碳酸盐岩中缝洞方解石成岩环境的矿物地球化学判识——以塔河油田的沙79井和沙85井为例

摘要在塔里木盆地塔河油田4区沙79井、6区沙85井奥陶系鹰山组岩芯的详细观察基础上,对裂隙、溶洞及巨型洞穴中的方解石晶体的晶胞参数、化学成分、碳、氧同位素、流体包裹体中的氢同位素等分析与研究表明,至少存在两种成岩环境:一是以大气淡水表生环境,方解石中晶胞参数(c)=17.057~17.062,Fe2O3＝0.06%~0.07%,Sr=53.3×10-6~96.2×10-6、Ba=19×10-6~28×10-6,Mg/Ca(×103)＝1.94~5.14,Sr/Ba＝2.12~5.24,δ18OPDB较低（-15‰~-17‰）、较低δ13CPDB（-4‰~-2.0‰）,不含或较少含烃类,流体包裹体中氢δDPDB＝-94.99‰~-109.54‰为特征;另一是地层混合水埋藏环境为主,方解石中晶胞参数(c)=17.064~17.065（个别达17.212）、Fe2O3＝0.06%~0.18%,Sr=111×10-6~208×10-6、Ba=215×10-6~479×10-6,Mg/Ca(×103)＝1.53~1.76,Sr/Ba＝0.49~0.58,方解石δ18OPDB低（-9.6‰~-13.7‰）、流体包裹体中氢δDPDB＝-77.5‰~-88.2‰为特征;另外,在巨型洞穴中方解石中组分的剧烈变化反映了洞穴充填发生于不同的水文地质—地球化学体系。     

桂北泗里口老堡组硅质岩的常量、稀土元素特征及成因指示

桂北泗里口老堡组为一套埃迪卡拉纪—寒武纪过渡时期（大约550～540 Ma）深水盆地沉积的硅质岩。它们的SiO2含量普遍高（平均93.8%）;Al2O3含量为0.17%～4.92%,沿剖面自下而上明显增加,上部超过2%;Al/(Al+Fe+Mn)比值多高于0.42;Fe/Ti比值大都小于16.3;Al2O3/( Al2O3+Fe2O3)比值多高于0.4,剖面上部样品的比值为0.8～0.9;Y/Ho比值为26.4～36.9,中、下部样品较高（多高于32）,上部样品的比值接近地壳值（27）;Eu/Eu*平均值为1.0,正异常不明显。剖面下部样品的∑REE含量低（15.9×10-6～27.1×10-6）,具有与现代海水相近的REE配分,没有正的Eu异常,不同于海底的热液流体和与其有关的碧玉的REE配分;中部样品的∑REE含量为26.2×10-6～49.4×10-6,由于所含陆源碎屑的增加,REE配分变得平坦,但仍有海水REE的某些特征;上部样品的∑REE含量为40.5×10-6～59×10-6,显示与平均页岩相似的平坦的REE配分,但∑REE含量仅为平均页岩的大约1/4～1/3。这些常量和稀土元素特征表明,海底热液和陆源碎屑都不可能成为泗里口老堡组硅质岩的重要物源。埃迪卡拉纪—寒武纪过渡时期华南深水盆地厚层硅质岩沉积反映了这一时期大气高CO2浓度,大量陆源化学风化的硅质流入海洋和大量生物的降解可能是造成这些硅质岩形成的基本原因。     

北秦岭西段早古生代埃达克岩地球化学特征及岩石成因

唐藏石英闪长岩体出露于北秦岭造山带西段,侵入于丹凤群火山沉积岩系之中,主要矿物组成为斜长石、角闪石、石英、钾长石、黑云母等,形成时代为454Ma。该岩体SiO2= 62.02％～64.26％;Al2O3=16.55%～17.45%,MgO=1.71%～2.09%, Sr = (1069～1296)×10-6（>400 ×10-6）,Y = (11.6～13.81)×10-6 （<18×10-6）,Yb = (0.96～1.14)×10-6（<1.9 ×10-6）,Sr/Y=80.98～108.19（>40）,稀土总量（∑REE=217.88×10-6～355.07×10-6）较高,LREE强烈富集,重稀土亏损,Eu负异常不明显（LREE/HREE=17.72~25.82;LaN/ YbN=44.56～53.85;δEu＝0.82～1.0）,显示出典型埃达克岩的岩石地球化学特点。在以原始地幔标准化的微量元素分布图中,大离子亲石元素（LILE）K、Th、Rb、Ba、Sr等富集,高场强元素(HFSE)Ta、Nb、Y、Yb等较相邻元素相对亏损,微量元素曲线分布形式及稀土元素配分模式与典型地区埃达克岩分布形式一致。研究表明,该岩体Na2O＝4.99%～6.91%, Na2O-2＞K2O,Mg#＝0.59～0.63, A/CNK=0.82～1.01,σ=4.24～2.24,为富钠偏铝质高镁埃达克岩。唐藏埃达克岩体岩浆源于早古生代秦岭商丹洋向北俯冲消减洋壳板片的部分熔融,岩浆在上升过程中与地幔楔发生反应。北秦岭早古生代埃达克岩的确定为探讨秦岭早古生代构造演化提供了新的证据。     

