从微量元素丰度研究铁质、硅质及玻璃质小球

由于宇宙尘的研究能为太阳系和银河系的起源和演化提供有意义的信息,近年来受到宇宙化学家和天文地质学家越来越多的重视,成了科学界一个很活跃的领域。在铁质、硅质和玻璃质小球中难熔亲铁元素Ir、Os等及亲铁元素Ni、Co、(Cr)及微量元素Sc的测定,在硅质和玻璃质小球中稀士元素的测定对于球粒来源的判别是非常重要的依据。然而由于宇宙尘样品很少,一般的化学分析方法很难给出可靠的数据,本工作是采用灵敏度高,取样量少,且具多元素分析能力的中子活化分析测定了上逑各种小球中难熔亲铁元素和其它微量元素的含量。实验结果表明宇宙尘中难熔亲铁元素、亲铁元素的含量高于地壳样品。从硅质和玻璃质两种球粒以及几种地壳样品与碳质球粒陨石型稀士和Sc的归一化模式图可以看出:地壳样品由于经历了化学分馏,稀士模式成斜线型,而硅质和玻璃质宇宙尘的归一化稀士模式成较平坦的未分馏型。事实表明中子活化分析是研究宇宙尘的较可取的方法。     

原子光谱测定中表面活性剂对铅锌矿粉末悬浮液雾化效率的影响

滇黔地区的"白泥塘层"与锰矿具有密切的成因联系,前人对其地球化学特征研究时关注的主要是硅质灰岩全岩,并非硅质成分本身,而硅质岩全岩能否真实地反映"白泥塘层"中硅质的来源有待研究。本文以滇黔地区"白泥塘层"硅质灰岩为研究对象,用盐酸去除硅质灰岩中的碳酸盐矿物,获得成分较为单一的硅质组分,采用ICP-MS和ICP-OES测定全岩与去除碳酸盐的硅质组分中的微量元素,通过对比两者的微量元素地球化学特征研究"白泥塘层"中硅质的来源问题。结果表明:去除碳酸盐的硅质组分的Th/U=0.02~0.05,低于全岩的Th/U值(0.08~0.2),Eu/Eu^*=0.86~1.54(均值1.15),显示为正Eu异常,此特征不同于全岩(全岩的Eu/Eu^*=0.87~0.93,均值0.90,显示为弱的负Eu异常);硅质组分及全岩的稀土含量均表现为轻稀土较重稀土富集,但硅质组分中的轻稀土所占比重大于全岩。以上特征确切地表明了"白泥塘层"硅质灰岩中的硅质成分来自于热水,对于解释二叠系时期锰矿的形成具有重要的指示意义。     

浙江北部的孤峰组

浙北孤峰组,原系栖霞组中的纯灰岩段与龙潭组中A煤段之间的一套含有硅质层或硅质结核的硅质灰岩、硅质泥岩夹薄层灰岩之浅海相沉积。      

熔体包裹体研究的一些问题——以加拿大Durparquet地区的玄武岩和斑岩中的熔体包裹体为例

<正>Durparquet地区位于加拿大Abitibi太古宙地质省中,产有玄武岩,英云闪长岩和斑岩。对这三种岩石中的熔体包裹体和流体包裹体进行研究表明,在斑岩中主要见到结晶质熔体包裹体,玻璃质熔体包裹体和少量熔体-流体包裹体。在玻璃质熔体包裹体和结晶质熔体包裹体中常见去玻化存在,这种包裹体常呈黑色,同时见有流体     

月尘的性质及危害评述

月尘是广泛分布于月球表面的微小颗粒,大小约在30 nm~20 μm之间,95%以上小于2 μm,中值粒径约为100~300 nm,形态复杂多变,以玻璃小球、气泡构造、棱角状碎片为主,含有大量纳米颗粒金属铁和玻璃质,玻璃质含量超过50%,尤其是＜2 μm的部分中,玻璃质含量高达80%~90%,化学成分与月壤基本类似,在不同地貌单元也体现出SiO₂含量的差异.月尘的成分和颗粒特征使其具有独特的电磁性质和生物毒性,容易粘附于航天器表面和进入航天员体内,危害航天器和航天员的安全和健康,严重影响月面探测的正常实施.因此,对月尘的研究是保证月面探测工程正常实施的迫切需要;同时,月尘是月球表面物质经历长期的太空作用形成的,在颗粒成分和结构特征上保留了其演化过程的重要信息,是研究月表物质和大气演化、太空风化作用等科学问题的关键线索.但是目前对月尘的颗粒微观成分和结构差异、电磁特性和光学特性,纳米金属铁的特征和成因等方面的研究还不够深入,限制了月表物质演化历史的研究和月尘粘结腐蚀性、生物毒理学具体机理的认识.在月尘研究中利用模拟月尘弥补月尘样品稀缺的局限,并通过模拟实验加强以上方面的研究,能够更好地满足科学问题和工程探测的实际需要.      

