The composition of the Earth

Compositional models of the Earth are critically dependent on three main sources of information: the seismic profile of the Earth and its interpretation, comparisons between primitive meteorites and the solar nebula composition, and chemical and petrological models of peridotite-basalt melting relationships. Whereas a family of compositional models for the Earth are permissible based on these methods, the model that is most consistent with the seismological and geodynamic structure of the Earth comprises an upper and lower mantle of similar composition, an Fe---Ni core having between 5% and 15% of a low-atomic-weight element, and a mantle which, when compared to CI carbonaceous chondrites, is depleted in Mg and Si relative to the refractory lithophile elements.The absolute and relative abundances of the refractory elements in carbonaceous, ordinary, and enstatite chondritic meteorites are compared. The bulk composition of an average CI carbonaceous chondrite is defined from previous compilations and from the refractory element compositions of different groups of chondrites. The absolute uncertainties in their refractory element compositions are evaluated by comparing ratios of these elements. These data are then used to evaluate existing models of the composition of the Silicate Earth.The systematic behavior of major and trace elements during differentiation of the mantle is used to constrain the Silicate Earth composition. Seemingly fertile peridotites have experienced a previous melting event that must be accounted for when developing these models. The approach taken here avoids unnecessary assumptions inherent in several existing models, and results in an internally consistent Silicate Earth composition having chondritic proportions of the refractory lithophile elements at 2.75 times that in CI carbonaceous chondrites. Element ratios in peridotites, komatiites, basalts and various crustal rocks are used to assess the abundances of both non-lithophile and non-refractory elements in the Silicate Earth. These data provide insights into the accretion processes of the Earth, the chemical evolution of the Earth's mantle, the effect of core formation, and indicate negligible exchange between the core and mantle throughout the geologic record (the last 3.5 Ga).The composition of the Earth's core is poorly constrained beyond its major constituents (i.e. an Fe---Ni alloy). Density contrasts between the inner and outer core boundary are used to suggest the presence ( 10 ± 5%) of a light element or a combination of elements (e.g., O, S, Si) in the outer core. The core is the dominant repository of siderophile elements in the Earth. The limits of our understanding of the core's composition (including the light-element component) depend on models of core formation and the class of chondritic meteorites we have chosen when constructing models of the bulk Earth's composition.The Earth has a bulk Fe/Al of 20 ± 2, established by assuming that the Earth's budget of Al is stored entirely within the Silicate Earth and Fe is partitioned between the Silicate Earth ( 14%) and the core ( 86%). Chondritic meteorites display a range of Fe/Al ratios, with many having a value close to 20. A comparison of the bulk composition of the Earth and chondritic meteorites reveals both similarities and differences, with the Earth being more strongly depleted in the more volatile elements. There is no group of meteorites that has a bulk composition matching that of the Earth's.     

在CTMAB存在下应用苯基萤光酮分光光度法测定岩矿中微量锡

本文研究了在ＣＴＭＡＢ存在下，应用苯基萤光酮分光光度法测定微量锡的条件。该法灵敏度高，操作简便，可用于测定岩矿样品中的微量锡。     

东濮凹陷黄河南地区下第三系沉积体系与油气评价

为了加速东濮凹陷黄河南地区油气勘探的步伐,本文根据现代沉积体系理论,综合运用地质、测井和地震资料,首次在东濮凹陷黄河南地区下第三系中系统地确定了冲积扇、河流、扇三角洲、三角洲—滑塌浊积扇、滩坝、近岸水下扇和轴向重力流水道等7种类型的沉积体系,并描述了这些沉积体系在地质、测井和地震等方面的沉积特征。结合盆地断裂活动特点,指出充填盆地沉积体系的演化具有明显的阶段性,沉积体系的平面展布具有不对称性,从而建立盆地沉积体系演化模式。同时,结合油气勘探实践指出富集油气的有利相带。     

地质统计学方法在井间储层参数预测中的应用

本文探讨了利用地质统计学中的三种克立格方法进行井间储层参数预测的原理及方法,并在某油田中应用,通过最优性检验,建立起了适合研究区地质特点的各种储层参数的最佳估计模型,揭示了储层参数在三维空间的变化规律,为建立三维储层预测模型开辟了新的方法。     

双峰县金坑冲金矿地质特征及找矿前景

本文概述了金坑冲金矿地质特征,并对其矿化规律作了总结。在此基础上,依据地质类比与土壤地球化学测量成果,指出王家湾一丫头山一带,是找石英脉一蚀变岩型金矿的远景区。     

上海附近地区水域的地质灾害及其对工程建筑的影响

本区水域的地质灾害分为直接的、潜在的和人为的三种,类型有冲刷槽、滑坡、活动沙波和沙脊、不稳定岸坡、快速侵蚀和堆积,浅滩和暗礁,埋藏古河道、古洼地、埋藏基岩、含气沉积物、“鸡蛋壳”地层,断层和地震,人为障碍物等。本文讨论了各类水域地质灾害的分布、特征、对工程建筑的影响和防治措施。     

中长期预报区内地震烈度的评估方法

本文中作者以祁连山中段为研究区域提出了评估中长期预报区内烈度的方法。本方法的特点是对相对稳定的发震地段在某预报期内进行烈度概率分析。文申指出了本方法与确定性方法以及地震危险性分析方法的不同之处。计算表明,对本区,烈度提高一度,遭受该烈度袭击的概率即减少20％左右。根据计算结果,将研究区域划分为若干小区,给出了每小区Ⅵ——Ⅷ度发生的概率,并以此作为估算预报期内损失期望值的依据。     

太原盆地历史地震活动特征及未来地震形势估计

对公元1000－1985年太原盆地M≥4.0地震进行了时序分析，结果表明，它们在时间轴上和山西地震带及至华北地区有着相似的平静一起伏变化特点，以此划出4个地震活动期和若干活动幕，指出活动最大地震存在逐步升级现象；在空间上重复性高，形成3个地震巢和以巢为主的地震条带与地震跳迁现象，认为在2000年前后，太原盆地将处在地震高活动时段，有可能在地震巢附近发生若干个中强地震，山西和华北地区强震活动也有可能与之同步。     

新疆库松木切克山喇嘛萨依式铜矿的勘查标志

本文通过对库松木切克山喇嘛萨依铜矿地质特征及控矿因素的研究,总结出该类矿床的若干勘查标志,其中地层层位、含矿岩相、地球化学异常、容矿岩石、围岩蚀变、活化脉体及同生断裂等最为明显。在区域内如能确定出这些标志,尤其是标志组合的存在,则将可能取得该类矿床找矿的新突破。     

江西省大地热流与铀矿关系的初步研究

本文根据江西省大地构造、铀矿分布和大地热流实测资料,证明大地热流异常和铀矿均受深大断裂和深部构造变异带的控制,铀矿化能在一定程度上引起热流异常,并据此初步探讨了根据大地热流异常寻找铀矿床的可能性。