有机质碳同位素热力学分馏与天然气碳同位素组成

干酪根中不同结构和官能团具有不同的碳同位素组成,这种差异可以用有机质碳同位素热力学同位素因子（β因子）进行预测。煤岩模拟实验产物中,δ13CCO2相对烃类气体而言明显偏重,这与干酪根中羧基的β13C较大有关。含水实验产物的δ13CCO2轻于无水实验产物的δ13CCO2是由于含水实验中所增加CO2的碳同位素组成相对较轻造成的,含水实验增加的CO2产率是由β13C相对较小的部分亚甲基碳通过断裂、氢转移、以及与水反应转变而来。模拟实验低温阶段（≤300℃）,甲氧基中的甲基断裂可能的甲烷形成的主要方式。而甲氧基的β13C大于甲基,所以低温阶段出现了甲烷碳同位素组成先较重后变轻的现象。     

北京十三陵中元古界长城系沉积相标志及沉积环境演化模式

北京十三陵地区中元古界长城系包括5个组：常州沟组、串岭沟组、团山子组、大红峪组、高于庄组，前2个组主要由碎屑岩组成，后3个组主要由碳酸盐岩组成。众多的沉积相标志从不同侧面说明：常州沟组沉积属于滨浅海碎屑岩沉积环境；从串岭沟组开始，其沉积环境向碳酸盐岩沉积环境过渡；后3个组沉积时的环境为典型的陆表海碳酸盐岩沉积环境。在综合研究的基础上给出了沉积环境演化模式。另外，长城系还有许多特殊的沉积现象值得进一步研究和讨论：世界上最古老的宇宙球粒；高于庄组白云岩层面上双脊波痕的内碎屑颗粒成因和硅化白云岩内青鱼骨状层理及硅质团粒的成因；特别是在大红峪组首次发现太阳星云物质－碳质球粒陨石。     

交互四元体系Li+, Mg2+//SO2-4, B4O2-7H2O 288 K

采用等温溶解平衡法研究了288K时Li+, Mg2+//SO2-4, B4O2-7- H2O四元体系的固液相平衡关系,测定了该四元体系在288K时平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及密度组成图。研究结果表明：交互四元体系Li+, Mg2+//SO2-4, B4O2-7- H2O 288K时平衡相图中有2个共饱点,5条单变量曲线,4个结晶区对应的平衡固相分别为Li2B4O7·3H2O,Li2SO4·H2O,MgB4O7·9H2O和MgSO4·7H2O。     

评价生物气生成量、生成期的碳同位素平衡法及其应用

生物气的生成期对其成藏有至关重要的制约作用,但目前国内外尚缺少可信、有效方法来对此进行评价。针对这一难题,考虑到无论生物气的生成机理如何,转化前的有机质和转化后的残余有机质及产物的13C、12C的总量应该守恒,本文探索并建立了评价生物气生成量的碳同位素平衡法,并利用松辽盆地的实际分析数据,对这一评价方法（模型）进行了标定和应用。结果表明:Ⅰ、Ⅱ、Ⅲ型有机质累计产生物成因甲烷气的量分别约为193.94 ml/g、175.64 ml/g、161.71 ml/g。区内源岩生物气的生成量约为385.4×1012 m3;生物气的主要生成期在嫩江组沉积末期之前;区内生物气的可能资源量介于11.40×1011～24.8×1011 m3之间。     