四川盆地碳酸盐岩中硅质特征及其对储层的影响

四川盆地碳酸盐岩储层为我国主要海相储层之一。通过分析四川盆地碳酸盐岩中硅质的宏观、微观特征,提出硅质以互层、混积、充填、交代的形式存在于碳酸盐岩中。互层硅质、充填硅质和交代硅质中二氧化硅来源以火山喷发为主,但后期沉积机制不同;混积硅质中二氧化硅来源于陆源碎屑,对物源方向具有一定的指向意义,沉积机制为陆源混积。互层硅质、充填硅质、交代硅质对储层形成具有双重意义,混积硅质对储层形成起严重破坏性作用。     

磷块岩中的硅质组分和硅质岩

磷块岩中存在着大量硅质组分和硅质层。硅质矿物以自生石英、硅质条带、燧石结核、硅质胶结物和硅质交代物的形式产出。硅质胶结物有四种结构形式,在剖面和平面上与其它成分胶结物有一定的演变关系。硅化作用有众多的宏观和微观形态,硅化结果使P_2O_5含量大大下降。盆地型磷块岩硅化作用的硅源可能来自海底火山活动,台地型磷块岩硅化作用的硅源主要与陆源水的混合有关。     

四川盆地下古生界硅质页岩层系中硅质来源及其对有机质保存的影响初探

四川盆地下古生界两套硅质页岩层系(寒武系底部页岩和奥陶系—志留系五峰组—龙马溪组页岩)是其重要的页岩气产层,五峰组—龙马溪组硅质含量与TOC及含气量呈正相关性,暗示硅质矿物对该地区页岩气的生成具有重要意义。但硅质来源复杂,且存在后期硅质流体的注入。因此,本文在总结前人的研究成果基础上,对四川盆地寒武系底部硅质岩系和五峰组—龙马溪组硅质岩系的硅质特征进行了详细的岩石学分析,揭示了3种硅质来源特征:(1)同沉积无机硅质流体;(2)生物硅;(3)后期无机硅质流体。其中寒武系底部以同沉积无机硅质流体和生物硅来源为主,同沉积硅质流体导致有机质快速石化埋藏,有机质内部结构及形态保存较好;五峰组—龙马溪组硅质来源以后期无机硅质流体和生物硅来源为主,有机质在保存过程中受硅质流体的影响很小,有机质腐泥化作用充分,内部结构和形态多数保存较差。该研究初步揭示了两套页岩层系的硅质发育岩石学特征,及其对有机质保存的影响,期望能为四川盆地两套页岩气储层差异性提供新的思路和基础地质数据。     

高压溶出硅质结疤物的形态结构研究

利用工艺矿物学研究手段,对氧化铝生产高压溶出过程硅质结疤物的形貌结构进行深入研究,从而为预防和治理硅结疤提供了理论依据。研究结果表明:单套管预热器中硅质结疤物为钠硅质渣,呈微细粒状,与铝针铁矿一起填充在晶形规整、晶体粗大的赤铁矿晶体间的空隙里;压煮器中硅质结疤物为少量的微细粒钠硅质渣,与氢氧化镁基体共同沉积于钛的第一沉积旋回的层间局部;停留罐中硅质结疤物以水化石榴子石和橄榄石为主,它们以微细粒状填充于针铁矿晶体间隙中,有少量针状碳酸钠及钠硅渣;闪蒸器中硅质结疤物主要是铁石榴子石和Na2Ca3Si3O10相,前者与Al2O3(Al2O3·3H2O)共生成为球粒状结构中填隙物的主要成分,后者以微细粒状与氢氧化铝相混合成为纹层状结构中的主要成分。     

