山东大张矽卡岩型铁矿床中铁的富集机制 ——来自流体包裹体和氢、氧同位素的证据

大张铁矿是鲁西地区近年来新发现的一个重要的矽卡岩型矿床.矿体主要赋存于石英二长闪长岩与奥陶系马家沟组灰岩接触带及其附近.根据脉体穿插关系和交代蚀变特征,将大张矽卡岩型铁矿床成矿过程划分为矽卡岩阶段、氧化物阶段、硫化物阶段和碳酸盐阶段.通过对透辉石、绿帘石、石英和方解石等透明矿物显微观察发现,大张铁矿中流体包裹体类型主要...     

青海玉树东莫扎抓铅锌矿床地质特征及碳氢氧同位素地球化学研究

东莫扎抓铅锌矿床位于青藏高原羌塘地体东北缘,是"三江"北段铅锌铜银多金属成矿带中的典型代表,对该矿床地质特征和成因类型的研究有助于理解区域铅锌铜银多金属成矿规律,对区域找矿具有重要意义.笔者通过详细的矿区地质考察、系统的矿石光薄片显微镜下鉴定和矿石中方解石的碳、氢、氧同位素分析测试,概述了东莫扎抓铅锌矿床的地质特征和成矿流体的碳、氢、氧同位素组成特征.东莫扎抓铅锌矿床矿体呈似层状展布,产状严格受到矿区逆冲断层的控制,赋矿围岩为上三叠统结扎群波里拉组灰岩和下一中二叠统开心岭群尕迪考组灰岩,发育强白云石化和弱硅化,矿物组合简单,主要为闪锌矿+方铅矿+黄铁矿+白云石+方解石+重晶石,矿石结构以皮壳状、草莓状等胶状结构和他形粒状结构为主,矿石构造为浸染状、角砾状、团块状和脉状.矿石中方解石的δ~(13)C_(V-PDB)值、δ~(18)O_(V-SMOW)值分别为δD_(V-SMOW)值分别为-1.8‰～+3.3‰、+6.1‰～+24.6‰和-137‰～-53‰,计算得到成矿流体的δ~(18)O_(流体)值为-0.5‰～+13.8‰.研究结果表明,东莫扎抓铅锌矿床的成矿流体主要来自盆地封存热卤水和大气降水,金属物质可能由区域流体在长距离迁移过程中通过与碳酸盐岩地层相互作用,以及淋滤含矿地层底部的火山岩而得来,成矿过程中伴随着碳酸盐岩的溶解作用,可能存在有机质的参与.据此,笔者将东莫扎抓矿床归为发育在碰撞造山带中受逆冲推覆断裂构造控制的类MVT铅锌矿床,并初步建立了东莫扎抓铅锌矿床的构造控矿模型.     

湘中邵阳凹陷二叠系龙潭组页岩含气性特征与气体成因

针对湘中地区邵阳凹陷二叠系龙潭组页岩气资源评价,部署了页岩气调查井2015H-D3井,通过现场解析气等相关样品测试定量分析了页岩含气性特征及其影响因素,并借助气体稳定碳、氢同位素对气体成因进行了初步探讨.结果显示:钻深从150m处开始出现气显,随深度增加,解析气含量呈现先逐渐增大后减小的趋势,300～425m为最高含气层段,累计厚度达125m,现场解析气含量全部大于0.5m^3/t,最高为2.35m^3/t,平均1m^3/t,证实龙潭组具良好页岩气资源潜力.当埋深大于300m时,解析气含量受有机碳含量控制,而埋深小于300m时,解析气含量并不简单受控于有机碳含量,而是受到保存条件的严重制约.气体碳、氢同位素测试显示δ13C1介于-29.87‰～-36.82‰,平均为-34.52‰,δ¹³C_2介于-29.45‰～-31.02‰,平均为-30.09‰,δD1介于-131.20‰～-178.40‰,平均为-167.40‰.气体成因分析揭示龙潭组页岩气属热成因中的油型气类型.基于沉积现象判断龙潭组为海陆过渡相环境,与氢同位素判断结果基本吻合,但目前还无法确定具体判定区间.     

断陷盆地高原面典型岩溶洼地旱季土壤水氢氧同位素时空差异特征

以云南省蒙自断陷盆地东山山区典型岩溶洼地为研究区,通过野外采集土壤样品与实验室测试分析相结合的方法,运用稳定同位素技术研究旱季不同深度土壤水氢氧同位素组成,揭示区内土壤水氢氧同位素时空变化特征,为进一步研究云南断陷盆地山区土壤水分运移机制和当地农业合理利用和管理水资源提供科学依据。结果表明:(1)土壤水δD、δ18O同位素值的变化范围分别为-128.3‰~-27.6‰和-17.5‰~2.5‰,平均值分别为-96.1‰±20.7‰和-12.3‰±3.7‰,降雨转化为土壤水和水分在土壤中重新分布时发生一定程度的氢氧同位素分馏。(2)旱季两个月份土壤水氢氧同位素组成发生变化,4月份土壤水δD、δ18O同位素平均值分别为-86.3‰±23.83‰和-10.6‰±4.3‰,显著高于2月份(δD:-106.1‰±9.5‰;δ18O:-14.1‰±1.6‰)(p<0.05),主要和4月份土壤水的蒸发作用强烈有关。(3)在空间上,坡地与洼地之间土壤水氢氧同位素组成存在差异,2月份坡地与洼地之间土壤水δD、δ18O值差异显著(p<0.05),洼地土壤水δD、δ18O比坡地偏轻;4月份坡地与洼地之间土壤水δD、δ18O值差异不显著(p>0.05)。(4)土壤垂直剖面方向上土壤水δD、δ18O值随着土壤深度的增加而减小,浅层土壤水δ18O和深层土壤水δ18O存在显著差异,2月份浅层土壤水δ18O比深层土壤水δ18O偏正2.8‰,4月份浅层土壤水δ18O比深层土壤水δ18O偏正10.5‰。      

