Macrocrystal Garnet and Its Inclusions in Kimberlite Pipes from the Mengyin Area, Shandong Province, China

Abstract: Based on previous studies of kimberlite xenoliths and diamond inclusions in this region, macrocrystal garnet was analyzed with the electric microprobe technique (EPMA). The garnet is collected from the Shengli No.1 kimberlite pipe in the Mengyin area of Shandong Province, China. The results indicate that the garnet contains two kinds of multiphase inclusions: one is K-, B-, and Cl-bearing oxygen-free phase, K- and Cl-bearing oxygen-free phase, and volatile-bearing garnet inclusions (in1 and in3); and the other is chlorite, phlogopite, apatite and calcite (in2). It is suggested that the formation of garnet and its inclusions is associated with strongly reduced mantle fluid. Such a fluid was transformed from ultra-deep high-reduction oxygen-free fluid into low-reduction alkaline fluid, and finally into oxidized fluid with low oxygen fugacity. This result confirms that the Mengyin area underwent metamorphism of slightly active deep fluid, and provides evidence for searching diamond by means of indicative minerals.     

Methane microseepage from different sectors of the Yakela condensed gas field in Tarim Basin,Xinjiang, China

Methane microseepage is the result of natural gas migration from subsurface hydrocarbon accumulations to the Earth’s surface, and it is quite common in commercial petroleum fields. While the role of microseepage as a pathfinder in petroleum exploration has been known for about 80 a, its significance as an atmospheric CH₄ source has only recently been studied, and flux data are currently available only in the USA and Europe. With the aim of increasing the global data-set and better understanding flux magnitudes and variabilities, microseepage is now being extensively studied in China. A static flux chamber method was recently applied to study microseepage emissions into the atmosphere in four different sectors of the Yakela condensed gas field in Tarim Basin, Xinjiang, China, and specifically in: (a) a faulted sector, across the Luntai fault systems; (b) an oil–water interface sector, at the northern margin of the field; (c) an oil–gas interface sector, in the middle of the field; (d) an external area, outside the northern gas field boundaries. The results show that positive CH₄ fluxes are pervasive in all sectors and therefore, only part of the CH₄ migrating from the deep oil–gas reservoirs is consumed in the soil by methanotrophic oxidation. The intensity of gas seepage seems to be controlled by subsurface geologic settings and lateral variabilities of natural gas pressure in the condensed gas field. The highest CH₄ fluxes, up to ∼14 mg m⁻² d⁻¹ (mean of 7.55 mg m⁻² d⁻¹) with higher spatial variability (standard deviation, σ: 2.58 mg m⁻² d⁻¹), occur in the Luntai fault sector. Merhane flux was lower in the oil–water area (mean of 0.53 mg m⁻² d⁻¹) and the external area (mean of 1.55 mg m⁻² d⁻¹), and at the intermediate level in the gas–oil sector (mean of 2.89 mg m⁻² d⁻¹). These values are consistent with microseepage data reported for petroleum basins in the USA and Europe. The build-up of methane concentration in the flux chambers is always coupled with an enrichment of ¹³C, from δ¹³C₁ of −46‰ to −42.5‰ (VPDB), which demonstrates that seeping methane is thermogenic, as that occurring in the deep Yakela reservoir. Daily variations of microseepage are very low, with minima in the afternoon, corresponding to higher soil temperature (and higher methanotrophic consumption), and maxima in the early morning (when soil temperatures are lowest). A preliminary and rough estimate of the total amount of CH₄ exhaled from the Yakela field is in the order of 10² tonnes a⁻¹.     

利用红柳沙包氢氧同位素重建罗布泊地区近160年间气候要素

新疆罗布泊地区存在的红柳沙包不仅是高分辨率的计年载体,同时蕴古丰富的环境演化信息.本文通过对罗布泊地区典型红柳沙包沉积纹层样品的氧氢同位素测定和分析,建立了红柳沙包沉积纹层的δD和δ18O序列,并依此重建了罗布泊地区过去163年间的平均气温、相对湿度、降水量等气候要素变化序列.重建结果表明,3月份平均气温为7.39℃,...     

