西藏扎布耶盐湖卤水演化的Pitzer模型模拟

扎布耶盐湖是西藏高原代表性的富锂硼碳酸盐型盐湖。本文利用Pitzer模型模拟计算了西藏扎布耶盐湖冬季与夏季卤水、补给河流-泉水的低温(2℃)、常温(25℃)和高温(50℃)蒸发结晶过程,结果表明,扎布耶盐湖卤水可以由现代成分的河流-泉水蒸发浓缩形成,扎布耶盐湖的沉积组合与河泉水蒸发浓缩的矿物结晶规律吻合;而冬、夏卤水蒸发模拟结果与卤水蒸发实验结果基本吻合,但对矿物结晶顺序、矿物组合规律以及温度-季节性成分变化的影响等方面,提供了更多更详细的数据与认识。说明Pitzer模型对研究西藏富锂硼碳酸盐型盐湖的地球化学成因和盐田工艺都具有重要参考价值。     

Multiple Isotopic Components in Quaternary Volcanic Rocks of the Cascade Arc near Crater Lake, Oregon

Quaternary lavas and pyroclastic rocks of Mount Mazama, CraterLake caldera, and the surrounding area have variable Sr, Nd,and Pb isotopic compositions. High-alumina olivine tholeiites(HAOT) have ⁸⁷Sr/⁸⁶Sr ratios of 0.70346–0.70364; basalticandesite, 0–70349–0.70372; shoshonitic basalticandesite, 0.70374–0.70388; and andesite, 0.70324–0.70383.Dacites of Mount Mazama have ⁸⁷Sr/⁸⁶Sr ratios of 0.70348–0.70373.Most rhyodacites converge on 0.7037. However, rhyodacite ofthe caldera-forming, climactic eruption has ⁸⁷Sr/⁸⁶Sr=0.70354because of an admixed low-⁸⁷Sr/⁸⁶Sr component. Andesitic tomafic-cumulate scoriae of the climactic eruption, and enclavesin preclimactic rhyodacites, cluster in two groups but shownearly the entire ⁸⁷Sr/⁸⁶Sr range of the data set, confirmingpreviously suggested introduction of diverse parental magmasinto the growing climactic chamber. Pb and Nd isotope ratiosdisplay less variation (²⁰⁶Pb/²⁰⁴Pb= 18.838–18.967, ²⁰⁷Pb/²⁰⁴Pb=15.556–15.616,²⁰⁸Pb/²⁰⁴Pb=38.405–38.619; _Nd= +3.9 to +6.1) and generallycovary with ⁸⁷Sr/⁸⁶ Sr ratios. Radiogenic isotope data fromCrater Lake plot with published data for other Cascade volcanoeson isotope ratio correlation diagrams. The isotopic data for the Crater Lake area require sources ofprimitive magmas to consist of depleted mantle and a subductioncomponent, introduced in variable quantity to the depleted mantlewedge. Variable degrees of melting of this heterogeneous mantle,possibly at different depths, produced the diversity of isotopiccompositions and large-ion lithophile element (LILE) abundancesin primitive magmas. Trace element ratios do not indicate presenceof an ocean island basalt (OIB) source component that has beenreported in lavas of some other Cascade volcanoes. Crustal contamination may have affected isotope ratios and LILEconcentrations in evolved HAOT, where initial LILE concentrationswere low. Contamination is more difficult to detect in the calcalkalinelavas because of their higher LILE concentrations and the smallisotopic contrast with likely contaminants, such as mid- tolower-crustal rocks thought to be equivalents of igneous rocksof the Klamath Mountains and associated lower crust. Crustalassimilation appears to be required for calcalkaline rocks onlyby ¹⁸O values, which vary from lows of +5.6 to + 6.0% in HAOTand primitive basaltic andesites to a high of +7.0% in dacite,a range that is too high to be explained by plagioclase-dominatedclosed-system fractional crystallization. Elevated ¹⁸O valuesof differentiated lavas may be attributed to interaction withrelatively ¹⁸O-rich, ⁸⁷Sr-poor crustal rocks. Variably fused granitoid blocks ejected in the climactic eruption,and rarely in late Pleistocene eruptive units, have ¹⁸Opl of–3.4 to +6.5% and ¹⁸O_qz of –2.2 to +8.0% but haveSr, Nd, and Pb isotope ratios similar to volcanic rocks (e.g.⁸⁷Sr/⁸⁶Sr0.7037). Rb and Sr data for glass separates from granodioritessuggest that the source pluton is Miocene. Glass from granodioritehas ⁸⁷Sr/⁸⁶Sr ratios as high as 0.70617. Oxygen isotope fractionationbetween quartz, plagioclase, and glass indicates requilibrationof O isotopes at magmatic temperatures, after ¹⁸O/¹⁶O had beenlowered by exchange with meteoric hydrothermal fluids. Unmeltedgranodiorite xenoliths from pre-climactic eruptive units have¹⁸O values that are consistent with onset of hydrothermal exchangeearly during growth of the climactic magma chamber. Assimilationof such upper-crustal granodiorite apparently lowered ¹⁸O valuesof rhyodacites without significantly affecting their magmaticcompositions in other ways.     