我国不同储量丰度大中型气田形成的聚散气速率特征

通过我国41个大中型气田天然气扩散散失量计算和地质储量、含气面积及形成时期统计,对其扩散散失气速率、聚气速率和聚散气速率比值进行了研究,得到我国41个大中型气田天然气扩散散失气速率为0.2×106～49.5×106 m3/km2Ma,平均为7.2×106 m3/km2Ma,聚气速率为2.1×106～528.1×106 m3/km2Ma,平均为79.4×106 m3/km2Ma,聚散气速率比值为1.5～94.2,平均为14.5。通过我国41个大中型气田储量丰度与聚散气速率比值关系研究得到,二者为正比关系,聚散气速率比值越大,大中型气田储量丰度越高;反之则越低。我国要形成高储量丰度大中型气田的聚散气速率比值最小应大于4.1,中等储量丰度大中型气田形成的聚散气速率比值在4.1～2.3之间,低储量丰度大中型气田形成的聚散气速率比值应小于2.3。     

柴达木西部钻孔盐类矿物及环境意义初步研究

柴达木盆地位于青藏高原北部,沉积和储存了巨量的蒸发岩。其独特的地理位置、构造特征、盐类沉积和其它资源优势,成为地学领域各方向学者关注的焦点。2008年,中德合作在盆地西部取得千米深的钻孔,上部400 m表现为碳酸盐粘土层与盐层的交替,盐层的矿物种类是石盐（NaCl）,石膏（CaSO4·2H2O）,芒硝（Na2SO4·10H2O）,无水芒硝（Na2SO4）,钙芒硝（Na2Ca(SO4)2）,杂卤石（K2MgCa2(SO4)4·2H2O）,尤钠钙矾（Na4Ca(SO4)3·2H2O）和白钠镁矾（Na2Mg(SO4)2·4H2O）,以石盐和石膏为主。碳酸盐粘土层中还出现了少量重晶石（BaSO4）、碳酸钠钙石（Ca2Na2(CO3)3）、钠钙矾（Ca2Na3(SO4)3(OH)）、苏打石（NaHCO3）、斜碳钠钙石（Na2Ca(CO3)2·5H2O）、一水碳酸钠（Na2CO3·H2O）和水硼镁石（CaMg(B3O3(OH)5)2·6H2O）。碳酸盐粘土层中不同形态的石膏单晶、双晶和集合体,形成于次生浓卤水溶液,晶体形状与生长速度、溶液性质和环境条件有关。单盐矿物石盐、石膏和无水芒硝从卤水中直接结晶,复盐钙芒硝、白钠镁矾和尤钠钙矾则由单盐反应形成。尤钠钙矾为罕见的亚稳定矿物,柴达木盆地和青藏高原其它地区的研究中尚未见报道,该矿物形成温度远高于室温,可能是由石膏或无水芒硝在富Na SO4卤水溶液中反应形成。根据矿物种类、组合和阳离子含量推断,古卤水类型主要为Na Cl型,其次为Na Ca SO4、Na SO4、Na SO4 Cl、Na Ca SO4 Cl,少数层位为Ca SO4和Na Mg SO4型卤水。盐层和碳酸盐粘土层的交替说明,1 Ma以来钻孔所在区域为干湿交替气候,18个成盐阶段或气候干旱阶段出现在0.97~0.03 Ma,最早的两个蒸发阶段为0.96~0.97 Ma和0.87 Ma,其它蒸发阶段出现在0.78~0.03 Ma,厚盐层集中出现在0.5~0.03 Ma。     

甘肃北山火石山哈尔根头口布花岗岩年代学、地球化学及其地质意义

首次利用锆石LAICPMS UPb法测得甘肃火石山东北部侵位于长城系、蓟县系以及志留系中的哈尔根头口布花岗岩形成于中泥盆世早期（同位素年龄为387.6±8.2Ma）,同时发现该花岗岩体内存在晚蓟县世产物（继承性锆石年龄1172±7Ma）。哈尔根头口布花岗岩体主要由钾长花岗岩、二长花岗岩、花岗岩组成,岩石具有高硅（SiO2含量为70.28％~79.4%）、富碱（Na2O＋K2O为6.52%~9.11%）、低铝（Al2O3含量为8.82%~14.05%）、低Sr（含量为40~150×10-6,平均为101.5×10-6）的特征、岩石的δ<3.3、A/CNK值为0.8~1.1,为钙碱性准铝质到弱过铝质岩石;稀土元素具有明显的LREE富集(LREE/HREE=2.89~16.4, LaN/YbN= 1.82~25.18)和Eu亏损,相对富集Rb、Th、Ce和Sm,而亏损Ta、Nb、Zr、Hf。综合分析认为该花岗岩为A型花岗岩,产于构造挤压向构造伸展转换的地质背景之中。     

