广西佛子冲铅锌矿田成岩成矿时代研究

广西佛子冲铅锌矿田位于桂东南博白-岑溪多金属成矿带的NE端,区内发育燕山期花岗岩、花岗闪长岩、二长花岗斑岩和英安质凝灰熔岩等;其中花岗闪长岩和二长花岗斑岩与铅锌成矿关系密切,成矿岩体形成时代分别为156Ma和127Ma。     

羌塘盆地侏罗系碎屑岩储集层综合评价

运用储层综合评判分析方法对羌塘盆地侏罗系碎屑岩储集层进行分析和评价。首先选择影响储层性质的8种参数,包括定性参数,如岩性、成岩作用、储集空间类型和定量参数,如储层厚度、孔隙结构、物性等,对其进行单因素评价。在此基础上,根据各单因素对储层贡献的大小,确定各单因素的加权系数。最后,利用评判分析方法,计算各剖面的综合判别得分。综合判别分析评价表明,北羌塘坳陷中部、东部和中央隆起带北缘发育好储层;北羌塘坳陷西部发育中等储层;而南羌塘坳陷储层较差。     

青藏高原北部新生代陆相盆地石油地质条件及勘探前景

青藏高原北部陆相盆地中烃源岩发育层位包括始新统风火山组、渐新统雅西措组和中新统五道梁组。古近系雅西措组烃源岩,特别是灰岩属于中好烃源岩范畴,有机质类型较好,且烃源岩主体处于成熟阶段,是藏北高原新生代陆相盆地主力烃源岩的发育层位。陆相盆地储集岩较发育,储层较丰富,发育层位包括风火山组和雅西措组,其中雅西措组是储层主力分布层位。对测区分析数据表明：通天河盆地具备一定规模的生油岩厚度,而且有机质丰度为沱沱河地区最高,表明其勘探前景较好。     

大民屯凹陷烃源岩有机质丰度的恢复

烃源岩有机质丰度的恢复具有重要的现实和理论意义。笔者在对比多种方法的基础上,对大民屯凹陷的烃源岩的有机质丰度进行了恢复。     

Mesozoic-Cenozoic tectonics and geodynamics of Altai, Tien Shan, and Northern Kazakhstan, from apatite fission-track data

Apatite fission-track (AFT) thermochronological modeling as a diagnostic tool for periods of stability (peneplanation) and tectonic activity (orogeny) has been broadly used in tectonic studies of Central Asia in recent years. We discuss more than 100 AFT ages of samples from the Kyrgyz Tien Shan and Altai and compare them with AFT data from northern Kazakhstan. Geological, geomorphological, and AFT data indicate intense activity in the Late Cenozoic Eurasian continental interior. The impact from the India-Eurasia collision on the northern Tien Shan, Altai, and northern Kazakhstan regions showed up at 11, 5, and 3 Ma, respectively, as a result of stress propagation into the continent, with the ensuing reactivation and mountain growth. We hypothesize that a distant effect of the Late Cenozoic India-Eurasia collision was to rejuvenate Paleozoic fault zones and to deform the Mesozoic sedimentary cover north of the collision front as far as the West Siberian Plate. The reactivation facilitated formation of tectonic oil and gas traps. The activity in northern Central Asia under the effect of the Indian indentation into Eurasia appears to continue and may evolve to include uplift of southern West Siberian plate with uplift.     

节理岩体卸荷强度特性的试验研究

卸荷状态工程岩体的强度特性与传统的加载岩体有本质的区别。目前对于岩石卸荷强度特性的研究比较多见,但对于含节理的岩体在卸荷应力状态下的强度特性,尤其是节理面对其强度的影响研究实属少见。本文通过岩体三轴模拟试验研究了卸荷应力状态下节理岩体的破坏特征,突出考虑了节理面性质对卸荷强度的影响,在此基础上提出了节理岩体卸荷强度准则的一般表达式并进行了对比验证。     