青海湖沉积物中的甾醇及其演化

Ｃ_２７，Ｃ_２８和Ｃ_２９甾醇（△５.２２，△２２，△５和△５.２４（２８）和５α－甾烷醇）在青海湖三孔近代沉积物（ＱＨ，ＱＥ和ＱＯ）中被检出。其中以Ｃ_２９甾醇占优势。在ＱＥ和ＱＧ孔沉积物中还检出了低浓度的三个Ｃ_３０甾醇（４α，２３，２４－三甲基－５α－胆甾－２２Ｅ－烯醇（甲藻甾醇），４α－甲基－２４－乙基－５α－胆甾－２２Ｅ－烯醇和４α－甲基－２４－乙基－５α－胆甾烷醇］。在ＱＨ和ＱＧ孔上部层段沉积物中，Ｃ_２７，Ｃ_２９.饱和的和不饱和的甾醇的碳数分布的平行性，甾烷醇/△５－甾醇及△２２－/△５.２２－甾醇的比值随沉积物埋深而增加提供了甾酸氢化作用的间接证据。青海湖沉积物中的甾醇主要来自湖区丰富的高等植物和湖中的藻类等。在ＱＧ孔８０～１００ｃｍ和１２０～１４０ｃｍ层段沉积物中，５ａ－胆甾烷醇浓度迅速增加可能反映特殊的生物（介形类）对该二层段沉积物中高浓度的胆甾烷醇的贡献。     

The Chemical Nature of Phosphorus in Subtropical Lake Sediments

The phosphorus (P) composition of sediment profiles in three subtropical lakes of contrasting trophic state in Florida, USA, was determined by sequential fractionation and solution ³¹P NMR spectroscopy. Sediment from Lake Annie, an oligo-mesotrophic sinkhole with moderately acidic sediment (pH 5.4; loss on ignition 58 %), contained higher total P concentrations than sediment from eutrophic Lake Okeechobee (pH 7.7, loss on ignition 36 %) and hyper-eutrophic Lake Apopka (pH 7.5, loss on ignition 69 %). The chemical nature of sediment P varied markedly among the three lakes, suggesting the predominance of different diagenetic processes. Lake Okeechobee sediment was dominated by inorganic P, indicating the dominance of abiotic reactions; Lake Annie sediment contained abundant organic P throughout the sediment profile, indicating the importance of organic P stabilization at acidic pH; Lake Apopka contained almost half of its sediment P in microbial biomass, indicating the importance of biotic processes in regulating P dynamics. Solution ³¹P NMR spectroscopy of NaOH–EDTA extracts revealed that organic P occurred mainly as phosphomonoesters in all lakes. However, sediment from Lake Apopka also contained abundant phosphodiesters and was the only lake to contain detectable concentrations of polyphosphate, perhaps due to a combination of alternating redox conditions and high concentrations of inorganic phosphate and organic carbon. Organic P concentrations determined by sequential fractionation and solution ³¹P NMR spectroscopy were similar for all lakes when microbial P was included in values for sequential fractionation. We conclude that the chemical nature of sediment P varies markedly depending on trophic state and can provide important information on the dominant processes controlling P cycling in subtropical lakes.     