A Study of Mesoproterozoic Iron Cosmic Micro-spherules from 1.8 Ga and 1.6 Ga Old Strata in the Ming Tombs District, Beijing

Numerous iron cosmic micro-spherules have been discovered from Mesoproterozoic strata including the Changzhougou Formation(1.8 Ga) and the Dahongyu Formation(1.6 Ga) of the Ming Tombs district,Beijing.There are 1 to 30 grains of cosmic spherules per 2 kg of a sandstone sample taken from the bottom of a coarse sandstone bed of the Changzhougou Formation and 56 grains per 3.69 kg of a rock sample from silicified carbonate rocks of the Dahongyu Formation.The surface textures of cosmic spherules analyzed by means of the secondary electron imagery are identical with those reported from references either domestic or abroad.So far the geo-ages of 1.8 Ga and 1.6 Ga of cosmic spherules from the Changzhougou and Dahongyu formations might be older than those reported in the world.Table 1 gives the electron probe analysis data of cosmic spherules for 30 spherule grains and 44 testing points as follows(%):FeO,80-95;Cr_2O_3;0-9.56;NiO,0-0.78;CoO,0-0.46; indicating that the Cr_2O_3 content is higher and FeO content lower in the Changzhougou Formation than in the Dahongyu Formation.The helium isotopic data of cosmic spherules as well as their host rocks vary greatly between the Changzhougou and the Dahongyu formations as shown in Table 2.The data of cosmic spherules of the Changzhougou Formation vs the Dahongyu Formation are 57.5/1.23 in ~3He/~4He(10~(-8));and 55.54/809.60 in ~4He(10~(-6)cm~3STP/g);those of coarse sandstone of the Changzhougou Formation vs silicified carbonate of the Dahongyu Formation are 3.39/2.59 in ~3He/~4He(10~(-8)) and 4.56/2.34 in ~3He(10~(-6)cm~3STP/g).The ratio of analytic data of helium isotopes are different for cosmic spherules and their host rocks;for example,the ~3He/~4He(10~(-8)) values are 16.96 and 0.48,and the ~4He (10~(-6)cm~3STP/g) are 12.18 and 345.98 for the Changzhougou and Dahongyu formations respectively.It was reported that the world's oldest micrometeorites had been found in the Meso-Proterozoic Satakunta Formation,Finland.However,the cosmic spherules from the Meso-Proterozoic Changzhougou and Dahongyu formations are 200 to 400 Ma older than those from the Satakunta Formation.Besides,one carbonaceous chondrite grain was discovered for the first time as the earliest remain formed in the solar nebula from the Dahongyu Formation.     

Discovery of Cosmic Spherules from the Mesoproterozoic Strata and its Significance—in Case of the Ming Tombs Area, Beijing

This study covers cosmic spherules derived from the Mesoproterozoic Dahongyu Formation in the Ming Tombs area, Beijing. The cosmic spherules include iron oxide cosmic spherules, carbonaceous chondrites, and atomic iron “steely bead”-shaped cosmic spherules. The mineral assemblage of silicon carbide, forsterite, zircon, and glass spherules and fragments were picked from melt-silicified carbonate of the Mesoproterozoic Dahongyu Formation (ca. 1625 Ma). Cosmic spherule assemblages are solely discovered from sedimentary rocks in China. Platinum group elements (PGE) were determined for the first time in cosmic spherules and associated minerals. PGE comparative observation between meteorite and cosmic spherules is presented in this study. It is recognized that an extraterrestrial meteorite impact event might have occurred in the Dahongyu Stage. The main evidence is a large number of iron cosmic spherules in silicified oncolitic limestone, and associated cosmic silicon carbide, glass spherules, and fragments, as well as the presence of forsterite. The impact-volcanic crater is characteristic of a big black shale block dropped into the bended silicified limestone.     

