龙木错与结则茶卡盐湖卤水兑卤及蒸发析盐规律研究

本文以西藏龙木错与结则茶卡为对象,研究了两盐湖卤水在不同兑卤比情况下,混合卤各组分的变化,并对兑卤后的混合卤水进行了15°C蒸发过程的研究。实验分别对两种原料卤水和兑卤后卤水蒸发所得的9个卤水样品进行了常量化学组分分析,研究了兑卤后卤水蒸发过程中盐类的富集行为和析出规律。混合卤蒸发析盐规律结果基本符合Na+、K+、Mg2+//Cl–、24SO?-H2O(15°C)五元水盐体系相图。     

Mechanisms of magmatic gas loss along the Southeast Indian Ridge and the Amsterdam -St. Paul Plateau

New analyses of He, Ne, Ar and CO₂ trapped in basaltic glasses from the Southeast Indian Ridge (Amsterdam-St. Paul (ASP) region) show that ridge magmas degas by a Rayleigh distillation process. As a result, the absolute and relative noble gas abundances are highly fractionated with ⁴He/⁴⁰Ar* ratios as high as 620 compared to a production ratio of ∼3 (where ⁴⁰Ar* is ⁴⁰Ar corrected for atmospheric contamination). There is a good correlation between ⁴He/⁴⁰Ar* and the MgO content of the basalt, suggesting that the amount of gas lost from a particular magma is related to the degree of crystallization. Fractional crystallization forces oversaturation of CO₂ because CO₂ is an incompatible element. Therefore, crystallization will increase the fraction of gas lost from the magma. The He-Ar-CO₂-MgO-TiO₂ compositions of the ASP basalts are modeled as a combined fractional crystallization-fractional degassing process using experimentally determined noble gas and CO₂ solubilities and partition coefficients at reasonable magmatic pressures (2-4 kbar). The combined fractional crystallization-degassing model reproduces the basalt compositions well, although it is not possible to rule out depth of eruption as a potential additional control on the extent of degassing. The extent of degassing determines the relative noble gas abundances (⁴He/⁴⁰Ar*) and the ⁴⁰Ar*/CO₂ ratio but it cannot account for large (>factor 50) variations in He/CO₂, due to the similar solubilities of He and CO₂ in basaltic magmas. Instead, variations in CO₂/³He (≡C/³He) trapped in the vesicles must reflect similar variations in the primary magma. The controls on C/³He in mid-ocean ridge basalts (MORBs) are not known. There are no obvious correlated variations between C/³He and tracers of mantle heterogeneity (³He/⁴He, K/Ti etc.), implying that the variations in C/³He are not likely to be a feature of the mantle source to these basalts. Mixing between MORB-like sources and more enriched, high ³He/⁴He sources occurs on and near the ASP plateau, resulting in variable ³He/⁴He and K/Ti compositions (and many other tracers). Using ⁴He/⁴⁰Ar* to track degassing, we demonstrate that mixing systematics involving He isotopes are determined in large part by the extent of degassing. Relatively undegassed lavas (with low ⁴He/⁴⁰Ar*) are characterized by steep ³He/⁴He-K/Ti mixing curves, with high He/Ti ratios in the enriched magma (relative to He/Ti in the MORB magma). Degassed samples (high ⁴He/⁴⁰Ar*) on the other hand have roughly equal He/Ti ratios in both end-members, resulting in linear mixing trajectories involving He isotopes. Some degassing of ASP magmas must occur at depth, prior to magma mixing. As a result of degassing prior to mixing, mixing systematics of oceanic basalts that involve noble gas-lithophile pairs (e.g. ³He/⁴He vs. ⁸⁷Sr/⁸⁶Sr or ⁴⁰Ar/³⁶Ar vs. ²⁰⁶Pb/²⁰⁴Pb) are unlikely to reflect the noble gas composition of the mantle source to the basalts. Instead, the mixing curve will reflect the extent of gas loss from the magmas, which is in turn buffered by the pressure of combined crystallization-degassing and the initial CO₂ content.     

植被覆盖度遥感估算研究进展

植被覆盖度是刻画地表植被覆盖的重要参数,在全球变化研究、地表过程模拟和水文生态模型中发挥着重要作用.遥感能够反映不同空间尺度的植被覆盖信息及其变化趋势,是获取区域及全球植被覆盖度参数的一个重要手段.综合分析了用于植被覆盖度估算的遥感数据源,包括高光谱数据、多光谱数据、微波数据和激光雷达数据.而且分析了各种常用的植被覆盖度遥感估算方法及其优缺点,并评价了现有基于遥感数据的植被覆盖度产品及存在问题.最后,针对目前研究中存在的问题,讨论了植被覆盖度遥感估算研究的发展趋势,指出高时空分辨率长时间序列的全球植被覆盖度数据集、多源遥感数据融合和同化技术是未来植被覆盖度遥感估算研究的主要方向.     