Mineralogy and Geochemistry of Major,Trace and Rare Earth Elements in Sediments of the Hypersaline Urmia Salt Lake,Iran

Urmia Salt Lake(USL) is a hypersaline lake located at the NW corner of the Iran platform. The lake area is estimated to have been over 5000 km~2 at one point, but has now decreased to 1000 km~2 in the last two decades. It contains 4.6×10~9 tons of halite and other detrital and evaporative minerals such as calcite, aragonite, dolomite, quartz, feldspars, augite and sylvite. This study examined the mineralogy and geochemistry of bed sediments along the mid-east toward NE bank sediments collected from 1.5 meters depth and nearby augite placer. Due to the diverse lithology of the surrounding geology, bed sediments vary from felsic in the mid-east to mafic in the northeast. Weathering of tephrite and adakite rocks of the Islamic Island at the immediate boundary has produced a large volume of augite placer over a 40 km length, parallel to the shoreline. Based on the study result, weathering increases from south to north and the geochemistry of the sediments shows enrichment of Mg O, Ca O, Sr and Ba associated with Sr deployment in all samples. Rare earth elements(REE) patterns normalized to the upper continental crust(UCC) indicated LREEs enrichment compared to HREEs with an elevated anomaly of Eu, possibly due to surface absorbance of Mn and Fe minerals, associated with Sr elevation originating from adakites in the lake basin vicinity.     

Fractal Analysis of the Gray-Scale Intensity Data of Finely Laminated Sediments from Bainbridge Crater Lake, Galápagos

The gray-scale intensity data of finely laminated sediments from Bainbridge Crater Lake, Galápagos, were analyzed in terms of Hurst exponent and fractal dimension. The sediment record preserved in this volcanic maar provides a continuous history of past El Niño/Southern Oscillation (ENSO) events over the last 6200 years. Accelerator mass spectrometry radiocarbon data show that sedimentation rate was not constant for whole core. To take into consideration this fact gray-scale intensity data from analyses of X-radiography images of a 4.1 m long core from this basin were divided into Data 1 and Data 2. Data 1 corresponds to the more recent part of stratigraphic sequence, which was deposited since 3000 yr BP; Data 2 is from the earlier part of record between 6200 and 3000 yr BP. A persistent behavior with a Hurst exponent of H = 0.88 and H = 0.8 was found by power spectrum analysis method for Data 1 and Data 2, respectively. The width method of analysis shows that ENSO fluctuation before 3000 yr BP had a persistent behavior on a time-scale up to 26 years, while the more recent El Niño occurrences have a persistent behavior on a time-scale up to 5.6 years.     

Mineralogy and Petrology of Erta Ale and Boina Volcanic Series, Afar Rift, Ethiopia

