watersheds separated by up to 30 km. When this magnetic variation is compared with Gaussian-filtered rainfall variations observed in New York City and Philadelphia over the past 120–250 years there is a strong correlation suggesting that magnetic concentration variations can record regional rainfall variations with an approximately 50 year period. This result indicates that magnetics could be used to document regional variations in climatic change.     

基于MODIS数据中国天山积雪面积时空变化特征分析

基于2011-2015年MOD10A2积雪产品和气象数据,通过几何校正、去云预处理,应用归一化差分积雪指数算法等获取中国境内天山山区积雪覆盖面积数据,分析了积雪面积的时空变化特征及与气温降水的关系。结果表明：（1）年内积雪面积呈单峰变化,9月开始积累,次年1月达峰值,3月气温回暖消融加速,至7月最小。春秋季波动较大但没有明显的增减趋势,夏季积雪面积最小,冬季最大且呈减小趋势。（2）2001-2015年积雪覆盖面积整体上呈减少趋势,积雪覆盖率最大值的波动比最小值的波动更加剧烈。（3）积雪覆盖率随着海拔升高而增大,海拔<1 500 m区域积雪覆盖率低于10%,海拔>4 500 m以上区域平均可达70%,为常年稳定积雪区。积雪覆盖率在西北坡最高,南坡最低。（4）年均气温升高是积雪覆盖面积减小的主因,年积雪覆盖面积变化与年降水量变化保持一致的下降趋势。     

南岭山脉及周边鸟类β多样性分析

根据南岭山脉及周边46个地点的鸟类物种多样性数据,结合系统发育关系,运用β多样性比较南岭3个动物地理亚区的物种和谱系差异,探讨南岭地区是否构成华中区和华南区动物地理分界的一部分。结果表明：1）3个区域间物种构成和谱系构成的差异较小,闽广沿海亚区和东部丘陵平原亚区之间的差异主要源于物种丰富度的高低差别,闽广沿海亚区和西部山地高原亚区之间的差异主要源于物种组成和谱系结构两方面的替换;2）留鸟、夏候鸟和冬候鸟会对差异格局造成不同的影响,其中以留鸟各区域间的差异格局最为明显,将夏候鸟和冬候鸟并入分析后,各区域间的差异会缩小;3）鸟类群落在东西间和南北间均会发生明显的谱系分离,东西间的谱系分离主要发生在距离较远的地点之间,南北间的谱系分离在较远地点和较近地点之间均有发生。综合结果,南岭山脉的南侧和北侧的鸟类群落在谱系构成上发生了快速的改变,支持南岭山脉作为华中区和华南区动物地理分界的一部分。     

The Rocky Mountains And The Southwest: Using Feature Names To Study Two Iconic Subregions In The American West

Geographic regions can be defined in many ways, including via physiography, historical development patterns, language, and culture. After broadly surveying different methods of regionalization and their influences on studies of the American West, this article uses a vernacular‐mapping approach to: first, propose distinctive toponyms that are relatively unique to cultures situated in the American Rocky Mountains and Southwest areas; second, map the spatial distributions of these toponyms across the western American landscape; and, third, compare the resulting distributions to the geographies of western businesses that incorporate regional terms into their corporate names. Notably, while the Rocky Mountains and the Southwest are iconic American regions that have captured the imagination for centuries, their cultural geographies are relatively underexplored in the literature. This article makes a modest contribution to this research gap by using geographic information systems (GIS) to map high concentrations of culturally distinctive feature names. The results reveal that the boundaries of vernacular Southwest and Rocky Mountain regions correspond relatively well with boundaries delineated with physiographic characteristics     

中亚天山山区冰雪变化及其对区域水资源的影响

冰川和积雪是构成山区固体水库的主体,对区域水资源稳定性具有调节功能,但深受气候变化的影响。以中亚天山为研究区域,基于长时间序列的观测数据,分别从冰川、积雪、水储量、径流等方面进行分析,并选取阿克苏河、开都河及乌鲁木齐河3个典型流域,研究天山山区冰雪变化对流域水资源的影响。结果表明：① 冰川退缩速率与面积的函数关系为f（x） = -0.53×x^-0.15 （R² = 0.42,RMSE = 0.086）,说明小型冰川对气候变化的响应更为敏感。同时,中低海拔区域的冰川退缩速率大于高海拔区域;② 2003-2015年天山山区水储量的递减速率为-0.7±1.53 cm/a,天山中部区域的递减速率最大,这一结果与该区域冰川急剧退缩相吻合;③ 近半个多世纪以来,冰雪融水径流增加是这3个典型流域径流量增加的主要原因,其中阿克苏河增幅最大（达0.4×10⁸ m³/a）。但自20世纪90年代中期以来,3个流域的径流量都呈减少趋势,与流域内冰川面积减少、厚度变薄及平衡线海拔升高的关系密切。研究结果揭示了气候变化驱动下的山区固态水体储量变化对流域水资源的影响机制,以期为流域水资源管理提供有价值的决策参考。     

晚冰期以来大柴旦盐湖沉积记录的古气候演变及其尘暴事件

本文选择大柴旦盐湖DCD03沉积剖面柱硼镁石矿层下伏土黄色淤泥质粉砂层为研究对象,基于AMS ₁₄C年代学、岩性地层学、矿物学以及地球化学等研究方法,旨在探讨土黄色湖相淤泥质粉砂沉积记录的尘暴事件,以及重建晚冰期以来西风环流显著影响区的水文气候变化。研究结果表明,DCD03沉积剖面的淤泥质粉砂样品粒度频率曲线呈现为双峰态,主峰(均值10 μm)反映了河流作用携带入湖的细粒组分,次峰(﹥32 μm)则反映了风力作用以及河流作用等携带入湖的粗粉砂粒组分。大于64 μm的砂砾组分可能代表外源风尘物质的输入,由尘暴天气携带入湖。大柴旦地区晚冰期以来依次出现了博令和阿勒罗德暖期(12.94~12.17 cal. ka BP)、新仙女木冷期(12.17~11.37 cal. ka BP)、不稳定的早全新世气候(11.37~8.64 cal. ka BP)以及趋于偏冷干的中全新世早期(8.64~7.39 cal. ka BP)。