赣西北狮子岭花岗岩型锂-钽矿床的矿物学特征及成矿机制

赣西北狮子岭岩体是九岭地区新发现的一个花岗岩型锂、钽矿化岩体, 前人对其矿物学特征以及锂、钽成矿机制的认识较为薄弱。本文在详细野外工作的基础上, 利用光学显微镜、电子探针(EPMA)和激光剥蚀等离子体质谱仪(LA-ICP-MS)对狮子岭岩体中云母族矿物和稀有金属矿物(铌钽锰矿、钽铌锰矿、细晶石、含铌钽锡石和磷锂铝石)的产状、结构、化学成分以及类型进行研究。结果表明: 从二云母花岗岩、锂(白)云母碱长花岗岩、黄玉锂云母碱长花岗岩到似伟晶岩, 云母的种类发生变化, 云母中K/Rb、K/Cs比值逐渐降低, Li、Rb、Cs、F含量逐渐升高, 部分云母发育成分环带; 铌钽矿物具有较高的Ta/(Ta+Nb)、Mn/(Fe+Mn)值, 发育岩浆成因的成分环带; 含铌钽锡石具有较高的Nb₂O₅+Ta₂O₅含量; 在锂(白)云母碱长花岗岩、黄玉锂云母碱长花岗岩和似伟晶岩中, 细晶石和磷锂铝石常与钠长石及锂云母等矿物共生。据此认为, 狮子岭岩体中的云母族矿物存在两种演化序列, 即铁叶云母→黑鳞云母→铁锂云母→锂云母和白云母→锂白云母(铁锂云母)→锂云母, 二者均向着富Li的方向演化, 且均为岩浆结晶分异的结果; 云母族矿物与稀有金属矿物的类型、成分以及结构特征均表明狮子岭岩体具有高度演化特征; 岩浆体系中Li、F、P等组分的富集有利于狮子岭岩体中稀有金属矿物的结晶; 狮子岭岩体Li、Ta矿化主要由岩浆的结晶分异作用所控制。

     

四川攀西裂谷带峨眉玄武岩的岩石学及其成因研究

峨眉玄武岩属典型的大陆拉斑玄武岩。该玄武岩是在特定的温度、压力、氧逸度条件及裂谷的构造背景下形成的。它同时遭受分离结晶作用和地壳的同化混染作用。且可以用Depaolo AFC模型描述之。通过计算所获得的图解表现了C_L~i/C_（o,L）~i,F和r之间的相互关系（i为不相容的微量元素）。用B_（13）层玄武岩数据计算的C_（o,L）~（La）值为6.15ppm,F为0.75,r为0.75。     

Chrome spinel in normal MORB‐type greenstones from the Paleozoic–Mesozoic Mino terrane,East Takayama area,central Japan: Crystallization course with a U‐turn

Phenocrystic chrome spinel crystallized in normal MORB‐type greenstones in the East Takayama area. Associated phenocryst minerals show a crystallization sequence that was olivine first, followed by plagioclase, and finally clinopyroxene. Chrome spinel ranges from 0.54 to 0.77 in Mg/(Mg+Fe²⁺) and 0.21 to 0.53 in Cr/(Cr+Al); the Fe³⁺ content varies from 0.07 to 0.22 p.f.u. (O = 4). Significant compositional differences of spinel were observed among the phenocryst mineral assemblages. Chrome spinel in the olivine–spinel assemblage shows a wide range in Cr/(Cr+Al), and is depleted in Fe²⁺ and Fe³⁺. Chrome spinel in the olivine–plagioclase–clinopyroxene–spinel assemblage is Fe²⁺‐ and Fe³⁺‐rich at relatively high Cr/(Cr+Al) ratios. Basalt with the olivine–plagioclase–spinel assemblage contains both aluminous spinel and Fe²⁺‐ and Fe³⁺‐rich spinel. The assumed olivine–spinel equilibrium suggests that chrome spinel in the olivine–spinel assemblage changed in composition from Cr‐ and Fe²⁺‐rich to Al‐ and Mg‐rich with the progress of fractional crystallization. Chrome spinel in the olivine–plagioclase–clinopyroxene–spinel assemblage, on the other hand, exhibits the reversed variations in Mg/(Mg+Fe²⁺) and in Cr/(Cr+Al) ratios that decrease and increase with the fractional crystallization, respectively. The entire crystallization course of chrome spinel, projected onto the Mg/(Mg+Fe²⁺)–Cr/(Cr+Al) diagram, exhibits a U‐turn, and appears to be set on a double‐lane route. The U‐turn point lies in the compositional field of chrome spinel in the olivine–plagioclase–spinel assemblage, and may be explained by plagioclase fractionation that began during the formation of the olivine–plagioclase–spinel assemblage.     