Erta Ale and Boina are two volcanic areas in northern Afar riftwhere a complete suite of products from mildly alkalic transitionalbasalts to peralkaline rhyolites have been erupted in very recentQuaternary time. Subaphyric lava samples of both localities,representing the entire sequence of erupted magmas, have beenselected for a mineralogical study and all the main mineralphases analysed with the microprobe. Results confirm that ErtaAle and Boina rocks can be explained as suites of liquids producedby fractional crystallization of transitional basalts at shallowcrustal levels. The crystallization history is reconstructedand temperature and oxygen fugacity are evaluated. The differentiationprocesses are quantitatively reconstructed using the compositionsof analysed microphenocrysts to compute the fraction of thesolids separating at each step of fractionation. Slight butclear chemical differences in the parent basalt are reflectedin the two series particularly in the late stages of fractionation.The slightly more alkalic Boina series was produced under fO²controlled by QFM buffer; olivine was stable all along the crystallizationinterval and clinopyroxenes have compositions intermediate betweenthose considered typical of respectively tholeiitic and alkalicsuites. The main differences between the two series are a shiftin the appearance of oxides towards more evolved liquids, crystallizationat Erta Ale of more calcic plagioclase and more magnesian olivineand clinopyroxene than those observed at Boina from liquidswith the same Ca/(Na + Ca) and Mg/(Fe + Mg) and the lack ofalkali feldspar in Erta Ale rhyolites. Together with the lowerCa content of Erta Ale clinopyroxenes, they are the expressionof the more tholeiitic affinity of Erta Ale rocks. Departuresfrom the typical mineralogy of the series are observed for someErta Ale basalt and rhyolite and variously explained as an expressionof a slight difference in the primary nature of the magma, asa liquid-xenocrysts mixing and as fO₂ changes in an open system. Present address: Bureau de Reacherches Géologiques et Minières, Département Géothermie, Orléans, France.     

Aluminium in Lake Cuicocha,Ecuador, an Andean Crater Lake: Filterable,Gelatinous and Microcrystal Al Occurrence

In Lake Cuicocha watershed, a young caldera lake, soils consist of volcanic deposits with a high SiO₂ and Al₂O₃ content; these andisols are in an early stage of development; and in drainage water from the watershed, aluminium concentrations reach 15.0 μmol L⁻¹. Total aluminium concentrations in Lake Cuicocha water raises up to 7.2 μmol L⁻¹, with nearly 70% occurring as filterable Al at neutral to weak alkaline conditions. Al polymerization to gelatinous aggregates of a few hundred micrometres in diameter as well as the occurrence of Al microcrystals like gibbsite as an ageing product of gelatinous Al polymers was noted in the lake water. The gelatinous Al leads to the formation of larger aggregates resulting in flocs of bacteria, algae, microorganisms and detritus.     

苏州西山震裂锥:太湖冲击坑又一新证据

震裂锥已被公认为陨石冲击地球表面遗留的标志。研究及统计资料表明,震裂锥与陨石冲击形成的中、大型冲击坑 有关。太湖西山震裂锥呈圆锥形,锥体表面有自锥顶向下辐射的锥纹,锥纹具有分叉的特征,这些特征与震裂锥的国际公 认的定义和标准相符。此外,西山震裂锥还具有其特有的其他特征：碎裂岩化显著;气化-熔融现象发育;锥体表面具网 状构造及波纹状、蜂窝状等多种气印。岩相学研究显示,震裂锥及含锥岩石中冲击变质现象明显,微页理（PDFs）、微裂 隙（PFs） 以及靶岩熔融现象发育。以上这些冲击变质的标志,可证明西山震裂锥是冲击成因,而非地表水风化淋溶石灰岩 的喀斯特或风蚀成因的凤稜石。西山震裂锥的发现、太湖湖底冲击击变角砾岩“太湖石”的确定,为太湖冲击坑的研究增 添了新的诊断性证据;加上早期研究确定的、冲击回落至太湖湖底淤泥层中的冲击溅射物,这些众多证据为确定“太湖冲 击坑”或“太湖冲击事件”展示了美好前景。但是,要确定太湖冲击坑的具体位置、大小及构造模式等,尚需更多的深入 研究。     

The Origins of Glass and Amphibole in Spined--Wehrlite Xenoliths from Foster Crater, McMurdo Volcanic Group, Antarctica