四川盆地下古生界硅质页岩层系中硅质来源及其对有机质保存的影响初探

四川盆地下古生界两套硅质页岩层系是其重要的页岩气产层,五峰组—龙马溪组硅质含量与TOC及含气量呈正相关性,暗示硅质矿物对该地区页岩气的生成具有重要意义。但硅质来源复杂,且存在后期硅质流体的注入。因此,本文在总结前人的研究成果基础上,对四川盆地寒武系底部硅质岩系与五峰组—龙马溪组硅质岩系的硅质特征进行了详细的岩石学分析,揭示了3种硅质来源特征：①同沉积无机硅质流体;②生物硅;③后期无机硅质流体。其中寒武系底部以同沉积无机硅质流体与生物硅来源为主,同沉积硅质流体导致有机质快速石化埋藏,有机质内部结构及形态保存较好;五峰组—龙马溪组硅质来源以后期无机硅质流体与生物硅来源为主,有机质在保存过程中受硅质流体的影响很小,有机质腐泥化作用充分,内部结构和形态多数保存较差。该研究初步揭示了两套页岩层系的硅质发育岩石学特征,及其对有机质保存的影响,期望能为四川盆地两套页岩气储层差异性提供新的思路与基础地质数据。     

Chemistry and surface morphology of soil particles from Luna 20 LRL sample 22003

Six siliceous glass spheres, five siliceous glass-bonded agglutinates and one breccia fragment from Luna 20 LRL sample number 22003 were analyzed by optical microscope, scanning electron microscope, scanning electron microprobe and energy-dispersive techniques. The data suggest that most of the glass spheres were probably derived locally by meteoritic impact processes and that most craters on their surfaces may have occurred from impacts of relatively high velocity particles in the impact-produced debris cloud while the glass sphere was at elevated temperatures. This is suggested by the nature of the craters, the partially buried fragments of plagioclase surrounded by radiating fractures and by the apparent absence of craters on the glass surfaces of the glass-bonded agglutinates. One glass sphere has a surface suggestive of a complex multiple impact origin involving liquid siliceous material and numerous siliceous spherules from 0.1 μm to 1 μm in diameter that may have formed from vaporization and condensation processes possibly in a relatively large scale meteoritic impact event.The surfaces of the siliceous glass spheres have several different types of materials. Concentration of metallic iron spherules on the surfaces of the glass spheres is generally lower than for similar Apollo 11 and 12 glass spheres. This is consistent with reduction processes being of primary importance in the formation of this metallic iron. Surface material composed only of Ca, C and O₂, possibly CaCO₃, is probably derived from carbonaceous chondrites. Splashes of material rich in Ca, Al, Fe, K and Cl occur. The origin of the relatively low temperature chlorine-bearing melt is unknown but it may be related to vaporization and condensation processes, possibly volcanic in nature, or possibly to partial fusion of components of carbonaceous chondrites. Siliceous surface material rich in potassium may represent either fused splash material of granitic composition or material enriched by vaporization and condensation processes.     

稀土元素地球化学对太古宙花岗岩类成因的判别

太古宙花岗岩类的成因是地学界争论颇久的问题。本文以稀土元素地球化学理论论证了北京、辽吉地区某些花岗岩为岩浆成因而非混合岩构成的“地层”。文章论述了主元素特征为钾质花岗岩的岩体实是钾化的TTG岩体 ,论述了主元素成分相同的TTG岩石具不同的稀土图谱 ;被长英质细脉注入的TTG岩石受混染作用改造稀土图谱也发生了变化 ;各种各样非TTG成分的岩石由于硅质的渗透被改造为TTG质岩石。这些实例说明 ,必须进行岩石学、矿物学和地球化学的综合研究才能判定太古宙形形色色的花岗质岩石。     

Trace element concentrations in silicate spherules from oceanic sediments

The possible existence of meteoritic spherules was investigated among several silicate spherules separated from oceanic sediments and analyzed by means of INAA (instrumental neutron activation analysis).A 0.72 mg glassy spherule was found to have uniform enrichment of 4 ~ 5 for the refractory REE (rare earth elements) and Sc with substantial depletion of Ce relative to chondritic abundances. This implies that this spherule is meteoritic in origin and that the enrichment of refractory elements was established by high temperature heating in a high O/H environment, possibly at the time of entering the Earth's atmosphere.The other three analyzed spherules showed major and trace element abundances that are consistent with an origin in the oceanic environment.     