Contamination characteristics of heavy metals in wetland soils along a tidal ditch of the Yellow River Estuary, China

Surface soils (0–20 cm) were collected from along a tidal ditch of the Yellow River Estuary in August of 2007. Samples were subjected to a total digestion technique before they were analyzed for total concentrations of As, Cr, Cd, Cu, Ni, Pb, Zn, P and S in order to investigate heavy metal contamination levels in wetland soils nearby the tidal ditches and their main sources. Results showed that the mean concentrations of these heavy metals except for As and Cd were lower than the Class I criteria. Nearly all sampling sites showed lower contamination levels for As and Cd, while no contamination levels for other heavy metals. Cr, Cu, and Ni mainly originated from parent rocks, and Pb and As might originate from tidal seawater and oil field pollution, respectively; while Cd and Zn mainly originated from parent rocks and tidal seawater. Most of heavy metals showed significant correlations with total concentrations of P and S, however, no significant correlations were observed between them and soil pH, slat and soil organic matter.     

面向实际应用的舰艇水下磁场标准化建模方法

舰艇消磁是有效防护舰艇遭受水雷攻击的重要手段之一,高效精准的测磁技术是舰艇消磁的前提。针对舰艇首次消磁工作中使用手提式测磁仪与大平面测磁阵列之间的测量点位置差异问题,提出基于磁偶极子阵列的舰艇水下磁场换算方法,引入舰艇几何模型标准化数据库,计算出舰艇水下标准测量点处的磁场,解决了测量点位置差异导致无法发挥消磁站自动化大平面测磁的实际难题,该方法可推广适用于大部分舰艇消磁站。     

人字桥梁多维地震作用下振动台试验研究

设计制作一座人字曲线桥模型,进行了多维输入的振动台试验,分析了结构在地震作用下的震害现象,并探讨了多维输入下的地震响应特点。结果表明:人字曲线桥梁梁体和桥墩主要表现为以弯曲裂缝为主的破坏模式,竖向输入是梁跨中裂缝出现的主要原因,桥墩裂缝主要受水平输入的影响。梁跨中加速度响应受竖向输入影响最大,墩顶纵桥向加速度响应受竖向输入分量影响并不显著。单维竖向输入降低墩体竖向加速度响应,三向输入则加大墩体竖向加速度响应;对于人字桥梁伸缩缝宽度设置,分支直梁处可只考虑纵桥向地震输入,分支曲梁处则要考虑水平双向地震输入。     

辽西下白垩统义县组湖相碳酸盐岩及其沉积环境研究

辽西地区下白垩统义县组是热河生物群产出的主要地层,其中产出大量精美的生物化石,但是由于受到后期构造破坏和风化作用影响,难以开展野外工作,热河生物群产出的古地理环境及盆地沉积环境的研究程度仍然较低。该组地层中湖相碳酸盐岩比较发育,本次工作主要对辽西义县组老公沟—金刚山剖面4个沉积层中产出的多层湖相碳酸盐岩沉积层进行了深入研究。通过野外工作结合室内镜下鉴定,分析了义县组湖相碳酸盐岩的产出状态和岩石类型,划分出5个岩相类型和两个相组合。结合野外实测剖面中碳酸盐岩与其它沉积岩层的组合关系对义县组湖相碳酸盐沉积环境进行了探讨,发现义县组湖相碳酸盐岩主要为洪水—漫湖沉积体系中较浅的储水洼地和滨浅湖半咸水沉积环境,并建立了义县组湖相碳酸盐岩沉积相模式。     

中国南海莺－琼盆地油气源对比的成熟度证据

中国南海莺－琼盆地油气源对比的成熟度证据陈军红，傅家谟，盛国英，周毅（中国科学院广州地球化学研究所，广州５１０６４０）张启明（中国海洋石油南海酉部公司石油勘探开发研究院，广东湛江５２４０５７）关键词中国南海，莺－琼盆地，成熟度，油气源油气源对比对含油...     

The Paleoproterozoic McArthur River (HYC) Pb/Zn/Ag deposit of northern Australia: organic geochemistry and ore genesis

Polycyclic aromatic hydrocarbons (PAHs) in ore and mudstone within the McArthur River ore deposit show compound distribution patterns similar to those of hydrothermally generated petroleum in the Guaymas Basin and significantly different from those found in conventional oil. PAH abundances and their isomer distributions result from a temperature gradient between the source of mineralizing fluids and the sediments fringing the ore system during ore formation. Along with other geochemical, geological, paleobiological and mineralogical lines of evidence, these data provide strong evidence that the ore formed within partially lithified sediments under marine conditions. Given that the McArthur River ore body is an exquisitely preserved example of a sediment-hosted base-metal deposit, these results may be widely applicable. The McArthur deposit is also a rich repository of paleobiological information, allowing studies of the microbiology of ore formation and the paleobiology of an ancient hydrothermal system, as is discussed elsewhere.