Vesicular interstitial glass in four kaersutite-bearing spinel–wehrlitexenoliths from Foster Crater, Antarctica has reacted with hostolivine (Fo_75–79) and clinopyroxene (Ca₄₇ Mg₄₅ Fe₈) andcontains a microphenocryst assemblage of spinel, olivine, andclinopyroxene together with later rhonite and plagioclase. Electronmicroprobe analyses of the glasses have low SiO₂ (46–49wt. per cent) and MgO (2.2–3.7) contents and high contentsof alkalis, TiO₂ (3.4–4.8), Al₂O₃ (18.1–20.6) andP₂O₅ (1.1–1.3). Olivine microphenocryst cores in glassare magnesian (up to Fo₈₈) and must have precipitated from moreprimitive liquids; rim compositions are Fe-rich (Fo₇₅) and inequilibrium with glass. Continuous core to rim zonation in theolivine microphenocrysts indicate that glass compositions havefractionated due to crystallization of the enclosed mineralassemblage. Mass balance addition calculations, using the compositionsand proportions of the crystals in glass, produce melt compositionsappropriate to primary alkali basaltic magmas. Glasses showlight rare earth element (REE) enrichment relative to chondrites(Ce/YbN = 10.5) and, together with Ba, Rb, Cr, Hf, Ta, and Thare similar to many of the basanites from the Erebus VolcanicProvince. Textural relationships of the kaersutite are complex owing tothe instability of kaersutite in the presence of melt. However,in the association with glass we observe textural evidence suchas olivine and clinopyroxene microphenocrysts, identical tothe liquidus phases of the glasses, enclosed by kaersutite crystals.We believe that relationships such as this link the crystallizationof kaersutite to mafic melt which infiltrated and reacted withthe host wehrlite. Thus, the melt did not form in situ withinthe xenolith but originated elsewhere in the upper mantle.     

Origin of Phenocrysts and Compositional Diversity in Pre-Mazama Rhyodacite Lavas, Crater Lake, Oregon

Phenocrysts in porphyritic volcanic rocks may originate in avariety of ways in addition to nucleation and growth in thematrix in which they are found. Porphyritic rhyodacite lavasthat underlie the eastern half of Mount Mazama, the High Cascadeandesite/dacite volcano that contains Crater Lake caldera, containevidence that bears on the general problem of phenocryst origin.Phenocrysts in these lavas apparently formed by crystallizationnear the margins of a magma chamber and were admixed into convectingmagma before eruption. About 20 km³ of pre-Mazama rhyodacite magma erupted during arelatively short period between400 and 500 ka; exposed pre-Mazamadacites are older and less voluminous. The rhyodacites formedas many as 40 lava domes and flows that can be assigned to threeeruptive groups on the basis of composition and phenocryst content.Phenocryst abundance decreases (from 32 to 8 vol.%) and SiO₂content increases (from 68 to 73 wt.%) in the apparent orderof eruption. Phenocrysts (plagioclase, orthopyroxene, augite,and Fe-Ti oxides) are commonly fragmental or form polycrystallineaggregates with interstitial glass. Discrete phenocrysts withcomplete euhedral outlines are rare except for small elongatedcrystals. The abundance of discrete phenocrysts increases withthat of aggregates. The grain-size of minerals in the aggregatescovers the range of discrete phenocrysts (0.2–4.2 mm).Rim compositions of phenocrysts and the range of chemical zoningare almost uniform among the three rhyodacite groups, regardlessof whether crystals are discrete or in aggregates. However,a small fraction of phenocrysts, especially small elongatedcrystals, have different compositions: plagioclase with Fe-richcores and augite with Wo-poor cores, both of which are characteristicof crystals in undercooled andesite enclaves in the rhyodacites.The majority of phenocrysts were derived by disintegration ofpolycrystalline aggregates; rare, small phenocrysts crystallizedin andesitic magma similar to that represented by the andesiteenclaves. The modal and chemical compositions of the rhyodacites can beexplained by different degrees of admixing of crystals, representedby the aggregates, into magma having 4 vol.% ‘true’phenocrysts, mainly plagioclase. The aggregates may be partsof the rind formed by in situ crystallization near the walland roof of the magma chamber. The rind was disrupted duringor just before eruption, and pieces were variably disaggregatedand incorporated into erupting magma. The amount of rind incorporateddeclined during the sequence of eruptions. Owing to vesiculationof interstitial liquid and shearing during flow, crystals inthe aggregates were separated and became phenocrysts. Pre-Mazamarhyodacite was erupted dominantly as lava, as opposed to thecompositionally similar rhyodacite pumice of the Holocene caldera-formingeruption of Mount Mazama, apparently because its source chamberwas crystallizing inward rather than actively growing.     