浙黔桂地区寒武纪硅质岩的地球化学特征及其形成背景

本文采用常量和稀土元素地球化学方法对浙黔桂地区寒武纪硅质岩的形成背景进行了研究。研究表明,硅质岩的A12O3/（A12O3＋Fe2O3）为0.56~0.87;Ce/Ce＊为0.74±0.19;Lan/Cen为0.90~1.58;Lan/Ybn平均为6.38,轻稀土明显富集,这些特征表明研究区硅质岩形成于大陆边缘环境或大陆边缘与深海过渡带。形成于裂陷盆地初期的硅质岩,比古华南残留洋盆和扬子陆块边缘的硅质岩轻稀土元素更加富集。构造拉张期形成的硅质岩为热液成因硅质岩,其稀土配分模式显示出轻稀土相对亏损、Eu正异常特征;构造稳定期形成的硅质岩为沉积成因硅质岩,稀土配分模式显示出轻稀土相对富集、Eu弱负异常特征。由硅质岩稀土配分模式的差异性反映出寒武纪时期的拉张为幕式拉张。位于扬子地台边缘的硅质岩所具有的Ce负异常,暗示着江南造山带寒武纪后曾发生过由东向西的大规模逆冲推覆。     

云南鲁春晚三叠世硅质岩的地球化学特征及成因

云南鲁春晚三叠世火山沉积盆地是在江达－维西火山弧的基础上，通过拉张作用形成的碰撞后拉张盆地，盆地内广泛发育一套由玄武岩和流纹岩组成的“双峰式”火山岩及与其相伴的硅质岩。硅质岩可分为灰质硅质岩和纹层状硅质岩两类。通过对两类硅质岩所进行的地球化学研究和分析，表明云南鲁春晚三叠世火山沉积盆地中的凝灰质硅质岩属火山沉积成因，在而纹层状硅质岩为海底喷流热液／热泉（热水）沉积成因的热水硅质岩。     

Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland,and their corruption during high-grade metamorphism

Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*_SN, Eu/Eu*_SN, and Y_SN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43–60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but are beginning to lose the distinct La, Eu and Y positive anomalies and are interpreted as metasomatised chemical sediments. Finally there are some siliceous samples with completely different trace element patterns that are interpreted as rocks of non-sedimentary origin, and include metasomatised mafic rocks. The positive La/La*_SN, Eu/Eu*_SN and Y_SN anomalies found in Isua BIFs and other Eoarchaean Greenland samples, such as G91/26 from Akilia, suggests that the processes of carbonate ion complexation controlling the REE − Y patterns were already established in the hydrosphere at the start of the sedimentary record 3,600–3,850 Ma ago. This is in accord with the presence of Eoarchaean siderite-bearing marbles of sedimentary origin, and suggests that CO₂ may have been a significant greenhouse gas at that time.     

Composition of rare earth elements in settling particles collected in the highly productive North Pacific Ocean and Bering Sea: Implications for siliceous-matter dissolution kinetics and formation of two REE-enriched phases

Settling particles were sampled monthly for 1 year using an automated time-series sediment trap positioned at similar depths at two sites of high diatomaceous productivity in the North Pacific Ocean and Bering Sea. The particles were analyzed for rare earth elements (REEs) by inductively coupled plasma mass spectrometry (ICP-MS) with and without chemical treatment of the bulk samples to isolate siliceous fractions. The REE composition of the bulk samples is explained largely by the contribution of two distinct components: (i) carbonate with a higher REE concentration, a negative Ce anomaly and lighter REE (LREE) enrichment; (ii) opal with a lower REE concentration, a weaker negative Ce anomaly and heavier REE (HREE) enrichment.The siliceous fractions of settling particles are characterized by high Si/Al ratios (30-190), reflecting high diatom productivity at the studied sites. The La/Al ratio of the siliceous fraction is close to that of the upper crust, but the Lu/Al and Lu/La ratios are significantly higher than those of the upper crust or airborne particles, indicating the presence of excess HREEs in the siliceous fraction. Diatoms are believed to be important carriers of HREEs.The Ce anomaly, Eu anomaly, slope of the REE pattern, and ΣREE of the siliceous fraction vary exponentially with decreasing total mass flux. They can be well-reproduced according to the differential dissolution kinetics of elements in the order of Ce < lighter REEs (LREEs) < Eu = heavier REEs (HREEs) < Si from settling particles, where the dissolution rate is critically reduced through particle aggregation. This order is consistent with the vertical distribution of dissolved REEs and Si in oceans. The differential dissolution kinetics leads to HREE enrichment of the original diatoms and REE enrichment of dissolved diatoms. The Lu/Si ratio of the siliceous fraction of settling particles recovered from some of the highest diatom fluxes is identical to that of the two elements dissolved in deep seawater, providing further evidence for the dissolution of siliceous matter in deep water.     