吉林省南部宇宙尘的化学组成特征

在吉林省南部元古宇石英岩内发现磁性微球粒３９２枚,根据其产状,形貌及一般特征,微结构和化学组成表明为陨石消融型宇宙尘,由４亚４小类组成一个宇宙尘系列,（１）金属球粒;（２）纯铁球粒,（ｂ）ＦＣＮ型（天然不锈钢）球粒;（２）氧化物球粒（ａ）普通铁质宇宙尘（ｂ）铬铁氧化物球粒;（３）玻璃质球粒;（４）氧化物－金属过渡型球粒,其母体要能是一分异的ＦＣＮ型石－铁陨石质陨星体,核部为ＦＣＮ合金,经消融分异作     

吉林省南部元古宙宇宙尘的某些特征及其意义

吉林省南部元古宙宇宙尘的某些特征及其意义徐光荣梁宜林张林（长春工业高等专科学校，长春１３００２１）林文蔚陈克樵梁细荣王安平（中国地质科学院矿床地质研究所，北京１０００３７）（长春科技大学，长春１３００２６）关键词宇宙尘高铬特征共轭性吉林作者在吉林省南...     

Isotopic compositions of oxygen, iron, chromium, and nickel in cosmic spherules: Toward a better comprehension of atmospheric entry heating effects

Large, correlated, mass-dependent enrichments in the heavier isotopes of O, Cr, Fe, and Ni are observed in type-I (metal/metal oxide) cosmic spherules collected from the deep sea. Limited intraparticle variability of oxygen isotope abundances, typically <5‰ in δ¹⁸O, indicates good mixing of the melts and supports the application of the Rayleigh equation for the calculation of fractional evaporative losses during atmospheric entry. Fractional losses for oxygen evaporation from wüstite, assuming a starting isotopic composition equal to that of air (δ¹⁸O = 23.5‰; δ¹⁷O = 11.8‰), are in the range 55%-77%, and are systematically smaller than evaporative losses calculated for Fe (69%-85%), Cr (81%-95%), and especially Ni (45%-99%). However, as δ¹⁸O values increase, fractional losses for oxygen approach those of Fe, Cr, and Ni indicating a shift in the evaporating species from metallic to oxidized forms as the spherules are progressively oxidized during entry heating. The observed unequal fractional losses of O and Fe can be reconciled by allowing for a kinetic isotope mass-dependent fractionation of atmospheric oxygen during the oxidation process and/or that some metallic Fe may have undergone Rayleigh evaporation before oxidation began.In situ measurements of oxygen isotopic abundances were also performed in 14 type-S (silicate) cosmic spherules, 13 from the Antarctic ice and one from the deep sea. Additional bulk Fe and Cr isotopic abundances were determined for two type-S deep-sea spherules. The isotopic fractionation of Cr isotopes suggest appreciable evaporative loss of Cr, perhaps as a sulfide. The oxygen isotopic compositions for the type-S spherules range from δ¹⁸O = −2‰ to + 27‰. The intraspherule isotopic variations are typically small, ∼5% relative, except for the less-heated porphyritic spherules which have preserved large isotopic heterogeneities in at least one case. A plot of δ¹⁷O vs. δ¹⁸O values for these spherules defines a broad parallelogram bounded at higher values of δ¹⁷O by the terrestrial fractionation line, and at lower values of δ¹⁷O by a line parallel to it and anchored near the isotopic composition of δ¹⁸O = −2.5‰ and δ¹⁷O = −5‰. Lack of independent evidence for substantial evaporative losses suggests that much of this variation reflects the starting isotopic composition of the precursor materials, which likely resembled CO, CM, or CI chondrites. However, the enrichments in heavy isotopes indicate that some mixing with atmospheric oxygen was probably involved during atmospheric entry for some of the spherules. Isotopic fractionation due to evaporation of incoming grain is not required to explain most of the oxygen isotopic data for type-S spherules. However spherules with barred olivine textures that are thought to have experienced a more intense heating than the porphyritic ones might have undergone some distillation. Two cosmic spherules, one classified as a radial pyroxene type and the other showing a glassy texture, show unfractionated oxygen isotopic abundances. They are probably chondrule fragments that survived atmospheric entry unmelted.Possible reasons type-I spherules show larger degrees of isotopic fractionation than type-S spherules include: a) the short duration of the heating pulse associated with the high volatile content of the type-S spherule precursors compared to type-I spherules; b) higher evaporation temperatures for at least a refractory portion of the silicates compared to that of iron metal or oxide; c) lower duration of heating of type-S spherules compared to type-I spherules as a consequence of their lower densities.     