环境温度对盐湖卤水化学组成及储卤层渗透性变化的制约

柴达木盆地昆特依盐湖浅部储卤层是一个多场耦合的动态平衡系统,受到水动力、气候、化学等多种因素控制。本文对昆特依盐湖浅部储卤层不同季节(夏季和冬季)卤水组成和储卤层渗透性特征进行了分析研究。结果表明:卤水中的主要离子含量从夏季到冬季发生了明显的变化,其中,K、Mg、Ca、Cl的含量都相应增加,增加幅度为:Cl、Mg、K、Ca;而SO_4~(2-)和Na的含量却均有下降,且SO_4~(2-)下降更显著;抽水试验计算结果发现,从夏季到冬季,钻孔ZK08渗透系数K由178m/d降至97m/d。本文研究表明,随着环境温度的降低,芒硝(Na_2SO_4)从卤水中结晶析出,是以上现象发生的主要原因,随着芒硝的析出,促进了含K、Mg、Ca等硫酸盐矿物(杂卤石)的溶解,使得卤水中K、Mg、Ca浓度增加;另一方面,析出的芒硝一定程度上堵塞了储卤层的孔隙,卤水的粘度也因温度降低而增加,这两个因素共同作用降低了储卤层渗透性。     

长白山火山活动历史、岩浆演化与喷发机制探讨

广义的长白山火山在我国境内包括著名的天池火山、望天鹅火山、图们江火山和龙岗火山,是我国最大的第四纪火山岩分布区。图们江火山和望天鹅火山活动都始于上新世,喷发活动分别介于上新世—中更新世（5.5~0.19 Ma）和上新世—早更新世（4.77 ~2.12 Ma）。天池火山和龙岗火山属于第四纪火山,喷发活动从早更新世（~2 Ma）持续到全新世。图们江火山岩为溢流式喷发的拉斑玄武岩,望天鹅火山、天池火山和龙岗火山母岩浆都是钾质粗面玄武岩,但经历了不同的演化过程。天池火山和望天鹅火山都经历了钾质粗面玄武岩造盾、粗面岩造锥和晚期碱性酸性岩浆（碱流岩和碱性流纹岩）的喷发;龙岗火山来自地幔的钾质粗面玄武岩浆则未经演化和混染直接喷出地表。图们江火山岩以溢流式喷发的拉斑玄武岩为主,少量玄武质粗安岩等。天池火山造盾之后,地壳岩浆房和地幔岩浆房具互动式喷发特点,来自地幔的钾质粗面玄武岩浆一方面在天池火山锥体内外形成诸多小火山渣锥,另一方面持续补给地壳岩浆房发生岩浆分离结晶作用和混合作用,分别导致双峰式火山岩分布特征和触发千年大喷发。火山岩微量元素和Sr-Nd-Pb同位素示踪揭示,长白山东（图们江火山、望天鹅火山和天池火山）、西（龙岗火山）两区显示地幔非均一性,东区岩浆源区具有软流圈地幔与富集岩石圈地幔混合特征,西区岩浆源区具有相对亏损的较原始地幔特征。西太平洋板块俯冲—东北亚大陆弧后引张是长白山火山活动的动力学机制。     

Characterizing Major Controls on Spatial and Seasonal Variations in Chemical Composition of Surface and Pore Brine of Maharlu Lake,Southern Iran