肋柱式锚杆支挡结构的徐变次内力分析

采用老化徐变理论和等效弹性模量法,对肋柱式锚杆支挡结构的徐变影响提出了具体计算方法,并通过实例计算了支挡结构的徐变次内力。计算结果表明,在逆作法条件下,随着开挖深度的加大,岩土侧向压力也增大,使后期施工的混凝土构件产生的徐变次内力也随之增大;考虑徐变后使结构设计更加安全可靠,尤其坡脚处后期浇筑的混凝土构件,更要关注徐变的影响。     

Zircon M257 ‐ a Homogeneous Natural Reference Material for the Ion Microprobe U‐Pb Analysis of Zircon

We introduce and propose zircon M257 as a future reference material for the determination of zircon U‐Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS‐determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for ²⁰⁶pb/²³⁸U and 0.7392 ± 0.0003 for ²⁰⁷pb/²³⁵U. Its ²⁰⁶pb/²³⁸U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U‐Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ～ 840 μg g^?1 U (Th/U ～ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit‐cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U‐Pb age, and the calculated alpha fluence of 1.66 × 10¹⁸ g^?1. This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc‐silicate skarn.     

Composition-Induced Variations in SIMS Instrumental Mass Fractionation during Boron Isotope Ratio Measurements of Silicate Glasses

An analytical artefact is reported here related to differences in instrumental mass fractionation between NIST SRM glasses and natural geological glasses during SIMS boron isotope determinations. The data presented demonstrated an average 3.4‰ difference between the NIST glasses and natural basaltic to rhyolitic glasses mainly in terms of their sputtering-induced fractionation of boron isotopes. As no matrix effect was found among basaltic to rhyolitic glasses, instrumental mass fractionation of most natural glass samples can be corrected by using appropriate glass reference materials. In order to confirm the existence of the compositionally induced variations in boron SIMS instrumental mass bias, the observed offset in SIMS instrumental mass bias has been independently reproduced in two laboratories and the phenomenon has been found to be stable over a period of more than one year. This study highlights the need for a close match between the chemical composition of the reference material and the samples being investigated.     

Recommended Values of 239Pu, 240Pu and 239+240Pu Concentrations in Reference Material IAEA-315 (Marine Sediment) Estimated by Thermal Ionisation Mass Spectrometry, Inductively Coupled Plasma-Mass Spectrometry and Alpha Spectrometry

The recommended concentrations of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu in reference material IAEA‐315 (marine sediment) were estimated by three analytical methods: isotope dilution thermal ionisation mass spectrometry (TIMS), isotope dilution inductively coupled plasma‐mass spectrometry (ICP‐MS) and alpha spectrometry. The determination of ²³⁹Pu and ²⁴⁰Pu (^239+240Pu by alpha spectrometry) was carried out with samples from randomly selected bottles using each method. Plutonium‐238 was also measured by alpha spectrometry. A plutonium‐242 reference material was used as a spike for the quantitative analysis. The influence of ²⁴²Pu in the samples was therefore calculated; however, this contribution was less than the range of uncertainty and did not influence the final results. The obtained data were statistically analysed using variance component analysis and paired comparison. The combined standard uncertainties from “method/measurement”, “bottle” and “sub‐sample” were in the order of 3 to 6%. The main contributions to the uncertainty were from the material heterogeneity and from systematic differences between methods. Based on this study with twenty‐seven analyses using 10–14 g sample mass, concentrations of (38 ± 3) Bq kg^?1, (28 ± 3) Bq kg^?1 and (66 ± 4) Bq kg^?1 are proposed as recommended values for ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu, respectively, and (9.5 ± 0.4) Bq kg^?1 for ²³⁸Pu as an information value in reference material IAEA‐315. In mass concentration units, these amount to (16.4 ± 1.2) ng kg^?1, (3.3 ± 0.4) ng kg^?1 and (0.015 ± 0.003) ng kg^?1 for ²³⁹Pu, ²⁴⁰Pu and ²³⁸Pu, respectively. The certified reference materials NIST 4350B and NIST 4354 were also analysed by TIMS for quality assurance of the method used in this study.