构造圈闭有效性的数学判别

构造圈闭有效性的数学判别，是将以往的定性分析发展为定量分析。本方法以同沉积原理为基础，用数学方法分析的构造顶部与翼部的地层厚度变化关系，计算出了不同地质历史时期的构造生长指数，绘制地质年代与构造生长指数的关系曲线，进而结合分轩模拟结果分析构造圈闭的有效性。给出了本方法在海相碳酸岩地区某构造圈闭的应用实例。用此方法进行构造圈评价可使油气探更逼近目标，减少预探风险，提高钻井成功率。     

北海断层封闭性分析

多数北海构造圈闭至少需要一条断层来充当封闭性断层。在北海进行区域研究时，从１０１个勘探目标和２５个油气田中选择了４００多个断层加以分析，这些断层切穿了来自多种沉积环境（海相、海陆过渡相、陆相）碎屑岩沉积层序。本次研究的重点是地质历史时期中可以起到压力或运移遮挡的断层封闭性。通过绘制多种参数，如断层走向、断距、储层厚度、深度、有效厚度与总厚度比值、孔隙度、砂岩有效连通性等与断层封闭性能的关系图，确定各种参数间的分布趋势和相关关系。以预测断层封闭特点、断层分布方向与封闭性之间存在着某种相关关系，断距经过校正到占储层厚度一定比例之后，与断层封闭性之间存在着比例关系，大多数断距大于储层厚度的断层都是封闭性断层。在断层封闭性预测中最有用的参数是断距，有效厚度与总厚度的比伍（净／总）和砂岩有效连通性。本次研究的结论对在北海盆地碎屑岩沉积层序中进行油气勘探和开发时的断层封闭性预测有广泛的适用性，或许也可以应用于其它地区。     

Ar-Ar chronology of the Martian meteorite ALH84001: evidence for the timing of the early bombardment of Mars

ALH84001, a cataclastic cumulate orthopyroxenite meteorite from Mars, has been dated by Ar-Ar stepped heating and laser probe methods. Both methods give ages close to 3,900 Ma. The age calculated is dependent on assumptions made about 39Ar recoil effects and on whether significant quantities of 40Ar from the Martian atmosphere are trapped in the meteorite. If, as suggested by xenon and nitrogen isotope studies, Martian atmospheric argon is present, then it must reside predominantly in the K-rich phase maskelynite. Independently determined 129Xe abundances in the maskelynite can be used to place limits on the concentration of the atmospheric 40Ar. These indicate a reduction of around 80 Ma to ages calculated on the assumption that no Martian atmosphere is present. After this correction, the nominal ages obtained are: 3940 +/- 50, 3870 +/- 80, and 3970 +/- 100 Ma. by stepped heating, and 3900 +/- 90 Ma by laser probe (1 sigma statistical errors), giving a weighted mean value of 3,920 Ma. Ambiguities in the interpretation of 39Ar recoil effects and in the contribution of Martian atmospheric 40Ar lead to uncertainties in the Ar-Ar age which are difficult to quantify, but we suggest that the true value lies somewhere between 4,050 and 3,800 Ma. This age probably dates a period of annealing of the meteorite subsequent to the shock event which gave it its cataclastic texture. The experiments provide the first evidence of an event occurring on Mars coincident with the time of the late heavy bombardment of the Moon and may reflect a similar period of bombardment in the Southern Highlands of Mars. Whether the age determined bears any relationship to the time of carbonate deposition in ALH84001 is not known. Such a link depends on whether the temperature associated with the metasomatic activity was sufficient to cause argon loss from the maskelynite and/or whether the metasomatism and metamorphism were linked in time through a common heat source.