Major, trace element and oxygen isotope study of glass cosmic spherules of chondritic composition: The record of their source material and atmospheric entry heating

New geochemical data on cosmic spherules (187 major element, 76 trace element, and 10 oxygen isotope compositions) and 273 analyses from the literature were used to assess the chemical diversity observed among glass cosmic spherules with chondritic composition. Three chemical groups of glass spherules are identified: normal chondritic spherules, CAT-like spherules (where CAT refers to Ca-Al-Ti-rich spherules), and high Ca-Al spherules. The transition from normal to high Ca-Al spherules occurs through a progressive enrichment in refractory major elements (on average from 2.3 wt.% to 7.0 wt.% for CaO, 2.8 wt.% to 7.2 wt.% for Al₂O₃, and 0.14 wt.% to 0.31 wt.% for TiO₂) and refractory trace elements (from 6.2 μg/g to 19.3 μg/g for Zr and 1.6CI-4.3CI for Rare Earth Elements-REEs) relative to moderately refractory elements (Mg, Si) and volatile elements (Rb, Na, Zn, Pb). Based on a comparison with experimental works from the literature, these chemical groups are thought to record progressive heating and evaporation during atmospheric entry. The evaporative mass losses evaluated for the high Ca-Al group (80-90%) supersede those of the CAT spherules which up to now have been considered as the most heated class of stony cosmic spherules. However, glass cosmic spherules still retain isotopic and elemental evidence of their source and precursor mineralogy. Four out of the 10 normal and high Ca-Al spherules analysed for oxygen isotopes are related to ordinary chondrites (δ¹⁸O = 13.2-17.3‰ and δ¹⁷O = 7.6-9.2‰). They are systematically enriched in Ni and Co (Ni = 24-500 μg/g) with respect to spherules related to carbonaceous chondrites (Ni < 1.2 μg/g, δ¹⁸O = 13.1-28.0‰ and δ¹⁷O = 5.1-14.0‰). REE abundances in cosmic spherules, which are not fractionated according to parent body or atmospheric entry heating, can then be used to unravel the precursor mineralogy. Spherules with flat REE pattern close to unity when normalized to CI are the most abundant in our dataset (54%) and likely derive from homogeneous, fine-grained chondritic precursors. Other REE patterns fall into no more than five categories, a surprising reproducibility in view of the mineralogical heterogeneity of chondritic lithologies at the micrometeorite scale.     

鄂尔多斯盆地煤成烃潜力与成气热模拟实验

鄂尔多斯盆地煤的Ｒｏｃｋ Ｅｖａｌ分析结果表明，在肥煤—焦煤阶段，Ｓ１＋Ｓ２达最大值，随后生烃潜力减弱。煤的Ｐｙ ＧＣ分析及热模拟成气实验结果证实煤成气具有３个生气高峰，分别相应于Ｒｏ，ｍ０５％～０７％、１０％～１４％及２５％，表明煤成气具多阶段性的特点。这一规律性的认识有助于煤成气的勘探和开发。同时，随煤级增高，煤成烃特征亦发生有规律的变化：异构烃减少，正构烃增加；类异戊二烯烷烃分布亦存在多变性或多阶段的演化特点；苯系化合物具波动性变化特征。     

西成矿田海底热水喷溢沉积成因硅质岩及其与矿化关系

硅质(化)岩与铅锌矿化关系十分密切是西成矿田显著特征之一,特别是毕家山型矿床,其主要矿体的容矿岩石为硅质岩,本文重点研究了该矿田硅质岩岩石学和地球化学特征及其与矿体(层)时空关系,认为该区硅质岩不是正常生物化学沉积成因的,而属热水沉积形成;并讨论了硅质岩与矿化关系以及硅质在成矿中的作用,为确定该类矿床的成因提供了重要证据.