东北地区中元古代地层划分与对比研究

根据全国地层委员会中国中新元古代地层年表的新方案和近年的来新研究成果,对东北地区中元古代地层岩性、同位索年龄、叠层石以及地层接触关系等进行了研究,对区内中元古界岩石地层单位进行了核实,辽宁的长城系(1.8～1.6 Ga)包括常州沟组、串岭沟组、团山子组、大红峪组,蓟县系(1.6～1.4 Ga)包括高于庄组、杨庄组、雾迷...     

辽宁兴城地区前寒武纪地层序列和不整合

辽宁兴城地区位于华北克拉通中、新元古代燕山裂陷槽盆地（燕辽海盆）的东南边缘,地层序列和沉积特征与同属盆地边缘区的河北滦县、北京南口、以及太行山区等地类似。研究区新太古代花岗岩之上沉积了长城系（常州沟组、串岭沟组、团山子组、大红峪组）,蓟县系（高于庄组、杨庄组、雾迷山组）,以及青白口系（长龙山组、景儿峪组）。与天津蓟县中、新元古界标准剖面相比,本区地层厚度较薄、长城系碳酸盐岩较少、碎屑物粒度较粗、部分层位（铁岭组、洪水庄组、下马岭组？）缺失,几大沉积层序的底界超覆明显,体现了典型的古陆边缘特征。中元古界常州沟组至团山子组为一套局限分布的滨、浅海相海进至海退旋回沉积,常州沟组滨海相砂岩与下伏新太古代花岗岩沉积接触;大红峪组沉积时期广泛海侵,以石英砂岩和粉砂质页岩为主,下部发育复成分角砾岩和石英砂岩质砾岩,与下伏地质体有沉积接触（非整合）、角度不整合、微角度不整合、岩溶不整合等多种接触关系,说明大红峪组沉积之前发生过沉积间断和地层褶皱变形,“兴城运动”所指的不整合并非单纯的海进超覆成因;蓟县系高于庄组下部为一套海侵陆源碎屑岩序列,不整合在大红峪组和新太古代花岗岩之上,中、上部为碳酸盐岩台地沉积;蓟县系杨庄组和雾迷山组总体为碳酸盐岩,仅含少量陆源碎屑成分或薄层;新元古界青白口系长龙山组为又一套陆源碎屑岩海进序列,平行不整合在蓟县系雾迷山组或待建系下马岭组？角砾状含燧石白云质灰岩之上,指示了芹峪上升和蔚县上升影响期间的岩溶平原发育历史;寒武系昌平组角砾状白云质灰岩平行不整合在景儿峪组中、薄层白云质灰岩之上。上述不整合及地层建造特征还说明山海关古陆长期存在并对辽西南部的沉积古地理有明显影响。此外,大红峪组的沉积在区内具有承前启后的意义,自大红峪组沉积开始本区与燕辽海盆完全连通,整个盆地的演化也从强烈断陷向稳定沉降转变。     

中国晚前寒武纪年表和年代地层序列

本文依据2009年11月24日全国地层委员会前寒武纪分会扩大会议上形成的一个共识,对中国晚前寒武纪年表进行重新标定:即长城系限定在1.8～1.6Ga,包括常州沟组、串岭沟组、团山子组、大红峪组;蓟县系限定在1.6～1.4Ga,包括高于庄组、杨庄组、雾迷山组、洪水庄组、铁岭组;待建系1.4～1.0Ga,蓟县剖面上仅发育下马岭组;青白口系限定在1.0～0.78Ga,包括骆驼岭组和景儿峪组;南华系限定在780～635Ma及震旦系限定在635～542Ma。关于最新的江南古陆晚前寒武纪地层中的一系列锆石U-Pb数据,应标定在青白口系上部。另外,华北古陆上最新的锆石U-Pb测年结果,初步揭示华北古陆前寒武系火山岩省的存在和分布范围,结合全球大陆动力学的基本特征,有利于我们建立一个前寒武纪统一的、精确的和具有年代系统的高精度年龄的基础剖面。     

焦作矿区太原组宇宙尘的发现及其特征

<正> 宇宙尘的研究,有助于了解太阳系的起源与演化;有助于地层的划分与对比和估计沉积速率等。1876年莫雷(Murray)描述宇宙尘微球粒以来,一些科学家也在深海沉积物中发现了这种磁性微球粒,同时利用现代技术在高空中也收集到微球粒,证实了宇宙尘的存