K-Ar Geochronology of Mesozoic Mafic Dikes in Shandong Province, Eastern China: Implications for Crustal Extension

Based on K-Ar isotope analyses, Mesozoic mafic (and alkali ultramafic) dikes from western and eastern Shandong Province, China, are dated at 88.2±1.70 Ma to 169.5±3.7 Ma with the majority of ages ranging from 90 Ma to 140 Ma. The emplacement of the dikes suggests a major Yanshanian (Cretaceous) crustal extension in Shandong province. Together with other available age data, this study suggests four periods of crustal extension at about 80 Ma, 100 Ma, 120 Ma and 140 Ma, respectively. Besides the effect of collapse of the Yanshanian orogenic belt on the emplacement of the mafic dikes in Shandong in the Cretaceous, the mantle plume and the extensive left-lateral advection and extension of the Tanlu fault also have controlled the crustal extension and the emplacement of the mafic dikes in eastern Shandong and western Shandong, respectively.     

菊花石及其他两种放射状形貌对比研究

通过天青石菊花石形貌与红柱石菊花石钟乳石截面放射状形貌的对比,找出它们形成的共同规律,并从形貌细节差异上分析了其形成机制和条件的差别。     

内蒙古乌兰泡湿地环带状植被区土壤有机质及全氮空间分异规律

本文以乌兰泡湿地为研究对象,对该区环带状植被区湿地土壤有机质有全氮的空间分布规律进行了初步研究,结果表明不同植被区养发含量分异趋势一致,但水平分异显著,沿土壤水分梯度变化而变化,表现为蓼区＞香蒲区＞芦苇区,反映出距泡心越远含量越低的规律;各植被区土壤碳氮比都相对较低（在5－12之间）,表层土壤碳氮经值也沿土吉水分梯度变化,表现为芦苇区＞香莆区＞蓼区;泡沼湿地土壤与草原土壤的碳氮比对水分条件及有机质和全氮的含量的响应差异显著;水分和植被是影响其水平分异的关键因子,而湿地土壤pH值并不是影响土壤有机质及全氮分异的主要因子。     

四川盆地威远气田碳酸盐岩中有机包裹体研究

本文通过对威远、资阳地区上震旦统碳酸盐岩储集层中有机包裹体的研究,提出有机包裹体多分布于储层孔洞缝中所充填的三期矿物中,研究区油气运移的主要通道是溶蚀孔洞和裂缝。并根据不同期次充填矿物中有机包裹体特征、均一温度及单个有机包裹体成分,追索了研究区油气热演化程度、油气运移期次、油气运移的深度和温度。研究结果表明,研究区存在三次主要的油气运移和聚集,其各自演化的程度及油气运移的深度和温度皆不同。     

冀北丰宁银(金)矿床地质、地球化学特征及成因

冀北丰宁银(金)矿床的成矿深度＜1 km,成矿温度＜300℃,成矿时间晚于次火山隐爆成岩作用1.0 Ma以上,是与隐爆作用有关的陆相次火山浅成低温热液型银多金属矿床.次火山隐爆作用只是一种构造动力因素,起到动力源和提供扩容空间的间接成矿作用,而直接的成矿环境为浅成低温水热流体的成矿演化体系.热液流体大致可分为两类:一是富含SiO2的热流体,存在于每次隐爆作用之中,起到胶结花岗质角砾的作用,并有少量金属硫化物(如黄铁矿等)沉淀;二是有大量地下水参与的含矿水热流体,形成于隐爆作用发生之后,此阶段的热液活动导致Au,Ag,Pb,Zn,Fe,Cu等金属及其化合物的富集与沉淀.     

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℃,...     

地震力作用下单排与双排桩支挡结构性状试验对比分析

桩板式挡土结构由抗滑桩发展而来,可用于一般地区、浸水地区和地震区的边坡工程支挡;对于地震区边坡,采用单排或双排支挡结构的形式及其支挡效果尚缺少深入研究。本文基于地震力作用下单排、双排桩板结构在不同加载等级时的桩身土压力、土体加速度、桩身位移等变化的振动台模型试验结果,对比采用单排、双排桩板结构边坡的支挡效果,得出静力状态和不同加速度峰值地震力作用桩前后土压力分布、桩后土体加速度分布和桩体位移的一些规律,为今后边坡桩板式支挡结构的抗震设计提供参考。     

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.