Maharlu Lake with Na–Cl water type is the terminal point of a closed basin in southern Iran. A total of 10 water samples from two rivers discharging to the lake and 78 water samples of surface and pore brine of Maharlu Lake have been collected from different depths (surface, 20, 50 and 100 cm) of four sampling stations along the lake during a period of lake water-level fluctuation (November 2014–July 2015). To investigate chemical interaction between lake surface water and shallow pore water and to understand the major factors governing chemical composition of Maharlu brine, concentrations of major and minor (boron, bromide and lithium) solutes, pH and total dissolved solids have been measured in collected water samples. Saturation indices of evaporite minerals in collected water samples have been also calculated. The chemical behavior of dissolved solutes and evaporative evolution of the lake brine during a hydrological period have been simulated using PHREEQC. The results of our investigations indicated that chemical composition of lake surface water and pore brine of Maharlu Lake are mainly connected with lake water-level fluctuations and distance from input rivers (and depth), respectively. Hydrochemical investigations and statistical analysis showed that the brines chemistry of Maharlu is mainly controlled by three processes: brine evaporative evolution, dissolution–precipitation and diagenetic evolution of secondary carbonates.     

洪湖特色水产品对湖水及沉积物中有机氯农药的积累模式

对洪湖水体、表层沉积物和特色水产品(鲫鱼、莲藕等)进行了调查采样,采用美国EPA方法进行了有机氯农药的提取,用带有电子捕获器的气相色谱(GC-ECD)进行了有机氯农药含量的测定.结果表明:六六六和滴滴涕各异构体在湖水、表层沉积物、特色水产品中绝大部分都有检出,湖水中六六六和滴滴涕的质量浓度远低于其在表层沉积物和特色水产品中的质量分数,这与有机氯农药疏水亲颗粒和溶脂性的特性有关.以分配系数、生物积累因子和生物区系-底泥生物积累因子为基础,建立了洪湖特色水产品对水体及表层沉积物中有机氯农药的积累模式,所得结果能够为洪湖湿地保护与生态恢复措施的决策与制定提供科学依据.     

Geochemical Characteristics of Amino Acids in Sediments of Lake Taihu, A Large, Shallow, Eutrophic Freshwater Lake of China

To examine the biogeochemistry of amino acids (AAs) in the sediment of Lake Taihu, surface sediments (0–3 cm) and deeper sediments (18–21 cm) were collected at 21 sites from different ecotype zones of the lake. AAs were extracted from the sediments, and the total hydrolyzable amino acids (THAA) were determined by high-performance liquid chromatography instrument. The THAA contents in Taihu sediment were much lower than that in marine sediments, ranging from 6.84 to 38.24 μmol g⁻¹ in surface sediments and from 2.91 to 18.75 μmol g⁻¹ in deeper sediments in Taihu, respectively. AAs were a major fraction of the organic matter (OM) and organic nitrogen in Taihu sediments. The AAs on average contributed 8.2% of organic carbon (OC) and 25.0% of total nitrogen (TN) from surface sediments, and 5.9% of OC and 20.5% of TN in deeper sediments, respectively. AA composition provided very useful information about the degradation of OM. Glycine (Gly) and lysine (Lys) were the predominant forms of AAs in the sediments, irrespective of lake regions, followed by alanine, glutamic acid, serine (Ser), and aspartic acid (Asp). The high concentrations of Gly, Lys, and Ser suggested that these forms of AAs were relatively refractory during OM degradation in sediments. The relationship between the Asp/Gly ratio and Ser + Thr [mol%] indicated that OM in surface sediment was relatively fresher than that in deeper sediments. The AAs-based degradation index (DI) gave a similar conclusion. The composition and DI of AAs in surface sediments are markedly different across different zones in Taihu. The percentages of AAs to organic carbon (AA-C%) and total nitrogen (AA-N%) were higher in phytoplankton-dominated zones than those in macrophyte-dominated zones. These results suggest that DI could provide useful information about the degradation of OM in shallow lakes such as Taihu.     