脉冲星对氢原子钟的频率驾驭算法研究

氢原子钟具有较高的短期稳定度,将其作为主钟可在短期内产生高精度的本地时间信号.但氢钟存在频率漂移现象,导致其长期稳定度较差,从而影响本地时间的准确性.毫秒脉冲星自转高度稳定,借助于其长期稳定度高的特性,可定期实现对氢原子钟的频率驾驭,并对实时信号加以控制.首先分析了国际脉冲星计时阵(International Pulsar Timing Array,IPTA)第二批发布数据中四颗毫秒脉冲星的稳定度随时间的变化,同时采用哈达玛方差分析了中国科学院国家授时中心(National Time Service Center,NTSC)一台氢钟的频率稳定性能,最终给出了利用脉冲星驾驭氢原子钟频率的方法.     

渤海湾盆地石炭纪—二叠纪煤的有机组分红外光谱研究

通过对渤海湾盆地石炭纪－二叠纪煤中主要有机组分进行显微傅里叶红外分析,揭示了孢子体,角质体,树脂体及基质镜质体等有机组分化学组成,结构的特点和对油气形成贡献的差异。结果表明,角质体,树脂体和孢子体都具有富氢指数高,富氧指数低的特点,但树脂体对油气生成的贡献更大而且时间较早,孢子体较差而且时间较晚,就基质镜质体而言,晚石炭世太原组（Ｃ２ｔ）煤比早二叠世山西组（Ｐ１ｓ）煤富氢指数高,富脂链参数也大,表     

An infrared spectroscopic study of lawsonite to 20 GPa

The infrared spectrum of CaAl₂Si₂O₇ · H₂O-lawsonite, has been characterized to pressures of 20 GPa at 300 K. Our results constrain the response to compression of the silicate tetrahedra, hydroxyl units, and water molecules in this material. The asymmetric and symmetric stretching and bending vibrations of the Si₂O₇ groups (at zero pressure frequencies between 600 and 1000 cm⁻¹) increase in frequency with pressure at rates between 3.6 and 5.9 cm⁻¹/GPa. All silicate modes appear to shift continuously with pressure to 20 GPa, although the lowest frequency stretching vibration becomes unresolvable above 18 GPa, and a splitting of the main bending vibration is observed near this pressure. The O-H stretches of the hydroxyl units exhibit a discontinuity in their mode shifts at ∼8–9 GPa, which we interpret to be produced by a pressure-induced change in hydrogen bonding. The stretching and bending vibrations of the water molecule are relatively unaffected by compression to 20 GPa, thus demonstrating that the structural cavities in which water molecules reside are relatively rigid. Significant changes in the amplitude of the O-H stretches of the hydroxyl and water units are observed at this pressure as well; nevertheless, our results demonstrate that the dominant structural units in lawsonite persist metastably at 300 K with only modest structural modifications well beyond the known stability field of this phase. Received: 10 July 1998 / Revised, accepted: 23 October 1998     

SiO bonded interactions in coesite: a comparison of crystalline, molecular and experimental electron density distributions

Bond critical point properties of electron density distributions calculated for representative Si₅O₁₆ moieties of the structure of coesite are compared with those observed and calculated for the bulk crystal. The values calculated for the moieties agree with those observed to within ∼5%, on average, whereas those calculated for the crystal agree to within ∼10%. As the SiOSi angles increase and the SiO bonds shorten, there is a progressive build-up in the calculated electron density along the bonds. This is accompanied by an increase in both the curvatures of the electron density, both perpendicular and parallel to each bond, and the Laplacian of the electron density distribution at the bond critical points. The cross sections of the bonds at the critical points become more circular as the angle approaches 180o. Also, the bonded radius of the oxide anion decreases about twice as much as that of the Si cation as the SiO bond length decreases and the fraction of s-character of the bond is indicated to increase. A knowledge of electron density distributions is central to our understanding of the forces that govern the structure, properties, solid state reactions, surface reactions and phase transformations of minerals. The software (CRYSTAL95 and TOPOND) used in this study to calculate the bond critical properties of the electron density and Laplacian distributions is bound to promote a deeper understanding of crystal chemistry and properties. Received: 23 February 1998 / Revised, accepted: 16 July 1998     

伟晶岩绿柱石矿物学及其通道水氢同位素研究进展

自然界绿柱石存在三个类质同象系列,即“八面体”绿柱石（ｃ／ａ＝０．９９１￣０．９９６）,“正常”绿柱石和“四面体”绿柱石。绿柱石矿物精细结构研究表明,二价离子置换八面体中Ａｌ,Ｌｉ置换四面体中Ｂｅ,而碱离子被绿柱石通道所容纳,用于补偿低价阳离子置换Ａｌ八面体和Ｂｅ四面体引起的电价不足。伟晶岩绿柱石通常含有〉１．６ｗｔ％的通道水,而包裹体中流体仅为０．１５ｗｔ％左右。室温下绿柱石通道中存在１型和Ⅱ