滦平球状闪长岩岩相学特征和球状构造成因探讨

文章对滦平球状闪长岩作了详细的岩相学研究,并据此提出岩体中球状构造的形成机理。根据球核的不同,可将球分为三种类型,包括以同源岩浆组分为核的球、以异源捕虏体为核的球和没有明显壳层结构的球。球中壳层一方面表现为基本不含角闪石的浅色层和含有一定角闪石的暗色层交替发育的矿物组成韵律,另一方面表现为斑状半自形一它形斜长石梳状层与细粒半自形一自形斜长石层互层的矿物结构韵律。球中斑状斜长石显示清晰的格子双晶,而主岩和基质中的斜长石则为聚片双晶。研究表明,所描述的球状构造是通过岩浆同化捕虏体和岩浆结晶综合作用形成的。球壳的矿物组成韵律和矿物结构韵律受岩浆中水含量变化的控制。     

印度洋Carlsberg洋脊玄武岩岩石地球化学特征及其地质意义

本文对采自印度洋Carlsberg脊14个站位的新鲜玄武岩样品进行了常量和微量元素组成分析,旨在研究岩浆源区地幔的性质以及岩浆作用过程。研究结果表明:该区玄武岩为典型的源于亏损型地幔的大洋中脊玄武岩,不同样品经历了不同程度的结晶分异作用,演化过程主要受控于橄榄石的结晶分异作用,部分样品中有单斜辉石结晶分异作用的影响,斜长石的结晶分异作用不显著;玄武岩岩浆来源于亏损型尖晶石二辉橄榄岩地幔的熔融,主微量元素组成中尚未见到富集型组分混入的证据;源区地幔不同比例的熔融作用及其后岩浆演化过程的差异是造成不同样品间地球化学性质差异的主要原因,彼此独立的局部岩浆作用过程是岩浆作用差异的主控制因素。Carlsberg脊玄武岩整体与全球标准大洋中脊玄武岩(N-MORB)平均组分相近,不同脊段间岩浆源区地幔的组成、熔融程度(比例)和熔融深度等无明显差异,这种特征向南直到CIR的北段。     

富锂氟含稀有矿化花岗质岩石的对比和成因思考

Li-F花岗质岩石以超酸性、过铝、富含H2O、F、B、P等挥发性组分和富含Li、Rb、Cs、Be、Ta、Nb、Sn、W等亲石稀有金属元素为主要特征，以黄玉－锂云母－钠长石花岗岩为典型代表。从该类岩石地质产状的多样性和可对比性、空间分布的规律性、矿物岩石的结构构造、硅酸盐－熔体包裹体特征以及实验岩石学的研究成果等方面，综合论证该类岩石主要是从经过分异演化而形成的残余熔浆中直接结晶而在的；充分的分离结晶作用，是产生这种残余熔浆的主要机制；岩体的空间分带特征和各带之间的渐变过渡关系，为分离结晶作用的途径和演化方向提供了重要信息；熔体中挥发性组分的大量存在，是分离结晶作用能充分进行的关键因素；亲石稀有金属元素在流／熔配分中倾向于进入熔体相，是残余熔体中逐步富集这些稀有金属元素的主要原因；岩浆－热液过渡阶段出溶的流体相与已晶出的共存固相之间的相互作用，造成了广泛的交代蚀变现象；残余熔浆在不同地质和物理化学环境中的侵位、结晶和演化，造成了Li-F花岗质岩石在产状、结构构造和矿物组合等方面的多样性。     

应用风云气象卫星及融合降水资料改进地表参数模拟

气象卫星资料不仅对天气、气候研究非常重要, 对于地表参数模拟和预报也具有重要意义。本文首次将全国自动站观测、卫星降水估计和地面观测融合降水资料(CMORPH)以及风云二号D星(FY-2D)积雪覆盖率数据应用到了高分辨率陆面资料同化系统(u-HRLDAS)。融合降水资料用于驱动u-HRLDAS, 同时用于计算雪水当量;积雪覆盖率资料作为u-HRLDAS强迫变量。区域模拟结果表明, 积雪覆盖率对于地表反照率、地表温度以及地气交换通量模拟有极其重要的影响。密云站土壤湿度模拟结果表明, 融合降水资料准确度优于全球陆面资料同化系统(GLDAS)再分析资料。小汤山站单点验证结果表明, 应用融合降水资料及卫星积雪覆盖率资料可以改进地表温度及地气交换通量的模拟。