火山喷爆与太湖成因

以详尽野外地质成果与实物证据首次发现湖内最新的地质事件——火山喷爆活动, 并划定该事件的时代、地点, 重新认识太湖地区、特别是自中生代以来的地质演变史、演变方式, 勾划出太湖湖盆形成的前提条件、内在因果原因.其后采用了本地区第四系变化、考古成果、古脊椎动物化石记录与古籍记载等丰富资料证明该区实际存在的沉降现象.沉降速率、成湖过程与成湖时代.最后以详实资料阐述了太湖及其周边未来演变规律以供地方规划与发展经济所利用.      

Mineralogy, Textures and P-T Relationships of a Suite of Xenoliths from the Monaro Volcanic Province, New South Wales, Australia

Intraplate basalts of the Eocene–Oligocene Monaro VolcanicProvince (MVP), in southeastern New South Wales, include lower-crustaland refractory to weakly metasomatized upper-mantle xenoliths.Lower-crustal-derived xenoliths appear to be all two-pyroxeneplagioclase granulites (Cpx_{Fe:Mg:Ca 0·17–0·56:0·63–0·77:0·28–0·89}Opx_{Fe:Mg:Ca 0·39–0·52:1·37–1·47:0·02}An_72–86 and An_48–50) but may also include garnetpyroxenites at depth. Mantle-derived xenoliths are principallyspinel-bearing lherzolites (Fo_{89·8–90·6}Cpx_{Fe:Mg:Ca 0·07–0·45:0·70–1·70:0·01–0·94}Opx_{Fe:Mg:Ca 0·16–0·19:1·62–1·75:0·01–0·10})but also include amphibole ± spinel-bearing lherzolite(Fo_{88·7–89·1} Cpx_{Fe:Mg:Ca 0·09–0·21:0·61–0·91:0·73–0·93}Opx_{Fe:Mg:Ca 0·09–0·31:0·70–1·54:0·03–0·91}),spinel-bearing harzburgite (Fo_{90·5–90·7}Cpx_{Fe:Mg:Ca 0·08:0·91–0·93:0·74–0·84}Opx_{Fe:Mg:Ca 0·16–0·18:1·73–1·79:0·00–0·02}),wehrlite, pyroxenite (Cpx_{Fe:Mg:Ca 0·08–0·10:0·84–0·90:0·80–0·85}Opx_{Fe:Mg:Ca 0·16–0·33:1·51–1·73:0·02–0·03})and rare garnet pyroxenite (Gt_{Fe:Mg:Ca 0·83–0·95:1·60–1·70:0·45–0·48}Cpx_{Fe:Mg:Ca 0·14–0·21:0·69–0·77:0·78–0·86}Opx _{Fe:Mg:Ca 0·31–0·42:1·43–1·56:0·02–0·03})and amphibole–apatite composites. Xenolith textures aregenerally weakly to moderately foliated, a few are mosaic-porphyroblasticand rare samples are veined or highly strained. MVP xenolithsappear to have equilibrated under similar pressure–temperature(P–T) conditions to other southeastern Australian xenolithsequivalent to the South Eastern Australia (SEA) palaeogeotherm.P–T estimates for the MVP suite of xenoliths reveal aheterogeneous lower crust and upper mantle that is thickly underplatedto c. 1·8 GPa or c. 50 km depth. MVP xenolith P–Tdata are compared with those used to derive the SEA palaeogeotherm,which is shown to be in need of revision using more modern geothermometersand geobarometers and new xenolith coexisting mineral data. KEY WORDS: xenolith; petrography; texture; geotherm; Monaro; eastern Australia     

Natural Evaporation of Dangxiongcuo Salt Lake Spring Brine in Tibet,China

正1 Introduction Dangxiongcuo salt lake(Figure 1),which is located in the southwest of Tibet,China,is rich in valuable mineral elements like lithium,potassium,boron,rubidium,caesium